Caveolae and the cardiac myocyte

Caveolae, invaginated lipid rafts, orchestrate signalling in the cardiac myocyte. Here we highlight advances in the field which are relevant to the role of caveolae in these cells. Recent analysis of the molecular organisation and structure of the coat complex, which lines the internal surface of caveolae, suggest a stable inner caveolin layer covered with a filamentous cavin network. Ubiquitous caveolin 1 (Cav1) and muscle-specific Cav3 are expressed and functionally relevant in the cardiac cell. Caveolin acts as a constitutive brake on a number of signalling proteins (e.g. endothelial nitric oxide synthase, eNOS) in the myocyte, but the molecular basis of these interactions has been questioned. The position of cavins within the coat confers a lability to these proteins and this is supported by data showing cavin detachment from caveolae with osmotic stress in non-cardiac cells, and cavin translocation to caveolae in response to b-adrenoceptor signalling in cardiac cells. The protection that caveolae and/or caveolin provide against ischaemia-reperfusion injury, together with evidence that Cav3 overexpression can reverse some characteristics of the failing myocyte, suggest that these structures are a potential target of cardiac disease treatments in the future.