Substrate-recognition component of a DCX (DDB1-CUL4-X-box) E3 ubiquitin-protein ligase complex involved in cell cycle control and autophagy (PubMed:20921139, PubMed:23524951, PubMed:24587252, PubMed:33854232, PubMed:33854235, PubMed:33854239, PubMed:32333458). The DCX(AMBRA1) complex specifically mediates the polyubiquitination of target proteins such as BECN1, CCND1, CCND2, CCND3, ELOC and ULK1 (PubMed:23524951, PubMed:33854232, PubMed:33854235, PubMed:33854239). Acts as an upstream master regulator of the transition from G1 to S cell phase: AMBRA1 specifically recognizes and binds phosphorylated cyclin-D (CCND1, CCND2 and CCND3), leading to cyclin-D ubiquitination by the DCX(AMBRA1) complex and subsequent degradation (PubMed:33854232, PubMed:33854235, PubMed:33854239). By controlling the transition from G1 to S phase and cyclin-D degradation, AMBRA1 acts as a tumor suppressor that promotes genomic integrity during DNA replication and counteracts developmental abnormalities and tumor growth (PubMed:33854232, PubMed:33854235, PubMed:33854239). AMBRA1 also regulates the cell cycle by promoting MYC dephosphorylation and degradation independently of the DCX(AMBRA1) complex: acts via interaction with the catalytic subunit of protein phosphatase 2A (PPP2CA), which enhances interaction between PPP2CA and MYC, leading to MYC dephosphorylation and degradation (PubMed:25803737, PubMed:25438055). Acts as a regulator of Cul5-RING (CRL5) E3 ubiquitin-protein ligase complexes by mediating ubiquitination and degradation of Elongin-C (ELOC) component of CRL5 complexes (PubMed:25499913, PubMed:30166453). Acts as a key regulator of autophagy by modulating the BECN1-PIK3C3 complex: controls protein turnover during neuronal development, and regulates normal cell survival and proliferation (PubMed:21358617). In normal conditions, AMBRA1 is tethered to the cytoskeleton via interaction with dyneins DYNLL1 and DYNLL2 (PubMed:20921139). Upon autophagy induction, AMBRA1 is released from the cytoskeletal docking site to induce autophagosome nucleation by mediating ubiquitination of proteins involved in autophagy (PubMed:20921139). The DCX(AMBRA1) complex mediates 'Lys-63'-linked ubiquitination of BECN1, increasing the association between BECN1 and PIK3C3 to promote PIK3C3 activity (By similarity). In collaboration with TRAF6, AMBRA1 mediates 'Lys-63'-linked ubiquitination of ULK1 following autophagy induction, promoting ULK1 stability and kinase activity (PubMed:23524951). Also activates ULK1 via interaction with TRIM32: TRIM32 stimulates ULK1 through unanchored 'Lys-63'-linked polyubiquitin chains (PubMed:31123703). Also acts as an activator of mitophagy via interaction with PRKN and LC3 proteins (MAP1LC3A, MAP1LC3B or MAP1LC3C); possibly by bringing damaged mitochondria onto autophagosomes (PubMed:21753002, PubMed:25215947). Also activates mitophagy by acting as a cofactor for HUWE1; acts by promoting HUWE1-mediated ubiquitination of MFN2 (PubMed:30217973). AMBRA1 is also involved in regulatory T-cells (Treg) differentiation by promoting FOXO3 dephosphorylation independently of the DCX(AMBRA1) complex: acts via interaction with PPP2CA, which enhances interaction between PPP2CA and FOXO3, leading to FOXO3 dephosphorylation and stabilization (PubMed:30513302). May act as a regulator of intracellular trafficking, regulating the localization of active PTK2/FAK and SRC (By similarity). Also involved in transcription regulation by acting as a scaffold for protein complexes at chromatin (By similarity). Protein modification; protein ubiquitination. Component of the DCX(AMBRA1) E3 ubiquitin ligase complex, also named CRL4(AMBRA1), at least composed of CUL4 (CUL4A or CUL4B), DDB1, AMBRA1 and RBX1 (PubMed:25499913, PubMed:16949367, PubMed:30166453, PubMed:33854232, PubMed:33854239). Interacts with BECN1 (PubMed:21358617, PubMed:25438055). Probably forms a complex with BECN1 and PIK3C3 (By similarity). Interacts with BECN2 (PubMed:23954414). Interacts with BCL2; leading to prevent interaction with BCN1 and autophagy, interaction is disrupted upon autophagy induction (PubMed:21358617). Interacts with ULK1 (PubMed:25438055). Interacts (via PxP motifs) with PPP2CA; enhancing interaction between PPP2CA and MYC or FOXO3 (PubMed:25438055, PubMed:30513302). Forms a complex with PPP2CA and BECN1; AMBRA1 and BECN1 components of the complex regulate MYC stability via different pathways (PubMed:25803737). Interacts (TQT motifs) with DYNLL1 and DYNLL2; tethering AMBRA1 and the BECN1-PIK3C3 complex in absence of autophagy (PubMed:20921139). Interacts with TRAF6; interaction is required to mediate 'Lys-63'-linked ubiquitination of ULK1 (PubMed:23524951). Interacts with TRIM32; promoting activation of ULK1 by TRIM32 via unanchored 'Lys-63'-linked polyubiquitin chains (PubMed:31123703). Interacts with PRKN (By similarity). Interacts (via LIR motif) with LC3 (MAP1LC3A, MAP1LC3B or MAP1LC3C) (PubMed:25215947, PubMed:30217973). Interacts with HUWE1 (PubMed:30217973). Interacts with PTK2/FAK (By similarity). Interacts with SRC; required for SRC trafficking to autophagosomes (By similarity). Localizes to the cytoskeleton in absence of autophagy induction (PubMed:20921139). Upon autophagy induction, AMBRA1 relocalizes to the endoplasmic reticulum to enable autophagosome nucleation (PubMed:20921139). Partially localizes at mitochondria in normal conditions (PubMed:21358617). Localizes also to discrete punctae along the ciliary axoneme (By similarity). Negatively regulated by microRNA 7-3HG (miR7-3HG), which targets the 3' untranslated (3'-UTR) region of AMBRA1 transcripts, leading to a decrease of AMBRA1 mRNA and protein levels, thereby inhibiting autophagy (PubMed:28059583). Strongly up-regulated during egulatory T-cells (Treg) differentiation (PubMed:30513302). The PxP motifs mediate interaction with the catalytic subunit of protein phosphatase 2A (PPP2CA). The TQT motifs mediate interaction with the dynein light chain proteins DYNLL1 and DYNLL2, tethering AMBRA1 to the cytoskeleton in absence of autophagy. The LIR motif (LC3-interacting region) is required for the interaction with the ATG8 family proteins GABARAP and MAP1LC3B. Phosphorylation at Ser-52 by MTOR inhibits its ability to regulate autophagy and mediate ubiquitination of ULK1 (PubMed:23524951). Phosphorylation by ULK1 in response to autophagy induction abolishes interaction with DYNLL1 and DYNLL2, releasing AMBRA1 from the cytoskeletal docking site to induce autophagosome nucleation (PubMed:20921139). Phosphorylation by MTOR inhibits interaction with PPP2CA and subsequent dephosphorylation of MYC (PubMed:25438055). Phosphorylation at Ser-1043 by CHUK/IKKA promotes its interaction with ATG8 family proteins GABARAP and MAP1LC3B and its mitophagic activity (PubMed:30217973). Ubiquitinated by RNF2 via 'Lys-48'-linkage in unstressed cells, leading to its degradation by the proteasome (PubMed:25499913). Induction of autophagy promotes stabilization via interaction with CUL4 (CUL4A or CUL4B) and DDB1 (PubMed:25499913). Upon prolonged starvation, ubiquitinated and degraded, terminating the autophagy response (PubMed:25499913). Undergoes proteolytic processing by caspase-6 (CASP6), caspase-7 (CASP7) and caspase-8 (CASP8) during apoptosis, resulting in the dismantling of the autophagic machinery and the accomplishment of the programmed cell death program (PubMed:22441670). Also cleaved by calpains during apoptosis, which mediate a complete proteolytic degradation (PubMed:22441670). Belongs to the WD repeat AMBRA1 family.