Molecular heterogeneity of protein kinase C expression in human ventricle

Abstract

Objective: Although activation of protein kinase C (PKC) modulates the function of normal cardiac myocytes and likely plays a role in the pathogenesis of cardiomyopathic disease states, the molecular basis of PKC expression in human ventricle has not been examined in detail. Methods: We have performed Western analysis and immunohistochemistry on explanted human cardiac tissue from nondiseased and diseased specimens using isoform-specific antibodies directed against all known PKC isozymes. Results: In homogenates from left and right ventricle, all isoforms except PKC-g and u were detected by immunoblotting, with confirmation using a second antibody directed against a different epitope when possible. For PKC-bII, d, and´, data indicated that these isoforms were variably phosphorylated in vivo, resulting in multiple bands during immunoblotting. Because of potential antibody cross-reactivity, reverse transcriptase polymerase chain reaction (RT-PCR) was performed which confirmed expression of PKC-a, bI, and z. Immunohistochemistry demonstrated that all isoforms detected in ventricular homogenate by Western analysis could be localized to cardiac myocytes. From a methodologic standpoint, significant degradation of PKC isoforms could be demonstrated when samples were either frozen or allowed to remain at room temperature, compared to immediate subcellular fractionation. Conclusions: These findings indicate that the PKC expression in human ventricular myocytes is remarkably diverse, with multiple conventional, novel, and atypical isoforms present, and highlight the importance of sample preparation in comparative studies of PKC isoform expression.

α1‐Adrenoceptor activation of PKC‐ε causes heterologous desensitization of thromboxane receptors in the aorta of spontaneously hypertensive rats

“…The variation in relative intensity of these two molecular weight bands in 36 weeks WKY and SHR implies the presence of mixtures of isoforms in their aortic smooth muscle. Indeed, several of the PKC isoforms have similar molecular weights (Ohanian et al, 1996;Shin et al, 2000;Sampson et al, 2007). The present results thus support the interpretation that variations in PKC isozymes underlie the desensitization of TP receptors observed in the SHR aorta.…”

Regulation of membrane-associated iPLA2 activity by a novel PKC isoform in ventricular myocytes

“…All PKC isoforms, apart from PKC-␥ and -, have been detected in human ventricular myocytes (26). Cardiac myocytes isolated from other species demonstrate a different pattern of expression of PKC isoforms.…”

PKCβII modulation of myocyte contractile performance

“…In particular, it is known that PKCβ II expression and activity increases during the development of cardiac hypertrophy and the progression to heart failure [3,6–8]. While up-regulation of this isoform is linked to cardiac dysfunction in humans [3,7,8], the functional role played by PKCβ II in modulating contractile function remains uncertain.…”

“…PKCα, the other major classical isoform expressed in mammalian heart also modulates PLB phosphorylation [2]. Given PKC-α and -β both increase in failing hearts [3,7,13], the influence of PKCβ II on myofilament and Ca 2+ cycling targets continues to be of interest.…”