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1.  An evidence based hypothesis on the existence of two pathways of mitochondrial crista formation 
eLife  null;5:e18853.
Metabolic function and architecture of mitochondria are intimately linked. More than 60 years ago, cristae were discovered as characteristic elements of mitochondria that harbor the protein complexes of oxidative phosphorylation, but how cristae are formed, remained an open question. Here we present experimental results obtained with yeast that support a novel hypothesis on the existence of two molecular pathways that lead to the generation of lamellar and tubular cristae. Formation of lamellar cristae depends on the mitochondrial fusion machinery through a pathway that is required also for homeostasis of mitochondria and mitochondrial DNA. Tubular cristae are formed via invaginations of the inner boundary membrane by a pathway independent of the fusion machinery. Dimerization of the F1FO-ATP synthase and the presence of the MICOS complex are necessary for both pathways. The proposed hypothesis is suggested to apply also to higher eukaryotes, since the key components are conserved in structure and function throughout evolution.
DOI: http://dx.doi.org/10.7554/eLife.18853.001
eLife digest
Cells contain compartments called mitochondria, which are often called the powerhouses of the cell because they provide energy that drives vital cellular processes. Mitochondria have two membranes: an outer and an inner membrane. The outer membrane separates the mitochondria from the rest of the cell. The inner membrane is elaborately folded and the folds – called cristae – create a larger space to accommodate all of the protein machinery involved in producing energy. The cristae can be shaped as flat sac-like structures called lamellar cristae or as tubes known as tubular cristae.
Mitochondria are dynamic and are constantly fusing with other mitochondria and splitting up. Even though the internal architecture of mitochondria was first revealed around 60 years ago, it is still not clear how the cristae form. Harner et al. now address this question in yeast cells by combining imaging, biochemistry and genetic approaches.
The experiments show that lamellar cristae form when two mitochondria fuse with each other. The outer membranes merge and then the inner membranes start to fuse around their edges to generate the sac-like structure of lamellar cristae. A yeast protein called Mgm1 (known as Opa1 in mammals) drives the fusion of the inner membranes, but this process only takes place when enzymes called F1FO-ATP synthases on the inner membrane form pairs with one another. These F1FO-ATP synthase pairs stabilize the cristae membranes as they curve to form the sac-like structure. Later on, the formation of a group of proteins called the MICOS complex halts the fusion process to prevent the lamellar cristae from completely separating from the rest of the inner membrane.
Harner et al. also found that tubular cristae form using a different mechanism when the inner membrane of the mitochondria grows inwards. This process also requires pairs of F1FO-ATP synthases and the MICOS complex, but does not involve Mgm1/Opa1. Together, these findings show that lamellar and tubular cristae in yeast form using two different mechanisms. Since the key components of these mechanisms are also found in virtually all other eukaryotes, the findings of Harner et al. are also likely to apply to many other organisms including animals.
DOI: http://dx.doi.org/10.7554/eLife.18853.002
doi:10.7554/eLife.18853
PMCID: PMC5138035  PMID: 27849155
mitochondria; crista formation; mitochondrial fusion; Mgm1/Opa1; MICOS; F1FO-ATP synthase; S. cerevisiae
2.  The yeast Saccharomyces cerevisiae: an overview of methods to study autophagy progression 
Macroautophagy (hereafter autophagy) is a highly evolutionarily conserved process essential for sustaining cellular integrity, homeostasis, and survival. Most eukaryotic cells constitutively undergo autophagy at a low basal level. However, various stimuli, including starvation, organelle deterioration, stress, and pathogen infection, potently upregulate autophagy. The hallmark morphological feature of autophagy is the formation of the double-membrane vesicle known as the autophagosome. In yeast, flux through the pathway culminates in autophagosome-vacuole fusion, and the subsequent degradation of the resulting autophagic bodies and cargo by vacuolar hydrolases, followed by efflux of the breakdown products. Importantly, aberrant autophagy is associated with diverse human pathologies. Thus, there is a need for ongoing work in this area to further understand the cellular factors regulating this process. The field of autophagy research has grown exponentially in recent years, and although numerous model organisms are being used to investigate autophagy, the baker’s yeast Saccharomyces cerevisiae remains highly relevant, as there are significant and unique benefits to working with this organism. In this review, we will focus on the current methods available to evaluate and monitor autophagy in S. cerevisiae, which in several cases have also been subsequently exploited in higher eukaryotes.
doi:10.1016/j.ymeth.2014.12.008
PMCID: PMC4355233  PMID: 25526918
Atg8; autophagosome; mitophagy; PAS; phagophore; vacuole
3.  Lipid partitioning at the nuclear envelope controls membrane biogenesis 
Molecular Biology of the Cell  2015;26(20):3641-3657.
Cells adjust the flux of lipid intermediates toward membranes or storage in response to their metabolic status. In response to growth cues, spatiotemporal activation of Pah1 at discrete subdomains of the nuclear envelope acts as a switch to promote lipid storage. This lipid rewiring controls organelle morphology.
Partitioning of lipid precursors between membranes and storage is crucial for cell growth, and its disruption underlies pathologies such as cancer, obesity, and type 2 diabetes. However, the mechanisms and signals that regulate this process are largely unknown. In yeast, lipid precursors are mainly used for phospholipid synthesis in nutrient-rich conditions in order to sustain rapid proliferation but are redirected to triacylglycerol (TAG) stored in lipid droplets during starvation. Here we investigate how cells reprogram lipid metabolism in the endoplasmic reticulum. We show that the conserved phosphatidate (PA) phosphatase Pah1, which generates diacylglycerol from PA, targets a nuclear membrane subdomain that is in contact with growing lipid droplets and mediates TAG synthesis. We find that cytosol acidification activates the master regulator of Pah1, the Nem1-Spo7 complex, thus linking Pah1 activity to cellular metabolic status. In the absence of TAG storage capacity, Pah1 still binds the nuclear membrane, but lipid precursors are redirected toward phospholipids, resulting in nuclear deformation and a proliferation of endoplasmic reticulum membrane. We propose that, in response to growth signals, activation of Pah1 at the nuclear envelope acts as a switch to control the balance between membrane biogenesis and lipid storage.
doi:10.1091/mbc.E15-03-0173
PMCID: PMC4603934  PMID: 26269581
4.  Aim24 and MICOS modulate respiratory function, tafazzin-related cardiolipin modification and mitochondrial architecture 
eLife  2014;3:e01684.
Structure and function of mitochondria are intimately linked. In a search for components that participate in building the elaborate architecture of this complex organelle we have identified Aim24, an inner membrane protein. Aim24 interacts with the MICOS complex that is required for the formation of crista junctions and contact sites between inner and outer membranes. Aim24 is necessary for the integrity of the MICOS complex, for normal respiratory growth and mitochondrial ultrastructure. Modification of MICOS subunits Mic12 or Mic26 by His-tags in the absence of Aim24 leads to complete loss of cristae and respiratory complexes. In addition, the level of tafazzin, a cardiolipin transacylase, is drastically reduced and the composition of cardiolipin is modified like in mutants lacking tafazzin. In conclusion, Aim24 by interacting with the MICOS complex plays a key role in mitochondrial architecture, composition and function.
DOI: http://dx.doi.org/10.7554/eLife.01684.001
eLife digest
Respiration is vital to all living things because it is the process by which nutrients are converted into useful energy. Within our cells, organelles called mitochondria harness this energy and store it within molecules of ATP. This energy can then be released, when it is needed, by breaking down an ATP molecule into simpler chemicals.
When viewed under an electron microscope, it can be seen that an individual mitochondrion has two membranes: a highly folded inner membrane, and an outer membrane that is fairly smooth. However, some of the genes, proteins and other molecules that determine the complex shapes of mitochondria have not been identified.
Using a technique called mass spectrometry, a protein called Aim24 was previously shown to accumulate at the sites where the two membranes of a mitochondrion make contact with each other. Now, Harner et al. have discovered that Aim24 proteins are transported into mitochondria and embedded within the inner membranes. Aim24 is needed to assemble and maintain the stability of the protein complex that anchors the inner membrane to the outer membrane: mitochondria that lack the Aim24 protein have an irregular structure.
Furthermore, Harner et al. showed that Aim24 is needed to form other protein complexes—also within the inner membrane—that work together to harness the energy that is released when nutrients are broken down, so that it can be stored as ATP. Cells that lack the Aim24 gene also showed changes in the kinds of molecules found within the membranes of the mitochondria.
This work shows how difficult it can be to determine how the shapes of structures within cells, such as mitochondria, are controlled—as one protein can have many roles that cannot be easily teased apart. The on-going challenge is to uncover how different proteins, and other molecules in the membranes of mitochondria, interact to determine the structure, and consequently function, of the mitochondria in a cell.
DOI: http://dx.doi.org/10.7554/eLife.01684.002
doi:10.7554/eLife.01684
PMCID: PMC3975624  PMID: 24714493
mitochondria; contact sites; MICOS complex; cardiolipin; aim24; mitofilin; S. cerevisiae
5.  An autophagy-independent role for LC3 in equine arteritis virus replication 
Autophagy  2013;9(2):164-174.
Equine arteritis virus (EAV) is an enveloped, positive-strand RNA virus. Genome replication of EAV has been associated with modified intracellular membranes that are shaped into double-membrane vesicles (DMVs). We showed by immuno-electron microscopy that the DMVs induced in EAV-infected cells contain double-strand (ds)RNA molecules, presumed RNA replication intermediates, and are decorated with the autophagy marker protein microtubule-associated protein 1 light chain 3 (LC3). Replication of EAV, however, was not affected in autophagy-deficient cells lacking autophagy-related protein 7 (ATG7). Nevertheless, colocalization of DMVs and LC3 was still observed in these knockout cells, which only contain the nonlipidated form of LC3. Although autophagy is not required, depletion of LC3 markedly reduced the replication of EAV. EAV replication could be fully restored in these cells by expression of a nonlipidated form of LC3. These findings demonstrate an autophagy-independent role for LC3 in EAV replication. Together with the observation that EAV-induced DMVs are also positive for ER degradation-enhancing α-mannosidase-like 1 (EDEM1), our data suggested that this virus, similarly to the distantly-related mouse hepatitis coronavirus, hijacks the ER-derived membranes of EDEMosomes to ensure its efficient replication.
doi:10.4161/auto.22743
PMCID: PMC3552881  PMID: 23182945
arterivirus; autophagy; double-membrane vesicles; LC3; nidoviruses
6.  A Neurotoxic Glycerophosphocholine Impacts PtdIns-4, 5-Bisphosphate and TORC2 Signaling by Altering Ceramide Biosynthesis in Yeast 
PLoS Genetics  2014;10(1):e1004010.
Unbiased lipidomic approaches have identified impairments in glycerophosphocholine second messenger metabolism in patients with Alzheimer's disease. Specifically, we have shown that amyloid-β42 signals the intraneuronal accumulation of PC(O-16:0/2:0) which is associated with neurotoxicity. Similar to neuronal cells, intracellular accumulation of PC(O-16:0/2:0) is also toxic to Saccharomyces cerevisiae, making yeast an excellent model to decipher the pathological effects of this lipid. We previously reported that phospholipase D, a phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2)-binding protein, was relocalized in response to PC(O-16:0/2:0), suggesting that this neurotoxic lipid may remodel lipid signaling networks. Here we show that PC(O-16:0/2:0) regulates the distribution of the PtdIns(4)P 5-kinase Mss4 and its product PtdIns(4,5)P2 leading to the formation of invaginations at the plasma membrane (PM). We further demonstrate that the effects of PC(O-16:0/2:0) on the distribution of PM PtdIns(4,5)P2 pools are in part mediated by changes in the biosynthesis of long chain bases (LCBs) and ceramides. A combination of genetic, biochemical and cell imaging approaches revealed that PC(O-16:0/2:0) is also a potent inhibitor of signaling through the Target of rampamycin complex 2 (TORC2). Together, these data provide mechanistic insight into how specific disruptions in phosphocholine second messenger metabolism associated with Alzheimer's disease may trigger larger network-wide disruptions in ceramide and phosphoinositide second messenger biosynthesis and signaling which have been previously implicated in disease progression.
Author Summary
Accelerated cognitive decline in Alzheimer's patients is associated with distinct changes in the abundance of choline-containing lipids belonging to the platelet activating factor family. In particular, PC(O-16:0/2:0) or C16:0 platelet activating factor (PAF), is specifically elevated in brains of Alzheimer's patients. Since elevated intraneuronal levels of PC(O-16:0/2:0) are thought to contribute to the loss of neuronal cells it is imperative to identify the underlying mechanisms contributing to the toxic effects of PC(O-16:0/2:0). In this study, we have determined that elevated levels of PC(O-16:0/2:0) has negative effects upon the distribution of phosphoinositides at the plasma membrane leading to a potent inhibition of target of rapamycin (TOR) signaling. We further show that the changes in phosphoinositide distribution are due to changes in ceramide metabolism. In conclusion, our study suggests that the toxicity associated with aberrant metabolism of glycerophosphocholine lipids species is likely due to the remodeling of phosphoinositide and ceramide metabolism and that therapeutic strategies which target these disruptions may be effective in ameliorating Alzheimer's Disease pathology.
doi:10.1371/journal.pgen.1004010
PMCID: PMC3900389  PMID: 24465216
7.  Understanding phosphatidylinositol-3-phosphate dynamics during autophagosome biogenesis 
Autophagy  2012;8(12):1868-1870.
Autophagosomes, the hallmark of autophagy, are double-membrane vesicles sequestering cytoplasmic components. They are generated at the phagophore assembly site (PAS), the phagophore being the precursor structure of these carriers. According to the current model, autophagosomes result from the elongation and reorganization of membranes at the PAS/phagophore driven by the concerted action of the autophagy-related (Atg) proteins. Once an autophagosome is completed, the Atg proteins that were associated with the expanding phagophore are released in the cytoplasm and reused for the biogenesis of new vesicles. One molecular event required for autophagosome formation is the generation of phosphatidylinositol 3-phosphate (PtdIns3P) at the PAS. Our data indicate that in addition to the synthesis of this lipid, the dephosphorylation of PtdIns3P is also crucial for autophagy progression. In the absence of Ymr1, a specific PtdIns3P phosphatase and the only yeast member of the myotubularin protein family, Atg proteins remain associated with complete autophagosomes, which are thus unable to fuse with the vacuole.
doi:10.4161/auto.22162
PMCID: PMC3541308  PMID: 22992453
PAS; Ymr1; autophagosome; autophagy; phagophore; phosphatidylinositol-3-phosphate; phosphoinositide phosphatases
8.  Regulation of lipid droplet and membrane biogenesis by the acidic tail of the phosphatidate phosphatase Pah1p 
Molecular Biology of the Cell  2013;24(13):2124-2133.
Binding and dephosphorylation of the yeast lipin Pah1p by its phosphatase Nem1p-Spo7p is essential for its membrane targeting and is mediated by a C-terminal acidic stretch on Pah1p. This results in the recruitment of Pah1p to the vicinity of lipid droplets, where it controls triglyceride and droplet biogenesis in an acidic tail–dependent manner.
Lipins are evolutionarily conserved phosphatidate phosphatases that perform key functions in phospholipid, triglyceride, and membrane biogenesis. Translocation of lipins on membranes requires their dephosphorylation by the Nem1p-Spo7p transmembrane phosphatase complex through a poorly understood mechanism. Here we identify the carboxy-terminal acidic tail of the yeast lipin Pah1p as an important regulator of this step. Deletion or mutations of the tail disrupt binding of Pah1p to the Nem1p-Spo7p complex and Pah1p membrane translocation. Overexpression of Nem1p-Spo7p drives the recruitment of Pah1p in the vicinity of lipid droplets in an acidic tail–dependent manner and induces lipid droplet biogenesis. Genetic analysis shows that the acidic tail is essential for the Nem1p-Spo7p–dependent activation of Pah1p but not for the function of Pah1p itself once it is dephosphorylated. Loss of the tail disrupts nuclear structure, INO1 gene expression, and triglyceride synthesis. Similar acidic sequences are present in the carboxy-terminal ends of all yeast lipin orthologues. We propose that acidic tail–dependent binding and dephosphorylation of Pah1p by the Nem1p-Spo7p complex is an important determinant of its function in lipid and membrane biogenesis.
doi:10.1091/mbc.E13-01-0021
PMCID: PMC3694796  PMID: 23657815
9.  Phosphatidylinositol-3-Phosphate Clearance Plays a Key Role in Autophagosome Completion 
Current biology : CB  2012;22(17):1545-1553.
Summary
Background
The biogenesis of autophagosomes, the hallmark of autophagy, depends on the function of the autophagy-related (Atg) proteins and the generation of phosphatidylinositol-3-phosphate (PtdIns3P) at the phagophore assembly site (PAS), the location where autophagosomes arise. The current model is that PtdIns3P is involved primarily in the recruitment of Atg proteins to the PAS and that once an autophagosome is complete, the Atg machinery is released from its surface back into the cytoplasm and reused for the formation of new vesicles.
Results
We have identified a PtdIns3P phosphatase, Ymr1, that is essential for the normal progression of both bulk and selective types of autophagy. This protein is recruited to the PAS at an early stage of formation of this structure through a process that requires both its GRAM domain and its catalytic activity. In the absence of Ymr1, Atg proteins fail to dissociate from the limiting membrane of autophagosomes, and these vesicles accumulate in the cytoplasm.
Conclusions
Our data thus reveal a key role for PtdIns3P turnover in the regulation of the late steps of autophagosome biogenesis and indicate that the disassembly of the Atg machinery from the surface of autophagosomes is a requisite for their fusion with the vacuole.
doi:10.1016/j.cub.2012.06.029
PMCID: PMC3615650  PMID: 22771041
10.  Suppression of α-synuclein toxicity and vesicle trafficking defects by phosphorylation at S129 in yeast depends on genetic context 
Human Molecular Genetics  2012;21(11):2432-2449.
The aggregation of α-synuclein (αSyn) is a neuropathologic hallmark of Parkinson's disease and other synucleinopathies. In Lewy bodies, αSyn is extensively phosphorylated, predominantly at serine 129 (S129). Recent studies in yeast have shown that, at toxic levels, αSyn disrupts Rab homeostasis, causing an initial endoplasmic reticulum-to-Golgi block that precedes a generalized trafficking collapse. However, whether αSyn phosphorylation modulates trafficking defects has not been evaluated. Here, we show that constitutive expression of αSyn in yeast impairs late-exocytic, early-endocytic and/or recycling trafficking. Although members of the casein kinase I (CKI) family phosphorylate αSyn at S129, they attenuate αSyn toxicity and trafficking defects by an S129 phosphorylation-independent mechanism. Surprisingly, phosphorylation of S129 modulates αSyn toxicity and trafficking defects in a manner strictly determined by genetic background. Abnormal endosome morphology, increased levels of the endosome marker Rab5 and co-localization of mammalian CKI with αSyn aggregates are observed in brain sections from αSyn-overexpressing mice and human synucleinopathies. Our results contribute to evidence that suggests αSyn-induced defects in endocytosis, exocytosis and/or recycling of vesicles involved in these cellular processes might contribute to the pathogenesis of synucleinopathies.
doi:10.1093/hmg/dds058
PMCID: PMC3349423  PMID: 22357655
11.  A role for Atg8–PE deconjugation in autophagosome biogenesis 
Autophagy  2012;8(5):780-793.
Formation of the autophagosome is likely the most complex step of macroautophagy, and indeed it is the morphological and functional hallmark of this process; accordingly, it is critical to understand the corresponding molecular mechanism. Atg8 is the only known autophagy-related (Atg) protein required for autophagosome formation that remains associated with the completed sequestering vesicle. Approximately one-fourth of all of the characterized Atg proteins that participate in autophagosome biogenesis affect Atg8, regulating its conjugation to phosphatidylethanolamine (PE), localization to the phagophore assembly site and/or subsequent deconjugation. An unanswered question in the field regards the physiological role of the deconjugation of Atg8–PE. Using an Atg8 mutant that bypasses the initial Atg4-dependent processing, we demonstrate that Atg8 deconjugation is an important step required to facilitate multiple events during macroautophagy. The inability to deconjugate Atg8–PE results in the mislocalization of this protein to the vacuolar membrane. We also show that the deconjugation of Atg8–PE is required for efficient autophagosome biogenesis, the assembly of Atg9-containing tubulovesicular clusters into phagophores/autophagosomes, and for the disassembly of PAS-associated Atg components.
doi:10.4161/auto.19385
PMCID: PMC3378420  PMID: 22622160
12.  Guidelines for the use and interpretation of assays for monitoring autophagy 
Klionsky, Daniel J. | Abdalla, Fabio C. | Abeliovich, Hagai | Abraham, Robert T. | Acevedo-Arozena, Abraham | Adeli, Khosrow | Agholme, Lotta | Agnello, Maria | Agostinis, Patrizia | Aguirre-Ghiso, Julio A. | Ahn, Hyung Jun | Ait-Mohamed, Ouardia | Ait-Si-Ali, Slimane | Akematsu, Takahiko | Akira, Shizuo | Al-Younes, Hesham M. | Al-Zeer, Munir A. | Albert, Matthew L. | Albin, Roger L. | Alegre-Abarrategui, Javier | Aleo, Maria Francesca | Alirezaei, Mehrdad | Almasan, Alexandru | Almonte-Becerril, Maylin | Amano, Atsuo | Amaravadi, Ravi K. | Amarnath, Shoba | Amer, Amal O. | Andrieu-Abadie, Nathalie | Anantharam, Vellareddy | Ann, David K. | Anoopkumar-Dukie, Shailendra | Aoki, Hiroshi | Apostolova, Nadezda | Arancia, Giuseppe | Aris, John P. | Asanuma, Katsuhiko | Asare, Nana Y.O. | Ashida, Hisashi | Askanas, Valerie | Askew, David S. | Auberger, Patrick | Baba, Misuzu | Backues, Steven K. | Baehrecke, Eric H. | Bahr, Ben A. | Bai, Xue-Yuan | Bailly, Yannick | Baiocchi, Robert | Baldini, Giulia | Balduini, Walter | Ballabio, Andrea | Bamber, Bruce A. | Bampton, Edward T.W. | Juhász, Gábor | Bartholomew, Clinton R. | Bassham, Diane C. | Bast, Robert C. | Batoko, Henri | Bay, Boon-Huat | Beau, Isabelle | Béchet, Daniel M. | Begley, Thomas J. | Behl, Christian | Behrends, Christian | Bekri, Soumeya | Bellaire, Bryan | Bendall, Linda J. | Benetti, Luca | Berliocchi, Laura | Bernardi, Henri | Bernassola, Francesca | Besteiro, Sébastien | Bhatia-Kissova, Ingrid | Bi, Xiaoning | Biard-Piechaczyk, Martine | Blum, Janice S. | Boise, Lawrence H. | Bonaldo, Paolo | Boone, David L. | Bornhauser, Beat C. | Bortoluci, Karina R. | Bossis, Ioannis | Bost, Frédéric | Bourquin, Jean-Pierre | Boya, Patricia | Boyer-Guittaut, Michaël | Bozhkov, Peter V. | Brady, Nathan R | Brancolini, Claudio | Brech, Andreas | Brenman, Jay E. | Brennand, Ana | Bresnick, Emery H. | Brest, Patrick | Bridges, Dave | Bristol, Molly L. | Brookes, Paul S. | Brown, Eric J. | Brumell, John H. | Brunetti-Pierri, Nicola | Brunk, Ulf T. | Bulman, Dennis E. | Bultman, Scott J. | Bultynck, Geert | Burbulla, Lena F. | Bursch, Wilfried | Butchar, Jonathan P. | Buzgariu, Wanda | Bydlowski, Sergio P. | Cadwell, Ken | Cahová, Monika | Cai, Dongsheng | Cai, Jiyang | Cai, Qian | Calabretta, Bruno | Calvo-Garrido, Javier | Camougrand, Nadine | Campanella, Michelangelo | Campos-Salinas, Jenny | Candi, Eleonora | Cao, Lizhi | Caplan, Allan B. | Carding, Simon R. | Cardoso, Sandra M. | Carew, Jennifer S. | Carlin, Cathleen R. | Carmignac, Virginie | Carneiro, Leticia A.M. | Carra, Serena | Caruso, Rosario A. | Casari, Giorgio | Casas, Caty | Castino, Roberta | Cebollero, Eduardo | Cecconi, Francesco | Celli, Jean | Chaachouay, Hassan | Chae, Han-Jung | Chai, Chee-Yin | Chan, David C. | Chan, Edmond Y. | Chang, Raymond Chuen-Chung | Che, Chi-Ming | Chen, Ching-Chow | Chen, Guang-Chao | Chen, Guo-Qiang | Chen, Min | Chen, Quan | Chen, Steve S.-L. | Chen, WenLi | Chen, Xi | Chen, Xiangmei | Chen, Xiequn | Chen, Ye-Guang | Chen, Yingyu | Chen, Yongqiang | Chen, Yu-Jen | Chen, Zhixiang | Cheng, Alan | Cheng, Christopher H.K. | Cheng, Yan | Cheong, Heesun | Cheong, Jae-Ho | Cherry, Sara | Chess-Williams, Russ | Cheung, Zelda H. | Chevet, Eric | Chiang, Hui-Ling | Chiarelli, Roberto | Chiba, Tomoki | Chin, Lih-Shen | Chiou, Shih-Hwa | Chisari, Francis V. | Cho, Chi Hin | Cho, Dong-Hyung | Choi, Augustine M.K. | Choi, DooSeok | Choi, Kyeong Sook | Choi, Mary E. | Chouaib, Salem | Choubey, Divaker | Choubey, Vinay | Chu, Charleen T. | Chuang, Tsung-Hsien | Chueh, Sheau-Huei | Chun, Taehoon | Chwae, Yong-Joon | Chye, Mee-Len | Ciarcia, Roberto | Ciriolo, Maria R. | Clague, Michael J. | Clark, Robert S.B. | Clarke, Peter G.H. | Clarke, Robert | Codogno, Patrice | Coller, Hilary A. | Colombo, María I. | Comincini, Sergio | Condello, Maria | Condorelli, Fabrizio | Cookson, Mark R. | Coombs, Graham H. | Coppens, Isabelle | Corbalan, Ramon | Cossart, Pascale | Costelli, Paola | Costes, Safia | Coto-Montes, Ana | Couve, Eduardo | Coxon, Fraser P. | Cregg, James M. | Crespo, José L. | Cronjé, Marianne J. | Cuervo, Ana Maria | Cullen, Joseph J. | Czaja, Mark J. | D'Amelio, Marcello | Darfeuille-Michaud, Arlette | Davids, Lester M. | Davies, Faith E. | De Felici, Massimo | de Groot, John F. | de Haan, Cornelis A.M. | De Martino, Luisa | De Milito, Angelo | De Tata, Vincenzo | Debnath, Jayanta | Degterev, Alexei | Dehay, Benjamin | Delbridge, Lea M.D. | Demarchi, Francesca | Deng, Yi Zhen | Dengjel, Jörn | Dent, Paul | Denton, Donna | Deretic, Vojo | Desai, Shyamal D. | Devenish, Rodney J. | Di Gioacchino, Mario | Di Paolo, Gilbert | Di Pietro, Chiara | Díaz-Araya, Guillermo | Díaz-Laviada, Inés | Diaz-Meco, Maria T. | Diaz-Nido, Javier | Dikic, Ivan | Dinesh-Kumar, Savithramma P. | Ding, Wen-Xing | Distelhorst, Clark W. | Diwan, Abhinav | Djavaheri-Mergny, Mojgan | Dokudovskaya, Svetlana | Dong, Zheng | Dorsey, Frank C. | Dosenko, Victor | Dowling, James J. | Doxsey, Stephen | Dreux, Marlène | Drew, Mark E. | Duan, Qiuhong | Duchosal, Michel A. | Duff, Karen E. | Dugail, Isabelle | Durbeej, Madeleine | Duszenko, Michael | Edelstein, Charles L. | Edinger, Aimee L. | Egea, Gustavo | Eichinger, Ludwig | Eissa, N. Tony | Ekmekcioglu, Suhendan | El-Deiry, Wafik S. | Elazar, Zvulun | Elgendy, Mohamed | Ellerby, Lisa M. | Eng, Kai Er | Engelbrecht, Anna-Mart | Engelender, Simone | Erenpreisa, Jekaterina | Escalante, Ricardo | Esclatine, Audrey | Eskelinen, Eeva-Liisa | Espert, Lucile | Espina, Virginia | Fan, Huizhou | Fan, Jia | Fan, Qi-Wen | Fan, Zhen | Fang, Shengyun | Fang, Yongqi | Fanto, Manolis | Fanzani, Alessandro | Farkas, Thomas | Farre, Jean-Claude | Faure, Mathias | Fechheimer, Marcus | Feng, Carl G. | Feng, Jian | Feng, Qili | Feng, Youji | Fésüs, László | Feuer, Ralph | Figueiredo-Pereira, Maria E. | Fimia, Gian Maria | Fingar, Diane C. | Finkbeiner, Steven | Finkel, Toren | Finley, Kim D. | Fiorito, Filomena | Fisher, Edward A. | Fisher, Paul B. | Flajolet, Marc | Florez-McClure, Maria L. | Florio, Salvatore | Fon, Edward A. | Fornai, Francesco | Fortunato, Franco | Fotedar, Rati | Fowler, Daniel H. | Fox, Howard S. | Franco, Rodrigo | Frankel, Lisa B. | Fransen, Marc | Fuentes, José M. | Fueyo, Juan | Fujii, Jun | Fujisaki, Kozo | Fujita, Eriko | Fukuda, Mitsunori | Furukawa, Ruth H. | Gaestel, Matthias | Gailly, Philippe | Gajewska, Malgorzata | Galliot, Brigitte | Galy, Vincent | Ganesh, Subramaniam | Ganetzky, Barry | Ganley, Ian G. | Gao, Fen-Biao | Gao, George F. | Gao, Jinming | Garcia, Lorena | Garcia-Manero, Guillermo | Garcia-Marcos, Mikel | Garmyn, Marjan | Gartel, Andrei L. | Gatti, Evelina | Gautel, Mathias | Gawriluk, Thomas R. | Gegg, Matthew E. | Geng, Jiefei | Germain, Marc | Gestwicki, Jason E. | Gewirtz, David A. | Ghavami, Saeid | Ghosh, Pradipta | Giammarioli, Anna M. | Giatromanolaki, Alexandra N. | Gibson, Spencer B. | Gilkerson, Robert W. | Ginger, Michael L. | Ginsberg, Henry N. | Golab, Jakub | Goligorsky, Michael S. | Golstein, Pierre | Gomez-Manzano, Candelaria | Goncu, Ebru | Gongora, Céline | Gonzalez, Claudio D. | Gonzalez, Ramon | González-Estévez, Cristina | González-Polo, Rosa Ana | Gonzalez-Rey, Elena | Gorbunov, Nikolai V. | Gorski, Sharon | Goruppi, Sandro | Gottlieb, Roberta A. | Gozuacik, Devrim | Granato, Giovanna Elvira | Grant, Gary D. | Green, Kim N. | Gregorc, Ales | Gros, Frédéric | Grose, Charles | Grunt, Thomas W. | Gual, Philippe | Guan, Jun-Lin | Guan, Kun-Liang | Guichard, Sylvie M. | Gukovskaya, Anna S. | Gukovsky, Ilya | Gunst, Jan | Gustafsson, Åsa B. | Halayko, Andrew J. | Hale, Amber N. | Halonen, Sandra K. | Hamasaki, Maho | Han, Feng | Han, Ting | Hancock, Michael K. | Hansen, Malene | Harada, Hisashi | Harada, Masaru | Hardt, Stefan E. | Harper, J. Wade | Harris, Adrian L. | Harris, James | Harris, Steven D. | Hashimoto, Makoto | Haspel, Jeffrey A. | Hayashi, Shin-ichiro | Hazelhurst, Lori A. | He, Congcong | He, You-Wen | Hébert, Marie-Josée | Heidenreich, Kim A. | Helfrich, Miep H. | Helgason, Gudmundur V. | Henske, Elizabeth P. | Herman, Brian | Herman, Paul K. | Hetz, Claudio | Hilfiker, Sabine | Hill, Joseph A. | Hocking, Lynne J. | Hofman, Paul | Hofmann, Thomas G. | Höhfeld, Jörg | Holyoake, Tessa L. | Hong, Ming-Huang | Hood, David A. | Hotamisligil, Gökhan S. | Houwerzijl, Ewout J. | Høyer-Hansen, Maria | Hu, Bingren | Hu, Chien-an A. | Hu, Hong-Ming | Hua, Ya | Huang, Canhua | Huang, Ju | Huang, Shengbing | Huang, Wei-Pang | Huber, Tobias B. | Huh, Won-Ki | Hung, Tai-Ho | Hupp, Ted R. | Hur, Gang Min | Hurley, James B. | Hussain, Sabah N.A. | Hussey, Patrick J. | Hwang, Jung Jin | Hwang, Seungmin | Ichihara, Atsuhiro | Ilkhanizadeh, Shirin | Inoki, Ken | Into, Takeshi | Iovane, Valentina | Iovanna, Juan L. | Ip, Nancy Y. | Isaka, Yoshitaka | Ishida, Hiroyuki | Isidoro, Ciro | Isobe, Ken-ichi | Iwasaki, Akiko | Izquierdo, Marta | Izumi, Yotaro | Jaakkola, Panu M. | Jäättelä, Marja | Jackson, George R. | Jackson, William T. | Janji, Bassam | Jendrach, Marina | Jeon, Ju-Hong | Jeung, Eui-Bae | Jiang, Hong | Jiang, Hongchi | Jiang, Jean X. | Jiang, Ming | Jiang, Qing | Jiang, Xuejun | Jiang, Xuejun | Jiménez, Alberto | Jin, Meiyan | Jin, Shengkan V. | Joe, Cheol O. | Johansen, Terje | Johnson, Daniel E. | Johnson, Gail V.W. | Jones, Nicola L. | Joseph, Bertrand | Joseph, Suresh K. | Joubert, Annie M. | Juhász, Gábor | Juillerat-Jeanneret, Lucienne | Jung, Chang Hwa | Jung, Yong-Keun | Kaarniranta, Kai | Kaasik, Allen | Kabuta, Tomohiro | Kadowaki, Motoni | Kågedal, Katarina | Kamada, Yoshiaki | Kaminskyy, Vitaliy O. | Kampinga, Harm H. | Kanamori, Hiromitsu | Kang, Chanhee | Kang, Khong Bee | Kang, Kwang Il | Kang, Rui | Kang, Yoon-A | Kanki, Tomotake | Kanneganti, Thirumala-Devi | Kanno, Haruo | Kanthasamy, Anumantha G. | Kanthasamy, Arthi | Karantza, Vassiliki | Kaushal, Gur P. | Kaushik, Susmita | Kawazoe, Yoshinori | Ke, Po-Yuan | Kehrl, John H. | Kelekar, Ameeta | Kerkhoff, Claus | Kessel, David H. | Khalil, Hany | Kiel, Jan A.K.W. | Kiger, Amy A. | Kihara, Akio | Kim, Deok Ryong | Kim, Do-Hyung | Kim, Dong-Hou | Kim, Eun-Kyoung | Kim, Hyung-Ryong | Kim, Jae-Sung | Kim, Jeong Hun | Kim, Jin Cheon | Kim, John K. | Kim, Peter K. | Kim, Seong Who | Kim, Yong-Sun | Kim, Yonghyun | Kimchi, Adi | Kimmelman, Alec C. | King, Jason S. | Kinsella, Timothy J. | Kirkin, Vladimir | Kirshenbaum, Lorrie A. | Kitamoto, Katsuhiko | Kitazato, Kaio | Klein, Ludger | Klimecki, Walter T. | Klucken, Jochen | Knecht, Erwin | Ko, Ben C.B. | Koch, Jan C. | Koga, Hiroshi | Koh, Jae-Young | Koh, Young Ho | Koike, Masato | Komatsu, Masaaki | Kominami, Eiki | Kong, Hee Jeong | Kong, Wei-Jia | Korolchuk, Viktor I. | Kotake, Yaichiro | Koukourakis, Michael I. | Flores, Juan B. Kouri | Kovács, Attila L. | Kraft, Claudine | Krainc, Dimitri | Krämer, Helmut | Kretz-Remy, Carole | Krichevsky, Anna M. | Kroemer, Guido | Krüger, Rejko | Krut, Oleg | Ktistakis, Nicholas T. | Kuan, Chia-Yi | Kucharczyk, Roza | Kumar, Ashok | Kumar, Raj | Kumar, Sharad | Kundu, Mondira | Kung, Hsing-Jien | Kurz, Tino | Kwon, Ho Jeong | La Spada, Albert R. | Lafont, Frank | Lamark, Trond | Landry, Jacques | Lane, Jon D. | Lapaquette, Pierre | Laporte, Jocelyn F. | László, Lajos | Lavandero, Sergio | Lavoie, Josée N. | Layfield, Robert | Lazo, Pedro A. | Le, Weidong | Le Cam, Laurent | Ledbetter, Daniel J. | Lee, Alvin J.X. | Lee, Byung-Wan | Lee, Gyun Min | Lee, Jongdae | lee, Ju-hyun | Lee, Michael | Lee, Myung-Shik | Lee, Sug Hyung | Leeuwenburgh, Christiaan | Legembre, Patrick | Legouis, Renaud | Lehmann, Michael | Lei, Huan-Yao | Lei, Qun-Ying | Leib, David A. | Leiro, José | Lemasters, John J. | Lemoine, Antoinette | Lesniak, Maciej S. | Lev, Dina | Levenson, Victor V. | Levine, Beth | Levy, Efrat | Li, Faqiang | Li, Jun-Lin | Li, Lian | Li, Sheng | Li, Weijie | Li, Xue-Jun | Li, Yan-Bo | Li, Yi-Ping | Liang, Chengyu | Liang, Qiangrong | Liao, Yung-Feng | Liberski, Pawel P. | Lieberman, Andrew | Lim, Hyunjung J. | Lim, Kah-Leong | Lim, Kyu | Lin, Chiou-Feng | Lin, Fu-Cheng | Lin, Jian | Lin, Jiandie D. | Lin, Kui | Lin, Wan-Wan | Lin, Weei-Chin | Lin, Yi-Ling | Linden, Rafael | Lingor, Paul | Lippincott-Schwartz, Jennifer | Lisanti, Michael P. | Liton, Paloma B. | Liu, Bo | Liu, Chun-Feng | Liu, Kaiyu | Liu, Leyuan | Liu, Qiong A. | Liu, Wei | Liu, Young-Chau | Liu, Yule | Lockshin, Richard A. | Lok, Chun-Nam | Lonial, Sagar | Loos, Benjamin | Lopez-Berestein, Gabriel | López-Otín, Carlos | Lossi, Laura | Lotze, Michael T. | Low, Peter | Lu, Binfeng | Lu, Bingwei | Lu, Bo | Lu, Zhen | Luciano, Fréderic | Lukacs, Nicholas W. | Lund, Anders H. | Lynch-Day, Melinda A. | Ma, Yong | Macian, Fernando | MacKeigan, Jeff P. | Macleod, Kay F. | Madeo, Frank | Maiuri, Luigi | Maiuri, Maria Chiara | Malagoli, Davide | Malicdan, May Christine V. | Malorni, Walter | Man, Na | Mandelkow, Eva-Maria | Manon, Stephen | Manov, Irena | Mao, Kai | Mao, Xiang | Mao, Zixu | Marambaud, Philippe | Marazziti, Daniela | Marcel, Yves L. | Marchbank, Katie | Marchetti, Piero | Marciniak, Stefan J. | Marcondes, Mateus | Mardi, Mohsen | Marfe, Gabriella | Mariño, Guillermo | Markaki, Maria | Marten, Mark R. | Martin, Seamus J. | Martinand-Mari, Camille | Martinet, Wim | Martinez-Vicente, Marta | Masini, Matilde | Matarrese, Paola | Matsuo, Saburo | Matteoni, Raffaele | Mayer, Andreas | Mazure, Nathalie M. | McConkey, David J. | McConnell, Melanie J. | McDermott, Catherine | McDonald, Christine | McInerney, Gerald M. | McKenna, Sharon L. | McLaughlin, BethAnn | McLean, Pamela J. | McMaster, Christopher R. | McQuibban, G. Angus | Meijer, Alfred J. | Meisler, Miriam H. | Meléndez, Alicia | Melia, Thomas J. | Melino, Gerry | Mena, Maria A. | Menendez, Javier A. | Menna-Barreto, Rubem F. 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Ashutosh | Rathmell, Jeffrey C. | Ravikumar, Brinda | Ray, Swapan K. | Reed, Bruce H. | Reed, John C. | Reggiori, Fulvio | Régnier-Vigouroux, Anne | Reichert, Andreas S. | Reiners, John J. | Reiter, Russel J. | Ren, Jun | Revuelta, José L. | Rhodes, Christopher J. | Ritis, Konstantinos | Rizzo, Elizete | Robbins, Jeffrey | Roberge, Michel | Roca, Hernan | Roccheri, Maria C. | Rocchi, Stephane | Rodemann, H. Peter | Rodríguez de Córdoba, Santiago | Rohrer, Bärbel | Roninson, Igor B. | Rosen, Kirill | Rost-Roszkowska, Magdalena M. | Rouis, Mustapha | Rouschop, Kasper M.A. | Rovetta, Francesca | Rubin, Brian P. | Rubinsztein, David C. | Ruckdeschel, Klaus | Rucker, Edmund B. | Rudich, Assaf | Rudolf, Emil | Ruiz-Opazo, Nelson | Russo, Rossella | Rusten, Tor Erik | Ryan, Kevin M. | Ryter, Stefan W. | Sabatini, David M. | Sadoshima, Junichi | Saha, Tapas | Saitoh, Tatsuya | Sakagami, Hiroshi | Sakai, Yasuyoshi | Salekdeh, Ghasem Hoseini | Salomoni, Paolo | Salvaterra, Paul M. | Salvesen, Guy | Salvioli, Rosa | Sanchez, Anthony M.J. | Sánchez-Alcázar, José A. | Sánchez-Prieto, Ricardo | Sandri, Marco | Sankar, Uma | Sansanwal, Poonam | Santambrogio, Laura | Saran, Shweta | Sarkar, Sovan | Sarwal, Minnie | Sasakawa, Chihiro | Sasnauskiene, Ausra | Sass, Miklós | Sato, Ken | Sato, Miyuki | Schapira, Anthony H.V. | Scharl, Michael | Schätzl, Hermann M. | Scheper, Wiep | Schiaffino, Stefano | Schneider, Claudio | Schneider, Marion E. | Schneider-Stock, Regine | Schoenlein, Patricia V. | Schorderet, Daniel F. | Schüller, Christoph | Schwartz, Gary K. | Scorrano, Luca | Sealy, Linda | Seglen, Per O. | Segura-Aguilar, Juan | Seiliez, Iban | Seleverstov, Oleksandr | Sell, Christian | Seo, Jong Bok | Separovic, Duska | Setaluri, Vijayasaradhi | Setoguchi, Takao | Settembre, Carmine | Shacka, John J. | Shanmugam, Mala | Shapiro, Irving M. | Shaulian, Eitan | Shaw, Reuben J. | Shelhamer, James H. | Shen, Han-Ming | Shen, Wei-Chiang
Autophagy  2012;8(4):445-544.
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
doi:10.4161/auto.19496
PMCID: PMC3404883  PMID: 22966490
LC3; autolysosome; autophagosome; flux; lysosome; phagophore; stress; vacuole
13.  Autophagy regulation through Atg9 traffic 
The Journal of Cell Biology  2012;198(2):151-153.
Rapid membrane expansion is the key to autophagosome formation during nutrient starvation. In this issue, Yamamoto et al. (2012. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201202061) now provide a mechanism for vesicle-mediated initiation of autophagosome biogenesis. They show that Atg9 vesicles, produced de novo during starvation, are ∼30–60 nm in size and contain ∼30 molecules of Atg9. These vesicles assemble to form an autophagosome, and subsequently, the Atg9 embedded in the outer membrane is recycled to avoid degradation.
doi:10.1083/jcb.201206119
PMCID: PMC3410426  PMID: 22826119
14.  Autophagy: New Questions from Recent Answers 
ISRN Molecular Biology  2012;2012:738718.
Macroautophagy (hereafter autophagy) is currently one of the areas of medical life sciences attracting a great interest because of its pathological implications and therapy potentials. The discovery of the autophagy-related genes (ATGs) has been the key event in this research field because their study has led to the acquisition of new knowledge about the mechanism of this transport pathway. In addition, the investigation of these genes in numerous model systems has revealed the central role that autophagy plays in maintaining the cell homeostasis. This process carries out numerous physiological functions, some of which were unpredicted and thus surprising. Here, we will review some of the questions about the mechanism and function of autophagy that still remain unanswered, and new ones that have emerged from the recent discoveries.
doi:10.5402/2012/738718
PMCID: PMC4890908  PMID: 27335669
15.  Selective Types of Autophagy 
doi:10.1155/2012/156272
PMCID: PMC3432363  PMID: 22956958
16.  A dual role for K63-linked ubiquitin chains in multivesicular body biogenesis and cargo sorting 
Molecular Biology of the Cell  2012;23(11):2170-2183.
Many yeast and some mammalian multivesicular body (MVB) cargoes display modification by K63-linked ubiquitin chains (K63Ub), which are required for their efficient sorting. Yeast UBD-containing ESCRT proteins are modified by the ubiquitin ligase Rsp5—some likely by K63Ub. A failure to generate K63Ub in yeast leads to MVB ultrastructure alteration.
In yeast, the sorting of transmembrane proteins into the multivesicular body (MVB) internal vesicles requires their ubiquitylation by the ubiquitin ligase Rsp5. This allows their recognition by the ubiquitin-binding domains (UBDs) of several endosomal sorting complex required for transport (ESCRT) subunits. K63-linked ubiquitin (K63Ub) chains decorate several MVB cargoes, and accordingly we show that they localize prominently to the class E compartment, which accumulates ubiquitylated cargoes in cells lacking ESCRT components. Conversely, yeast cells unable to generate K63Ub chains displayed MVB sorting defects. These properties are conserved among eukaryotes, as the mammalian melanosomal MVB cargo MART-1 is modified by K63Ub chains and partly missorted when the genesis of these chains is inhibited. We show that all yeast UBD-containing ESCRT proteins undergo ubiquitylation and deubiquitylation, some being modified through the opposing activities of Rsp5 and the ubiquitin isopeptidase Ubp2, which are known to assemble and disassemble preferentially K63Ub chains, respectively. A failure to generate K63Ub chains in yeast leads to an MVB ultrastructure alteration. Our work thus unravels a double function of K63Ub chains in cargo sorting and MVB biogenesis.
doi:10.1091/mbc.E11-10-0891
PMCID: PMC3364180  PMID: 22493318
17.  SNARE proteins are required for macroautophagy 
Cell  2011;146(2):290-302.
SUMMARY
Macroautophagy mediates the degradation of long-lived proteins and organelles via the de novo formation of double-membrane autophagosomes that sequester cytoplasm and deliver it to the vacuole/lysosome; however, relatively little is known about autophagosome biogenesis. Atg8, a phosphatidylethanolamine-conjugated protein, was previously proposed to function in autophagosome membrane expansion, based on the observation that it mediates liposome tethering and hemifusion in vitro. We show here that with physiological concentrations of phosphatidylethanolamine, Atg8 does not act as a fusogen. Rather, we provide evidence for the involvement of exocytic Q/t-SNAREs in autophagosome formation, acting in the recruitment of key autophagy components to the site of autophagosome formation, and in regulating the organization of Atg9 into tubulovesicular clusters. Additionally, we found that the endosomal Q/t-SNARE Tlg2 and the R/v-SNAREs Sec22 and Ykt6 interact with Sso1-Sec9, and are required for normal Atg9 transport. Thus, multiple SNARE-mediated fusion events are likely to be involved in autophagosome biogenesis.
doi:10.1016/j.cell.2011.06.022
PMCID: PMC3143362  PMID: 21784249
Atg9; fusion; lysosome; membrane biogenesis; protein targeting; secretory pathway; stress; tubulovesicular clusters; vacuole; yeast
18.  Autophagy: More Than a Nonselective Pathway 
Autophagy is a catabolic pathway conserved among eukaryotes that allows cells to rapidly eliminate large unwanted structures such as aberrant protein aggregates, superfluous or damaged organelles, and invading pathogens. The hallmark of this transport pathway is the sequestration of the cargoes that have to be degraded in the lysosomes by double-membrane vesicles called autophagosomes. The key actors mediating the biogenesis of these carriers are the autophagy-related genes (ATGs). For a long time, it was assumed that autophagy is a bulk process. Recent studies, however, have highlighted the capacity of this pathway to exclusively eliminate specific structures and thus better fulfil the catabolic necessities of the cell. We are just starting to unveil the regulation and mechanism of these selective types of autophagy, but what it is already clearly emerging is that structures targeted to destruction are accurately enwrapped by autophagosomes through the action of specific receptors and adaptors. In this paper, we will briefly discuss the impact that the selective types of autophagy have had on our understanding of autophagy.
doi:10.1155/2012/219625
PMCID: PMC3362037  PMID: 22666256
19.  Reticulophagy and Ribophagy: Regulated Degradation of Protein Production Factories 
During autophagy, cytosol, protein aggregates, and organelles are sequestered into double-membrane vesicles called autophagosomes and delivered to the lysosome/vacuole for breakdown and recycling of their basic components. In all eukaryotes this pathway is important for adaptation to stress conditions such as nutrient deprivation, as well as to regulate intracellular homeostasis by adjusting organelle number and clearing damaged structures. For a long time, starvation-induced autophagy has been viewed as a nonselective transport pathway; however, recent studies have revealed that autophagy is able to selectively engulf specific structures, ranging from proteins to entire organelles. In this paper, we discuss recent findings on the mechanisms and physiological implications of two selective types of autophagy: ribophagy, the specific degradation of ribosomes, and reticulophagy, the selective elimination of portions of the ER.
doi:10.1155/2012/182834
PMCID: PMC3299282  PMID: 22481944
20.  The puzzling origin of the autophagosomal membrane 
Autophagy is one of the newest and fastest emerging research areas in biomedical life sciences. Autophagosomes, large double-membrane vesicles enclosing cytoplasmic components targeted for degradation, are the hallmark of this catabolic pathway. The origin of the lipid bilayers composing these transport carriers has been the central enigma of the field since the discovery of autophagy. A series of recent studies has implicated several cellular organelles as the possible source of the autophagosomal membranes, if anything further clouding our view. In this compendium, we will discuss these apparently contradictory results and briefly emphasize the relevance of determining the lipid source used for autophagy for future translational research, for example in drug discovery programs.
doi:10.3410/B3-25
PMCID: PMC3229206  PMID: 22162728
21.  Mobility and Interactions of Coronavirus Nonstructural Protein 4▿† 
Journal of Virology  2011;85(9):4572-4577.
Green fluorescent protein (GFP)-tagged mouse hepatitis coronavirus nonstructural protein 4 (nsp4) was shown to localize to the endoplasmic reticulum (ER) and to be recruited to the coronavirus replicative structures. Fluorescence loss in photobleaching and fluorescence recovery after photobleaching experiments demonstrated that while the membranes of the ER are continuous with those harboring the replicative structures, the mobility of nsp4 at the latter structures is relatively restricted. In agreement with that observation, nsp4 was shown to be engaged in homotypic and heterotypic interactions, the latter with nsp3 and nsp6. In addition, the coexpression of nsp4 with nsp3 affected the subcellular localization of the two proteins.
doi:10.1128/JVI.00042-11
PMCID: PMC3126240  PMID: 21345958
22.  Unconventional Use of LC3 by Coronaviruses through the Alleged Subversion of the ERAD Tuning Pathway 
Viruses  2011;3(9):1610-1623.
Pathogens of bacterial and viral origin hijack pathways operating in eukaryotic cells in many ways in order to gain access into the host, to establish themselves and to eventually produce their progeny. The detailed molecular characterization of the subversion mechanisms devised by pathogens to infect host cells is crucial to generate targets for therapeutic intervention. Here we review recent data indicating that coronaviruses probably co-opt membranous carriers derived from the endoplasmic reticulum, which contain proteins that regulate disposal of misfolded polypeptides, for their replication. In addition, we also present models describing potential mechanisms that coronaviruses could employ for this hijacking.
doi:10.3390/v3091610
PMCID: PMC3187687  PMID: 21994798
coronaviruses; nidoviruses; double-membrane vesicles; MHV; SARS-coronavirus; autophagy; EDEMosomes; EDEM1; OS-9; ERAD; ER quality control
23.  Phosphorylation of a membrane curvature–sensing motif switches function of the HOPS subunit Vps41 in membrane tethering 
The Journal of Cell Biology  2010;191(4):845-859.
An AP-3–binding site required for vesicle–vacuole fusion is masked when Vps41 is associated with highly curved membranes, such as endosomes, but is exposed at membranes with lower curvature, such as vacuoles, because of phosphorylation of the membrane-binding motif.
Tethering factors are organelle-specific multisubunit protein complexes that identify, along with Rab guanosine triphosphatases, transport vesicles and trigger their SNARE-mediated fusion of specific transport vesicles with the target membranes. Little is known about how tethering factors discriminate between different trafficking pathways, which may converge at the same organelle. In this paper, we describe a phosphorylation-based switch mechanism, which allows the homotypic vacuole fusion protein sorting effector subunit Vps41 to operate in two distinct fusion events, namely endosome–vacuole and AP-3 vesicle–vacuole fusion. Vps41 contains an amphipathic lipid-packing sensor (ALPS) motif, which recognizes highly curved membranes. At endosomes, this motif is inserted into the lipid bilayer and masks the binding motif for the δ subunit of the AP-3 complex, Apl5, without affecting the Vps41 function in endosome–vacuole fusion. At the much less curved vacuole, the ALPS motif becomes available for phosphorylation by the resident casein kinase Yck3. As a result, the Apl5-binding site is exposed and allows AP-3 vesicles to bind to Vps41, followed by specific fusion with the vacuolar membrane. This multifunctional tethering factor thus discriminates between trafficking routes by switching from a curvature-sensing to a coat recognition mode upon phosphorylation.
doi:10.1083/jcb.201004092
PMCID: PMC2983053  PMID: 21079247
24.  The Coronavirus Nucleocapsid Protein Is Dynamically Associated with the Replication-Transcription Complexes▿ †  
Journal of Virology  2010;84(21):11575-11579.
The coronavirus nucleocapsid (N) protein is a virion structural protein. It also functions, however, in an unknown way in viral replication and localizes to the viral replication-transcription complexes (RTCs). Here we investigated, using recombinant murine coronaviruses expressing green fluorescent protein (GFP)-tagged versions of the N protein, the dynamics of its interactions with the RTCs and the domain(s) involved. Using fluorescent recovery after photobleaching, we showed that the N protein, unlike the nonstructural protein 2, is dynamically associated with the RTCs. Recruitment of the N protein to the RTCs requires the C-terminal N2b domain, which interacts with other N proteins in an RNA-independent manner.
doi:10.1128/JVI.00569-10
PMCID: PMC2953146  PMID: 20739524
25.  An Atg9-containing compartment that functions in the early steps of autophagosome biogenesis 
The Journal of Cell Biology  2010;190(6):1005-1022.
A reservoir of Atg9-containing vesicles and tubules provides the initial membranes necessary for autophagophore formation in yeast.
Eukaryotes use the process of autophagy, in which structures targeted for lysosomal/vacuolar degradation are sequestered into double-membrane autophagosomes, in numerous physiological and pathological situations. The key questions in the field relate to the origin of the membranes as well as the precise nature of the rearrangements that lead to the formation of autophagosomes. We found that yeast Atg9 concentrates in a novel compartment comprising clusters of vesicles and tubules, which are derived from the secretory pathway and are often adjacent to mitochondria. We show that these clusters translocate en bloc next to the vacuole to form the phagophore assembly site (PAS), where they become the autophagosome precursor, the phagophore. In addition, genetic analyses indicate that Atg1, Atg13, and phosphatidylinositol-3-phosphate are involved in the further rearrangement of these initial membranes. Thus, our data reveal that the Atg9-positive compartments are important for the de novo formation of the PAS and the sequestering vesicle that are the hallmarks of autophagy.
doi:10.1083/jcb.200912089
PMCID: PMC3101592  PMID: 20855505

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