Calcium-dependent phospholipid-binding protein that plays a role in calcium-mediated intracellular processes. Involved in the TNF-alpha receptor signaling pathway in a calcium-dependent manner. Exhibits calcium-dependent phospholipid binding properties. Plays a role in neuronal progenitor cell differentiation; induces neurite outgrowth via a AKT-dependent signaling cascade and calcium-independent manner. May recruit target proteins to the cell membrane in a calcium-dependent manner. May function in membrane trafficking. Involved in TNF-alpha-induced NF-kappa-B transcriptional repression by inducing endoprotease processing of the transcription factor NF-kappa-B p65/RELA subunit. Also induces endoprotease processing of NF-kappa-B p50/NFKB1, p52/NFKB2, RELB and REL. Homodimer; homodimerizes via its C2 domains. Interacts with p65/RELA (via N-terminus); this interaction induces proteolytic cleavage of p65/RELA subunit and inhibition of NF-kappa-B transcriptional activity. Interacts (via VWFA domain) with ACTB, CCDC22, MYCBP2, PPP5C, RDX and UBE2O. Translocates to the cell membrane in a calcium-dependent manner. C2 domains are necessary for calcium-dependent cell membrane association. C2 domains are necessary for neuronal progenitor cell differentiation in a calcium-independent manner. Belongs to the copine family.