Hsp20 and its cardioprotection.

The small heat shock protein Hsp20, also referred to as P20/HspB6, is expressed in the brain, stomach, liver, lung, kidney, blood, smooth muscle, skeletal muscle, and cardiac tissue. Although Hsp20 is not heat-inducible, several cellular signaling pathways appear to regulate its biologic functions. In recent years, tremendous advances have been made in elucidating the significance of Hsp20 in smooth muscle and its potential benefits on coronary vasculature. Of interest, recent findings have demonstrated that sustained beta-adrenergic stimulation results in expression and phosphorylation of cardiac Hsp20. Moreover, Hsp20 overexpression enhances cardiac function and renders cardioprotection against beta-agonist-mediated apoptosis and ischemia/reperfusion injury ex vivo and in vivo. This article reviews the new findings on translocation of Hsp20 in response to various stimuli and the multiple cellular targets of Hsp20, with special emphasis on its protective effects in the heart.