GPR101 drives growth hormone hypersecretion and gigantism in mice via constitutive activation of Gs and Gq/11

Growth hormone (GH) is a key modulator of growth and GH over-secretion can lead to gigantism. One form is X-linked acrogigantism (X-LAG), in which infants develop GH-secreting pituitary tumors over-expressing the orphan G-protein coupled receptor, GPR101. The role of GPR101 in GH secretion remains obscure. We studied GPR101 signaling pathways and their effects in HEK293 and rat pituitary GH3 cell lines, human tumors and in transgenic mice with elevated somatotrope Gpr101 expression driven by the rat Ghrhr promoter ( Ghrhr Gpr101 ) . Here, we report that Gpr101 causes elevated GH/prolactin secretion in transgenic Ghrhr Gpr101 mice but without hyperplasia/tumorigenesis. We show that GPR101 constitutively activates not only G s , but also G q/11 and G 12/13 , which leads to GH secretion but not proliferation. These signatures of GPR101 signaling, notably PKC activation, are also present in human pituitary tumors with high GPR101 expression. These results underline a role for GPR101 in the regulation of somatotrope axis function. Growth hormone (GH) is a major modulator of physical growth and metabolism that is under tight regulatory control. Here the authors describe the signaling profile of GPR101, an orphan receptor that enhances GH secretion principally via constitutively activated Gs-PKA and Gq/11-PKC pathways.