CREG, a new regulator of ERK1/2 in cardiac hypertrophy

OBJECTIVES: The cellular repressor of E1A-stimulated genes (CREG), a mannose-6-phosphate-containing secreted glycoprotein, enhances differentiation and inhibits proliferation. In this study, our aim was to understand the role of CREG in cardiac hypertrophy. METHODS: Two models of cardiac hypertrophy were used: the in vivo pressure-overloaded rat cardiac hypertrophy and the in vitro stretched neonatal rat cardiomyocyte hypertrophy. CREG's function in cardiac cells was investigated after over-expression or antisense inhibition of CREG. RESULTS: We found reduced CREG expression in rat hearts after the in vivo overload, as shown by Northern blot analysis. CREG over-expression inhibited cardiac cell growth, as demonstrated by reduced protein content, cell area and ERK1/2 level in cultured neonatal rat cardiomyocytes, and by the reduced proliferation of cultured neonatal rat cardiac fibroblasts. Additionally, over-expression of CREG dampened the stretched cardiomyocyte hypertrophy through ERK1/2. On the other hand, the opposite effects were observed when CREG expression was decreased using antisense. This modulation of CREG expression resulted in no changes in the cardiomyocyte expressions of the hypertrophic or apoptotic signaling molecules such as protein kinase C (PKC) epsilon, PKC beta1, PKC alpha, PKC beta2, PKC delta, JNK1/2, p38, p53, Bax, Bcl2 and Fas. CONCLUSIONS: CREG was found to inhibit cardiac cell growth as a novel regulator of ERK1/2 and might participate in the development of cardiac hypertrophy under pressure overload. The insight that CREG inhibited the growth in rat hearts in vivo and in cardiac cells in vitro provides new clues for further investigation of the mechanism of heart remodeling.