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1.  Molecular views of Arf-like small GTPases in cilia and ciliopathies 
Experimental cell research  2013;319(15):2316-2322.
The primary cilia are microtubule-based organelles that protrude from most of the eukaryotic cells. Recognized as the cell’s antenna, primary cilia function as a signaling hub for many physiologically and developmentally important signaling cascades. Ciliary dysfunction causes a wide spectrum of syndromic human genetic diseases collectively termed "ciliopathies”. Mounting evidences have shown that various small GTPases have been implicated in the context of cilia as well as human ciliopathies. However, how these small GTPases affect cilia formation and function remains poorly understood. Here we review and discuss the ciliary role of three Arf-like small GTPases (Arls), Arl3, Arl6, and Arl13b.
doi:10.1016/j.yexcr.2013.03.024
PMCID: PMC3742637  PMID: 23548655
2.  The emerging role of Arf/Arl Small GTPases in Cilia and Ciliopathies 
Journal of cellular biochemistry  2012;113(7):2201-2207.
Once overlooked as an evolutionary vestige, the primary cilium has recently been the focus of intensive studies. Mounting data show that this organelle is a hub for various signaling pathways during vertebrate embryonic development and pattern formation. However, how cilia form and how cilia execute the sensory function still remain poorly understood. Cilia dysfunction is correlated with a wide spectrum of human diseases, now termed ciliopathies. Various small GTPases, including the members in Arf/Arl, Rab, and Ran subfamilies, have been implicated in cilia formation and/or function. Here we review and discuss the role of one particular group of small GTPase, Arf/Arl, in the context of cilia and ciliopathy.
doi:10.1002/jcb.24116
PMCID: PMC4133128  PMID: 22389062
Arf/Arl; cilia; ciliopathies
3.  Transition fibre protein FBF1 is required for the ciliary entry of assembled intraflagellar transport complexes 
Nature communications  2013;4:10.1038/ncomms3750.
Sensory organelle cilia play critical roles in mammalian embryonic development and tissue homeostasis. Intraflagellar transport (IFT) machinery is required for the assembly and maintenance of cilia. Yet how this large complex passes through the size-dependent barrier at the ciliary base remains enigmatic. Here we report that FBF1, a highly conserved transition fibre protein, is required for the ciliary import of assembled IFT particles at the cilia base. We cloned dyf-19, the C. elegans homolog of human FBF1, in a whole-genome screen for ciliogenesis mutants. DYF-19 localizes specifically to transition fibres and interacts directly with the IFT-B component DYF-11/IFT54. Although not a structural component of transition fibres, DYF-19 is essential for the transit of assembled IFT particles through the ciliary base. Furthermore, we found that human FBF1 shares conserved localization and function with its worm counterpart. We conclude that FBF1 is a key functional transition fibre component that facilitates the ciliary entry of assembled IFT machinery.
doi:10.1038/ncomms3750
PMCID: PMC3856926  PMID: 24231678
4.  The effectiveness of Tai Chi on the physical and psychological well-being of college students: a study protocol for a randomized controlled trial 
Trials  2014;15:129.
Background
The physical and mental health of college-age youths tends to continuously decline around the world. It is therefore important to promote health during this period. As a traditional Chinese mind-body exercise, Tai Chi Chuan (TCC) may be an available selection. However for the college student population, the evidence is unclear as to whether TCC can be recommended as an effective exercise for promoting their physical and psychological wellbeing. Therefore high quality, rigorous, prospective, and well-controlled randomized trials are needed to further understand TCC serving as a psychological and physical intervention in college age populations.
Method/Design
We designed a randomized, single-blind, parallel-controlled trial with a sample size of 206 participants. All the participants who meet the inclusion criteria come from Fujian University of Traditional Chinese Medicine (FJTCM). Participants of the TCC training group will receive TCC training at a frequency of five days per week for one hour per day for 12 weeks. No specific exercise will be administered on the participants in the control group. Both physical and mental health outcomes, including balance ability, lower limb proprioception, flexibility, physical fitness, self-efficacy, psychological symptoms, attention span, stress, self-esteem, mood and mindfulness, quality of life, and quality of sleep. Safety outcomes will be evaluated by blinded operators at baseline, 12 and 24-weeks post-intervention.
Discussion
This protocol presents an objective design of a randomized, single-blind trial that will test the effectiveness and safety of TCC on the physical and psychological wellbeing of college students. If the outcome is positive, the results will provide higher quality evidence of TCC on the physical and mental health of college age populations.
Trial registration
Chinese Clinical Trial Registry: ChiCTR-TRC-13003328.
doi:10.1186/1745-6215-15-129
PMCID: PMC4000322  PMID: 24742146
Tai Chi Chuan; College students; Psychological well-being; Physical health
5.  SUMOylation of the small GTPase ARL-13 promotes ciliary targeting of sensory receptors 
The Journal of Cell Biology  2012;199(4):589-598.
SUMOylation of the small GTPase ARL13 is required for the proper ciliary targeting of sensory receptors and corresponding sensory functions.
Primary cilia serve as cellular antenna for various sensory signaling pathways. However, how the sensory receptors are properly targeted to the ciliary surface remains poorly understood. Here, we show that UBC-9, the sole E2 small ubiquitin-like modifier (SUMO)-conjugating enzyme, physically interacts with and SUMOylates the C terminus of small GTPase ARL-13, the worm orthologue of ARL13B that mutated in ciliopathy Joubert syndrome. Mutations that totally abolish the SUMOylation of ARL-13 do not affect its established role in ciliogenesis, but fail to regulate the proper ciliary targeting of various sensory receptors and consequently compromise the corresponding sensory functions. Conversely, constitutively SUMOylated ARL-13 fully rescues all ciliary defects of arl-13–null animals. Furthermore, SUMOylation modification of human ARL13B is required for the ciliary entry of polycystin-2, the protein mutated in autosomal dominant polycystic kidney disease. Our data reveal a novel but conserved role for the SUMOylation modification of ciliary small GTPase ARL13B in specifically regulating the proper ciliary targeting of various sensory receptors.
doi:10.1083/jcb.201203150
PMCID: PMC3494855  PMID: 23128241
6.  The BBSome controls IFT assembly and turnaround in cilia 
Nature cell biology  2012;14(9):950-957.
The bidirectional movement of intraflagellar transport (IFT) particles, which are composed of motors, IFT-A and IFT-B subcomplexes, and cargos, is required for cilia biogenesis and signaling 1, 2. A successful IFT cycle depends on the massive IFT particle to be properly assembled at the ciliary base and turned around from anterograde to retrograde transport at the ciliary tip. However, how IFT assembly and turnaround are regulated in vivo remains elusive. From a whole-genome mutagenesis screen in C. elegans, we identified two hypomorphic mutations in dyf-2 and bbs-1 as the only mutants showing normal anterograde IFT transport but defective IFT turnaround at the ciliary tip. Further analyses revealed that the BBSome 3, 4, a group of conserved proteins affected in human Bardet-Biedl syndrome (BBS) 5, assembles IFT complexes at the ciliary base, then binds to anterograde IFT particle in a DYF-2- (an ortholog of human WDR19) and BBS-1-dependent manner, and lastly reaches the ciliary tip to regulate proper IFT recycling. Our results unravel the BBSome as the key player regulating IFT assembly and turnaround in cilia.
doi:10.1038/ncb2560
PMCID: PMC3434251  PMID: 22922713
8.  Phosphoinositide Signaling Regulates the Exocyst Complex and Polarized Integrin Trafficking in Directionally Migrating Cells 
Developmental Cell  2012;22(1):116-130.
Summary
Polarized delivery of signaling and adhesion molecules to the leading edge is required for directional migration of cells. Here, we describe a role for the PIP2 synthesizing enzyme, PIPKIγi2, in regulation of exocyst complex control of cell polarity and polarized integrin trafficking during migration. Loss of PIPKIγi2 impaired directional migration, formation of cell polarity, and integrin trafficking to the leading edge. Upon initiation of directional migration PIPKIγi2 via PIP2 generation controls the integration of the exocyst complex into an integrin-containing trafficking compartment(s) that requires the talin-binding ability of PIPKIγi2, and talin for integrin recruitment to the leading edge. A PIP2 requirement is further emphasized by inhibition of PIPKIγi2-regulated directional migration by an Exo70 mutant deficient in PIP2 binding. These results reveal how phosphoinositide generation orchestrates polarized trafficking of integrin in coordination with talin that links integrins to the actin cytoskeleton, processes that are required for directional migration.
doi:10.1016/j.devcel.2011.10.030
PMCID: PMC3266520  PMID: 22264730
Cell Migration; Phosphatidylinositol-4; 5-biphosphate; Cell Polarity; Integrin; Exocyst
9.  An association between type Iγ PI4P 5-kinase and Exo70 directs E-cadherin clustering and epithelial polarization 
Molecular Biology of the Cell  2012;23(1):87-98.
Type Iγ phosphatidylinositol-4-phosphate 5-kinase and Exo70 cooperate in the directed targeting of E-cadherin on the plasma membrane to newly formed adherens junctions. This promotes the regional accumulation of E-cadherin, expansion and maturation of adherens junctions, and differentiation of the lateral membrane domain.
E-Cadherin–mediated formation of adherens junctions (AJs) is essential for the morphogenesis of epithelial cells. However, the mechanisms underlying E-cadherin clustering and AJ maturation are not fully understood. Here we report that type Iγ phosphatidylinositol-4-phosphate 5-kinase (PIPKIγ) associates with the exocyst via a direct interaction with Exo70, the exocyst subunit that guides the polarized targeting of exocyst to the plasma membrane. By means of this interaction, PIPKIγ mediates the association between E-cadherin and Exo70 and determines the targeting of Exo70 to AJs. Further investigation revealed that Exo70 is necessary for clustering of E-cadherin on the plasma membrane and extension of nascent E-cadherin adhesions, which are critical for the maturation of cohesive AJs. In addition, we observed phosphatidylinositol-4,5-bisphosphate (PI4,5P2) accumulation at E-cadherin clusters during the assembly of E-cadherin adhesions. PIPKIγ-generated PI4,5P2 is required for recruiting Exo70 to newly formed E-cadherin junctions and facilitates the assembly and maturation of AJs. These results support a model in which PIPKIγ and PIPKIγ-generated PI4,5P2 pools at nascent E-cadherin contacts cue Exo70 targeting and orient the tethering of exocyst-associated E-cadherin. This could be an important mechanism that regulates E-cadherin clustering and AJ maturation, which is essential for the establishment of solid, polarized epithelial structures.
doi:10.1091/mbc.E11-05-0449
PMCID: PMC3248907  PMID: 22049025
10.  Gangliosides and β1-integrin are required for caveolae and membrane domains 
Traffic (Copenhagen, Denmark)  2009;11(3):348-360.
Caveolae are plasma membrane domains involved in the uptake of certain pathogens and toxins. Internalization of some cell surface integrins occurs via caveolae suggesting caveolae may play a crucial role in modulating integrin-mediated adhesion and cell migration. Here we demonstrate a critical role for gangliosides (sialo-glycosphingolipids) in regulating caveolar endocytosis in human skin fibroblasts. Pretreatment of cells with endoglycoceramidase (cleaves glycosphingolipids) or sialidase (modifies cell surface gangliosides and glycoproteins) selectively inhibited caveolar endocytosis by >70%, inhibited the formation of plasma membrane domains enriched in sphingolipids and cholesterol (“lipid rafts”), reduced caveolae and caveolin-1 at the plasma membrane by ~80%, and blunted activation of β1-integrin, a protein required for caveolar endocytosis in these cells. These effects could be reversed by a brief incubation with gangliosides (but not with asialo-gangliosides or other sphingolipids) at 10°C, suggesting that sialo-lipids are critical in supporting caveolar endocytosis. Endoglycoceramidase treatment also caused a redistribution of focal adhesion kinase, paxillin, talin, and PIP Kinase Iγ away from focal adhesions. The effects of sialidase or endoglycoceramidase on membrane domains and the distribution of caveolin-1 could be recapitulated by β1-integrin knockdown. These results suggest that both gangliosides and β1-integrin are required for maintenance of caveolae and plasma membrane domains.
doi:10.1111/j.1600-0854.2009.01022.x
PMCID: PMC2852475  PMID: 20051050
caveolar endocytosis; glycosphingolipids; caveolin-1; sialidase; endoglycoceramidase; focal adhesions
11.  The small GTPases ARL-13 and ARL-3 coordinate intraflagellar transport and ciliogenesis 
The Journal of Cell Biology  2010;189(6):1039-1051.
Cilia intraflagellar transport and ciliogenesis are regulated by two small GTPases that maintain binding between IFT subcomplexes.
Intraflagellar transport (IFT) machinery mediates the bidirectional movement of cargos that are required for the assembly and maintenance of cilia. However, little is known about how IFT is regulated in vivo. In this study, we show that the small guanosine triphosphatase (GTPase) adenosine diphosphate ribosylation factor–like protein 13 (ARL-13) encoded by the Caenorhabditis elegans homologue of the human Joubert syndrome causal gene ARL13B, localizes exclusively to the doublet segment of the cilium. arl-13 mutants have shortened cilia with various ultrastructural deformities and a disrupted association between IFT subcomplexes A and B. Intriguingly, depletion of ARL-3, another ciliary small GTPase, partially suppresses ciliogenesis defects in arl-13 mutants by indirectly restoring binding between IFT subcomplexes A and B. Rescue of arl-13 mutants by ARL-3 depletion is mediated by an HDAC6 deacetylase-dependent pathway. Thus, we propose that two conserved small GTPases, ARL-13 and ARL-3, coordinate to regulate IFT and that perturbing this balance results in cilia deformation.
doi:10.1083/jcb.200912001
PMCID: PMC2886347  PMID: 20530210
12.  Type I gamma phosphatidylinositol phosphate kinase modulates invasion and proliferation and its expression correlates with poor prognosis in breast cancer 
Introduction
The loss of E-cadherin based cell-cell contacts and tumor cell migration to the vasculature and lymphatic system are hallmarks of metastasis of epithelial cancers. Type I gamma phosphatidylinositol phosphate kinase (PIPKIγ), an enzyme that generates phosphatidylinositol 4,5-bisphosphate (PI4,5P2) a lipid messenger and precursor to many additional second messengers, was found to regulate E-cadherin cell-cell contacts and growth factor-stimulated directional cell migration, indicating that PIPKIγ regulates key steps in metastasis. Here, we assess the expression of PIPKIγ in breast cancers and have shown that expression correlated with disease progression and outcome.
Methods
Using a tissue microarray, we analyzed 438 breast carcinomas for the levels of PIPKIγ and investigated the correlation of PIPKIγ expression with patient survival via Kaplan-Meier survival analysis. Moreover, via knockdown of the expression of PIPKIγ in cultured breast cancer cells with siRNA, the roles of PIPKIγ in breast cancer migration, invasion, and proliferation were examined.
Results
Tissue microarray data shows that ~18% of the cohort immunostained showed high expression of PIPKIγ. The Kaplan-Meier survival analysis revealed a significant inverse correlation between strong PIPKIγ expression and overall patient survival. Expression of PIPKIγ correlated positively with epidermal growth factor receptor (EGFR) expression, which regulates breast cancer progression and metastasis. In cultured breast cancer cells, PIPKIγ is required for growth factor stimulated migration, invasion, and proliferation of cells.
Conclusions
The results reveal a significant correlation between PIPKIγ expression and the progression of breast cancer. This is consistent with PIPKIγ 's role in breast cancer cell migration, invasion, and proliferation.
doi:10.1186/bcr2471
PMCID: PMC2880426  PMID: 20074374
13.  Type Iγ phosphatidylinositol phosphate kinase is required for EGF-stimulated directional cell migration 
The Journal of Cell Biology  2007;178(2):297-308.
Phosphatidylinositol 4,5-bisphosphate (PI4,5P2) modulates a plethora of cytoskeletal interactions that control the dynamics of actin assembly and, ultimately, cell migration. We show that the type Iγ phosphatidylinositol phosphate kinase 661 (PIPKIγ661), an enzyme that generates PI4,5P2, is required for growth factor but not G protein–coupled receptor–stimulated directional migration. By generating PI4,5P2 and regulating talin assembly, PIPKIγ661 modulates nascent adhesion formation at the leading edge to facilitate cell migration. The epidermal growth factor (EGF) receptor directly phosphorylates PIPKIγ661 at tyrosine 634, and this event is required for EGF-induced migration. This phosphorylation regulates the interaction between PIPKIγ661 and phospholipase Cγ1 (PLCγ1, an enzyme previously shown to be involved in the regulation of EGF-stimulated migration). Our results suggest that phosphorylation events regulating specific PIPKIγ661 interactions are required for growth factor–induced migration. These interactions in turn define the spatial and temporal generation of PI4,5P2 and derived messengers required for directional migration.
doi:10.1083/jcb.200701078
PMCID: PMC2064448  PMID: 17635937
14.  Type Iγ phosphatidylinositol phosphate kinase modulates adherens junction and E-cadherin trafficking via a direct interaction with μ1B adaptin 
The Journal of Cell Biology  2007;176(3):343-353.
Assembly of E-cadherin–based adherens junctions (AJ) is obligatory for establishment of polarized epithelia and plays a key role in repressing the invasiveness of many carcinomas. Here we show that type Iγ phosphatidylinositol phosphate kinase (PIPKIγ) directly binds to E-cadherin and modulates E-cadherin trafficking. PIPKIγ also interacts with the μ subunits of clathrin adaptor protein (AP) complexes and acts as a signalling scaffold that links AP complexes to E-cadherin. Depletion of PIPKIγ or disruption of PIPKIγ binding to either E-cadherin or AP complexes results in defects in E-cadherin transport and blocks AJ assembly. An E-cadherin germline mutation that loses PIPKIγ binding and shows disrupted basolateral membrane targeting no longer forms AJs and leads to hereditary gastric cancers. These combined results reveal a novel mechanism where PIPKIγ serves as both a scaffold, which links E-cadherin to AP complexes and the trafficking machinery, and a regulator of trafficking events via the spatial generation of phosphatidylinositol-4,5-bisphosphate.
doi:10.1083/jcb.200606023
PMCID: PMC2063960  PMID: 17261850
15.  Tyrosine phosphorylation of type Iγ phosphatidylinositol phosphate kinase by Src regulates an integrin–talin switch 
The Journal of Cell Biology  2003;163(6):1339-1349.
Engagement of integrin receptors with the extracellular matrix induces the formation of focal adhesions (FAs). Dynamic regulation of FAs is necessary for cells to polarize and migrate. Key interactions between FA scaffolding and signaling proteins are dependent on tyrosine phosphorylation. However, the precise role of tyrosine phosphorylation in FA development and maturation is poorly defined. Here, we show that phosphorylation of type Iγ phosphatidylinositol phosphate kinase (PIPKIγ661) on tyrosine 644 (Y644) is critical for its interaction with talin, and consequently, localization to FAs. PIPKIγ661 is specifically phosphorylated on Y644 by Src. Phosphorylation is regulated by focal adhesion kinase, which enhances the association between PIPKIγ661 and Src. The phosphorylation of Y644 results in an ∼15-fold increase in binding affinity to the talin head domain and blocks β-integrin binding to talin. This defines a novel phosphotyrosine-binding site on the talin F3 domain and a “molecular switch” for talin binding between PIPKIγ661 and β-integrin that may regulate dynamic FA turnover.
doi:10.1083/jcb.200310067
PMCID: PMC2173703  PMID: 14691141
PIPKIγ661; focal adhesion; phosphotyrosine-binding domain; FAK; β-integrin
16.  Anti-HIV Agent Trichosanthin Enhances the Capabilities of Chemokines to Stimulate Chemotaxis and G Protein Activation, and This Is Mediated through Interaction of Trichosanthin and Chemokine Receptors 
Trichosanthin (TCS), an active protein component isolated from a traditional Chinese medicinal herb Trichosanthes kirilowii, has been shown to inhibit HIV infection and has been applied in clinical treatment of AIDS. The recent development that chemokines and chemokine receptors play important roles in HIV infection led us to investigate the possible functional interaction of TCS with chemokines and their receptors. This study demonstrated that TCS greatly enhanced both RANTES (regulated upon activation, normal T cell expressed and secreted)– and stromal cell–derived factor (SDF)-1α–stimulated chemotaxis (EC50 ≅ 1 nM) in leukocytes (THP-1, Jurkat, and peripheral blood lymphocyte cells) and activation of pertussis toxin–sensitive G proteins (EC50 ≅ 20 nM). TCS also significantly augmented chemokine-stimulated activation of chemokine receptors CCR5 and CXCR4 as well as CCR1, CCR2B, CCR3, and CCR4 transiently expressed in HEK293 cells. A mutant TCS with 4,000-fold lower ribosome-inactivating activity showed similar augmentation activity as wild-type TCS. Moreover, flow cytometry demonstrated that the specific association of TCS to the cell membranes required the presence of chemokine receptors, and laser confocal microscopy reveals that TCS was colocalized with chemokine receptors on the membranes. The results from TCS-Sepharose pull-down and TCS and chemokine receptor coimmunoprecipitation and cross-linking experiments demonstrated association of TCS with CCR5. Thus, our data clearly demonstrated that TCS synergizes activities of chemokines to stimulate chemotaxis and G protein activation, and the effects of TCS are likely to be mediated through its interaction with chemokine receptors.
PMCID: PMC2195565  PMID: 10429674
chemokine receptors; trichosanthin; G proteins; chemotaxis; HIV

Results 1-16 (16)