title: 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.
authors.affiliation: Laboratorio de Química de Proteoglicanos y Matriz Extracelular, IByME, Buenos Aires, Argentina. eleonora_pagano@yahoo.com.ar
authors.forename: Eleonora
authors.initials: E
authors.lastname: Pagano
authors.forename: Omar
authors.initials: O
authors.lastname: Coso
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Calvo
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology*; D050156:Adipogenesis / Q000235:genetics*; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D049109:Cell Proliferation; D066246:ErbB Receptors / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism
chemical_list: D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D018719:Erb-b2 Receptor Tyrosine Kinases