Tumor suppressor. Promotes rapid degradation of CTNNB1 and participates in Wnt signaling as a negative regulator. APC activity is correlated with its phosphorylation state. Activates the GEF activity of SPATA13 and ARHGEF4. Plays a role in hepatocyte growth factor (HGF)-induced cell migration (By similarity). Required for MMP9 up-regulation via the JNK signaling pathway in colorectal tumor cells. Acts as a mediator of ERBB2-dependent stabilization of microtubules at the cell cortex. It is required for the localization of MACF1 to the cell membrane and this localization of MACF1 is critical for its function in microtubule stabilization (By similarity). Forms homooligomers and heterooligomers with APC2. Interacts with PDZ domains of DLG1 and DLG3. Associates with catenins. Binds axin. Interacts with MAPRE2 and MAPRE3 (via C-terminus). Found in a complex consisting of ARHGEF4, APC and CTNNB1. Interacts with ARHGEF4 (via N-terminus) (By similarity). Interacts with MAPRE1 (via C-terminus); probably required for APC targeting to the growing microtubule plus ends (PubMed:15311282). Interacts with DIAPH1 and DIAPH2 (PubMed:15311282). Interacts with SCRIB; may mediate targeting to adherens junctions of epithelial cells (PubMed:16611247). Interacts with SPATA13 (via N-terminus and SH3 domain). Interacts with ASAP1 (via SH3 domain) (By similarity). Found in a complex composed of MACF1, APC, AXIN1, CTNNB1 and GSK3B. Interacts at the cell membrane with AMER1 and AMER2 (via ARM repeats) (By similarity). Interacts with KHDRBS1 (By similarity). The complex composed, at least, of APC, CTNNB1 and GSK3B interacts with JPT1; the interaction requires the inactive form of GSK3B (phosphorylated at 'Ser-9') (By similarity). Associated with the microtubule network at the growing distal tip of microtubules. Accumulates in the lamellipodium and ruffle membrane in response to hepatocyte growth factor (HGF) treatment. The MEMO1-RHOA-DIAPH1 signaling pathway controls localization of the phosphorylated form to the cell membrane. Expressed in liver, spleen, kidney, heart, lung, brain, stomach, intestine, testis and ovary. The microtubule tip localization signal (MtLS) motif; mediates interaction with MAPRE1 and targeting to the growing microtubule plus ends. Phosphorylated by GSK3B. Ubiquitinated, leading to its degradation by the proteasome. Ubiquitination is facilitated by Axin. Deubiquitinated by ZRANB1/TRABID (By similarity). Belongs to the adenomatous polyposis coli (APC) family.