Associates with the cytoplasmic domain of a variety of cadherins. The association of catenins to cadherins produces a complex which is linked to the actin filament network, and which seems to be of primary importance for cadherins cell-adhesion properties. Can associate with both E- and N-cadherins. Originally believed to be a stable component of E-cadherin/catenin adhesion complexes and to mediate the linkage of cadherins to the actin cytoskeleton at adherens junctions. In contrast, cortical actin was found to be much more dynamic than E-cadherin/catenin complexes and CTNNA1 was shown not to bind to F-actin when assembled in the complex suggesting a different linkage between actin and adherens junctions components. The homodimeric form may regulate actin filament assembly and inhibit actin branching by competing with the Arp2/3 complex for binding to actin filaments. Involved in the regulation of WWTR1/TAZ, YAP1 and TGFB1-dependent SMAD2 and SMAD3 nuclear accumulation (By similarity). May play a crucial role in cell differentiation. Monomer and homodimer; the monomer preferentially binds to CTNNB1 and the homodimer to actin (By similarity). Component of an cadherin:catenin adhesion complex composed of at least of CDH26, beta-catenin/CTNNB1, alpha-catenin/CTNNA1 and p120 catenin/CTNND1 (PubMed:28051089). Possible component of an E-cadherin/ catenin adhesion complex together with E-cadherin/CDH1 and beta-catenin/CTNNB1 or gamma-catenin/JUP; the complex is located to adherens junctions (By similarity). The stable association of CTNNA1 is controversial as CTNNA1 was shown not to bind to F-actin when assembled in the complex (By similarity). Alternatively, the CTNNA1-containing complex may be linked to F-actin by other proteins such as LIMA1 (By similarity). Binds AFDN and F-actin (By similarity). Interacts with ARHGAP21 (PubMed:16184169). Interacts with AJUBA (PubMed:12417594). Interacts with LIMA1 (PubMed:18093941). Interacts with vinculin/VCL (PubMed:26691986). Found at cell-cell boundaries and probably at cell-matrix boundaries. Expressed ubiquitously in normal tissues. Sumoylated. Phosphorylation seems to contribute to the strength of cell-cell adhesion rather than to the basic capacity for cell-cell adhesion. Germline CTNNA1 truncating mutations have been detected in patients with hereditary diffuse gastric cancer (HDGC) and may play a role in disease susceptibility. Diffuse gastric cancer is a malignant disease characterized by poorly differentiated infiltrating lesions resulting in thickening of the stomach. Malignant tumors start in the stomach, can spread to the esophagus or the small intestine, and can extend through the stomach wall to nearby lymph nodes and organs. It also can metastasize to other parts of the body. The disease is caused by variants affecting the gene represented in this entry. Expressed at high levels in the nervous system. Lacks the beta-catenin interaction domain. Belongs to the vinculin/alpha-catenin family.