G-protein coupled receptor family C group 5 member B is a protein that in humans is encoded by the GPRC5B gene.

The protein encoded by this gene is a member of the type 3 G protein-coupled receptor family. Members of this superfamily are characterized by a signature 7-transmembrane domain motif. The specific function of this protein is unknown; however, this protein may mediate the cellular effects of retinoic acid on the G protein signal transduction cascade.

Dominant mutations in GPRC5B have been identified as an ultra-rare cause of the neurological white matter disease Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC). Affected individuals present with early-onset macrocephaly, mild motor developmental delay, slowly progressive ataxia, and characteristic brain MRI findings including diffuse white matter abnormalities and subcortical cysts. Disruption of GPRC5B impairs brain water homeostasis, leading to the clinical and radiological features of this leukodystrophy.

This article incorporates text from the United States National Library of Medicine, which is in the public domain.