Functions as a scaffold protein implicated in the regulation of a large spectrum of both general and specialized signaling pathways. Involved in several processes such as innate immune response, inflammation and cell growth inhibition, apoptosis, cell survival, angiogenesis, cell migration and maturation. Also plays a role in cell cycle checkpoint control; reduces G1 phase cyclin levels resulting in G0/G1 cell cycle arrest. Mediates signal transduction by receptor-mediated inflammatory signals, such as the tumor necrosis factor (TNF), interferon (IFN) or lipopolysaccharide (LPS). Modulates the balance between phosphatidylinositol 3-kinase (PI3K)-AKT-mediated cell survival and apoptosis stimulated kinase (MAP3K5)-JNK signaling pathways; sequesters both AKT1 and MAP3K5 and counterbalances the activity of each kinase by modulating their phosphorylation status in response to pro-inflammatory stimuli. Acts as a regulator of the endoplasmic reticulum (ER) unfolded protein response (UPR) pathway; specifically involved in transduction of the ER stress-response to the JNK cascade through ERN1. Mediates TNF-alpha-induced apoptosis activation by facilitating dissociation of inhibitor 14-3-3 from MAP3K5; recruits the PP2A phosphatase complex which dephosphorylates MAP3K5 on 'Ser-966', leading to the dissociation of 13-3-3 proteins and activation of the MAP3K5-JNK signaling pathway in endothelial cells. Acts a negative regulator in the IFN-gamma-mediated JAK-STAT signaling cascade by inhibiting smooth muscle cell (VSMCs) proliferation and intimal expansion, and thus, prevents graft arteriosclerosis (GA). Acts as a GTPase-activating protein (GAP) for the ADP ribosylation factor 6 (ARF6). Promotes hydrolysis of the ARF6-bound GTP and thus, negatively regulates phosphatidylinositol 4,5-bisphosphate (PIP2)-dependent TLR4-TIRAP-MyD88 and NF-kappa-B signaling pathways in endothelial cells in response to lipopolysaccharides (LPS). Binds specifically to phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 3-phosphate (PtdIns3P). In response to vascular endothelial growth factor (VEGFA), acts as a negative regulator of the VEGFR2-PI3K-mediated angiogenic signaling pathway by inhibiting endothelial cell migration and tube formation. In the developing brain, promotes both the transition from the multipolar to the bipolar stage and the radial migration of cortical neurons from the ventricular zone toward the superficial layer of the neocortex in a glial-dependent locomotion process. Probable downstream effector of the Reelin signaling pathway; promotes Purkinje cell (PC) dendrites development and formation of cerebellar synapses. Functions also as a tumor suppressor protein in prostate cancer progression; prevents cell proliferation and epithelial-to-mesenchymal transition (EMT) through activation of the glycogen synthase kinase-3 beta (GSK3B)-induced beta-catenin and inhibition of PI3K-AKT and Ras-MAPK survival downstream signaling cascades, respectively (By similarity). Mediates TNF/TRAF2-induced MAP3K5-JNK activation, while it inhibits CHUK-NF-kappa-B signaling. Functions as a Ras GTPase-activating protein. May act as a tumor suppressor gene. On plasma membrane, exists in an inactive form complexed with TNFR1; in response to TNF-alpha, dissociates from TNFR1 complex, translocates to cytoplasm and forms part of an intracellular signaling complex comprising TRADD, RIPK1, TRAF2 and MAP3K5. Interacts (via NPXY motif) with DAB2 (via PID domain). Interacts (via PH domain) with ERN1. Part of a cytoplasmic complex made of HIPK1, DAB2IP and MAP3K5 in response to TNF-alpha; this complex formation promotes MAP3K5-JNK activation and subsequent apoptosis. Interacts (via N-terminal domain) with JAK2; the interaction occurs in a IFNG/IFN-gamma-dependent manner and inhibits JAK2 autophosphorylation activity. Interacts (via C2 domain) with GSK3B; the interaction stimulates GSK3B kinase activation. Interacts (via C2 domain) with PPP2CA. Interacts (via proline-rich motif) with a regulatory p85 subunit (via SH3 domain) of the PI3K complex; the interaction inhibits the PI3K-AKT complex activity in a TNF-alpha-dependent manner in prostate cancer (PCa) cells. Interacts with AKT1; the interaction is increased in a TNF-alpha-induced manner. Interacts (via C2 domain and active form preferentially) with KDR/VEGFR2 (tyrosine-phosphorylated active form preferentially); the interaction occurs at the late phase of VEGFA response and inhibits KDR/VEGFR2 activity. Interacts (via N-terminus C2 domain) with MAP3K5 ('Ser-966' dephosphorylated form preferentially); the interaction occurs in a TNF-alpha-induced manner. Interacts (via Ras-GAP domain) with the catalytic subunit of protein phosphatase PP2A; the interaction occurs in resting endothelial cells, is further enhanced by TNF-alpha stimulation and is required to bridge PP2A to MAP3K5. Interacts (via C-terminus PER domain) with TRAF2 (via zinc fingers); the interaction occurs in a TNF-alpha-dependent manner. Interacts with 14-3-3 proteins; the interaction occurs in a TNF-alpha-dependent manner. Interacts (via Ras-GAP domain) with RIPK1 (via kinase domain); the interaction occurs in a TNF-alpha-dependent manner (By similarity). Interacts with DAB1 and DAB2. Localized in soma and dendrites of Purkinje cells as well as in scattered cell bodies in the molecular layer of the cerebellum. Colocalizes with TIRAP at the plasma membrane. Colocalizes with ARF6 at the plasma membrane and endocytic vesicles. Translocates from the plasma membrane to the cytoplasm in response to TNF-alpha. Phosphatidylinositol 4-phosphate (PtdIns4P) binding is essential for plasma membrane localization (By similarity). Expressed in brain, lung, thymus, bladder and skeletal muscle. Up-regulatedd during prostate degeneration. Exists in a closed inactive form by an intramolecular interaction between the N- and the C-terminal domains. The proline-rich motif is critical both for PI3K-AKT activity inhibition and MAP3K5 activation. The PH and C2 domains are necessary for the binding to phosphatidylinositol phosphate. The Ras-GAP domain is necessary for its tumor-suppressive function. The C2 and Ras-GAP domains constitutively bind to MAP3K5 and facilitate the release of 14-3-3 proteins from MAP3K5. The PH and Ras-GAP domains, but not the NPXY motif, are crucial for its cell membrane localization and neuronal migration function. The PH domain is necessary but not sufficient to activate the JNK signaling pathway through ERN1 (By similarity). In response to TNF-alpha-induction, phosphorylated at Ser-535; phosphorylation leads to a conformational change, and thus, increases its association with 14-3-3 proteins, MAP3K5, RIPK1 and TRAF2 in endothelial cells; also stimulates regulatory p85 subunit sequestring and PI3K-p85 complex activity inhibition.