Cell surface glycoprotein receptor involved in the costimulatory signal essential for T-cell receptor (TCR)-mediated T-cell activation. Acts as a positive regulator of T-cell coactivation, by binding at least ADA, CAV1, IGF2R, and PTPRC. Its binding to CAV1 and CARD11 induces T-cell proliferation and NF- kappa-B activation in a T-cell receptor/CD3-dependent manner. Its interaction with ADA also regulates lymphocyte-epithelial cell adhesion. In association with FAP is involved in the pericellular proteolysis of the extracellular matrix (ECM), the migration and invasion of endothelial cells into the ECM. May be involved in the promotion of lymphatic endothelial cells adhesion, migration and tube formation. When overexpressed, enhanced cell proliferation, a process inhibited by GPC3. Acts also as a serine exopeptidase with a dipeptidyl peptidase activity that regulates various physiological processes by cleaving peptides in the circulation, including many chemokines, mitogenic growth factors, neuropeptides and peptide hormones. Removes N-terminal dipeptides sequentially from polypeptides having unsubstituted N-termini provided that the penultimate residue is proline. Belongs to the peptidase S9B family. DPPIV subfamily. Note: This description may include information from UniProtKB.
Molecular Function: dipeptidyl-peptidase activity; identical protein binding; protease binding; protein binding; protein homodimerization activity; receptor binding; serine-type endopeptidase activity; serine-type peptidase activity; viral receptor activity
Biological Process: behavioral fear response; cell adhesion; endothelial cell migration; entry of virus into host cell; positive regulation of cell proliferation; proteolysis; regulation of cell-cell adhesion mediated by integrin; regulation of insulin secretion; response to hypoxia; T cell activation; T cell costimulation