PKC{theta} via Activating Transcription Factor 2-Mediated CD36 Expression and Foam Cell Formation of Ly6Chi Cells Contributes to Atherosclerosis [Original Research Article]

Background—Although the role of thrombin in atherothrombosis is well studied, its role in the pathogenesis of diet-induced atherosclerosis is not known.Methods—Using a mouse model of diet-induced atherosclerosis and molecular biological approaches, here we have explored the role of thrombin and its G protein-coupled receptor (GPCR) signaling in diet-induced atherosclerosis. Results—In exploring the role of GPCR signaling in atherogenesis, we found that thrombin triggers foam cell formation via inducing CD36 expression and these events require Par1-mediated Gα12-Pyk2-Gab1-PKCθ-dependent ATF2 activation. Genetic deletion of PKCθ in ApoE-/- mice reduced western diet (WD)-induced plaque formation. Furthermore, thrombin induced Pyk2, Gab1, PKCθ and ATF2 phosphorylation, CD36 expression and foam cell formation in peritoneal macrophages of ApoE-/- mice. On the other hand, thrombin only stimulated Pyk2 and Gab1 but not ATF2 phosphorylation or its target gene CD36 expression in the peritoneal macrophages of ApoE-/-:PKCθ-/- mice and it had no effect on foam cell formation. In addition, the aortic root cross sections of WD-fed ApoE-/- mice showed increased Pyk2, Gab1, PKCθ and ATF2 phosphorylation and CD36 expression as compared to ApoE-/-:PKCθ-/- mice. Furthermore, while the monocytes from peripheral blood and aorta of WD-fed ApoE-/- mice were found to contain more of Ly6Chi cells than Ly6Clo cells, the monocytes from WD-fed ApoE-/-:PKCθ-/- mice were found to contain more of Ly6Clo cells than Ly6Chi cells. Interestingly, the Ly6Chi cells showed higher CD36 expression with enhanced capacity to form foam cells as compared to Ly6Clo cells. Conclusions—The above findings reveal for the first time that thrombin-mediated Par1-Gα12 signaling via targeting Pyk2-Gab1-PKCθ-ATF2-dependent CD36 expression might be playing a crucial role in diet-induced atherogenesis.