Protein kinase C and cardiac dysfunction: a review

Heart failure (HF) is a physiological state in which cardiac output is insufficient to meet the needs of the body. It is a clinical syndrome characterized by impaired ability of the left ventricle to either fill or eject blood efficiently. HF is a disease of multiple aetiologies leading to progressive cardiac dysfunction and it is the leading cause of deaths in both developed and developing countries. HF is responsible for about 73,000 deaths in the UK each year. In the USA, HF affects 5.8 million people and 550,000 new cases are diagnosed annually. Cardiac remodelling (CD), which plays an important role in pathogenesis of HF, is viewed as stress response to an index event such as myocardial ischaemia or imposition of mechanical load leading to a series of structural and functional changes in the viable myocardium. Protein kinase C (PKC) isozymes are a family of serine/threonine kinases. PKC is a central enzyme in the regulation of growth, hypertrophy, and mediators of signal transduction pathways. In response to circulating hormones, activation of PKC triggers a multitude of intracellular events influencing multiple physiological processes in the heart, including heart rate, contraction, and relaxation. Recent research implicates PKC activation in the pathophysiology of a number of cardiovascular disease states. Few reports are available that examine PKC in normal and diseased human hearts. This review describes the structure, functions, and distribution of PKCs in the healthy and diseased heart with emphasis on the human heart and, also importantly, their regulation in heart failure

Identification of the linker histone H1 as a protein kinase Cepsilon-binding protein in vascular smooth muscle

A variety of anchoring proteins target specific protein kinase C (PKC) isoenzymes to particular subcellular locations or multimeric signaling complexes, thereby achieving a high degree of substrate specificity by localizing the kinase in proximity to specific substrates. PKCε is widely expressed in smooth muscle tissues, but little is known about its targeting and substrate specificity. We have used a Far-Western (overlay) approach to identify PKCε-binding proteins in vascular smooth muscle of the rat aorta. Proteins of ~32 and 34 kDa in the Triton-insoluble fraction were found to bind PKCε in a phospholipid/diacylglycerol-dependent manner. Although of similar molecular weight to RACK-1, a known PKCε-binding protein, these proteins were separated from RACK-1 by SDS-PAGE and differential NaCl extraction and were not recognized by an antibody to RACK-1. The PKCε-binding proteins were further purified from the Tritoninsoluble fraction and identified by de novo sequencing of selected tryptic peptides by tandem mass spectrometry as variants of the linker histone H1. Their identity was confirmed by Western blotting with anti-histone H1 and the demonstration that purified histone H1 binds PKCε in the presence of phospholipid and diacylglycerol but absence of Ca2+. The interaction of PKCε with histone H1 was specific since no interaction was observed with histones H2A, H2S or H3S. Bound PKCε phosphorylated histone H1 in a phospholipid/diacylglycerol-dependent but Ca2+-independent manner. Ca2+-dependent PKC was also shown to interact with histone H1 but not other histones. These results suggest that histone H1 is both an anchoring protein and a substrate for activated PKCε and other PKC isoenzymes and likely serves to localize activated PKCs that translocate to the nucleus in the vicinity of specific nuclear substrates including histone H1 itself. Since PKC isoenzymes have been implicated in regulation of gene expression, stable interaction with histone H1 may be an important step in this process.Mingcai Zhao, Cindy Sutherland, David P. Wilson, Jingti Deng, Justin A. MacDonald, and Michael P. Wals