ZIP9 (Zinc transporter ZIP9, Solute carrier family 39 member 9) is a multi-pass (seven transmembrane regions) membrane protein that belongs to the ZIP transporter (TC 2.A.5) family. Zinc transporters all have transmembrane domains, and are encoded by two SLC (solute-linked carrier) gene families: ZnT (SLC30) and Zip (SLC39). There are at least 9 ZnT and 15 Zip transporters in human cells. Zip transporters are believed to increase intracellular zinc by promoting zinc uptake. This may be facilitated by vesicles within the cell that release release into the cytoplasm. Zip and ZnT transporter families exhibit tissue-specific expression and respond differently to zinc deficiency and excess. ZIP9 has been shown to localize to the trans-Golgi network regardless of zinc presence. ZIP9 is believed to function as a zinc homeostasis regulator acting in the secretory pathway.