Paxillin family members function as Csk-binding proteins that regulate Lyn activity in human and murine platelets. Biochem J 2007 Apr 15;403(2):275-81
Date
01/20/2007Pubmed ID
17233630Pubmed Central ID
PMC1874248DOI
10.1042/BJ20061618Scopus ID
2-s2.0-34247134920 (requires institutional sign-in at Scopus site) 24 CitationsAbstract
SFKs (Src family kinases) contribute importantly to platelet function in haemostasis. SFK activity is controlled by Csk (C-terminal Src kinase), which phosphorylates a C-terminal tyrosine residue on SFKs, resulting in inhibition of SFK activity. Csk is recruited to sites of SFK activity by tyrosine-phosphorylated Csk-binding proteins. Paxillin, a multidomain adaptor protein, has been shown to act as a Csk-binding protein and to inhibit Src activity during growth factor signalling. Human platelets express Hic-5, a member of the paxillin family; however, its ability to act as a Csk-binding protein has not been characterized. We sought to identify and characterize the ability of paxillin family members to act as Csk-binding proteins during platelet activation. We found that murine and human platelets differ in the complement of paxillin family members expressed. Human platelets express Hic-5, whereas murine platelets express paxillin and leupaxin in addition to Hic-5. In aggregating human platelets, Hic-5 was tyrosine phosphorylated and recruited Csk via its SH2 domains. In aggregating murine platelets, however, Csk bound preferentially to paxillin, even though both paxillin and Hic-5 were abundantly present and became tyrosine phosphorylated. The SFK Lyn, but not Src or Fyn, was associated with paxillin family members in resting and aggregated human and murine platelets. Lyn, however, was phosphorylated on its C-terminal inhibitory tyrosine residue only following platelet aggregation, which was coincident with recruitment of Csk to paxillin and/or Hic-5 in a manner dependent on prior alpha(IIb)beta3 engagement. These observations support the notion that Hic-5 and paxillin function as negative feedback regulators of SFKs in aggregated platelets and that, when both are present, paxillin is preferentially used.
Author List
Rathore VB, Okada M, Newman PJ, Newman DKAuthors
Debra K. Newman PhD Investigator in the Blood Research Institute department at BloodCenter of WisconsinDebra K. Newman PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
AnimalsBlood Platelets
Humans
Intracellular Signaling Peptides and Proteins
LIM Domain Proteins
Membrane Proteins
Mice
Mice, Inbred C57BL
Paxillin
Phosphoproteins
Phosphotyrosine
Platelet Aggregation
Platelet Glycoprotein GPIIb-IIIa Complex
Protein Binding
Proto-Oncogene Proteins c-fyn
src-Family Kinases