RIPK1

RIPK1 is a death-domain kinase that sits at the crossroads of TNF receptor-1 signaling, deciding between cell survival, apoptosis and necroptosis. TNF binding recruits RIPK1 into complex I, where K63-linked ubiquitination supports NF-kappaB activation and survival; loss of ubiquitin editing by CYLD or of complex-I integrity redirects RIPK1 toward RIPK3-driven necroptosis or, together with FADD and caspase-8, toward apoptosis. RIPK1 kinase activity is dispensable for NF-kappaB signaling but required for its death-inducing functions, which is why ATP-competitive inhibitors such as GSK2982772 are being tested in psoriasis, rheumatoid arthritis and ulcerative colitis. Human RIPK1 loss-of-function causes combined immunodeficiency with enterocolitis.