Grb2-associated binder (Gab) family of scaffolding adaptor proteins coordinate signaling cascades downstream of growth factor and cytokine receptors. In the heart, among EGF family members, neuregulin-1β (NRG-1β, a paracrine factor produced from endothelium) induced remarkable tyrosine phosphorylation of Gab1 and Gab2 via erythroblastic leukemia viral oncogene (ErbB) receptors. We examined the role of Gab family proteins in NRG-1β/ErbB-mediated signal in the heart by creating cardiomyocyte-specific Gab1/Gab2 double knockout mice (DKO mice). Although DKO mice were viable, they exhibited marked ventricular dilatation and reduced contractility with aging. DKO mice showed high mortality after birth because of heart failure. In addition, we noticed remarkable endocardial fibroelastosis and increase of abnormally dilated vessels in the ventricles of DKO mice. NRG-1β induced activation of both ERK and AKT in the hearts of control mice but not in those of DKO mice. Using DNA microarray analysis, we found that stimulation with NRG-1β upregulated expression of an endothelium-stabilizing factor, angiopoietin 1, in the hearts of control mice but not in those of DKO mice, which accounted for the pathological abnormalities in the DKO hearts. Taken together, our observations indicated that in the NRG-1β/ErbB signaling, Gab1 and Gab2 of the myocardium are essential for both maintenance of myocardial function and stabilization of cardiac capillary and endocardial endothelium in the postnatal heart.
Yoshikazu Nakaoka, Keigo Nishida, Masahiro Narimatsu, Atsunori Kamiya, Takashi Minami, Hirofumi Sawa, Katsuya Okawa, Yasushi Fujio, Tatsuya Koyama, Makiko Maeda, Manami Sone, Satoru Yamasaki, Yuji Arai, Gou Young Koh, Tatsuhiko Kodama, Hisao Hirota, Kinya Otsu, Toshio Hirano, Naoki Mochizuki
Gab1 and Gab2 are engaged in coordination of NRG-1β/ErbB signaling pathway in the myocardium.