J. Biol. Chem., Vol. 262, Issue 26, 12627-12631, Sep, 1987

Identification of glycoprotein Ib beta as one of the major proteins phosphorylated during exposure of intact platelets to agents that activate cyclic AMP-dependent protein kinase

JE Fox, CC Reynolds and MM Johnson

Platelet function is inhibited by prostaglandin E1, prostaglandin I2, or forskolin, agents that increase the intracellular concentration of cyclic AMP. The inhibition appears to result from cyclic AMP-stimulated phosphorylation of specific intracellular proteins. One of the major increases in phosphorylation occurs in a polypeptide of Mr = 24,000 (P24). In this study, an effort was made to identify P24. Platelets prelabeled with [32P]phosphate were incubated with prostaglandin E1, prostaglandin I2, or forskolin. Proteins that became phosphorylated were detected by autoradiography of sodium dodecyl sulfate- polyacrylamide gels. Several lines of evidence indicated that P24 was the beta-subunit of the plasma membrane glycoprotein (GP) Ib, a glycoprotein that is essential for the adhesion of platelets to damaged subendothelium, for the rapid response of platelets to thrombin, and for the attachment of the membrane skeleton to the cytoplasmic face of the plasma membrane. P24 co-migrated with GP Ib beta on reduced gels (Mr = 24,000) and also on nonreduced gels (when GP Ib beta is disulfide- linked to GP Ib alpha and migrates with Mr = 170,000). Like GP Ib beta, P24 was associated with actin filaments in Triton X-100 lysates. Like GP Ib beta, it was selectively associated with filaments of the membrane skeleton and was released from filaments when the Ca2+- dependent protease was active. Antibodies against GP Ib immunoprecipitated P24 from platelet lysates. Finally, exposure of Bernard-Soulier platelets (which lack GP Ib) to prostaglandin E1 resulted in phosphorylation of other polypeptides, but not of P24. These studies show that P24, one of the major polypeptides phosphorylated when platelets are exposed to agents that inhibit platelet function by increasing the concentration of cyclic AMP, is the beta-subunit of GP Ib.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				K. Dai, R. Bodnar, M. C. Berndt, and X. Du A critical role for 14-3-3{zeta} protein in regulating the VWF binding function of platelet glycoprotein Ib-IX and its therapeutic implications Blood, September 15, 2005; 106(6): 1975 - 1981. [Abstract] [Full Text] [PDF]

				R. J. Bodnar, X. Xi, Z. Li, M. C. Berndt, and X. Du Regulation of Glycoprotein Ib-IX-von Willebrand Factor Interaction by cAMP-dependent Protein Kinase-mediated Phosphorylation at Ser 166 of Glycoprotein Ibbeta J. Biol. Chem., November 27, 2002; 277(49): 47080 - 47087. [Abstract] [Full Text] [PDF]

				J. Yang, J. Wu, H. Jiang, R. Mortensen, S. Austin, D. R. Manning, D. Woulfe, and L. F. Brass Signaling through Gi Family Members in Platelets. REDUNDANCY AND SPECIFICITY IN THE REGULATION OF ADENYLYL CYCLASE AND OTHER EFFECTORS J. Biol. Chem., November 22, 2002; 277(48): 46035 - 46042. [Abstract] [Full Text] [PDF]

				V. Ramakrishnan, F. DeGuzman, M. Bao, S. W. Hall, L. L. Leung, and D. R. Phillips A thrombin receptor function for platelet glycoprotein Ib-IX unmasked by cleavage of glycoprotein V PNAS, February 13, 2001; 98(4): 1823 - 1828. [Abstract] [Full Text] [PDF]

				I. Elalamy, F. A. Said, M. Singer, J.-P. Couetil, and M. Hatmi Inhibition by Extracellular cAMP of Phorbol 12-Myristate 13-Acetate-induced Prostaglandin H Synthase-2 Expression in Human Pulmonary Microvascular Endothelial Cells. INVOLVEMENT OF AN ECTO-PROTEIN KINASE A ACTIVITY J. Biol. Chem., April 28, 2000; 275(18): 13662 - 13667. [Abstract] [Full Text] [PDF]

				R. J. Bodnar, M. Gu, Z. Li, G. D. Englund, and X. Du The Cytoplasmic Domain of the Platelet Glycoprotein Ibalpha Is Phosphorylated at Serine 609 J. Biol. Chem., November 19, 1999; 274(47): 33474 - 33479. [Abstract] [Full Text] [PDF]

				M. Torti, A. Bertoni, I. Canobbio, F. Sinigaglia, E. G. Lapetina, and C. Balduini Rap1B and Rap2B Translocation to the Cytoskeleton by von Willebrand Factor Involves Fcgamma II Receptor-mediated Protein Tyrosine Phosphorylation J. Biol. Chem., May 7, 1999; 274(19): 13690 - 13697. [Abstract] [Full Text] [PDF]

				M. Gu and X. Du A Novel Ligand-binding Site in the zeta -Form 14-3-3 Protein Recognizing the Platelet Glycoprotein Ibalpha and Distinct from the c-Raf-binding Site J. Biol. Chem., December 11, 1998; 273(50): 33465 - 33471. [Abstract] [Full Text] [PDF]

				M. Hatmi, J.-M. Gavaret, I. Elalamy, B. B. Vargaftig, and C. Jacquemin Evidence for cAMP-dependent Platelet Ectoprotein Kinase Activity That Phosphorylates Platelet Glycoprotein IV (CD36) J. Biol. Chem., October 4, 1996; 271(40): 24776 - 24780. [Abstract] [Full Text] [PDF]

				L. S. Bastian, M. Yagi, C. Chan, and G. J. Roth Analysis of the Megakaryocyte Glycoprotein IX Promoter Identifies Positive and Negative Regulatory Domains and Functional GATA and Ets Sites J. Biol. Chem., August 2, 1996; 271(31): 18554 - 18560. [Abstract] [Full Text] [PDF]

				F. A. Baglia, K. O. Badellino, C. Q. Li, J. A. Lopez, and P. N. Walsh Factor XI Binding to the Platelet Glycoprotein Ib-IX-V Complex Promotes Factor XI Activation by Thrombin J. Biol. Chem., January 11, 2002; 277(3): 1662 - 1668. [Abstract] [Full Text] [PDF]