Down-modulation of erbB2 activity is necessary but not enough in the differentiation of 3T3-L1 preadipocytes

PAGANO, E.; COSO, O.; CALVO J. C.

JOURNAL OF CELLULAR BIOCHEMISTRY

Año: 2007 p. 1 - 2

0730-2312

The high incidence of obesity-related pathologies, led to the study of the mechanisms involved in preadipose cell proliferation and differentiation. Here, we demonstrate that modulation of erbB2, plays a fundamental role during proliferation and adipogenic induction of preadipocytes. Using 3T3-L1 cells as model, we demonstrate that EGF (10 nM, 5 min) in addition to stimulate receptor tyrosine phosphorylation of both erbB2 and EGFR, is able to induce the heterodimer erbB2-EGFR. We treated proliferating 3T3-L1 cells with two inhibitors, AG 825 (IC50 0.35 µM, 54 times more selective for erbB2 than for EGFR, IC50 19 µM), and AG 879 (IC50 of 1 µM for erbB2 versus 500 µM for EGFR). We found that both inhibited the proliferation on a dose-dependent basis, reaching a 30% maximal inhibition at 100 µM (P < 0.001) for AG825, and a 20% maximal inhibition at 10 µM (P < 0.001) for AG 879. These results involve erbB2 in 3T3-L1 proliferation. When studying the differentiation process, we found that the action of MIX-Dexa immediately activates MEK, JNK and p38 kinases. We observed that PD98059 and SP600125 (MEK-ERK and JNK inhibitors, respectively) added 1 h prior to the MIX-Dexa induction produced a decrease in erbB2 expression after 6 h, which is even greater than the one produced by the inducers, MIX-Dexa. This work supports erbB2 as a key factor in 3T3-L1 adipogenesis, acting mostly and not only during the proliferative phase but also during the differentiation through modulation of both its expression and activity. J. Cell. Biochem. © 2007 Wiley-Liss, Inc.