A tyrosine-phosphorylated protein that binds to an important regulatory region on the cool family of p21-activated kinase-binding proteins

Shubha Bagrodia, Dennis Bailey, Zoe Lenard, Matt Hart, Jun Lin Guan, Richard T. Premont, Stephen J. Taylor, Richard A. Cerione

Research output: Contribution to journalArticle

177 Scopus citations

Abstract

The p21-activated kinases (Pak) are major targets of the small GTPases Cdc42 and Rac. We, and others, recently identified a family of proteins termed Cool/Pix, which interact with Pak3. In cells, p50(Cool-1) suppresses Pak activation by upstream activators; p85(Cool-1) has a permissive effect on Pak activation, and we now show that the closely related Cool-2 stimulates Pak kinase activity. To understand the differential regulation of Pak by Cool proteins, we screened for Cool-interacting proteins by affinity purification and microsequencing. This has led to the identification of two closely related proteins called Cat (Cool-associated, tyrosine phosphorylated), which contain a zinc finger followed by three ankyrin repeats. Cat-1 is identical to the recently identified binding partner for the β-adrenergic receptor kinase (βARK or GRK-2), which was shown to have Arf-GAP activity. Cat-1 and Cat-2 both bind to the COOH-terminal region of p85(Cool-1) and p85(Cool-2) but do not bind to p50(Cool-1). Cat-1 is tyrosine-phosphorylated in growing NIH 3T3 fibroblasts, and its tyrosine phosphorylation is increased following cell spreading on fibronectin, decreased in cells arrested in mitosis, and increased in the ensuing G1 phase. Cat proteins are tyrosine-phosphorylated when co-expressed in cells with the focal adhesion kinase Fak and Src. These findings suggest that in addition to playing a role in Cool/Pak interactions, Cat proteins may serve as points of convergence between G protein-coupled receptors, integrins, Arf GTPases, cell cycle regulators, and Cdc42/Rac/Pak signaling pathways.

Original languageEnglish (US)
Pages (from-to)22393-22400
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number32
DOIs
StatePublished - Aug 6 1999
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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