Different Neuroligands and Signal Transduction Pathways Stimulate CREB Phosphorylation at Specific Developmental Stages Along Oligodendrocyte Differentiation

Authors

  • Carmen Sato-Bigbee,

  • Shubhro Pal,

    1. Department of Neurology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia, U.S.A.
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  • Annie K. Chu


  • Abbreviations used : CamK, Ca2+/calmodulin-dependent kinase ; cAMP, cyclic AMP ; CREB, cyclic AMP-response element binding protein ; db-cAMP, dibutyryl cyclic AMP ; DMEM, Dulbecco's modified Eagle's medium ; MAPK, mitogen-activated protein kinase ; MBP, myelin basic protein ; MEK, MAPK kinase ; OLG, oligodendrocyte ; PBS, phosphate-buffered saline ; P-CREB, phosphorylated CREB ; PKA, cyclic AMP-dependent protein kinase ; PKC, protein kinase C ; RSK, ribosomal S6 kinase ; Tg, thapsigargin.

Address correspondence and reprint requests to Dr. C. Sato-Bigbee at Department of Biochemistry and Molecular Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, P.O. Box 980614, Richmond, VA 23298-0614, U.S.A.

Abstract

Abstract : We have shown previously that the pattern of expression of the transcription factor CREB (cyclic AMP-response element binding protein) in developing oligodendrocytes (OLGs) suggests a role during a period that precedes the peak of myelination in rat brain. We have now investigated the signaling pathways that could be responsible for activating CREB by phosphorylation at different stages along OLG maturation. CREB phosphorylation was studied in short-term cultures of immature OLG precursor cells and young OLGs isolated from 4- and 11-day-old rat cerebrum, respectively. The results indicated that at both developmental stages, CREB phosphorylation could be stimulated by either increased concentrations of cyclic AMP and cyclic AMP-dependent protein kinase activation or increased Ca2+ levels and a protein kinase C activity. The results also showed that CREB phosphorylation in immature OLG precursor cells could be up-regulated by treatment with histamine, carbachol, glutamate, and ATP (neuroligands known to increase Ca2+ levels in these cells), by signaling cascade(s) that involve a protein kinase C activity, as well as the mitogen-activated protein kinase pathway. In contrast, in cells isolated from 11-day-old rats, at a developmental stage that immediately precedes the beginning of the active period of myelin synthesis, CREB phosphorylation was only stimulated by treatment with the β-adrenergic agonist isoproterenol in a process that appears to be mediated by a cyclic AMP/cyclic AMP-dependent protein kinase-dependent pathway. These results support the idea that CREB could be a mediator of neuronal signals that, coupled to specific signal transduction cascades, may play different regulatory roles at specific stages along OLG differentiation.

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