Protein quality control in heart disease: Small heat shock proteins and autophagy

Disease-related stress to the myocardium, such as unremitting hypertension or myocardial injury, triggers hypertrophic growth that increases the risk of functional decompensation and malignant rhythm disturbance [1]. Hypertrophy and other forms of cardiac plasticity are associated with energy-dependent structural changes in cardiac myocytes and fibroblasts, coordinated angiogenic alterations in blood supply, adjustments in the consumption of energy-providing substrates, and, in the case of pathological cardiac hypertrophy, activation of a previously dormant "fetal gene program". Our understanding of mechanisms governing these remodeling reactions is incomplete, and deciphering them may yield insights into the pathogenesis of heart failure, a major source of morbidity and mortality worldwide. Diverse catabolic and anabolic processes contribute to remodeling of the healthy and diseased heart. Recent studies have demonstrated the importance of two inter-related mechanisms of protein quality control, small heat shock proteins (sHsp) and autophagy. The sHsps are molecular chaperones that bind unfolded aggregate-prone proteins to facilitate proper refolding or direct them for degradation by the autophagosome. Here, we will review this topic, focusing especially on the roles of two sHsps, HspB8 and αB-crystallin (CryAB, HspB5), in cardiac health and disease.