The role of Son of sevenless guanine nucleotide exchange factors in linking cell surface receptors with ras

Abstract

The Son of sevenless (Sos) proteins link cytokine stimulation of cell surface receptors to ras activation by facilitating ras GDP-GTP exchange. This linkage appears to be controlled largely by the regulated formation of complexes of Sos, receptor, and adaptor proteins in the vicinity of membrane-bound ras. Interaction of Sos with Grb2, Shc, and other adaptor proteins is important for Sos to couple to ligand-activated receptors. Phosphorylation of Sos in response to ligand stimulation of cells may result in feedback dissolution of complexes of Sos and other signaling proteins, thereby terminating receptor-mediated ras activation.