This gene encodes a member of the proline-rich protein family. The encoded protein has multiple proposed functions, including roles in pain suppression, penile erection, and protection of the eye surface. The QRFSR pentapeptide, known as opiorphin, is derived from the N-terminal of this protein. Opiorphin inhibits the enkephalin-inactivating peptidases neprilysin and aminopeptidase N, and this activity is thought to reduce sensitivity to painful stimuli by effecting enkephalin-related activation of opioid-dependent pathways. Opiorphin may also act as an anti-depressant. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Nov 2014].