Regulates the traffic and/or budding of caveolae. Plays a role in caveola formation in a tissue-specific manner. Required for the formation of caveolae in smooth muscle but not in the lung and heart endothelial cells. Regulates the equilibrium between cell surface-associated and cell surface-dissociated caveolae by promoting the rapid release of caveolae from the cell surface. Plays a role in the regulation of the circadian clock. Modulates the period length and phase of circadian gene expression and also regulates expression and interaction of the core clock components PER1/2 and CRY1/2 (By similarity). Seems to have an immune potentiation function, especially in the glioma (PubMed:15197346). Component of the CAVIN complex composed of CAVIN1, CAVIN2, CAVIN3 and CAVIN4. Interacts with PRKCD and with phosphatidylserine. Phosphatidylserine may form a bridge between PKC and PKC-binding partners and stabilize the binding. Interacts with PER2. Interacts with CAVIN1 and EPS15L1. Interacts (via leucine-zipper domain) with CAV1 in a cholesterol-sensitive manner. Localizes in the caveolae in a caveolin-dependent manner. Up-regulated by 1,2-dithiole-3-thione (D3T). The leucine-zipper domain is essential for its localization in the caveolae and for its interaction with CAV1 and EPS15L1. In vitro, phosphorylated by PRKCD. Belongs to the CAVIN family.