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. Author manuscript; available in PMC: 2014 Feb 19.
Published in final edited form as: J Thromb Haemost. 2013 Jan;11(1):35–46. doi: 10.1111/jth.12051

Figure 4. Regulation of platelet Rac1 activation and lamellipodia formation.

Figure 4

Upon stimulation of platelet GPCRs such as the PARs, TPs or P2Y12, Gαq mediates the activation of Rac1 through PLCβ [42]. Integrin- and GPVI-coupled Src family kinase (SFK) activation also supports Rac1 activation [30, 32, 71]. GPIb release of 14-3-3ζ also has a role in platelet Rac1 activation [72]. Gi coupled to P2Y1 receptors is also required for full platelet Rac1 activation [78]. Separate pools of Rac1 may work in distinct steps of the platelet activation process. A first pool proximal to SFK-coupled receptor activation drives PLCγ activation and calcium signaling to activate CalDEG-GEF1 and the Rap1 GTPase to support integrin αIIbβ3 activation [33, 84]. A second pool of Rac1 downstream of PLCγ and calcium signaling then supports secretion, aggregation and spreading events through the activation of Rac effectors, such as the WAVE and Arp2/3 system or the PAK kinases.