Inhibition of insulin-like growth factor-I signaling by ethanol in neuronal cells.
BACKGROUND
Ethanol inhibits insulin-like growth factor-I receptor (IGF-IR) activation. However, the potency of ethanol for inhibition of the IGF-IR and other receptor tyrosine kinases varies considerably among different cell types. We investigated the effect of ethanol on IGF-I signaling in several neuronal cell types.


METHODS
IGF-I signaling was examined in SH-SY5Y neuroblastoma cells, primary cultured rat cerebellar granule neurons, and rat NG-108 neuroblastoma x glioma hybrids. The tyrosine phosphorylation of IGF-IR, IRS-2, Shc, and p42/p44 MAP kinase (MAPK), and the association of Grb-2 with Shc, were examined by immunoprecipitations and Western blotting.


RESULTS
IGF-I-mediated tyrosine phosphorylation of MAPK was inhibited by ethanol in all cell lines. IGF-IR autophosphorylation was markedly inhibited by ethanol in SH-SY5Y cells, was only mildly inhibited in cerebellar granule neurons, and was unaffected in rat NG-108 cells. In vitro tyrosine autophosphorylation of immunopurified IGF-IR obtained from all cell lines was inhibited by ethanol. There was also differential ethanol sensitivity of IRS-2 and Shc phosphorylation, and the association of Shc with IRS-2, among the different cell types.


CONCLUSIONS
The findings demonstrate that IGF-I-mediated MAPK activation is a sensitive target of ethanol in diverse neuronal cell types. The data are consistent with ethanol-induced inhibition of IGF-IR activity, although the extent of IGF-IR tyrosine autophosphorylation per se is a poor marker of the inhibitory action of ethanol on this receptor. Furthermore, despite uniform inhibition of MAPK in the different neuronal cell types, tyrosine phosphorylation of proximal mediators of the IGF-IR are differentially inhibited by ethanol.
Hallak
H
H
Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Seiler
A E
AE
Green
J S
JS
Henderson
A
A
Ross
B N
BN
Rubin
R
R
D015153:Blotting, Western; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D002531:Cerebellum / Q000166:cytology; D004789:Enzyme Activation / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D010703:Phorbol Esters / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000187:drug effects / Q000378:metabolism
D002492:Central Nervous System Depressants; D010703:Phorbol Esters; D011994:Recombinant Proteins; D000431:Ethanol; D014443:Tyrosine; D007334:Insulin-Like Growth Factor I; D019950:Mitogen-Activated Protein Kinase 1