SLC39A9 transports zinc ions across cell and organelle membranes into the cytoplasm and regulates intracellular zinc homeostasis. It participates in zinc efflux out of the secretory compartments. In response to B cell receptor (BCR) activation, the zinc level it regulates enhances phosphorylation of AKT1 and MAPK3/MAPK1 (Erk1/2).

The protein has a second, distinct role as a membrane androgen receptor. Through a G protein, it mediates the non-classical androgen signalling pathway, which activates MAPK3/MAPK1 (Erk1/2) and the transcription factors CREB1 or ATF1. This pathway contributes to CLDN1 and CLDN5 expression and to tight junction formation between adjacent Sertoli cells. In vascular endothelial cells, androgen acting through SLC39A9 activates an inhibitory G protein, leading to AKT1 and MAPK3/MAPK1 activation, inhibitory phosphorylation of GSK3B and modulation of CCND1 transcription, which drives cell proliferation. SLC39A9 is described as having dual functions, as a membrane-bound androgen receptor and as an androgen-dependent zinc transporter, both mediated through an inhibitory G protein (Gi) that links MAP kinase and zinc signalling to an androgen-dependent apoptotic process.

The SLC39A9 gene belongs to the solute carrier family 39 and encodes a member of the ZIP transporter (TC 2.A.5) family. The protein is found in the trans-Golgi network membrane, cell membrane, perinuclear cytoplasm, mitochondrion and nucleus. NCBI Gene lists G protein-coupled receptor activity, androgen binding and zinc efflux transmembrane transporter activity among its molecular functions. The previous gene name was solute carrier family 39, member 9.