Adp

PIateIet membrane

FIGURE 2 Fcy receptor-mediated signal transduction. PF4-heparin-IgG complexes (1) bind to FcyRIIa, causing receptor clustering (2). The ITAMs on FcyRIIa are phosphorylated by PTKsrc (3). The phosphorylated ITAMs interact with SH domains on p72syk to phosphorylate PLCy2 (4). ADP receptors, activated via ADP and Gi proteins, generate PIP3 via PI 3-kinase (not shown) (5), which helps phosphorylate PLCy2. Activated PLCy2 acts on PIP2 to generate IP3, and DAG from phosphatidylinositol-bisphosphate (6). IP3 mobilizes Ca++ to the intracellular space via Ca++ channels (7) and together with DAG activates downstream PKC signaling pathways (8). Abbreviations: DAG, diacylglycerol; IP3, inositol triphosphate; ITAMs, immunoreceptor tyrosine activation motifs; PF4, platelet factor 4; PKC, protein kinase C; PLCy2, phospholipase Cy2; PIP3, phosphatidylinositol-trisphosphate; PTKĀ®rc, src protein tyrosine kinases.

FcyR lla clustering

FcyR lla clustering

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