Gab family proteins are essential for postnatal maintenance of cardiac function via neuregulin-1/ErbB signaling
Yoshikazu Nakaoka, … , Toshio Hirano, Naoki Mochizuki
Yoshikazu Nakaoka, … , Toshio Hirano, Naoki Mochizuki
Published July 2, 2007
Citation Information: J Clin Invest. 2007;117(7):1771-1781. https://doi.org/10.1172/JCI30651.
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Research Article Cardiology

Gab family proteins are essential for postnatal maintenance of cardiac function via neuregulin-1/ErbB signaling

Abstract

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.

Authors

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

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Figure 1

Gab1 and Gab2 are engaged in coordination of NRG-1β/ErbB signaling pathway in the myocardium.

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Gab1 and Gab2 are engaged in coordination of NRG-1β/ErbB signaling pathw...
Tyrosine phosphorylation of Gab1 (A) and Gab2 (B) and their association with SHP2 and p85 were analyzed by IP of the heart lysates. Mouse heart lysates were prepared at 5 minutes after injection with the cytokines and growth factors listed at top. Heart lysates were subjected to IP with anti-Gab1 (A) or anti-Gab2 (B) serum, followed by IB analysis using the Ab indicated at the left. (C) Activation levels of ERK and AKT were assessed by phospho-specific Ab. Tyrosine phosphorylation of Gab1 (D) Gab2 (E) and their association with SHP2 and p85 was examined by IP of cell lysates from neonatal rat cardiomyocytes (CM) or noncardiomyocytes (non-CM) stimulated with either NRG-1β (50 ng/ml) or HB-EGF (50 ng/ml) for 5 minutes. IP complexes were subjected to IB using the Ab indicated at the left. (F) NRG-1β– and HB-EGF–dependent activation of ERK and AKT was examined in CM and non-CM as in C. Tyrosine phosphorylation of Gab1 (G) and Gab2 (H) and their association with SHP2 and p85 in the mouse hearts were analyzed after injection with 5 μg of NRG-1β as in A and B, respectively. Heart lysates were prepared at the indicated time after injection. Gab1 and Gab2 underwent tyrosine phosphorylation and associated with SHP2 and p85 in a time-dependent manner upon NRG-1β stimulation. (I) Activation of ERK and AKT were assessed as in C. Arrows denote 2 isoforms of Gab1. Representative blots of 3 experiments are shown. PY99, antibody recognizing phospho-tyrosine.