GPRC6A is closely related to the CaSR, sharing 34% sequence conservation. Similar to the CaSR, GPRC6A is widely expressed, although its expression differs between species. In humans, GPRC6A is predominantly found in the brain, skeletal muscle, testis, leukocytes, liver, heart, kidney, and spleen, with low expression in the lungs, pancreas, placenta, and ovaries. GPRC6A is activated by L-amino acids, with L-Arg, L-Orn, L-Lys and L-Ala being the most potent. To better elucidate the physiological and pathological roles of GPCR6A, selective pharmacological tools are sorely needed[1].