Induction of newly synthesized proteins in astroglial cells exposed to lead.
Although astroglial cells accumulate lead (Pb), they appear to be less sensitive to its overt deleterious effects than are neurons. One possible mechanism in which as rocytes adapt to Pb may be by upregulating the expression of particular genes. This study evaluated the effect of exogenous Pb on proteins synthesized in primary rat astroglial cultures. Following incubations with 0-50 microM Pb acetate cells were radiolabeled with leucine for various time intervals. Proteins were subsequently analyzed using SDS-PAGE followed by fluorography. Changes observed within the first 24 hr resembled a classical stress response and included increased synthesis of proteins with apparent molecular weights of 90, 70, 32-35, and 23 kDa. The most notable change was the enhanced synthesis and abundance of the 23-kDa protein (p23) which persisted throughout a 14-day treatment period, whereas the synthesis of the other proteins declined. This protein did not appear to be induced in rat lung fibroblasts treated with similar concentrations of Pb. Subcellular fractionation indicated that p23 was localized to the cytosol. Treatment with actinomycin D or cycloheximide prior to the addition of Pb precluded induction of p23. Pulse labeling of cells following a 24-hr Pb exposure revealed that p23 continued to be synthesized for 12 but not 24 hr following removal of Pb. Pulse-chase experiments indicated that the protein was stable for at least 18 hr following the removal of Pb. Two-dimensional gel electrophoresis revealed that the 23-kDa Pb-induced protein consisted of multiple-charged species with pl values ranging from 4.3 to 7.8.
Opanashuk
L A
LA
Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, New York 14642.
Finkelstein
J N
JN
D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D003470:Culture Media; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D004355:Drug Stability; D015180:Electrophoresis, Gel, Two-Dimensional; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D007424:Intracellular Fluid / Q000378:metabolism; D007854:Lead / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley
D003470:Culture Media; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; C073446:protein p23; D007854:Lead