C3G is guanine nucleotide exchange factor for Rap1b, a protein of the Ras family involved in critical aspects of platelet function through the activation of integrin aIIbb3. Using transgenic mouse models, with specific expression in platelets, of full length C3G (tgC3G) or mutant lacking the GEF domain (tgC3GDCat), our group has unveiled an important role of C3G in primary hemostasis. Thus, C3G-Rap1 participates in thrombin-triggered platelet activation, aggregation and clotting through a PKC-mediated pathway. In addition, C3G-overexpressing platelets also show a stronger response to ADP, as compared to wt platelets. Based on these results, we have deepened into the role of C3G in platelet signaling by using several inhibitors of different platelets signaling pathways. This includes: clopidogrel and 2MeSAMP (for P2Y12 ADP receptor), MRS2179 (for P2Y1 ADP receptor), SB203580 (for p38a/b MAPK), U0126 (for ERK1/2), aspirin (for TXA2 synthesis) and wortmannin (for PI3K). We have performed activation, aggregation, and Rap1 activity assays in platelets stimulated with thrombin or ADP/fibrinogen in the presence or absence of the above referred inhibitors. Our results indicate that thrombin- or ADP-stimulated tgC3G platelets are more sensitive to the action of clopidogrel, SB203580, U0126 and aspirin, as compared to wild type platelets. In contrast, tgC3GDCat platelets are more resistant to these inhibitors than their corresponding control platelets. No differences were observed with the rest of inhibitors. These results suggest that C3G may participate in the activation of Rap1 mediated by ADP-P2Y12, but independent of PI3K. Furthermore, our results support a role for C3G in the thromboxane synthesis pathway, probably through modulating ERKs and p38a MAPK activities.

Resumen del póster presentado al XXXIX Congreso de la Sociedad Española de Bioquímica y Biología Molecular, celebrado en Salamanca del 5 al 8 de septiembre de 2016.

Peer reviewed