Membrane curvature association of amphipathic helix 8 drives constitutive GPCR endocytosis
Cellular signaling relies on the activity of transmembrane receptors and their presentation on the cellular surface. Their continuous insertion in the plasma membrane is balanced by constitutive and activity dependent internalization, which is orchestrated by adaptor proteins recognizing semi-specific motifs within the receptors intracellular regions. Here we describe a complementary and evolutionary conserved and refined trafficking mechanism for G-protein coupled receptors (GPCR). This mechanism relies on the insertion of their amphipathic helix 8 into the inner leaflet of lipid membranes, orthogonal to the transmembrane helices. These amphipathic helices dictate subcellular localization of the receptors and autonomously drive their endocytosis by cooperative assembly and association with areas of high membrane curvature. The strength of helix 8 membrane insertion propensity quantitatively predicts the rate of constitutive internalization of GPCRs. This discovery advances our understanding of membrane protein trafficking and highlights a new principle of receptor-lipid interactions that may have broader implications for cellular signaling and therapeutic targeting. One-Sentence SummaryReceptor proteins navigate cellular membranes by interacting with their curvature using an evolutionary conserved mechanism that relies on amphipathic helices and complements direct coupling to the endocytic protein machinery.