title: Cell-type-specific roles of IGF-1R and EGFR in mediating Zn2+-induced ERK1/2 and PKB phosphorylation.
abstract: Zn(2+) exerts insulin-mimetic and antidiabetic effects in rodent models of insulin resistance, and activates extracellular-signal-regulated kinases 1 and 2 (ERK1/2) and protein kinase B (PKB), key components of the insulin signaling pathway. Zn(2+)-induced signaling has been shown to be associated with an increase in the tyrosine phosphorylation of insulin receptor (IR), as well as of insulin-like growth factor 1 receptor (IGF-1R) and epidermal growth factor receptor (EGFR) in several cell types. However, the specific contribution of these receptor protein tyrosine kinases (R-PTKs) in mediating Zn(2+)-induced responses in a cell-specific fashion remains to be established. Therefore, using a series of pharmacological inhibitors and genetically engineered cells, we have investigated the roles of various R-PTKs in Zn(2+)-induced ERK1/2 and PKB phosphorylation. Pretreatment of Chinese hamster ovary (CHO) cells overexpressing a human IR (CHO-HIR cells) with AG1024, an inhibitor for IR protein tyrosine kinase (PTK) and IGF-1R-PTK, blocked Zn(2+)-induced ERK1/2 and PKB phosphorylation, but AG1478, an inhibitor for EGFR, was without effect in CHO cells. On the other hand, both of these inhibitors were able to attenuate Zn(2+)-induced phosphorylation of ERK1/2 and PKB in A10 vascular smooth muscle cells. In addition, in CHO cells overexpressing tyrosine kinase deficient IR, Zn(2+) was still able to induce the phosphorylation of these two signaling molecules, whereas the insulin effect was significantly attenuated. Furthermore, both Zn(2+) and insulin-like growth factor 1 failed to stimulate ERK1/2 and PKB phosphorylation in IGF-1R knockout cells. Also, Zn(2+)-induced responses in CHO-HIR cells were not associated with an increase in the tyrosine phosphorylation of the IR beta-subunit and insulin receptor substrate 1 in CHO-HIR cells. Taken together, these data suggest that distinct R-PTKs mediate Zn(2+)-evoked ERK1/2 and PKB phosphorylation in a cell-specific manner.
authors: Laboratory of Cell Signaling, Montreal Diabetes Research Center, Centre de Recherche, Centre Hospitalier de l'Université de Montréal (CRCHUM), Angus Campus, 2901 Rachel Est, Montreal, QC, H1W 4A4, Canada. npandey@ottawaheart.ca
authors: Nihar R
authors: NR
authors: Pandey
authors: George
authors: G
authors: Vardatsikos
authors: Mohamad Z
authors: MZ
authors: Mehdi
authors: Ashok K
authors: AK
authors: Srivastava
mesh_terms: D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011799:Quinazolines; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology; D015854:Up-Regulation; D015032:Zinc / Q000378:metabolism*
chemical_list: D055504:Insulin Receptor Substrate Proteins; D011799:Quinazolines; D020032:Tyrphostins; C447031:tyrphostin AG 1024; C101044:RTKI cpd; D066246:ErbB Receptors; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D015032:Zinc