Altered cAMP-mediated signalling and its role in the pathogenesis of dilated cardiomyopathy

Alterations in the level and function of proteins involved in cAMP-mediated signalling are important in the pathophysiology and treatment of dilated cardiomyopathy. What is unclear is the extent to which these alterations, which attenuate receptor-stimulated cAMP generation, contribute to the pathogenesis of dilated cardiomyopathy and the extent to which they constitute a beneficial compensatory response. Studies in animals involving overexpression and ablation of proteins or peptides involved in cAMP-mediated signalling have yielded disparate results that are difficult to reconcile with a simple hypothesis. Our ability to understand these differences is limited by the lack of information on how these different genetic manipulations affect the phosphorylation of individual substrates of protein kinase A (PK-A) through which cAMP signals are transduced. This is important in view of evidence that the phosphorylation of individual PK-A substrates can be regulated selectively in different intracellular compartments, and that the phosphorylation of some PK-A substrates is increased in dilated cardiomyopathy while the phosphorylation of others is reduced. Approaches that quantify changes in the phosphorylation of individual PK-A substrates in models of dilated cardiomyopathy will provide information that may allow a better understanding of the pathogenesis of the syndrome and a more rational approach to its treatment.