Intracellular regulation of the production and release of human erythroid-directed lymphokines.
Erythroid burst-promoting activity (BPA) is released from B lymphocytes in soluble (sBPA) and membrane-bound (mBPA) forms. To study intracellular processes involved in production of these physically separable factors, we measured their time course release into serum-free medium from B cells that were pulse-exposed for 5-240 min to nonmitogenic base medium or inhibitors of energy-dependent metabolism (2,4-dinitrophenol, sodium azide, and 2-deoxy-D-glucose), transcription and translation (actinomycin D and cycloheximide), replicative DNA synthesis (cytosine arabinoside), or posttranslational processing (monensin). mBPA and sBPA were initially detectable after 1 and 2 h, respectively. Maximum cumulative levels of 8 +/- 0.6 and 9 +/- 1.0 U/ml, respectively, were reached after 8 h. In contrast, cumulative mBPA and sBPA levels in medium prepared from cells treated with metabolic inhibitors were reduced by up to 90%. Both surface exfoliation and mBPA expression by intact plasma membranes were diminished. Whereas pulse-exposure to cytosine arabinoside had no effect, treatment with actinomycin D or cycloheximide abolished BPA expression. Exposure to monensin reduced mBPA and sBPA levels to zero in a concentration-and time-dependent fashion. We conclude that production and release of BPA is an energy-dependent process, requiring mRNA synthesis and translation and posttranslational remodeling of the protein but not replicative DNA synthesis.
Dainiak
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Department of Medicine, University of Connecticut Health Center, Farmington 06032.
Sorba
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S
D019297:2,4-Dinitrophenol; D001402:B-Lymphocytes / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D004140:Dinitrophenols / Q000494:pharmacology; D004920:Erythropoiesis; D006031:Glycosylation; D006801:Humans; D008222:Lymphokines / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D008985:Monensin / Q000494:pharmacology; D019714:Tissue Inhibitor of Metalloproteinases
D003598:Cytoskeletal Proteins; D004140:Dinitrophenols; D008222:Lymphokines; D019714:Tissue Inhibitor of Metalloproteinases; D004247:DNA; D008985:Monensin; D019297:2,4-Dinitrophenol