Structure-function analysis of nuclear receptor and cofactor action: evidence for a role in muscle.

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Hormone receptors have critical roles in almost all aspects of physiology by transducing the effects of hormones into metabolic responses. There are ~45 orphan hormone receptors encoded by distinct genes in humans, since all receptors are important in the treatment of human disease, the plethora of orphan receptors has been the catalyst for the development of a new paradigm, reverse endocrinology. Reverse endocrinology is the process whereby the orphan hormone receptor is used to search for a previously unknown hormone, and metabolic pathway. We are interested in the orphan hormone receptors, Rev-erbA and RVR, orphan members of the receptor superfamily. Rev-erb alpha expression is regulated by fibrates, widely used hypolipidemic drugs, and the circadian cycle. Rev-erbs mediate the regulation of lipid metabolism and peroxisomal beta oxidation. Furthermore, Rev-erbs are acutely induced during brain seizures, postulated to regulate cerebellar plasticity, and involved in growth control. In view of these critical regulatory roles, and the success of reverse endocrinology to date, we intend to complete the structural analysis of the Rev-erb and RVR as a tool to identify the hormone that binds this receptor. Hormone receptors recruit proteins called nuclear receptor cofactors, that function as regulators of gene expression. The cofactors regulate gene expression and development. Furthermore these cofactors, when misregulated result in the onset of disease and carcinogenesis, which underscores the need for achieving a high resolution view of their function in many tissues. Along these lines, we are interested in exmining the function of these cofactors in muscle. Understanding the molecular role of the NR cofactors during muscle differentiation will be a critical step toward elucidating the dysregulation-function of these proteins in muscle diseases, such as rhabdomyosarcoma and inflammatory myopathy that have cofactor deficiency.