scholarly journals The antiviral sirtuin 3 bridges protein acetylation to mitochondrial integrity and metabolism during human cytomegalovirus infection

2021 ◽  
Vol 17 (4) ◽  
pp. e1009506
Author(s):  
Xinlei Sheng ◽  
Ileana M. Cristea
Keyword(s):  
Human Cytomegalovirus ◽  
Structural Integrity ◽  
Hcmv Infection ◽  
Temporal Dynamics ◽  
Virus Production ◽  
Central Component ◽  
Mitochondrial Morphology ◽  
Protein Levels ◽  
Acetylation Status ◽  
And Function

Regulation of mitochondrial structure and function is a central component of infection with viruses, including human cytomegalovirus (HCMV), as a virus means to modulate cellular metabolism and immune responses. Here, we link the activity of the mitochondrial deacetylase SIRT3 and global mitochondrial acetylation status to host antiviral responses via regulation of both mitochondrial structural integrity and metabolism during HCMV infection. We establish that SIRT3 deacetylase activity is necessary for suppressing virus production, and that SIRT3 maintains mitochondrial pH and membrane potential during infection. By defining the temporal dynamics of SIRT3-substrate interactions during infection, and overlaying acetylome and proteome information, we find altered SIRT3 associations with the mitochondrial fusion factor OPA1 and acetyl-CoA acyltransferase 2 (ACAA2), concomitant with changes in their acetylation levels. Using mutagenesis, microscopy, and virology assays, we determine OPA1 regulates mitochondrial morphology of infected cells and inhibits HCMV production. OPA1 acetylation status modulates these functions, and we establish K834 as a site regulated by SIRT3. Control of SIRT3 protein levels or enzymatic activity is sufficient for regulating mitochondrial filamentous structure. Lastly, we establish a virus restriction function for ACAA2, an enzyme involved in fatty acid beta-oxidation. Altogether, we highlight SIRT3 activity as a regulatory hub for mitochondrial acetylation and morphology during HCMV infection and point to global acetylation as a reflection of mitochondrial health.

scholarly journals Human Cytomegalovirus Infection Dysregulates the Localization and Stability of NICD1 and Jag1 in Neural Progenitor Cells

2015 ◽  
Vol 89 (13) ◽  
pp. 6792-6804 ◽  
Author(s):  
Xiao-Jun Li ◽  
Xi-Juan Liu ◽  
Bo Yang ◽  
Ya-Ru Fu ◽  
Fei Zhao ◽  
...  
Keyword(s):  
Stem Cell ◽  
Notch Signaling ◽  
Progenitor Cells ◽  
Human Cytomegalovirus ◽  
Neural Progenitor Cells ◽  
Hcmv Infection ◽  
Fetal Brain ◽  
Neural Progenitor ◽  
Notch Signaling Pathway ◽  
Protein Levels

ABSTRACTHuman cytomegalovirus (HCMV) infection of the developing fetus frequently results in major neural developmental damage. In previous studies, HCMV was shown to downregulate neural progenitor/stem cell (NPC) markers and induce abnormal differentiation. As Notch signaling plays a vital role in the maintenance of stem cell status and is a switch that governs NPC differentiation, the effect of HCMV infection on the Notch signaling pathway in NPCs was investigated. HCMV downregulated mRNA levels of Notch1 and its ligand, Jag1, and reduced protein levels and altered the intracellular localization of Jag1 and the intracellular effector form of Notch1, NICD1. These effects required HCMV gene expression and appeared to be mediated through enhanced proteasomal degradation. Transient expression of the viral tegument proteins of pp71 and UL26 reduced NICD1 and Jag1 protein levels endogenously and exogenously. Given the critical role of Notch signaling in NPC growth and differentiation, these findings reveal important mechanisms by which HCMV disturbs neural cell developmentin vitro. Similar eventsin vivomay be associated with HCMV-mediated neuropathogenesis during congenital infection in the fetal brain.IMPORTANCECongenital human cytomegalovirus (HCMV) infection is the leading cause of birth defects that primarily manifest as neurological disabilities. Neural progenitor cells (NPCs), key players in fetal brain development, are the most susceptible cell type for HCMV infection in the fetal brain. Studies have shown that NPCs are fully permissive for HCMV infection, which causes neural cell loss and premature differentiation, thereby perturbing NPC fate. Elucidation of virus-host interactions that govern NPC proliferation and differentiation is critical to understanding neuropathogenesis. The Notch signaling pathway is critical for maintaining stem cell status and functions as a switch for differentiation of NPCs. Our investigation into the impact of HCMV infection on this pathway revealed that HCMV dysregulates Notch signaling by altering expression of the Notch ligand Jag1, Notch1, and its active effector in NPCs. These results suggest a mechanism for the neuropathogenesis induced by HCMV infection that includes altered NPC differentiation and proliferation.

scholarly journals Human Cytomegalovirus Infection Alters the Expression of Cellular MicroRNA Species That Affect Its Replication

2008 ◽  
Vol 82 (18) ◽  
pp. 9065-9074 ◽  
Author(s):  
Fu-Zhang Wang ◽  
Frank Weber ◽  
Carlo Croce ◽  
Chang-Gong Liu ◽  
Xudong Liao ◽  
...  
Keyword(s):  
Human Cytomegalovirus ◽  
Time Course ◽  
Hcmv Infection ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Pathway ◽  
Cellular Mirnas ◽  
Protein Levels ◽  
Cellular Processes ◽  
Cellular Genes ◽  
Genes Encoding

ABSTRACT The human genome encodes over 500 microRNAs (miRNAs), small RNAs (19 to 26 nucleotides [nt]) that regulate the expressions of diverse cellular genes. Many cellular processes are altered through a variety of mechanisms by human cytomegalovirus (HCMV) infection. We asked whether HCMV infection leads to changes in the expression of cellular miRNAs and whether HCMV-regulated miRNAs are important for HCMV replication. Levels of most miRNAs did not change markedly during infection, but some were positively or negatively regulated. Patterns of miRNA expression were linked to the time course of infection. Some similarly reregulated miRNAs share identical or similar seed sequences, suggesting coordinated regulation of miRNA species that have shared targets. miRNAs miR-100 and miR-101 were chosen for further analyses based on their reproducible changes in expression after infection and on the basis of having predicted targets in the 3′ untranslated regions (3′-UTR) of genes encoding components of the mammalian target of rapamycin (mTOR) pathway, which is important during HCMV infection. Reporter genes that contain the 3′-UTR of mTOR (predicted targets for miR-100 and miR-101) or raptor (a component of the mTOR pathway; predicted site for miR-100) were constructed. Mimics of miR-100 and miR-101 inhibited expression from the mTOR construct, while only miR-100 inhibited the raptor construct. Together, miR-100 and miR-101 reduced mTOR protein levels. While the miR-100 and miR-101 mimics individually modestly inhibited production of infectious progeny, much greater inhibition was achieved with a combination of both (33-fold). Our key finding is that HCMV selectively manipulates the expression of some cellular miRNAs to help its own replication.

scholarly journals Human Cytomegalovirus uses a Host Stress Response to Balance the Elongation of Saturated/Monounsaturated and Polyunsaturated Very Long Chain Fatty Acids

2021 ◽  
Author(s):  
Yuecheng Xi ◽  
Lena Lindenmayer ◽  
Ian Kline ◽  
Jens von Einem ◽  
John G. Purdy
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Lipid Metabolism ◽  
Er Stress ◽  
Human Cytomegalovirus ◽  
Hcmv Infection ◽  
Lipid Synthesis ◽  
Protein Levels ◽  
Hcmv Replication ◽  
Long Chain

ABSTRACTStress and virus infection are known to regulate lipid metabolism in cells. Human cytomegalovirus infection induces fatty acid (FA) elongation and increases the cellular abundance of lipids with very long-chain FA tails (VLCFAs). While reprogramming of metabolism can be stress-related, the role of stress in HCMV reprogramming of lipid metabolism is poorly understood. In this study, we engineered cells to knockout PKR-like ER kinase (PERK) in the ER stress pathway and measured lipid changes using lipidomics to determine if PERK is needed for lipid changes associated with HCMV infection. We found that in HCMV-infected cells, PERK promotes the increase in the levels of phospholipids with saturated FA (SFA) and monounsaturated FA (MUFA) VLCFAs tails. Consistent with the SFA/MUFA lipidome changes, PERK enhances the protein levels of FA elongase 7 (ELOVL7), which elongates SFA and MUFA VLCFAs. Additionally, we found that increases in the elongation of polyunsaturated fatty acids (PUFAs) associated with HCMV infection was independent of PERK and that lipids with PUFA tails accumulated in HCMV-infected PERK knockout cells. Consistent with the PUFA lipidome changes, the protein levels of ELOVL5, which elongates PUFAs, are increased by HCMV infection through a PERK-independent mechanism. These observations show that PERK differentially regulates ELOVL7 and ELOVL5, creating a balance between the synthesis of lipids with SFA/MUFA tails and PUFA tails. Additionally, we found that PERK was necessary for virus replication and the infectivity of released viral progeny. Overall, our findings indicate that PERK—and more broadly, ER stress—may be necessary for membrane biogenesis needed to generate infectious HCMV virions.IMPORTANCEHCMV is a common herpesvirus that establishes lifelong persistent infections. While infection is asymptomatic in most people, HCMV causes life-threatening illnesses in immunocompromised people, including transplant recipients and cancer patients. Additionally, HCMV infection is a leading cause of congenital disabilities. HCMV replication relies on lipid synthesis. Here, we demonstrated that the ER stress mediator, PERK, controls fatty acid (FA) elongation and cellular abundance of several types of lipids following HCMV infection. Specifically, we found that PERK promotes FA elongase 7 synthesis of lipids with saturated/monounsaturated very long-chain FA tails which are important for building the viral membrane of infectious HCMV virions. Overall, our study shows that PERK is an essential host factor that supports HCMV replication and promotes lipidome changes caused by HCMV infection.

scholarly journals Human Cytomegalovirus Infection Causes Premature and Abnormal Differentiation of Human Neural Progenitor Cells

2010 ◽  
Vol 84 (7) ◽  
pp. 3528-3541 ◽  
Author(s):  
Min Hua Luo ◽  
Holger Hannemann ◽  
Amit S. Kulkarni ◽  
Philip H. Schwartz ◽  
John M. O'Dowd ◽  
...  
Keyword(s):  
Human Cytomegalovirus ◽  
Neural Progenitor Cells ◽  
Hcmv Infection ◽  
Neural Progenitor Cell ◽  
Neural Progenitor ◽  
Culture Conditions ◽  
Phenotypic Change ◽  
Protein Levels ◽  
Human Neural Progenitor Cells

ABSTRACT Congenital human cytomegalovirus (HCMV) infection is a leading cause of birth defects, largely manifested as central nervous system (CNS) disorders. The principal site of manifestations in the mouse model is the fetal brain's neural progenitor cell (NPC)-rich subventricular zone. Our previous human NPC studies found these cells to be fully permissive for HCMV and a useful in vitro model system. In continuing work, we observed that under culture conditions favoring maintenance of multipotency, infection caused NPCs to quickly and abnormally differentiate. This phenotypic change required active viral transcription. Whole-genome expression analysis found rapid downregulation of genes that maintain multipotency and establish NPCs’ neural identity. Quantitative PCR, Western blot, and immunofluorescence assays confirmed that the mRNA and protein levels of four hallmark NPC proteins (nestin, doublecortin, sex-determining homeobox 2, and glial fibrillary acidic protein) were decreased by HCMV infection. The decreases required active viral replication and were due, at least in part, to proteasomal degradation. Our results suggest that HCMV infection causes in utero CNS defects by inducing both premature and abnormal differentiation of NPCs.

scholarly journals Human Cytomegalovirus Uses a Host Stress Response To Balance the Elongation of Saturated/Monounsaturated and Polyunsaturated Very-Long-Chain Fatty Acids

mBio ◽  
2021 ◽  
Vol 12 (3) ◽  
Author(s):  
Yuecheng Xi ◽  
Lena Lindenmayer ◽  
Ian Kline ◽  
Jens von Einem ◽  
John G. Purdy
Keyword(s):  
Fatty Acids ◽  
Lipid Metabolism ◽  
Er Stress ◽  
Human Cytomegalovirus ◽  
Hcmv Infection ◽  
Lipid Synthesis ◽  
Knock Out ◽  
Protein Levels ◽  
Hcmv Replication ◽  
Long Chain

ABSTRACT Stress and virus infection regulate lipid metabolism. Human cytomegalovirus (HCMV) infection induces fatty acid (FA) elongation and increases the abundance of lipids with very-long-chain FA (VLCFA) tails. While reprogramming of metabolism can be stress related, the role of stress in HCMV reprogramming of lipid metabolism is poorly understood. In this study, we engineered cells to knock out protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) in the ER stress pathway and measured lipid changes using lipidomics to determine if PERK is needed for lipid changes associated with HCMV infection. In HCMV-infected cells, PERK promotes increases in the levels of phospholipids with saturated FA (SFA) and monounsaturated FA (MUFA) VLCFA tails. Further, PERK enhances FA elongase 7 (ELOVL7) protein levels, which elongates SFA and MUFA VLCFAs. Additionally, we found that increases in the elongation of polyunsaturated fatty acids (PUFAs) associated with HCMV infection were independent of PERK and that lipids with PUFA tails accumulated in HCMV-infected PERK knockout cells. Additionally, the protein levels of ELOVL5, which elongates PUFAs, are increased by HCMV infection through a PERK-independent mechanism. These observations show that PERK differentially regulates ELOVL7 and ELOVL5, creating a balance between the synthesis of lipids with SFA/MUFA tails and PUFA tails. Additionally, we found that PERK was necessary for virus replication and the infectivity of released viral progeny. Overall, our findings indicate that PERK—and, more broadly, ER stress—may be necessary for the membrane biogenesis needed to generate infectious HCMV virions. IMPORTANCE HCMV is a common herpesvirus that establishes lifelong persistent infections. While infection is asymptomatic in most people, HCMV causes life-threatening illnesses in immunocompromised people, including transplant recipients and cancer patients. Additionally, HCMV infection is a leading cause of congenital disabilities. HCMV replication relies on lipid synthesis. Here, we demonstrated that the ER stress mediator PERK controls FA elongation and the cellular abundance of several types of lipids following HCMV infection. Specifically, PERK promotes FA elongase 7 synthesis and phospholipids with saturated/monounsaturated very-long-chain FA tails. Overall, our study shows that PERK is an essential host factor that supports HCMV replication and promotes lipidome changes caused by HCMV infection.

scholarly journals Nonenvelopment Role for the ESCRT-III Complex during Human Cytomegalovirus Infection

2018 ◽  
Vol 92 (12) ◽  
Author(s):  
Nicholas T. Streck ◽  
Jillian Carmichael ◽  
Nicholas J. Buchkovich
Keyword(s):  
Human Cytomegalovirus ◽  
Hcmv Infection ◽  
Viral Infections ◽  
Virus Production ◽  
Opportunistic Pathogen ◽  
Inducible Expression ◽  
Dominant Negative ◽  
Aaa Atpase ◽  
Viral Budding

ABSTRACTSecondary envelopment of human cytomegalovirus (HCMV) occurs through a mechanism that is poorly understood. Many enveloped viruses utilize the endosomal sorting complexes required for transport (ESCRTs) for viral budding and envelopment. Although there are conflicting reports on the role of the ESCRT AAA ATPase protein VPS4 in HCMV infection, VPS4 may act in an envelopment role similar to its function during other viral infections. Because VPS4 is normally recruited by the ESCRT-III complex, we hypothesized that ESCRT-III subunits would also be required for HCMV infection. We investigated the role of ESCRT-III, the core ESCRT scission complex, during the late stages of infection. We show that inducible expression of dominant negative ESCRT-III subunits during infection blocks endogenous ESCRT function but does not inhibit virus production. We also show that HCMV forms enveloped intracellular and extracellular virions in the presence of dominant negative ESCRT-III subunits, suggesting that ESCRT-III is not involved in the envelopment of HCMV. We also found that as with ESCRT-III, inducible expression of a dominant negative form of VPS4A did not inhibit the envelopment of virions or reduce virus titers. Thus, HCMV does not require the ESCRTs for secondary envelopment. However, we found that ESCRT-III subunits are required for efficient virus spread. This suggests a role for ESCRT-III during the spread of HCMV that is independent of viral envelopment.IMPORTANCEHuman cytomegalovirus (HCMV) is a prevalent opportunistic pathogen in the human population. For neonatal and immunocompromised patients, HCMV infection can cause severe and possibly life-threatening complications. It is important to define the mechanisms of the viral replication cycle in order to identify potential targets for new therapies. Secondary envelopment, or acquisition of the membrane envelope, of HCMV is a mechanism that needs further study. Using an inducible fibroblast system to carefully control for the toxicity associated with blocking ESCRT-III function, this study determines that the ESCRT proteins are not required for viral envelopment. However, the study does discover a nonenvelopment role for the ESCRT-III complex in the efficient spread of the virus. Thus, this study advances our understanding of an important process essential for the replication of HCMV.

scholarly journals Degradation of p21cip1 in Cells Productively Infected with Human Cytomegalovirus

2001 ◽  
Vol 75 (8) ◽  
pp. 3613-3625 ◽  
Author(s):  
Zhenping Chen ◽  
Eugene Knutson ◽  
Alexander Kurosky ◽  
Thomas Albrecht
Keyword(s):  
Cell Cycle ◽  
Human Cytomegalovirus ◽  
Blot Analysis ◽  
Hcmv Infection ◽  
Cyclin E ◽  
Dependent Manner ◽  
Calpain Activity ◽  
Protein Levels ◽  
Infected Cells ◽  
Rna Levels

ABSTRACT Human cytomegalovirus (HCMV) stimulates arrested cells to enter the cell cycle by activating cyclin-dependent kinases (Cdks), notably Cdk2. Several mechanisms are involved in the activation of Cdk2. HCMV causes a substantial increase in the abundance of cyclin E and stimulates translocation of Cdk2 from the cytoplasm to the nucleus. Further, the abundance of the Cdk inhibitors (CKIs) p21cip1/waf1(p21cip1) and p27kip1 is substantially reduced. The activity of cyclin E/Cdk2 increases as levels of CKIs, particularly p21cip1, fall. We have previously shown that these phenomena contribute to priming the cell for efficient replication of HCMV. In this study, the mechanisms responsible for the decrease in p21cip1 levels after HCMV infection were investigated by measuring p21cip1 RNA and protein levels in permissive human lung (LU) fibroblasts after HCMV infection. Northern blot analysis revealed that p21cip1 RNA levels increased briefly at 3 h after HCMV infection and then decreased to their nadir at 24 h; thereafter, RNA levels increased to about 60% of the preinfection level. Western blot analysis demonstrated that the relative abundance of p21cip1 protein roughly paralleled the observed changes in initial RNA levels; however, the final levels of protein were much lower than preinfection levels. After a transient increase at 3 h postinfection, p21cip1 abundance declined sharply over the next 24 h and remained at a very low level through 96 h postinfection. The disparity between p21cip1 RNA and protein levels suggested that the degradation of p21cip1 might be affected in HCMV-infected cells. Treatment of HCMV-infected cells with MG132, an inhibitor of proteasome-mediated proteolysis, provided substantial protection of p21cip1 in mock-infected cells, but MG132 was much less effective in protecting p21cip1 in HCMV-infected cells. The addition of E64d or Z-Leu-Leu-H, each an inhibitor of calpain activity, to HCMV-infected cells substantially increased the abundance of p21cip1 in a concentration-dependent manner. To verify that p21cip1 was a substrate for calpain, purified recombinant p21cip1 was incubated with either m-calpain or μ-calpain, which resulted in rapid proteolysis of p21cip1. E64d inhibited the proteolysis of p21cip1 catalyzed by either m-calpain or μ-calpain. Direct measurement of calpain activity in HCMV-infected LU cells indicated that HCMV infection induced a substantial and sustained increase in calpain activity, although there was no change in the abundance of either m- or μ-calpain or the endogenous calpain inhibitor calpastatin. The observed increase of calpain activity was consistent with the increases in intracellular free Ca2+ and phospholipid degradation in HCMV-infected LU cells reported previously from our laboratory. Considered together, these results suggest that the increase in calpain activity observed following HCMV infection contributes significantly to the reduction of p21cip1 levels and the resultant cell cycle progression.

scholarly journals Human cytomegalovirus infection interferes with major histocompatibility complex type II maturation and endocytic proteases in dendritic cells at multiple levels

2008 ◽  
Vol 89 (10) ◽  
pp. 2427-2436 ◽  
Author(s):  
Tobias Kessler ◽  
Michael Reich ◽  
Gerhard Jahn ◽  
Eva Tolosa ◽  
Alexander Beck ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Major Histocompatibility Complex ◽  
Human Cytomegalovirus ◽  
Hcmv Infection ◽  
Type Ii ◽  
Complex Type ◽  
Mhc Ii ◽  
Histocompatibility Complex ◽  
And Function

Human cytomegalovirus (HCMV) infection suppresses cellular immunity and results in viral persistence. Dendritic cells (DCs) are susceptible to HCMV, and the development and immune function of HCMV-infected DCs are impaired in vitro. HCMV-derived proteins interfere with different aspects of major histocompatibility complex type II (MHC II) maturation and function in genetically engineered cellular models. This study directly analysed the effect of HCMV on the MHC II-associated antigen processing and presentation machinery in HCMV-infected human DCs in vitro. HCMV-infected DCs failed to mature newly synthesized MHC II to the final stage of SDS-stable MHC II αβ dimer/peptide complexes, in contrast to mock-infected controls. MHC II biosynthesis was delayed and reduced, whilst MHC II stability remained unchanged. MHC II surface expression was decreased in the late phase of HCMV infection. In addition, infected DCs decreased the transcription rate of the MHC II-associated proteases cathepsins S, Z, B, H and L and asparagine-specific endopeptidase (AEP). This translated into reduced protein expression of cathepsins H and S, as well as AEP, and less-efficient proteolytic degradation of a peptide substrate by endocytic proteases from HCMV-infected DCs in vitro. Thus, HCMV infection interferes with MHC II biosynthesis and maturation, as well as with the expression and function of endocytic proteases in infected DCs.

scholarly journals Blocked O-GlcNAc cycling alters mitochondrial morphology, function, and mass

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Elizabeth O. Akinbiyi ◽  
Lara K. Abramowitz ◽  
Brianna L. Bauer ◽  
Maria S. K. Stoll ◽  
Charles L. Hoppel ◽  
...  
Keyword(s):  
Cellular Localization ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Mitochondrial Morphology ◽  
Post Translational Modification ◽  
Mitochondrial Content ◽  
Protein Levels ◽  
Cellular Environment ◽  
And Function ◽  
The Impact

AbstractO-GlcNAcylation is a prevalent form of glycosylation that regulates proteins within the cytosol, nucleus, and mitochondria. The O-GlcNAc modification can affect protein cellular localization, function, and signaling interactions. The specific impact of O-GlcNAcylation on mitochondrial morphology and function has been elusive. In this manuscript, the role of O-GlcNAcylation on mitochondrial fission, oxidative phosphorylation (Oxphos), and the activity of electron transport chain (ETC) complexes were evaluated. In a cellular environment with hyper O-GlcNAcylation due to the deletion of O-GlcNAcase (OGA), mitochondria showed a dramatic reduction in size and a corresponding increase in number and total mitochondrial mass. Because of the increased mitochondrial content, OGA knockout cells exhibited comparable coupled mitochondrial Oxphos and ATP levels when compared to WT cells. However, we observed reduced protein levels for complex I and II when comparing normalized mitochondrial content and reduced linked activity for complexes I and III when examining individual ETC complex activities. In assessing mitochondrial fission, we observed increased amounts of O-GlcNAcylated dynamin-related protein 1 (Drp1) in cells genetically null for OGA and in glioblastoma cells. Individual regions of Drp1 were evaluated for O-GlcNAc modifications, and we found that this post-translational modification (PTM) was not limited to the previously characterized residues in the variable domain (VD). Additional modification sites are predicted in the GTPase domain, which may influence enzyme activity. Collectively, these results highlight the impact of O-GlcNAcylation on mitochondrial dynamics and ETC function and mimic the changes that may occur during glucose toxicity from hyperglycemia.

Abstract 78: TNFR2 Stimulation Promotes Mitochondrial Fusion via Stat3 and NF-kB Dependent Activation of OPA1 Expression

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Jing-Liang Nan ◽  
Wei Zhu ◽  
Ying-Chao Wang ◽  
Zhi-Wei Zhong ◽  
Lian-lian Zhu ◽  
...  
Keyword(s):  
Mitochondrial Fusion ◽  
Mitochondrial Morphology ◽  
Protective Effects ◽  
Promoter Regions ◽  
Neonatal Cardiomyocytes ◽  
Protein Levels ◽  
Dynamic Simulation Model ◽  
Underlying Mechanisms ◽  
Reported Data ◽  
And Function

Background: TNFR2 stimulation is known to possess protective effects for the cardiomyocytes, however, the underlying mechanisms remain unknown. Methods and Results: Using cultured neonatal cardiomyocytes that were infected with lentivirus containing shRNA targeting TNFR1, we showed that TNFR2 activation by TNFα (5nmol/L) resulted in increased mitochondrial fusion, mitochondrial membrane potential which were associated with both elevated intracellular ATP levels and oxygen consumption rate. Intriguingly, these changes were associated with increased protein levels of OPA1, with no changes in the expression levels of Drp1, Mfn1, Mfn2. We went further and reproduced previously reported data that NF-kB acetylation (Lys310) was increased with TNFR2 activation. Interestingly, however, we also observed dose-dependent effects on increase in Stat3 acetylation. Using shRNA approach, we then demonstrated that either Stat3 or NF-kB knockdown can attenuate TNFR2 induced OPA1 expression. The close interaction between these two signalings was validated by co-IP assay and confocal immunofluorescence staining. Aided by bio-informatics searching, we then performed ChIP assay to show that the binding sites of OPA1 promoter regions for STAT3 (-156 to -167) and NFkB (-192 to -203) were adjacent. We further validated that p300 induced Stat3 acetylation was indispensable for complex formation by the interaction between Stat3-DBD and NF-kB -ΔRHD, which in turn was a key event for OPA1 transcription activation. And silence of p300 can abolish OPA1 upregulation upon TNFR2 activation. Computerized data analysis based on zdock and zrank score followed by molecular dynamic simulation model for the whole Stat3 structure revealed higher value of the exterior dielectric constant (obtained from MM/PBSA calculation) for the two sites, K370 and K383, of Stat3, suggesting the essential roles for these two sites for Stat3-NFkB interaction, which were confirmed by co-IP with Stat3-DBD mutants (K370Q,K370R,K383Q,K383R) approach. Conclusions: Our data suggested that p300 mediated Stat3 acetylation cooperates with NF-kB to modulate TNFR2 activation induced OPA1 upregulation, leading to improved mitochondrial morphology and function.

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