Identification of the kinase that activates a nonmetazoan STAT gives insights into the evolution of phosphotyrosine-SH2 domain signaling

摘要

Cells respond to extracellular cues using dedicated signaling pathways. Typically, a receptor protein located on the surface of a responding cell recognizes and binds to an inductive signaling molecule, initiating a cascade of site-specific phos-phorylations of intracellular proteins that are located downstream in the signal transduction pathway. Their phosphoryla-tion alters their biochemical activity or affinity for other proteins, and this alteration propagates the signal. In animal cells, phosphorylation on tyrosine residues is particularly important, because signal transduction pathways involving this modification frequently control cell growth or differentiation, and mutations in pathway components are sometimes oncogenic. We show that in a phosphotyrosine signaling pathway in a simple model organism a key component of the signaling machinery and the regulatory mechanism used differ radically from the animal paradigm.