Chapter 5 - GPR101, an orphan G-protein coupled receptor, with roles in growth, puberty, and possibly appetite regulation

Abstract

We recently described X-linked acrogigantism (X-LAG) in sporadic cases of infantile gigantism and a few familial cases of acromegaly in the context of the disorder known as familial isolated pituitary adenomas (FIPA). Both X-LAG and FIPA cases with early onset (in infancy or toddlerhood) gigantism shared copy number gains (CNG) of the distal long arm of chromosome X (Xq26). In all patients described to date with Xq26 CNG and gigantism and/or acromegaly, the only coding gene sequence shared by all chromosomal defects was that of GPR101, a class A, rhodopsin-like orphan guanine nucleotide-binding protein (G protein)-coupled receptor with an as-yet unidentified endogenous ligand. We review what is known about GPR101, specifically its expression profile and animal models, putative causation of X-LAG and other growth hormone-secreting lesions, and we provide an update on the efforts to both understand its function in growth, puberty, and appetite regulation, as well as to identify potential ligands, such as gonadotropin releasing hormone pentapeptide analogs and most recently N-3 docosapentaenoic acid-derived resolvin D5.