Increased rate of phosphorylation-dephosphorylation of the translational initiation factor eIF-4E correlates with the induction of protein and glycoprotein biosynthesis in activated B lymphocytes.

摘要: Abstract A 10-50-fold, biphasic increase in the rate of 32Pi labeling eIF-4E was closely correlated with induction protein and glycoprotein biosynthesis when resting murine splenic B lymphocytes (B cells) were activated by bacterial lipopolysaccharide or combination phorbol 12-myristate 13-acetate ionomycin. The fraction which phosphorylated only increased from 46% cells to 83% lipopolysaccharide-activated cells. This discrepancy between suggested that phosphoryl group turns over slowly compared turnover for phosphate moiety rapid (t1/2 = 2 h) comparison polypeptide chain, did not turn detectably 6 h. Neither kinase C nor a cyclic nucleotide-dependent appeared be involved phosphorylation cells, based on observations metabolic insensitive inhibitors H-7 HA1004, maximal occurred after activity "down-regulated" very low levels 13-acetate/ionomycin-activated Dephosphorylation vivo blocked okadaic acid (IC50 200 nM). These results indicate phosphorylation-dephosphorylation is associated high translation rates during activation implicate phosphatase-1 (or possibly-2A) dephosphorylation initiation factor.