Associates with proteins harboring glycine-rich transmembrane domains and ensures their efficient localization to the cell surface (PubMed:25999474). Regulates the assembly and activity of V-ATPase in colon cancer cells via its interaction with V-type proton ATPase subunit H (ATP6V1H) and contributes to V-ATPase-mediated pH alterations in cancer cells which play an important role in drug resistance and invasiveness of colon cancer cells (PubMed:25659576). Plays an important role in an atypical phagocytic activity of metastatic melanoma cells called cannibalism and is involved in the pH regulation of the intracellular vesicles in tumor cells (PubMed:19893578). Interacts with ATP6V1H in colon cancer cells (PubMed:25659576). Highly expressed in metastatic melanoma cells whereas it is undetectable in primary melanoma cells, healthy skin tissues and peripheral blood lymphocytes. Expressed in CD34(+) hematopoietic progenitor cells and during monocyte and granulocyte differentiation. Overexpressed in acute myeloid leukemia, in particular in those displaying granulocytic differentiation (at protein level). Transcriptionally repressed following hypoxia by HIF1A in leukemic cells. Belongs to the nonaspanin (TM9SF) (TC 9.A.2) family.