N-Methyl-D-aspartate inhibits apoptosis through activation of phosphatidylinositol 3-kinase in cerebellar granule neurons. A role for insulin receptor substrate-1 in the neurotrophic action of n-methyl-D-aspartate and its inhibition by ethanol.
Primary cultured rat cerebellar granule neurons underwent apoptosis when switched from medium containing 25 mM K+ to one containing 5 mM K+. N-methyl-D-aspartate (NMDA) protected granule neurons from apoptosis in medium containing 5 mM K+. Inhibition of apoptosis by NMDA was blocked by the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor LY294002, but it was unaffected by the mitogen-activated protein kinase kinase inhibitor PD 98059. The antiapoptotic action of NMDA was associated with an increase in the tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1), an increase in the binding of the regulatory subunit of PI 3-kinase to IRS-1, and a stimulation of PI 3-kinase activity. In the absence of extracellular Ca2+, NMDA was unable to prevent apoptosis or to phosphorylate IRS-1 and activate PI 3-kinase. Significant inhibition of NMDA-mediated neuronal survival by ethanol (10-15%) was observed at 1 mM, and inhibition was half-maximal at 45-50 mM. Inhibition of neuronal survival by ethanol corresponded with a marked reduction in the capacity of NMDA to increase the concentration of intracellular Ca2+, phosphorylate IRS-1, and activate PI 3-kinase. These data demonstrate that the neurotrophic action of NMDA and its inhibition by ethanol are mediated by alterations in the activity of a PI 3-kinase-dependent antiapoptotic signaling pathway.
Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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Zhang
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Rubin
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TA
Rooney
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002531:Cerebellum / Q000166:cytology / Q000201:enzymology*; D003594:Cytoplasmic Granules / Q000201:enzymology; D004789:Enzyme Activation; D000431:Ethanol / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009474:Neurons / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D000431:Ethanol; D016202:N-Methylaspartate; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases