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

Abstract

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 (IC(50) 0.35 microM, 54 times more selective for erbB2 than for EGFR, IC(50) 19 microM), and AG 879 (IC(50) of 1 microM for erbB2 versus 500 microM for EGFR). We found that both inhibited the proliferation on a dose-dependent basis, reaching a 30% maximal inhibition at 100 microM (P < 0.001) for AG825, and a 20% maximal inhibition at 10 microM (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.

Expression of erythroblastic leukemia viral oncogene homolog (erbBS) mRNAs and possible splice variants in 3T3-L1 preadipocytes

“…Expression of erbB2 at the protein level in 3T3-L1 cells (20) and its involvement in the proliferation/differentiation processes of these cells were previously observed (21). The present study completes our understanding of the expression, modulation and activation of the erbB receptors in the 3T3-L1 cell line and poses new questions regarding possible roles for erbB soluble forms in this adipogenic model.…”

“…Previously, we studied erbB1/EGFR, erbB2, erbB3 and erbB4 as well as ligands, heregulin and EGF, in terms of expression, activation and modulation during the adipogenic process in 3T3-L1 cells (20,21). In this study, the presence of full-length erbB mRNAs and, of splice or proteolytic variants were examined using RT-PCR.…”

Tumor-linked HER2 expression: association with obesity and lipid-related microenvironment

“…On the other hand, EGF was shown to stimulate proliferation in 3T3-L1 preadipocytes [80]. In addition, using the same 3T3-L1 cells, Pagano et al [81] demonstrated that EGF can induce the EGFR-HER2 heterodimerization and stimulate receptor tyrosine phosphorylation of both EGFR and HER2. A recent in vivo study (using ApoE −/− and C57BL/6 mice, Table 4 [82], [83], [84], [85], [86], [87], [88], [89]) has recorded the detrimental role of EGFR in the pathogenesis of obesity-related nephropathy [90].…”

“…Overall, the status of EGFR in the lipogenic environment is intricate. However, different in vitro and in vivo experiments and studies on human subjects revealed that EGFR could be modulated in the abovementioned circumstances [79], [80], [81], [90], [91]. …”

Fatty Acid Synthase: Association with Insulin Resistance, Type 2 Diabetes, and Cancer

“…Recent studies investigating the expression of receptors belonging to the epidermal growth factor receptor subfamily in the murine fibroblast cell line Swiss 3T3L1, which undergo naturally or hormonally induced adipocyte differentiation, have found that these fibroblasts express HER2, in addition to HER1, and in a quantity comparable to or even greater than the breast cancer cell line T47D (71 ). We are currently investigating whether these growth-factor receptors, the major contributors at the transcriptional and translational level to cancer-associated FASN overexpression, likewise play an active role in an FASN-related mechanism of switching from a mitogenic to a differentiating signaling pathway during adipogenesis (72 ).…”