Proline-rich protein 5 (PRR5), also known as Protor-1, is a 388 amino acid protein in Protor family, is thought to act as a tumor suppressor in breast and colorectal tumorigenesis. PRR5 is widely expressed and possesses two RICTOR interaction sites and a C-terminal Proline rich region. It promotes Rapamycin complex 2 (mTORC2) activity. There are four isoforms of PRR5 that are produced as a result of alternative splicing events and these isoforms play an important role in the modulation of platelet-derived growth factor signaling and in the regulation of PDGFR-β expression.Synonyms: PROTOR1, Proline-rich protein 5, Protein observed with Rictor-1, Protor-1