Regulatory Roles of the Ubiquitin-Proteasome System in Cardiomyocyte Apoptosis

Cardiovascular disease is the leading cause of death in the western world. The major contributor of all cardiovascular deaths is myocardial infarction, which often progresses into end-stage heart failure. The loss of cardiomyocytes is a key problem in the development of cardiovascular disease. Two main processes mediate cardiomyocyte loss: necrosis and apoptosis. In contrast to necrosis, apoptosis is a well regulated process essential in normal development and tissue homeostasis. Tight regulation of this process is crucial, especially in post mitotic cells lacking regenerative capacity, like cardiomyocytes. The ubiquitin-proteasome system, accounting for 80 to 90% of intracellular protein degradation, appears to be involved in the regulation of apoptosis. In this process, regulation is performed through the degradation of pro- and anti-apoptotic proteins involved in cell cycle control and specific apoptotic pathways. On the one hand, disturbances in this normally well regulated process are associated with a number of cardiovascular diseases. On the other hand, proteasomal dysfunction may result from ischemia, hypertrophy and heart failure, and a number of cardiomyopathies. This paper reviews the current knowledge on the role of the ubiquitin-proteasome systemmediated regulation of cardiomyocyte apoptosis in cardiovascular disease. Finally, within the ubiquitinproteasome system new molecular targets for treatment of cardiovascular disease are suggested.