Glucose regulates insulin mitogenic effect by modulating SHP-2 activation and localization in JAr cells.
The glucose effect on cell growth has been investigated in the JAr human choriocarcinoma cells. When JAr cells were cultured in the presence of 6 mm glucose (LG), proliferation and thymidine incorporation were induced by serum, epidermal growth factor, and insulin-like growth factor 1 but not by insulin. In contrast, at 25 mm glucose (HG), proliferation and thymidine incorporation were stimulated by insulin, serum, epidermal growth factor, and insulin-like growth factor 1 to a comparable extent, whereas basal levels were 25% lower than those in LG. HG culturing also enhanced insulin-stimulated insulin receptor and insulin receptor substrate 1 (IRS1) tyrosine phosphorylations while decreasing basal phosphorylations. These actions of glucose were accompanied by an increase in cellular tyrosine phosphatase activity. The activity of SHP-2 in HG-treated JAr cells was 400% of that measured in LG-treated cells. SHP-2 co-precipitation with IRS1 was also increased in HG-treated cells. SHP-2 was mainly cytosolic in LG-treated cells. However, HG culturing largely redistributed SHP-2 to the internal membrane compartment, where tyrosine-phosphorylated IRS1 predominantly localizes. Further exposure to insulin rescued SHP-2 cytosolic localization, thereby preventing its interaction with IRS1. Antisense inhibition of SHP-2 reverted the effect of HG on basal and insulin-stimulated insulin receptor and IRS1 phosphorylation as well as that on thymidine incorporation. Thus, in JAr cells, glucose modulates insulin mitogenic action by modulating SHP-2 activity and intracellular localization.
Bifulco
Giuseppe
G
Dipartimento di Ginecologia, Ostetricia e Fisiopatologia della Riproduzione Umana, Università degli Studi di Napoli Federico II, 80131 Naples, Italy.
Di Carlo
Costantino
C
Caruso
Matilde
M
Oriente
Francesco
F
Di Spiezio Sardo
Attilio
A
Formisano
Pietro
P
Beguinot
Francesco
F
Nappi
Carmine
C
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000187:drug effects*; D004261:DNA Replication / Q000187:drug effects; D004789:Enzyme Activation; D005947:Glucose / Q000494:pharmacology*; D006391:Hemangioma; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism; D014407:Tumor Cells, Cultured
C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526295:Irs1 protein, mouse; D020319:Oligodeoxyribonucleotides, Antisense; D010750:Phosphoproteins; D011972:Receptor, Insulin; D020929:Mitogen-Activated Protein Kinase Kinases; C516724:PTPN11 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; D005947:Glucose