title: RACK1: a novel substrate for the Src protein-tyrosine kinase.
abstract: RACK1 is one of a group of PKC-interacting proteins collectively called RACKs (Receptors for Activated C-Kinases). Previously, we showed that RACK1 also interacts with the Src tyrosine kinase, and is an inhibitor of Src activity and cell growth. PKC activation induces the intracellular movement and co-localization of RACK1 and Src, and the tyrosine phosphorylation of RACK1. To determine whether RACK1 is a Src substrate, we assessed phosphorylation of RACK1 by various tyrosine kinases in vitro, and by kinase-active and inactive mutants of Src in vivo. We found that RACK1 is a Src substrate. Moreover, Src activity is necessary for both the tyrosine phosphorylation of RACK1 and the binding of RACK1 to Src's SH2 domain that occur following PKC activation. To identify the tyrosine(s) on RACK1 that is phosphorylated by Src, we generated and tested a series of RACK1 mutants. We found that Src phosphorylates RACK1 on Tyr 228 and/or Tyr 246, highly-conserved tyrosines located in the sixth WD repeat that interact with Src's SH2 domain. We think that RACK1 is an important Src substrate that signals downstream of growth factor receptor tyrosine kinases and is involved in the regulation of Src function and cell growth.
authors.affiliation: Department of Medicine, Stanford University, Stanford, California, CA 94305, USA.
authors.forename: Betty Y
authors.initials: BY
authors.lastname: Chang
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Harte
authors.forename: Christine A
authors.initials: CA
authors.lastname: Cartwright
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D066246:ErbB Receptors / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016374:Oncogene Proteins v-abl / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D016374:Oncogene Proteins v-abl; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D014443:Tyrosine; D066246:ErbB Receptors; D017479:Receptors, Platelet-Derived Growth Factor; D019061:src-Family Kinases; D011493:Protein Kinase C