Cell membrane-cytoskeleton-associated protein that plays a role in the regulation of actin polymerization at the barbed end of actin filaments. Prevents F-actin heterodimeric capping protein (CP) activity at the leading edges of migrating cells, and hence generates uncapped barbed ends and enhances actin polymerization (PubMed:26466680). Plays a role in cell protrusion formations; involved in cell polarity, lamellipodial assembly, membrane ruffling and macropinosome formations (PubMed:19846667, PubMed:26578515, PubMed:26466680). Involved as well in cell migration and invadopodia formation during wound healing (PubMed:19846667, PubMed:26578515, PubMed:26466680). Required for CD28-mediated stimulation of NF-kappa-B signaling, involved in naive T cells activation, maturation into T memory cells, and differentiation into T helper and T regulatory cells (PubMed:27647349, PubMed:27647348, PubMed:28112205). Forms homodimers (PubMed:27647349, PubMed:27647348). Interacts (via C-terminus) with heterodimeric capping protein (CP); the interaction inhibits CP activity and hence promotes actin polymerization at the barbed end of actin filaments (PubMed:26466680). Colocalizes to dynamic vimentin filaments both in the central cytoplasm and at leading edges of migrating cells (PubMed:26578515, PubMed:26466680, PubMed:19846667). Colocalizes with F-actin, Arp2/3 complex and cortactin to leading edge lamellipodia, ruffles and macropinosomes of migrating cells (PubMed:26578515). Expressed in all tissues tested, including thymus, spleen, colon, leukocytes, peripheral blood, skin, skin keratinocytes and skin fibroblasts. Strong expression is detected in naive and memory CD4+ and CD8+ T cells, naive and memory B cells, regulatory T cells and NK cells, whereas it is poorly expressed in monocytes (PubMed:27647349). Expressed in fetal skin. The N-terminal leucine-rich repeat (LRR) domain is necessary for localization to vimentin filaments (PubMed:26466680). The C-terminus is necessary for localization to the cell membrane (PubMed:26578515). The disease is caused by variants affecting the gene represented in this entry. Belongs to the CARMIL family.