Biology subjects

Selzman, C. H.

Publications and source records attributed to Selzman, C. H..

4 recordsLinked to original sources

bioRxiv2025

PKC Promotes T-Tubule Membrane Loss by Activating a PKD-NFκB Endocytic Pathway

BackgroundIn heart disease, the membrane of the cardiomyocyte transverse-axial tubular system (TATS) deteriorates. This impairs contractility, hinders recovery and predisposes to arrhythmia. However, the key signals and cellular processes driving TATS loss are not understood. We investigated protein kinase C (PKC) and its downstream signals in animal and human cardiomyocytes. MethodsVentricular cardiomyocytes were isolated from healthy adult rat, rabbit and failing human hearts and treated with the PKC activator phorbol 12-myristat 13-acetat (PMA) or receptor-mediated agonists, alongside inhibitors targeting PKC, PKD, NF{kappa}B, MKK1-ERK1/2, NFAT, or endocytic pathways. TATS density was analyzed by confocal microscopy using lipophilic membrane dyes. Signaling pathway activation was determined by Western blotting and RNA sequencing. Ca2+ signals and contractility were assessed in rat cells. Mechanisms of TATS loss were studied using endocytosis assays involving fixable dextran. ResultsPMA induced severe TATS loss, which was prevented by inhibiting PKC, PKD, NF{kappa}B or MKK1, but not by blocking NFAT or p38 MAPK. Receptor-mediated PKC activation also decreased TATS density. All effective inhibitors suppressed I{kappa}B expression. RNA sequencing indicated PMA-mediated activation of the NF{kappa}B and MAPK/ERK pathways and genes related to endocytosis. NF{kappa}B inhibition did not suppress the MAPK pathway, but MKK inhibition suppressed NF{kappa}B. PMA decreased Ca2+ transient amplitudes and contractility, whereas NF{kappa}B inhibitors preserved both. Dextran assays revealed that TATS membranes were internalized via a macropinocytic process that followed saturation kinetics was upregulated by PMA, downregulated by NF{kappa}B inhibition, and required PI3K, myosin I, and clathrin-independent endocytosis and correlated with the rate of TATS loss. Key findings were consistent in human cardiomyocytes and in ex-vivo rat and rabbit myocardial slice culture. ConclusionsPKC activation drives TATS loss in human and animal myocytes via PKC-PKD-NF{kappa}B, T-tubules are degraded by endocytic internalization, offering a new perspective on how cardiomyocyte membranes may deteriorate in heart disease.

cell biology↗

bioRxiv2024

Increased CPT1a expression is a critical cardioprotective response to pathological stress that suppresses gene programs for remodeling and enables rescue by gene transfer

Text AbstractO_ST_ABSBackgroundC_ST_ABSCarnitine palmitoyl transferase 1 (CPT1) is a rate-limiting enzyme for long chain fatty acid oxidation (FAO) in cardiac mitochondria. In adult hearts, CPT1b predominates, while CPT1a is co-expressed at lower levels. Pathological stress on the heart induces greater CPT1a expression, and this coincides with a reduction in FAO, yet the role of CPT1a in pathological cardiac remodeling is unknown. MethodsCPT1 isoform expression was assayed in myocardium of human heart failure (HF) patients with nonischemic cardiomyopathy (NICM) and a preclinical mouse model of heart failure. To explore the role of CPT1a upregulation in response to pathological stress, mice were subjected to afterload stress via transverse aortic constriction (TAC) or sham surgery (sham) with cardiac-specific CPT1a knockdown or cardiac-specific, AAV9-mediated CPT1a overexpression (AAV9.cTNTN.Cpt1a), versus empty virus or PBS infusions as controls. MiR370, known to suppress hepatic CPT1a, was assayed and overexpressed to determine if miR370 regulates cardiac CPT1a expression. ResultsCPT1a protein was elevated and miR370 reduced in myocardium of male and female NICM patients (204% vs. non-failing unused donor hearts), as well as in failing mouse hearts. AAV mediated miR370 overexpression in mouse hearts suppressed CPT1a expression and attenuated the response of CPT1a to TAC. Preventing CPT1a upregulation in response to TAC in cardiac specific CPT1a knockout mice (csCPT1a ko) exacerbated adverse remodeling, causing severe dysfunction and increased mortality. In contrast, CPT1a overexpression (2.8 fold), attenuated impaired ejection fraction (EF, by 54%) and fractional shortening (FS, 65%) vs. PBS-infused TAC hearts (p<0.05). Delivery of AAV9.cTnT.Cpt1a 4 wks after TAC surgery, led to significant rescue of EF and FS vs. animals receiving empty virus and mitigated the exacerbated dysfunction of csCPT1a ko hearts at 4 wks TAC. RNA-seq and reverse transcription-quantitative PCR revealed a novel function of CPT1a in suppressing hypertrophic, profibrotic and cell death gene programs in both sham and TAC hearts, irrespective of changes in FAO. ConclusionsThe effects of CPT1a in the heart extend beyond FAO and include a non-canonical regulation of cardiac gene programs. In addition to an animal model of HF, CPT1a upregulation occurs in NICM, and is a critical cardioprotective adaptation to pathological stress.

physiology↗

bioRxiv2024

Integrating molecular and clinical variables to predict myocardial recovery

Mechanical unloading and circulatory support with left ventricular assist devices (LVADs) mediate significant myocardial improvement in a subset of advanced heart failure (HF) patients. The clinical and biological phenomena associated with cardiac recovery are under intensive investigation. Left ventricular (LV) apical tissue, alongside clinical data, were collected from HF patients at the time of LVAD implantation (n=208). RNA was isolated and mRNA transcripts were identified through RNA sequencing and confirmed with RT-qPCR. To our knowledge this is the first study to combine transcriptomic and clinical data to derive predictors of myocardial recovery. We used a bioinformatic approach to integrate 59 clinical variables and 22,373 mRNA transcripts at the time of LVAD implantation for the prediction of post-LVAD myocardial recovery defined as LV ejection fraction (LVEF) [≥]40% and LV end-diastolic diameter (LVEDD) [≤]5.9cm, as well as functional and structural LV improvement independently by using LVEF and LVEDD as continuous variables, respectively. To substantiate the predicted variables, we used a multi-model approach with logistic and linear regressions. Combining RNA and clinical data resulted in a gradient boosted model with 80 features achieving an AUC of 0.731{+/-}0.15 for predicting myocardial recovery. Variables associated with myocardial recovery from a clinical standpoint included HF duration, pre-LVAD LVEF, LVEDD, and HF pharmacologic therapy, and LRRN4CL (ligand binding and programmed cell death) from a biological standpoint. Our findings could have diagnostic, prognostic, and therapeutic implications for advanced HF patients, and inform the care of the broader HF population. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=170 HEIGHT=200 SRC="FIGDIR/small/589326v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@17f0503org.highwire.dtl.DTLVardef@2231c1org.highwire.dtl.DTLVardef@f0ac56org.highwire.dtl.DTLVardef@c278f3_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2023

Mitochondria possess a large, non-selective ionic current that is enhanced during cardiac injury.

Mitochondrial ion channels are essential for energy production and cell survival. To avoid depleting the electrochemical gradient used for ATP synthesis, channels so far described in the mitochondrial inner membrane open only briefly, are highly ion-selective, have restricted tissue distributions, or have small currents. Here, we identify a mitochondrial inner membrane conductance that has strikingly different behavior from previously described channels. It is expressed ubiquitously, and transports cations non-selectively, producing a large, up to nanoampere-level, current. The channel does not lead to inner membrane uncoupling during normal physiology because it only becomes active at depolarized voltages. It is inhibited by external Ca2+, corresponding to the intermembrane space, as well as amiloride. This large, ubiquitous, non-selective, amiloride-sensitive (LUNA) current appears most active when expression of the mitochondrial calcium uniporter is minimal, such as in the heart. In this organ, we find that LUNA current magnitude increases two- to threefold in multiple mouse models of injury, an effect also seen in cardiac mitochondria from human patients with heart failure with reduced ejection fraction. Taken together, these features lead us to speculate that LUNA current may arise from an essential protein that acts as a transporter under physiological conditions, but becomes a channel under conditions of mitochondrial stress and depolarization.

cell biology↗