Schwann cells stimulated by axolemma-enriched fractions express cyclic AMP responsive element binding protein.
Both axolemma-enriched fractions (AEF) and cyclic AMP have been shown to regulate the proliferation and differentiation of cultured primary Schwann cells (SC). We have evaluated the role of CREB, a transcription factor that binds to the cAMP-responsive element, in mediating the AEF-stimulated SC proliferation and differentiation. We detected CREB in nuclear extracts derived from SC stimulated with 40 micrograms/ml of AEF for 16, 24, 48, 72, and 96 hr, using a DNA-electrophoretic mobility shift assay. Unstimulated quiescent SC contained low levels of CREB which increased to a maximal level after 48 hr of AEF treatment. Using anti-CREB antibodies and Western blot analysis, after 24 hr of AEF treatment we first detected CREB as a 45 kDa protein which reached a maximal level of expression after 72 hr. Double labeled immunocytochemistry using anti-CREB and anti-5-bromo-2'-deoxy-uridine antibodies demonstrated maximal CREB expression after 72 hr of AEF treatment, closely coinciding with the temporal expression of SC proliferation. At all times examined, all AEF-treated SC labeled by anti-CREB antibodies were also labeled with anti-BrdU antibodies. These observations are consistent with the view that CREB could play an important role in the induction of SC proliferation by AEF.
Department of Cell Biology, Neurobiology, and Anatomy, Loyola University Medical Center, Maywood, Illinois, USA.
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Lee
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Sato-Bigbee
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De Vries
D000818:Animals; D001369:Axons / Q000378:metabolism*; D015153:Blotting, Western; D002455:Cell Division / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012583:Schwann Cells / Q000187:drug effects / Q000378:metabolism*; D013268:Stimulation, Chemical; D015854:Up-Regulation / Q000187:drug effects
D017362:Cyclic AMP Response Element-Binding Protein; D009687:Nuclear Proteins; D004247:DNA