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Bouillie S, Barel M, Frade R. Signaling Through the EBV/C3d Receptor (CR2, CD21) in Human B Lymphocytes: Activation of Phosphatidylinositol 3-Kinase via a CD19-Independent Pathway. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.1.136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
We herein analyzed the regulation of phosphatidylinositol 3-kinase (PI 3-kinase) activity by CR2 activated on B lymphocyte cell surface. We demonstrated that CR2 activation triggered in vivo PI 3-kinase activity and interaction of PI 3-kinase p85 subunit with a tyrosine-phosphorylated p95 component. The specificity of PI 3-kinase activity was controlled using wortmannin and LY294002. CR2 activation did not trigger tyrosine phosphorylation of PI 3-kinase p85 subunit, but induced direct interaction of tyrosine phosphorylated p95 with the Src homology 2 domain of p85 subunit, as shown using glutathione-S-transferase fusion proteins. Despite identical molecular masses, immunoblotting analysis demonstrated that tyrosine-phosphorylated p95 that interacted in vivo and in vitro with p85 was neither CD19, the 95-kDa proto-oncogene vav, nor Gab1 (a 95-kDa adaptor molecule). Furthermore, p95 tyrosine phosphoprotein also expressed in K562A cells (CR2+ CD19− cells) interacted with Src homology 2 domain of PI 3-kinase p85 subunit after CR2 activation. Activated CR2 did not interact directly with p85 subunit or tyrosine-phosphorylated p95. This suggests the presence of an intermediate molecule between activated CR2 and tyrosine-phosphorylated p95, which may be 3BP2. In addition, in contrast to CD19 activation, CR2 activation did not trigger interaction of CD19 or Vav with PI 3-kinase p85 subunit or coprecipitation of PI 3-kinase activity with CD19. Together, these data clearly demonstrated that CR2 activation triggered in vivo PI 3-kinase activation through a pathway distinct from that triggered through CD19 activation.
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Affiliation(s)
- Sylvie Bouillie
- Immunochimie des Régulations Cellulaires et des Interactions Virales, Institut National de la Santé et de la Recherche Médicale, Unit 354, Centre INSERM, Hôpital Saint-Antoine, Paris, France
| | - Monique Barel
- Immunochimie des Régulations Cellulaires et des Interactions Virales, Institut National de la Santé et de la Recherche Médicale, Unit 354, Centre INSERM, Hôpital Saint-Antoine, Paris, France
| | - Raymond Frade
- Immunochimie des Régulations Cellulaires et des Interactions Virales, Institut National de la Santé et de la Recherche Médicale, Unit 354, Centre INSERM, Hôpital Saint-Antoine, Paris, France
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