May act as a scaffolding protein within caveolar membranes (By similarity). 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 (PubMed:19546242). 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 (PubMed:10816572). 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 BMX, BTK, CTNNB1, CDH1, GLIPR2, JUP, NOSTRIN, SNAP25 and STX1A. Interacts with SLC7A9. Interacts with TGFBR1 (By similarity). Interacts with CTNNB1, CDH1 and JUP. Interacts with PACSIN2; this interaction induces membrane tubulation (PubMed:21610094). Interacts with CAVIN3 (via leucine-zipper domain) in a cholesterol-sensitive manner. Interacts with EHD2 in a cholesterol-dependent manner (By similarity). Interacts with CAVIN1 (PubMed:19546242). Forms a ternary complex with UBXN6 and VCP; mediates CAV1 targeting to lysosomes for degradation (By similarity). 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 (PubMed:16877379). Colocalized with DPP4 in membrane rafts. Potential hairpin-like structure in the membrane. Membrane protein of caveolae (By similarity). Adipose tissue, lung, heart, skeletal muscle, stomach, small bowel, kidney, spleen and testis (at protein level). The N-terminus of both isoforms are blocked. 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.