Muscle Creatine Kinase Deficiency Triggers Both Actin Depolymerization and Desmin Disorganization by Advanced Glycation End Products in Dilated Cardiomyopathy

Alterations in the balance of cytoskeleton as well as energetic proteins are involved in the cardiac remodeling occurring in dilated cardiomyopathy (DCM). We used two-dimensional DIGE proteomics as a discovery approach to identify key molecular changes taking place in a temporally controlled model of DCM triggered by cardiomyocyte-specific serum response factor (SRF) knock-out in mice. We identified muscle creatine kinase (MCK) as the primary down-regulated protein followed by alpha-actin and alpha-tropomyosin down-regulation leading to a decrease of polymerized F-actin. The early response to these defects was an increase in the amount of desmin intermediate filaments and phosphorylation of the alpha B-crystallin chaperone. We found that alpha B-crystallin and desmin progressively lose their striated pattern and accumulate at the intercalated disk and the sarcolemma, respectively. We further show that desmin is a preferential target of advanced glycation end products (AGE) in mouse and human DCM. Inhibition of CK in cultured cardiomyocytes is sufficient to recapitulate both the actin depolymerization defect and the modification of desmin by AGE. Treatment with either cytochalasin D or glyoxal, a cellular AGE, indicated that both actin depolymerization and AGE contribute to desmin disorganization. Heat shock-induced phosphorylation of alpha B-crystallin provides a transient protection of desmin against glyoxal in a p38 MAPK-dependent manner. Our results show that the strong down-regulation of MCK activity contributes to F-actin instability and induces post-translational modification of alpha B-crystallin and desmin. Our results suggest that AGE may play an important role in DCM because they alter the organization of desmin filaments that normally support stress response and mitochondrial functions in cardiomyocytes.