Guanyl-nucleotide exchange factor that regulates small GTPases of the Rab family (PubMed:20937701, PubMed:18559336). Converts GDP-bound inactive form of RAB27A and RAB27B to the GTP-bound active forms (PubMed:20937701, PubMed:18559336). Converts GDP-bound inactive form of RAB3A, RAB3C and RAB3D to the GTP-bound active forms, GTPases involved in synaptic vesicle exocytosis and vesicle secretion (By similarity). Plays a role in synaptic vesicle formation and in vesicle trafficking at the neuromuscular junction (By similarity). Involved in up-regulating a post-docking step of synaptic exocytosis in central synapses (By similarity). Probably by binding to the motor proteins KIF1B and KIF1A, mediates motor-dependent transport of GTP-RAB3A-positive vesicles to the presynaptic nerve terminals (By similarity). Plays a role in TNFA-mediated activation of the MAPK pathway, including ERK1/2 (PubMed:32761064). May link TNFRSF1A with MAP kinase activation (PubMed:9115275). May be involved in the regulation of TNFA-induced apoptosis (PubMed:11577081, PubMed:32761064). Interacts (via death domain) with TNFRSF1A (via death domain) (PubMed:9115275, PubMed:11577081). Interacts with PIDD1 (PubMed:10825539). Interacts with YWHAZ (PubMed:16959763). Interacts (via death domain) with KIF1B (By similarity). Interacts with KIF1A (By similarity). Interacts (via uDENN domain) with RAB3A, RAB3B, RAB3C and RAB3D; the GTP-bound form of the Rab proteins is preferred for interaction (By similarity). Expressed in testis, ovary, brain and heart (PubMed:8988362). Expressed in spleen, thymus, prostate, testis, ovary, small instestine and colon (PubMed:9115275). Expressed in liver (PubMed:9796103). Not detected in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Expressed in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Expressed in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Expressed in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Expressed in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Not detected in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Not detected in the brain, breast, kidney, lung, ovary, pancreas, testis, uterus, stomach and thyroid. Expressed in fetal brain and kidney. Expressed in fetal liver. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Overexpression of MADD activates the mitogen-activated protein (MAP) kinase extracellular signal-regulated kinase (ERK). Expression of the MADD death domain stimulates both the ERK and c-JUN N-terminal kinase MAP kinases and induces the phosphorylation of cytosolic phospholipase A2. Belongs to the MADD family. Extended N-terminus.