Functions as a key regulator of cell membrane composition by regulating protein surface expression. Also, plays a role in regulation of processes including cell migration, cell proliferation, cell contraction and cell adhesion. Regulates transepithelial migration of neutrophils into the alveolar lumen, potentially via mediation of cell surface expression of adhesion markers and lipid raft formation (By similarity). Negatively regulates caveolae formation by reducing CAV1 expression and CAV1 amount by increasing lysosomal degradation (By similarity). Facilitates surface trafficking and the formation of lipid rafts bearing GPI-anchor proteins (By similarity). Regulates surface expression of MHC1 and ICAM1 proteins increasing susceptibility to T-cell mediated cytotoxicity (By similarity). Regulates the plasma membrane expression of the integrin heterodimers ITGA6-ITGB1, ITGA5-ITGB3 and ITGA5-ITGB1 resulting in modulation of cell-matrix adhesion (By similarity). Also regulates many processes through PTK2 (By similarity). Regulates blood vessel endothelial cell migration and angiogenesis by regulating VEGF protein expression through PTK2 activation (By similarity). Regulates cell migration and cell contraction through PTK2 and SRC activation (By similarity). Regulates focal adhesion density, F-actin conformation and cell adhesion capacity through interaction with PTK2 (By similarity). Positively regulates cell proliferation (By similarity). Plays a role during cell death and cell blebbing. Promotes angiogenesis and vasculogenesis through induction of VEGFA via a HIF1A-dependent pathway (By similarity). Also plays a role in embryo implantation by regulating surface trafficking of integrin heterodimer ITGA5-ITGB3 (By similarity). Plays a role in placental angiogenesis and uterine natural killer cell regulation at the maternal-fetal placental interface, however not required in the maternal tissues for a viable pregnancy (By similarity). Involved in the early stages of embryogenic development and cardiogenesis, potentially via regulation of epithelial-mesenchymal transition timing (By similarity). May play a role in glomerular filtration (By similarity). Interacts with PTK2; regulates PTK2 activation and localization (By similarity). Interacts with ITGB3; regulates the levels of the heterodimer ITGA5-ITGB3 integrin surface expression (By similarity). Interacts with P2RX7 (via C-terminus) (By similarity). Interacts with ITGB1; the interaction may be direct or indirect and ITGB1 has a heterodimer form (By similarity). Localizes in cytoplasm, foot processes and cell bodies of podocytes and nucleus of endothelial cells of kidney (PubMed:24814193). Localizes to the apical cell surface in the luminal epithelium and glandular epithelium. Colocalized with ITGB1 and GPI-anchor proteins on plasma membrane (By similarity). Expressed in glomeruli. Belongs to the PMP-22/EMP/MP20 family.