Medical Cell Biology Commons^™

Phosphorylation Of Cyclophilin D At Serine 191 Regulates Mitochondrial Permeability Transition Pore Opening And Cell Death After Ischemia-Reperfusion, Stephen Hurst, Fabrice Gonnot, Maya Dia, Claire Crola Da Silva, Ludovic Gomez, Shey-Shing Sheu

Department of Medicine Faculty Papers

The mitochondrial permeability transition pore (mPTP) plays a critical role in the pathogenesis of cardiovascular diseases, including ischemia/reperfusion injury. Although the pore structure is still unresolved, the mechanism through which cyclophilin D (CypD) regulates mPTP opening is the subject of intensive studies. While post-translational modifications of CypD have been shown to modulate pore opening, specific phosphorylation sites of CypD have not yet been identified. We hypothesized here that phosphorylation of CypD on a serine residue controls mPTP opening and subsequent cell death at reperfusion. We combined in silico analysis with in vitro and genetic manipulations to determine potential CypD phosphorylation …

Rgs10 Shapes The Hemostatic Response To Injury Through Its Differential Effects On Intracellular Signaling By Platelet Agonists., Peisong Ma, Shuchi Gupta, Sara Sampietro, Daniel Dehelian, Valerie Tutwiler, Alan Tang, Timothy J. Stalker, Lawrence F. Brass

Department of Medicine Faculty Papers

Platelets express ≥2 members of the regulators of G protein signaling (RGS) family. Here, we have focused on the most abundant, RGS10, examining its impact on the hemostatic response in vivo and the mechanisms involved. We have previously shown that the hemostatic thrombi formed in response to penetrating injuries consist of a core of fully activated densely packed platelets overlaid by a shell of less-activated platelets responding to adenosine 5'-diphosphate (ADP) and thromboxane A2 (TxA2). Hemostatic thrombi formed in RGS10-/- mice were larger than in controls, with the increase due to expansion of the shell but not the core. Clot …

Niche Cadherins Control The Quiescence-To-Activation Transition In Muscle Stem Cells., Aviva J. Goel, Marysia-Kolbe Rieder, Hans-Henning Arnold, Glenn L. Radice, Robert S. Krauss

Department of Medicine Faculty Papers

Many adult stem cells display prolonged quiescence, promoted by cues from their niche. Upon tissue damage, a coordinated transition to the activated state is required because non-physiological breaks in quiescence often lead to stem cell depletion and impaired regeneration. Here, we identify cadherin-mediated adhesion and signaling between muscle stem cells (satellite cells [SCs]) and their myofiber niche as a mechanism that orchestrates the quiescence-to-activation transition. Conditional removal of N-cadherin and M-cadherin in mice leads to a break in SC quiescence, with long-term expansion of a regeneration-proficient SC pool. These SCs have an incomplete disruption of the myofiber-SC adhesive junction and …

Epitope Characterization Of Sero-Specific Monoclonal Antibody To Clostridium Botulinum Neurotoxin Type A., Cindi R Corbett, Erin Ballegeer, Kelly A Weedmark, M D Elias, Fetweh H Al-Saleem, Denise M Ancharski, Lance L Simpson, Jody D Berry

Department of Medicine Faculty Papers

Botulinum neurotoxins (BoNTs) are extremely potent toxins that can contaminate foods and are a public health concern. Anti-BoNT antibodies have been described that are capable of detecting BoNTs; however there still exists a need for accurate and sensitive detection capabilities for BoNTs. Herein, we describe the characterization of a panel of eight monoclonal antibodies (MAbs) generated to the non-toxic receptor-binding domain of BoNT/A (H(C)50/A) developed using a high-throughput screening approach. In two independent hybridoma fusions, two groups of four IgG MAbs were developed against recombinant H(C)50/A. Of these eight, only a single MAb, F90G5-3, bound to the whole BoNT/A protein …

Proliferating Cell Nuclear Antigen Is Required For Loading Of The Smcx/Kmd5c Histone Demethylase Onto Chromatin., Zhihui Liang, Marc Diamond, Johanna A Smith, Matthias Schnell, René Daniel

Department of Medicine Faculty Papers

UNLABELLED: ABSTRACT:

BACKGROUND: Histone methylation is regulated by a large number of histone methyltransferases and demethylases. The recently discovered SMCX/KMD5C demethylase has been shown to remove methyl residues from lysine 4 of histone H3 (H3K4), and constitutes an important component of the regulatory element-1-silencing transcription factor (REST) protein complex. However, little is known about the cellular mechanisms that control SMCX activity and intracellular trafficking.

RESULTS: In this study, we found that small interfering RNA-mediated knockdown of proliferating cell nuclear antigen (PCNA) resulted in the reduction of the chromatin-bound SMCX fraction. We identified a PCNA-interaction protein motif (PIP box) in the …

The Interplay Between Nf-Kappab And E2f1 Coordinately Regulates Inflammation And Metabolism In Human Cardiac Cells., Xavier Palomer, David Álvarez-Guardia, Mercy M Davidson, Tung O Chan, Arthur M Feldman, Manuel Vázquez-Carrera

Department of Medicine Faculty Papers

Pyruvate dehydrogenase kinase 4 (PDK4) inhibition by nuclear factor-κB (NF-κB) is related to a shift towards increased glycolysis during cardiac pathological processes such as cardiac hypertrophy and heart failure. The transcription factors estrogen-related receptor-α (ERRα) and peroxisome proliferator-activated receptor (PPAR) regulate PDK4 expression through the potent transcriptional coactivator PPARγ coactivator-1α (PGC-1α). NF-κB activation in AC16 cardiac cells inhibit ERRα and PPARβ/δ transcriptional activity, resulting in reduced PGC-1α and PDK4 expression, and an enhanced glucose oxidation rate. However, addition of the NF-κB inhibitor parthenolide to these cells prevents the downregulation of PDK4 expression but not ERRα and PPARβ/δ DNA binding activity, …

A Role For The Histone Deacetylase Hdac4 In The Life-Cycle Of Hiv-1-Based Vectors., Johanna A Smith, Jennifer Yeung, Gary D Kao, René Daniel

Department of Medicine Faculty Papers

HIV-1 integration is mediated by the HIV-1 integrase protein, which joins 3'-ends of viral DNA to host cell DNA. To complete the integration process, HIV-1 DNA has to be joined to host cell DNA also at the 5'-ends. This process is called post-integration repair (PIR). Integration and PIR involve a number of cellular co-factors. These proteins exhibit different degrees of involvement in integration and/or PIR. Some are required for efficient integration or PIR. On the other hand, some reduce the efficiency of integration. Finally, some are involved in integration site selection. We have studied the role of the histone deacetylase …

Increased Abundance Of The Receptor-Type Protein-Tyrosine Phosphatase Lar Accounts For The Elevated Insulin Receptor Dephosphorylating Activity In Adipose Tissue Of Obese Human Subjects, Falyaz Ahmad, Robert V. Considine, Barry J. Goldstein

Department of Medicine Faculty Papers

Protein-tyrosine phosphatases (PTPases) have an essential role in the regulation of the steady-state phosphorylation of the insulin receptor and other proteins in the insulin signalling pathway. To examine whether increased PTPase activity is associated with adipose tissue insulin resistance in human obesity we measured PTPase enzyme activity towards the insulin receptor in homogenates of subcutaneous adipose tissue from a series of six lean and six nondiabetic, obese (body mass index > 30) subjects. The obese subjects had a mean 1.74-fold increase in PTPase activity (P < 0.0001) with a striking positive correlation by linear regression analysis between PTPase activity and body mass index among all of the samples (R = 0.918; P < 0.0001). The abundance of three candidate insulin receptor PTPases in adipose tissue was also estimated by immunoblot analysis. The most prominent increase was a 2.03-fold rise in the transmembrane PTPase LAR (P < 0.001). Of the three PTPase examined, only immunodepletion of LAR protein from the homogenates with neutralizing antibodies resulted in normalization of the PTPase activity towards the insulin receptor, demonstrating that the increase in LAR was responsible for the enhanced PTPase activity in the adipose tissue from obese subjects. These studies suggest that increased PTPase activity towards the insulin receptor is a pathogenetic factor in the insulin resistance of adipose tissue in human obesity and provide evidence for a potential role of the LAR PTPase in the regulation of insulin signalling in disease states.

Insulin Receptor And Epidermal Growth Factor Receptor Dephosphorylation By Three Major Rat Liver Protein-Tyrosine Phosphatases Expressed In A Recombinant Bacterial System, Naotake Hashimoto, Wei-Ren Zhang, Barry J. Goldstein

Department of Medicine Faculty Papers

Protein-tyrosine phosphatases (PTPases) play an essential role in the regulation of signal transduction mediated by reversible protein-tyrosine phosphorylation. In order to characterize individual rat hepatic PTPases that might have specificity for autophosphorylated receptor tyrosine kinases, we isolated cDNA segments encoding three PTPases (PTPase 1B, LAR and LRP) that are expressed in insulin-sensitive liver and skeletal muscle tissue, and evaluated their catalytic activity in vitro. The intrinsic PTPase activities of the full-length PTPase 1B protein and the cytoplasmic domains of LAR and LRP were studied by expression of recombinant cDNA constructs in the inducible bacterial vector pKK233-2 using extracts of …

Identification Of Persistent Defects In Insulin Receptor Structure And Function In Capillary Endothelial Cells From Diabetic Rats, Ching Fai Kwok, Barry J. Goldstein, Dirk Muller-Wieland, Tian-Shing Lee, C. Ronald Kahn, George L. King

Department of Medicine Faculty Papers

Insulin actions and receptors were studied in capillary endothelial cells cultured from diabetic BB rats and their nondiabetic colony mates. The endothelial cells from diabetic rats of 2 mo duration had persistent biological and biochemical defects in culture. Compared with normal rats, endothelial cells from diabetic rats grew 44% more slowly. Binding studies of insulin and insulin-like growth factor I (IGF-I) showed that cells from diabetic rats had 50% decrease of insulin receptor binding (nondiabetic: 4.6 +/- 0.7; diabetic: 2.6 +/- 0.4% per milligram protein, P < 0.01), which was caused by a 50% decrease in the number of binding sites per milligram protein, whereas IGF-I binding was not changed. Insulin stimulation of 2-deoxy-glucose uptake and alpha-aminoisobutyric acid uptake were also severely impaired with a 80-90% decrease in maximal stimulation, in parallel with a 62% decrease in insulin-stimulated autophosphorylation (P < 0.05). ¹²⁵I-insulin cross-linking revealed an 140-kD alpha subunit of the insulin receptor similar to …