The platelet protein kinase C substrate pleckstrin binds directly to SDPR protein.
Pleckstrin is a modular platelet protein consisting of N- and C-terminal pleckstrin homology (PH) domains, a central dishevelled egl10 and pleckstrin (DEP) domain and a phosphorylation region. Following agonist-induced platelet stimulation, dimeric pleckstrin translocates to the plasma membrane, is phosphorylated and then monomerizes. A recent study found that pleckstrin null platelets from a knockout mouse have a defect in granule secretion, actin polymerization and aggregation. However, the mechanism of pleckstrin signaling for this function is unknown. Our recent studies have led to the identification of a novel pleckstrin-binding protein, serum deprivation response protein (SDPR), by co-immunoprecipitation, GST-pulldowns and nanospray quadruple time of flight mass spectrometry. We show that this interaction occurs directly through N-terminal sequences of pleckstrin. Both pleckstrin and SDPR are phosphorylated by protein kinase C (PKC), but the interaction between pleckstrin and SDPR was shown to be independent of PKC inhibition or activation. These results suggest that SDPR may facilitate the translocation of nonphosphorylated pleckstrin to the plasma membrane in conjunction with phosphoinositides that bind to the C-terminal PH domain. After binding of pleckstrin to the plasma membrane, its phosphorylation by PKC exerts downstream effects on platelet aggregation/secretion.
Baig
Akeel
A
Department of Pathology, McMaster University, Hamilton, ON, Canada. akeel.baig@gmail.com
Bao
Xiankun
X
Wolf
Marlene
M
Haslam
Richard J
RJ
D000818:Animals; D001792:Blood Platelets / Q000201:enzymology / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D018345:Mice, Knockout; D028044:Phosphate-Binding Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000097:blood*; D015398:Signal Transduction
D001798:Blood Proteins; C112303:CAVIN2 protein, human; D002352:Carrier Proteins; D028044:Phosphate-Binding Proteins; D010750:Phosphoproteins; C039077:platelet protein P47; D011493:Protein Kinase C