Hypoxic response of synaptosomal proteins in term guinea pig fetuses

Early events in the hypoxia-induced response trigger tyrosine phosphorylati on cascades involving a large number of enzymes and substrates. The resolvi ng power of advanced two-dimensional gel electrophoresis, followed by immun oblotting with specific antibodies to phosphotyrosine, has been used to ana lyze hypoxia-induced modifications in guinea pig brain synaptosomes. These procedures, in conjunction with computer-aided image analysis, are useful i n the differential display of gene products, providing comparison at the le vel of posttranslationally modified products. Studies were performed in cer ebral cortical synaptosomes from three normoxic and three hypoxic newborn g uinea pigs. To filter off background noise consisting of nonreproducible mi grating protein spots, only reproducible features of electrophoretic patter ns were considered. Immunoreactivity patterns obtained with anti-phosphotyr osine antibodies proved to be different in normoxic and hypoxic synaptosome s: of a total of 130 immunoreactive spots, 49 were tyrosine-phosphorylated in hypoxic synaptosomes only and 20 in the normoxic ones only. Our data sug gest that hypoxia extensively remodels the signaling pathway by switching o ff tyrosine phosphorylation of some cellular components (i.e., alpha-intern exin) and switching on tyrosine phosphorylation of some other proteins (i.e ., heat shock cognate 70, aconitase, 2',3'-cyclic nucleotide 3'-phosphodies terase, and pyruvate kinase).