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1.  Direct Renin Inhibition Exerts an Anti-hypertrophic Effect Associated with Improved Mitochondrial Function in Post-infarction Heart Failure in Diabetic Rats 
In addition to hypertension control, direct renin inhibition has been shown to exert direct beneficial effects on the heart in post-infarction cardiac remodeling. This study elucidates the possible contribution of mitochondria to the anti-hypertrophic effects of the direct renin inhibitor aliskiren in post-infarction heart failure complicated with diabetes in rats.
Diabetes was induced in male Sprague-Dawley rats by a single injection of streptozotocin (IP, 65 mg/kg body weight). After 7 days, the animals were randomly assigned to 4 groups: sham, heart failure, sham+aliskiren, and heart failure+aliskiren. Post-infarction HF was induced by coronary artery ligation for 4 weeks.
showed that heart failure reduced ejection fraction and cardiac output by 41% (P<0.01) and 42% (P<0.05), respectively, compared to sham-operated hearts. Cardiac dysfunction was associated with suppressed state 3 respiration rates and respiratory control index in mitochondria, and increased mitochondrial permeability transition pore (PTP) opening. In addition, heart failure reduced expression of the major mitochondrial sirtuin, SIRT3 and increased acetylation of cyclophilin D, a regulatory component of the PTP. Aliskiren significantly improved cardiac function and abrogated mitochondrial perturbations.
Our results demonstrate that aliskiren attenuates post-infarction remodeling which is associated with its beneficial effects on mitochondria.
PMCID: PMC3980674  PMID: 22613984
Post-myocardial infarction; Heart failure; Renin angiotensin system; Mitochondria
2.  Structural Bases of Coronavirus Attachment to Host Aminopeptidase N and Its Inhibition by Neutralizing Antibodies 
PLoS Pathogens  2012;8(8):e1002859.
The coronaviruses (CoVs) are enveloped viruses of animals and humans associated mostly with enteric and respiratory diseases, such as the severe acute respiratory syndrome and 10–20% of all common colds. A subset of CoVs uses the cell surface aminopeptidase N (APN), a membrane-bound metalloprotease, as a cell entry receptor. In these viruses, the envelope spike glycoprotein (S) mediates the attachment of the virus particles to APN and subsequent cell entry, which can be blocked by neutralizing antibodies. Here we describe the crystal structures of the receptor-binding domains (RBDs) of two closely related CoV strains, transmissible gastroenteritis virus (TGEV) and porcine respiratory CoV (PRCV), in complex with their receptor, porcine APN (pAPN), or with a neutralizing antibody. The data provide detailed information on the architecture of the dimeric pAPN ectodomain and its interaction with the CoV S. We show that a protruding receptor-binding edge in the S determines virus-binding specificity for recessed glycan-containing surfaces in the membrane-distal region of the pAPN ectodomain. Comparison of the RBDs of TGEV and PRCV to those of other related CoVs, suggests that the conformation of the S receptor-binding region determines cell entry receptor specificity. Moreover, the receptor-binding edge is a major antigenic determinant in the TGEV envelope S that is targeted by neutralizing antibodies. Our results provide a compelling view on CoV cell entry and immune neutralization, and may aid the design of antivirals or CoV vaccines. APN is also considered a target for cancer therapy and its structure, reported here, could facilitate the development of anti-cancer drugs.
Author Summary
The cell surface aminopeptidase N (APN), a membranebound metalloprotease target for cancer therapy, is a major cell entry receptor for coronaviruses (CoVs), agents that cause important respiratory and enteric diseases. In some CoVs, the virus envelope spike glycoprotein (S) mediates attachment of the virus particles to the host APN protein and cell entry, which is blocked by antibodies that prevent CoV infections. The crystal structures of the S proteins of two porcine CoV in complex with the pig APN (pAPN) or with a neutralizing antibody shown here, reveal how some CoV bind to its cell surface APN receptor and how antibodies prevent receptor binding and infection. The report uncovers a unique virus-receptor recognition mode that engages a glycan N-linked to the pAPN ectodomain, revealing structural determinants of the receptor-binding specificity in CoVs. Neutralizing antibodies target viral residues used for binding to the APN receptor and entry into host cells, showing that efficient CoV neutralization requires immune responses focused toward key receptor binding motifs in the virus envelope. These structural insights, together with the structure of the APN ectodomain, provide a compelling view of relevant cell membrane processes related to infectious diseases and cancer.
PMCID: PMC3410853  PMID: 22876187
3.  Aragon workers’ health study – design and cohort description 
Spain, a Mediterranean country with relatively low rates of coronary heart disease, has a high prevalence of traditional cardiovascular risk factors and is experiencing a severe epidemic of overweight/obesity. We designed the Aragon Workers’ Health Study (AWHS) to characterize the factors associated with metabolic abnormalities and subclinical atherosclerosis in a middle aged population in Spain free of clinical cardiovascular disease. The objective of this paper is to describe the study design, aims and baseline characteristics of participants in the AWHS.
Longitudinal cohort study based on the annual health exams of 5,400 workers of a car assembly plant in Figueruelas (Zaragoza, Spain). Study participants were recruited during a standardized clinical exam in 2009–2010 (participation rate 95.6%). Study participants will undergo annual clinical exams and laboratory assays, and baseline and triennial collection of biological materials for biobanking and cardiovascular imaging exams (carotid, femoral and abdominal ultrasonography, coronary calcium score, and ankle-arm blood pressure index). Participants will be followed-up for 10 years.
The average (SD) age, body mass index, and waist circumference were 49.3 (8.7) years, 27.7 (3.6) kg/m2 and 97.2 (9.9) cm, respectively, among males (N = 5,048), and 40.8 (11.6) years, 24.4 (3.8) kg/m2, and 81.9 (9.9) cm, among females (N = 351). The prevalence of overweight, obesity, current smoking, hypertension, hypercholesterolemia, and diabetes were 55.0, 23.1, 37.1, 40.3, 75.0, and 7.4%, respectively, among males, and 23.7, 8.3, 45.0, 12.1, 59.5, and 0.6%, respectively, among females. In the initial 587 study participants who completed all imaging exams (94.5% male), the prevalence of carotid plaque, femoral plaque, coronary calcium score >1 to 100, and coronary calcium score >100 was 30.3, 56.9, 27.0, and 8.8%, respectively. 67.7% of study participants had at least one plaque in the carotid or femoral arteries.
Baseline data from the AWHS show a high prevalence of cardiovascular risk factors and of sublinical atherosclerosis. Follow-up of this cohort will allow the assessment of subclinical atherosclerosis progression and the link of disease progression to traditional and emergent risk factors.
PMCID: PMC3439398  PMID: 22712826
4.  Antigenic modules in the N-terminal S1 region of the transmissible gastroenteritis virus spike protein 
The Journal of General Virology  2011;92(Pt 5):1117-1126.
The N-terminal S1 region of the transmissible gastroenteritis virus (TGEV) spike (S) glycoprotein contains four antigenic sites (C, B, D and A, from the N- to the C-terminal end) and is engaged in host-cell receptor recognition. The most N-terminal portion of the S1 region, which comprises antigenic sites C and B, is needed for the enteric tropism of TGEV, whereas the major antigenic site A at the C-terminal moiety is required for both respiratory and enteric cell tropism, and is engaged in recognition of the aminopeptidase N (APN) receptor. This study determined the kinetics for binding of a soluble S1 protein to the APN protein. Moreover, the S1 region of the TGEV S protein was dissected, with the aim of identifying discrete modules displaying unique antigenic sites and receptor-binding functions. Following protease treatments and mammalian cell expression methods, four modules or domains (D1–D4) were defined at the S1 region. Papain treatment identified an N-terminal domain (D1) resistant to proteolysis, whereas receptor binding defined a soluble and functional APN receptor-binding domain (D3). This domain was recognized by neutralizing antibodies belonging to the antigenic site A and therefore could be used as an immunogen for the prevention of viral infection. The organization of the four modules in the S1 region of the TGEV S glycoprotein is discussed.
PMCID: PMC3139418  PMID: 21228126
5.  T Cell/Transmembrane, Ig, and Mucin-3 Allelic Variants Differentially Recognize Phosphatidylserine and Mediate Phagocytosis of Apoptotic Cells 
T cell/transmembrane, Ig, and mucin (TIM) proteins, identified using a congenic mouse model of asthma, critically regulate innate and adaptive immunity. TIM-1 and TIM-4 are receptors for phosphatidylserine (PtdSer), exposed on the surfaces of apoptotic cells. Herein, we show with structural and biological studies that TIM-3 is also a receptor for PtdSer that binds in a pocket on the N-terminal IgV domain in coordination with a calcium ion. The TIM-3/PtdSer structure is similar to that of TIM-4/PtdSer, reflecting a conserved PtdSer binding mode by TIM family members. Fibroblastic cells expressing mouse or human TIM-3 bound and phagocytosed apoptotic cells, with the BALB/c allelic variant of mouse TIM-3 showing a higher capacity than the congenic C.D2 Es-Hba–allelic variant. These functional differences were due to structural differences in the BC loop of the IgV domain of the TIM-3 polymorphic variants. In contrast to fibroblastic cells, T or B cells expressing TIM-3 formed conjugates with but failed to engulf apoptotic cells. Together these findings indicate that TIM-3–expressing cells can respond to apoptotic cells, but the consequence of TIM-3 engagement of PtdSer depends on the polymorphic variants of and type of cell expressing TIM-3. These findings establish a new paradigm for TIM proteins as PtdSer receptors and unify the function of the TIM gene family, which has been associated with asthma and autoimmunity and shown to modulate peripheral tolerance.
PMCID: PMC3128800  PMID: 20083673
6.  Crystallization and preliminary crystallographic analysis of the measles virus hemagglutinin in complex with the CD46 receptor 
A complex of the measles virus hemagglutinin and the CD46 receptor representing the initial step of the cell infection has been crystallized.
The measles virus (MV) hemagglutinin (MV-H) mediates the attachment of MV particles to cell-surface receptors for entry into host cells. MV uses two receptors for attachment to host cells: the complement-control protein CD46 and the signalling lymphocyte activation molecule (SLAM). The MV-H glycoprotein from an Edmonston MV variant and the MV-binding fragment of the CD46 receptor were overproduced in mammalian cells and used to crystallize an MV-­H–CD46 complex. Well diffracting crystals containing two complexes in the asymmetric unit were obtained and the structure of the complex was solved by the molecular-replacement method.
PMCID: PMC2805546  PMID: 20057080
measles virus hemagglutinin; CD46 receptor; virus receptor; virus infection
7.  Redundant or separate entities?—roles of Twist1 and Twist2 as molecular switches during gene transcription 
Nucleic Acids Research  2010;39(4):1177-1186.
Twist1 and Twist2 are highly conserved members of the Twist subfamily of bHLH proteins responsible for the transcriptional regulation of the developmental programs in mesenchymal cell lineages. The regulation of such processes requires that Twist1 and Twist2 function as molecular switches to activate and repress target genes by employing several direct and indirect mechanisms. Modes of action by these proteins include direct DNA binding to conserved E-box sequences and recruitment of coactivators or repressors, sequestration of E-protein modulators, and interruption of proper activator/repressor function through protein–protein interactions. Regulatory outcomes of Twist1 and Twist2 are themselves controlled by spatial-temporal expression, phosphoregulation, dimer choice and cellular localization. Although these two proteins are highly conserved and exhibit similar functions in vitro, emerging literature have demonstrated different roles in vivo. The involvement of Twist1 and Twist2 in a broad spectrum of regulatory pathways highlights the importance of understanding their roles in normal development, homeostasis and disease. Here we focus on the mechanistic models of transcriptional regulation and summarize the similarities and differences between Twist1 and Twist2 in the context of myogenesis, osteogenesis, immune system development and cancer.
PMCID: PMC3045590  PMID: 20935057
8.  Candida albicans β-Glucan Exposure Is Controlled by the Fungal CEK1-Mediated Mitogen-Activated Protein Kinase Pathway That Modulates Immune Responses Triggered through Dectin-1 ▿ †  
Infection and Immunity  2010;78(4):1426-1436.
Innate immunity to Candida albicans depends upon the recognition of molecular patterns on the fungal cell wall. However, the masking of major components such as β-glucan seems to be a mechanism that fungi have evolved to avoid immune cell recognition through the dectin-1 receptor. Although the role of C. albicans mitogen-activated protein kinase (MAPK) pathways as virulence determinants has been established previously with animal models, the mechanism involved in this behavior is largely unknown. In this study we demonstrate that a disruption of the C. albicans extracellular signal-regulated kinase (ERK)-like 1 (CEK1)-mediated MAPK pathway causes enhanced cell wall β-glucan exposure, triggering immune responses more efficiently than the wild type, as measured by dectin-1-mediated specific binding and human dendritic cell (hDC)- and macrophage-mediated phagocytosis, killing, and activation of intracellular signaling pathways. At the molecular level, the disruption of CEK1 resulted in altered spleen tyrosine kinase (Syk), Raf-1, and ERK1/2 activations together with IκB degradation on hDCs and increased dectin-1-dependent activator protein 1 (AP-1) activation on transfected cells. In addition, concurring with these altered pathways, we detected increased reactive oxygen species production and cytokine secretion. In conclusion, the CEK1-mediated MAPK pathway is involved in β-glucan exposure in a fungal pathogen, hence influencing dectin-1-dependent immune cell recognition, thus establishing this fungal intracellular signaling route as a promising novel therapeutic target.
PMCID: PMC2849429  PMID: 20100861
9.  Structure of the Extracellular Portion of CD46 Provides Insights into Its Interactions with Complement Proteins and Pathogens 
PLoS Pathogens  2010;6(9):e1001122.
The human membrane cofactor protein (MCP, CD46) is a central component of the innate immune system. CD46 protects autologous cells from complement attack by binding to complement proteins C3b and C4b and serving as a cofactor for their cleavage. Recent data show that CD46 also plays a role in mediating acquired immune responses, and in triggering autophagy. In addition to these physiologic functions, a significant number of pathogens, including select adenoviruses, measles virus, human herpes virus 6 (HHV-6), Streptococci, and Neisseria, use CD46 as a cell attachment receptor. We have determined the crystal structure of the extracellular region of CD46 in complex with the human adenovirus type 11 fiber knob. Extracellular CD46 comprises four short consensus repeats (SCR1-SCR4) that form an elongated structure resembling a hockey stick, with a long shaft and a short blade. Domains SCR1, SCR2 and SCR3 are arranged in a nearly linear fashion. Unexpectedly, however, the structure reveals a profound bend between domains SCR3 and SCR4, which has implications for the interactions with ligands as well as the orientation of the protein at the cell surface. This bend can be attributed to an insertion of five hydrophobic residues in a SCR3 surface loop. Residues in this loop have been implicated in interactions with complement, indicating that the bend participates in binding to C3b and C4b. The structure provides an accurate framework for mapping all known ligand binding sites onto the surface of CD46, thereby advancing an understanding of how CD46 acts as a receptor for pathogens and physiologic ligands of the immune system.
Author Summary
The human membrane cofactor protein (MCP, CD46) is expressed on all nucleated cells and serves as a marker that prevents host cells from destruction by the immune system. It functions as a cofactor that helps to inactivate the C3b and C4b molecules, which are central components of the complement system. In addition to its role in regulation complement activation, CD46 is also used by a large number of pathogens, including measles virus and adenovirus, as a receptor to allow these pathogens to attach to the cell surface and initiate an infection. We have determined the three-dimensional structure of the bulk of the extracellular region of CD46 using X-ray crystallography. This structure provides detailed information about the location of previously identified residues that play a role in the interactions with C3b, C4b, and several pathogens, advancing an understanding of the function of the CD46 protein as a host and pathogen receptor. Moreover, the structure also reveals an unexpected, bent conformation of the protein that has implications for how the binding sites are presented at the cell surface.
PMCID: PMC2947992  PMID: 20941397
10.  Prophylactic uses of integrin CD18-βA peptide in a murine polymicrobial peritonitis model 
AIM: To evaluate the prophylactic properties of integrin CD18-βA peptide in a murine model of abdominal polymicrobial peritonitis and sepsis.
METHODS: Bacterial sepsis was induced in Institute of Cancer Research (ICR) mice by cecal ligation and puncture (CLP) surgery. Inflicted mice were then injected with either sterile saline or CD18-βA peptide intraperitoneally at 2 h after surgery, and were sacrificed at 12 and 24 h after surgery. Blood samples were immediately collected, and analyzed for endotoxin activity and tumor necrosis factor (TNF)-α and interleukin (IL)-6. Lungs and liver were studied for CD45+ leukocyte and CD3 mRNA content. Pulmonary expression of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM) and E-selectin was also determined.
RESULTS: Intraperitoneal injection of CD18-βA peptide significantly suppressed circulating endotoxin activity (P < 0.01) at 24 h, as well as serum levels of TNF-α (P < 0.05 at 12 and 24 h) and IL-6 (P < 0.01 at 12 h, P < 0.05 at 24 h) in CLP-inflicted mice. CD18-βA peptide also abrogated leukocyte infiltration into liver and lungs as unveiled by reduced CD45+ leukocyte and CD3 mRNA contents. Furthermore, the peptide significantly reduced pulmonary expression of VCAM (P < 0.01 at 12 h, P < 0.001 at 24 h), E-selectin (P < 0.01 at 12 and 24 h), and ICAM-1 (P < 0.01 at 12 h, P < 0.001 at 24 h). These actions of CD18-βA peptide collectively protected septic mice against lethality (P < 0.01).
CONCLUSION: CD18-βA peptide is a potent endotoxin antagonist that can protect surgical patients against sepsis-associated lethality.
PMCID: PMC2880778  PMID: 20518087
Bacterial endotoxin; Integrin CD18; Inflammation; Biotherapeutic peptide
11.  TIM-4 structures identify a Metal Ion-dependent Ligand Binding Site where phosphatidylserine binds 
Immunity  2007;27(6):941-951.
The T-cell immunoglobulin and mucin domain (TIM) proteins are important regulators of T cell responses. They have been linked to autoimmunity and cancer. Structures of the murine TIM-4 identified a Metal Ion-dependent Ligand Binding Site (MILIBS) in the immunoglobulin (Ig) domain of the TIM family. The characteristic CC’ loop of the TIM domain and the hydrophobic FG loop shaped a narrow cavity where acidic compounds penetrate and coordinate to a metal ion bound to conserved residues in the TIM proteins. The structure of phosphatidylserine bound to the Ig domain showed that the hydrophilic head penetrates into the MILIBS and coordinates with the metal ion, while the aromatic residues on the tip of the FG loop interacted with the fatty acid chains and could insert into the lipid bilayer. Our results also revealed a significant role of the MILIBS in trafficking of TIM-1 to the cell surface.
PMCID: PMC2330274  PMID: 18083575
asthma; autoimmunity; metal ions; phospholipids; crystallography
12.  Receptor Priming of Major Group Human Rhinoviruses for Uncoating and Entry at Mild Low-pH Environments 
Journal of Virology  2003;77(22):11985-11991.
Receptor priming of low-pH-triggered virus entry has been described for an enveloped virus (15). Here we show with major group human rhinoviruses (HRV) and its intercellular adhesion molecule-1 receptor that nonenveloped viruses follow this novel cell entry principle. In vitro the receptor primed HRV for efficient uncoating at mild low pH (5.5 to 6.0). Agents preventing endosomal acidification reduced or blocked rhinovirus cell infection, while nocodazole had no effect on infection of any serotype tested. The entry inhibitory effect of lysosomotropic agents was overcome by exposing cell-internalized HRV to mild low pH (5.5 to 6.0). We therefore conclude that receptor priming of major group HRV must occur in vivo as well. Cooperation of a cellular receptor and low pH in virus uncoating will polarize the exit of the genome to the receptor-bound, membrane-proximal region of the virus particle during acidification of endosomes. This process must be required for efficient penetration of the cellular membrane by viruses.
PMCID: PMC254263  PMID: 14581535
13.  Structural Analysis of Human Rhinovirus Complexed with ICAM-1 Reveals the Dynamics of Receptor-Mediated Virus Uncoating 
Journal of Virology  2003;77(11):6101-6107.
Intercellular adhesion molecule 1 (ICAM-1) functions as the cellular receptor for the major group of human rhinoviruses, being not only the target of viral attachment but also the mediator of viral uncoating. The configurations of HRV3-ICAM-1 complexes prepared both at 4°C and physiological temperature (37°C) were analyzed by cryoelectron microscopy and image reconstruction. The particle diameters of two complexes (with and without RNA) representing uncoating intermediates generated at 37°C were each 4% larger than that of those prepared at 4°C. The larger virus particle arose by an expansive movement of the capsid pentamers along the fivefold axis, which loosens interprotomer contacts, particularly at the canyon region where the ICAM-1 receptor bound. Particle expansion required receptor binding and preceded the egress of the viral RNA. These observations suggest that receptor-mediated uncoating could be a consequence of restrained capsid motion, where the bound receptors maintain the viral capsid in an expanded open state for subsequent genome release.
PMCID: PMC155003  PMID: 12743267
14.  The Domain Structure of ICAM-1 and the Kinetics of Binding to Rhinovirus 
Journal of Virology  1998;72(7):6244-6246.
Fragments of intercellular adhesion molecule 1 (ICAM- 1) containing only the two most N terminal of its five immunoglobulin SF domains bind to rhinovirus 3 with the same affinity and kinetics as a fragment with the entire extracellular domain. The fully active two-domain fragments contain 5 or 14 more residues than a previously described fragment that is only partially active. Comparison of X-ray crystal structures show differences at the bottom of domain 2. Four different glycoforms of ICAM- 1 bind with identical kinetics.
PMCID: PMC110451  PMID: 9621098

Results 1-14 (14)