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  • Title: Translocation of pleckstrin requires its phosphorylation and newly formed ligands.
    Author: Sloan DC, Wang P, Bao X, Haslam RJ.
    Journal: Biochem Biophys Res Commun; 2002 Apr 26; 293(1):640-6. PubMed ID: 12054651.
    Abstract:
    Pleckstrin is the major substrate of protein kinase C (PKC) in platelets. We sought to determine whether pleckstrin phosphorylation is sufficient to target the soluble protein to binding sites. Permeabilization of platelets by streptolysin O (SLO) was used to separate bound and soluble pleckstrin. Platelets were incubated with phorbol 12-myristate 13-acetate (PMA) and/or guanosine 5'-[gamma-thio]triphosphate (GTP[S]) in the presence of [gamma-(32)P]ATP and SLO. PMA stimulated pleckstrin phosphorylation, but this pleckstrin diffused from permeabilized platelets. Addition of GTP[S] with PMA caused up to 40-50% of pleckstrin to be retained within platelets and enhanced secretion of platelet 5-hydroxytryptamine. PKC alpha pseudosubstrate peptide inhibited pleckstrin phosphorylation, the binding of pleckstrin and secretion. After extraction of permeabilized platelets containing bound pleckstrin with Triton X-100, the protein was solubilized. Thus, phosphorylated pleckstrin was retained in platelets only after activation of GTP-binding proteins that stimulate the formation of membrane-bound pleckstrin ligands. Translocation of pleckstrin may facilitate the associated secretion.
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