Role of Extracellular Signal‐Regulated Protein Kinases 1 and 2 in Oligodendroglial Process Extension

Abstract

compared with cells treated with PMA alone. Furthertal and Health Sciences Center, University of British Columbia, more, these MEK inhibitor-pretreated cells were still via-Vancouver, British Columbia, V6T 2B5 Canada. ble but showed no process extensions up to 1 week later. Dr. R. L. Stariha and Dr. S. Kikuchi are co-first authors.Therefore, we propose that a threshold level of ERK activ-Abbreviations used: ERK, extracellular signal-regulated protein ity is required for the initiation of OLG process extension. kinase; GaIC, galactocerebroside; MAP2, microtubule-associated Key Words: Extracellular signal-regulated protein kiprotein 2; MAPK, mitogen-activated protein kinase; MBP, myelin nase-Extracellular signal-regulated protein kinase m~~basic protein; MEK, extracellular signal-regulated protein kinase kinase; MS, multiple sclerosis; OLG, oligodendrocyte; PAGE, polyforms-Mitogen-activated protein kinases-Oligodenacrylamide gel electrophoresis; PBS, phosphate-buffered saline; drocytes-Process extension-Protein kinase C activa-PBS~,phosphate-buffered saline containing 5% normal goat serum tion. and 0.2% Triton X-l00; PKC, protein kinase C; PMA, phorbol 12-J. Neurochem. 68, 945-953 (1997). myristate 13-acetate; SDS, sodium dodecyl sulfate. 945 946 R. L STARIHA ET AL

Isolation and Expression Pattern of Human Unc-33-Like Phosphoprotein 6/Collapsin Response Mediator Protein 5 (Ulip6/CRMP5): Coexistence with Ulip2/CRMP2 in Sema3A- Sensitive Oligodendrocytes

“…This time course is similar to that for the effect of phorbol ester on oligodendrocyte process extension (Stariha et al, 1997). Sema3A, via Ulip2/CRMP2 or Ulip6/CRMP5, may act on the dynamics of microtubules, leading to the decrease in process extension.…”

“…Sema3A, via Ulip2/CRMP2 or Ulip6/CRMP5, may act on the dynamics of microtubules, leading to the decrease in process extension. Several results support this hypothesis: (1) microtubules are present in oligodendrocytes and reflect oligodendrocyte function (Lunn et al, 1997), (2) Ulip2/CRMP2 mediates the dynamics of microtubules , and (3) protein kinase, which could phosphorylate the numerous phosphorylation sites of the Ulip/CRMPs, regulates oligodendrocyte process extension (Stariha et al, 1997) and can affect microtubule dynamics (Gotoh et al, 1991). Although these results show that oligodendrocytes are sensitive to Sema3A, other signals might also be mediated by Ulip/CRMPs (Wang and Strittmatter, 1997).…”

Classic 18.5- and 21.5-kDa Myelin Basic Protein Isoforms Associate with Cytoskeletal and SH3-Domain Proteins in the Immortalized N19-Oligodendroglial Cell Line Stimulated by Phorbol Ester and IGF-1

“…Such PMA-induced membrane ruffling has been employed in other investigations, which have demonstrated its ability to change the properties and appearance of the plasma membrane and rearrangement of the actin cytoskeleton in OLGs and other cells [53][54][55]. In this study, membranous protrusions or ruffles were seen immediately on introducing PMA into the cell medium, and often but not always disappeared within a few minutes (see below).…”

“…(This threonyl residue in the human 18.5-kDa MBP sequence corresponds to residues Thr95/Thr97 in the murine/bovine 18.5-kDa MBP sequences, respectively [11,15,35,74]). The PMA-stimulation activates PKC, which is upstream from MAPK [55]. The phosphorylated form was also enriched in membrane ruffles; the importance of phosphorylation of this threonyl residue is reviewed in references [8, 10-12, 15, 74, 75].…”

“…The PMA-stimulation of PKC in primary OLGs has been shown to result in activation of mitogen-activated protein kinase (MAPK) [55]. Using a phospho-specific antibody toward Thr98 (human 18.5-kDa sequence; bovine Thr97; murine Thr95) of MBP, an identified MAPK [56] and GSK-3β [57] phosphorylation site, we found that there was an overall increase in Thr98-phosphorylated MBP-C1 in PMA-stimulated N19-OLGs, including at ruffling sites (Fig.…”