HOMEPRODUCTSCOMPANYCONTACTFAQResearchDictionaryPharmaSign Up FREE or Login

Platelet alpha-granule and plasma membrane share two new components: CD9 and PECAM-1.

Abstract
CD9 (p24) and PECAM1 (CD31) antigens are well-defined components of the platelet plasma membrane. Both are integral glycoproteins (GPs) implicated in the adhesive and aggregative properties of human platelets. In the present report, we have investigated their subcellular localization using immunoelectron microscopy. The monospecificity of the two polyclonal antibodies used was confirmed by immunoblotting. On normal resting platelets, immunolabeling for CD9 and PECAM1 was found lining the plasma membrane and the luminal face of the open canalicular system. Some labeling was also consistently found on the alpha-granule limiting membrane. This was confirmed by double labeling experiments in which fibrinogen and von Willebrand factor (vWF) were used as alpha-granule markers. CD9 and PECAM-1 were found lining the membrane of the same granules that contained fibrinogen and vWF in their matrix. CD9 and PECAM-1 thus appear to have an intracellular distribution identical to GPIIb-IIIa, a major aggregation platelet receptor. To rule out a cross-reactivity of the two polyclonal antibodies with GPIIb/IIIa, we studied PECAM1 and CD9 expression on the platelets from a patient with type I Glanzmann's thrombasthenia whose platelets are devoid of GPIIb/IIIa. The same pattern of labeling was observed for both antigens as for normal platelets. Normal platelets were further observed after stimulation by agonists that either fail to induce (ADP) or induce granule secretion (thrombin). After treatment with ADP, platelets changed shape and centralized their granules; the plasma membrane immunolabeling remained unchanged; and gold particles were still found decorating the periphery of the centralized alpha-granules. After thrombin treatment, alpha-granules fused with the platelet membrane and secretion occurred. A significant increase of labeling was then observed on the platelet surface. From these results we conclude that the alpha-granule membrane contains two additional receptors in common with the plasma membrane. This suggests that alpha-granule membrane receptors may originate from a dual mechanism: direct targeting from the Golgi complex in megakaryocytes (for alpha-granule-specific receptors such as P-selectin) or by endocytosis from the plasma membrane (for proteins distributed in the two compartments).
AuthorsE M Cramer, G Berger, M C Berndt
JournalBlood (Blood) Vol. 84 Issue 6 Pg. 1722-30 (Sep 15 1994) ISSN: 0006-4971 [Print] United States
PMID8080982 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Antigens, CD
  • Antigens, Differentiation, Myelomonocytic
  • CD9 protein, human
  • Cell Adhesion Molecules
  • Membrane Glycoproteins
  • Platelet Endothelial Cell Adhesion Molecule-1
  • Platelet Membrane Glycoproteins
  • Tetraspanin 29
  • Adenosine Diphosphate
  • Thrombin
Topics
  • Adenosine Diphosphate (pharmacology)
  • Antigens, CD (blood)
  • Antigens, Differentiation, Myelomonocytic (blood)
  • Blood Platelets (immunology, ultrastructure)
  • Cell Adhesion Molecules (blood)
  • Cell Membrane (immunology)
  • Cytoplasmic Granules (immunology, ultrastructure)
  • Humans
  • Intracellular Membranes (immunology)
  • Membrane Glycoproteins
  • Microscopy, Immunoelectron
  • Platelet Endothelial Cell Adhesion Molecule-1
  • Platelet Membrane Glycoproteins (analysis, immunology)
  • Tetraspanin 29
  • Thrombasthenia (blood)
  • Thrombin (pharmacology)

Join CureHunter, for free Research Interface BASIC access!

Take advantage of free CureHunter research engine access to explore the best drug and treatment options for any disease. Find out why thousands of doctors, pharma researchers and patient activists around the world use CureHunter every day.
Realize the full power of the drug-disease research graph!


Choose Username:
Email:
Password:
Verify Password:
Enter Code Shown: