Progestin And AdipoQ Receptor Family, Member IV (PAQR4)

The PAQR family of proteins comprises an intriguing group of newly discovered receptors. Although the agonist is known for 5 of the 11 human PAQRs, most are considered “orphan” receptors. The fact that all five human class II receptors are activated by the same agonist ligand agonists for orphaned receptors could be predicted on the basis of phylogenetic analysis. Because PAQR1 and PAQR2 respond to adiponectin, we hypothesized that their closest human homologs, PAQR3 and PAQR4, could as well. PAQR3, but not PAQR4, can sense and respond to adiponectin, making PAQR3 a likely candidate for a third adiponectin receptor from the PAQR family. This finding is intriguing because PAQR3 has already been identified as a protein that prevents tumorigenesis.