Involved in the costimulatory signal essential for T-cell receptor (TCR)-mediated T-cell activation. Its binding to DPP4 induces T-cell proliferation and NF-kappa-B activation in a T-cell receptor/CD3-dependent manner. May act as a scaffolding protein within caveolar membranes. Interacts directly with G-protein alpha subunits and can functionally regulate their activity. Forms a stable heterooligomeric complex with CAV2 that targets to lipid rafts and drives caveolae formation. Recruits CTNNB1 to caveolar membranes and may regulate CTNNB1-mediated signaling through the Wnt pathway. Negatively regulates TGFB1-mediated activation of SMAD2/3 by mediating the internalization of TGFBR1 from membrane rafts leading to its subsequent degradation. Mediates the recruitment of CAVIN proteins (CAVIN1/2/3/4) to the caveolae. May act as a scaffolding protein within caveolar membranes. Forms a stable heterooligomeric complex with CAV2 that targets to lipid rafts and drives caveolae formation. Mediates the recruitment of CAVIN proteins (CAVIN1/2/3/4) to the caveolae (By similarity). Interacts directly with G-protein alpha subunits and can functionally regulate their activity (By similarity). Involved in the costimulatory signal essential for T-cell receptor (TCR)-mediated T-cell activation. Its binding to DPP4 induces T-cell proliferation and NF-kappa-B activation in a T-cell receptor/CD3-dependent manner (By similarity). Recruits CTNNB1 to caveolar membranes and may regulate CTNNB1-mediated signaling through the Wnt pathway (By similarity). Negatively regulates TGFB1-mediated activation of SMAD2/3 by mediating the internalization of TGFBR1 from membrane rafts leading to its subsequent degradation (By similarity). Homooligomer. Interacts (via the N-terminus) with DPP4; the interaction is direct. Forms a stable heterooligomeric complex with CAV2 that targets to lipid rafts and drives caveolae formation. Interacts with PACSIN2; this interaction induces membrane tubulation (By similarity). Interacts with BMX, BTK, CTNNB1, CDH1, GLIPR2, JUP, NOSTRIN, SNAP25 and STX1A. Interacts with SLC7A9. Interacts with TGFBR1. Interacts with CAVIN3 (via leucine-zipper domain) in a cholesterol-sensitive manner. Interacts with CAVIN1. Interacts with EHD2 in a cholesterol-dependent manner. Forms a ternary complex with UBXN6 and VCP; mediates CAV1 targeting to lysosomes for degradation. Interacts with ABCG1; this interaction regulates ABCG1-mediated cholesterol efflux (By similarity). Interacts with NEU3; this interaction enhances NEU3 sialidase activity within caveola. Interacts (via C-terminus) with SPRY1, SPRY2 (via C-terminus), SPRY3, and SPRY4 (By similarity). Colocalized with DPP4 in membrane rafts. Potential hairpin-like structure in the membrane. Membrane protein of caveolae (By similarity). Phosphorylated at Tyr-14 by ABL1 in response to oxidative stress. Ubiquitinated. Undergo monoubiquitination and multi- and/or polyubiquitination. Monoubiquitination of N-terminal lysines promotes integration in a ternary complex with UBXN6 and VCP which promotes oligomeric CAV1 targeting to lysosomes for degradation. Belongs to the caveolin family.