Koch, W. J. | bioRxiv Science

bioRxiv2021

Cardiomyocyte GSK-3β deficiency induces cardiac progenitor cell proliferation in the ischemic heart through paracrine mechanisms

Cardiomyopathy is an irreparable loss and novel strategies are needed to induce resident cardiac progenitor cell (CPC) proliferation in situ to enhance the possibility of cardiac regeneration. Here we sought to identify the potential roles of glycogen synthase kinase-3{beta} (GSK-3{beta}), a critical regulator of cell proliferation and differentiation, in CPC proliferation post-myocardial infarction (MI). Cardiomyocyte-specific conditional GSK-3{beta} knockout (cKO) and littermate control mice were employed and challenged with MI. Though cardiac left ventricular chamber dimension (LVID) and contractile functions were comparable at two-week post-MI, cKO mice displayed significantly preserved LV chamber and contractile function vs. control mice at four-weeks post-MI. Consistent with protective phenotypes, an increased percentage of c-kit-positive cells (KPCs) were observed in the cKO hearts at four and six-weeks post-MI which was accompanied by increased levels of cardiomyocyte proliferation. Further analysis revealed that the observed increased number of KPCs in the ischemic cKO hearts was mainly from a cardiac lineage as the majority of identified KPCs were negative for the hematopoietic lineage marker, CD45. Mechanistically, cardiomyocyte-GSK-3{beta} profoundly suppresses the expression and secretion of growth factors, including basic-FGF angiopoietin-2, erythropoietin, stem cell factor (SCF), PDGF-BB, G-CSF, and VEGF, post-hypoxia. In conclusion, our findings strongly suggest that loss of cardiomyocyte-GSK-3{beta} promotes cardiomyocyte and resident CPC proliferation post-MI. The induction of cardiomyocyte and CPC proliferation in the ischemic cKO hearts is potentially regulated by autocrine and paracrine signaling governed by dysregulated growth factors post-MI. A strategy to inhibit cardiomyocyte GSK-3{beta} could be helpful for the promotion of in situ cardiac regeneration post-ischemic injury.

molecular biology↗

bioRxiv2020

A Peptide of the Amino-Terminus of GRK2 Induces Hypertrophy and Yet Elicits Cardioprotection after Pressure Overload

G protein-coupled receptor (GPCR) kinase 2 (GRK2) expression and activity are elevated early on in response to several forms of cardiovascular stress and are a hallmark of heart failure. Interestingly, though, in addition to its well-characterized role in regulating GPCRs, mounting evidence suggests a GRK2 “interactome” that underlies a great diversity in its functional roles. Several such GRK2 interacting partners are important for adaptive and maladaptive myocyte growth; therefore, an understanding of domain-specific interactions with signaling and regulatory molecules could lead to novel targets for heart failure therapy. While elevated cardiac levels and activity of GRK2 contribute to adverse heart remodeling and contractile dysfunction, inhibition of GRK2 via overexpression of a carboxyl-terminal peptide, βARKct, or its amino-terminal domain Regulator of G protein Signaling (RGS) homology domain (βARKrgs) can enhance cardiac function and can prevent heart failure development via Gβγ or Gαq sequestration, respectively. Previously, our lab investigated cardiac-specific transgenic expression of a fragment of this RGS domain (βARKnt) (residues 50-145). In contrast to βARKrgs this fragment did not alter acute hypertrophy after pressure overload or demonstrate RGS activity in vivo against Gq-mediated signaling. Herein, we subjected these transgenic mice to pressure overload and found that unlike their littermate controls or previous GRK2 fragments, they exhibited an increased left ventricular wall thickness and mass prior to cardiac stress that underwent proportional hypertrophic growth to controls after acute pressure overload. Importantly, despite this enlarged heart, βARKnt mice did not undergo the expected transition to heart failure observed in controls. Further, βARKnt expression limited adverse left ventricular remodeling and increased cell survival signaling. These data support the idea that the βARKnt peptide embodies a distinct functional interaction and novel means of cardioprotection during pressure-overload induced heart failure.Competing Interest StatementThe authors have declared no competing interest.AbbreviationsGPCRG protein-coupled receptor;GRK2G protein-coupled receptor kinase 2;RGSregulator of G protein Signaling domain;βARbeta-adrenergic receptor;LVleft ventricular;TACtransverse aortic constriction;αMHCα-myosin heavy chain;NLCnon-transgenic littermate control;WGAwheat germ agglutinin;IPimmunoprecipitation;IP3Inositol 1,4,5-trisphosphate;125I-CYP[125I]cyanopindolol;HFpEFheart failure with preserved ejection fraction;HFrEFheart failure with reduced ejection fraction;InsRinsulin receptor;IRSinsulin receptor substrate;PI3Kphosphoinositide 3-kinase;PDK1 and 2phosphatidylinositol-dependent kinases;PKB/Aktprotein kinase B;AS160Akt substrate of 160 kilodaltons;GAPGTPase-activating protein;GSK3βglycogen synthase kinase 3β.View Full Text

physiology↗