Impairment of protein kinase C activity in twitcher Schwann cells in vitro.
Twitcher (twi/twi) is a murine model of globoid cell leukodystrophy in humans caused by a genetic deficiency in activity of galactosylceramidase. Our previous study demonstrated that the rate of Schwann cell proliferation in twi/twi was considerably lower than that of the control (+/+) in vitro. We hypothesize that the lower mitotic rate in twi/twi results from the metabolic perturbation of Schawann cells caused by an accumulation of the toxic metabolite of galactosylceramidase, psychosine, a potent inhibitor of protein kinase C (PKC). Mouse Schwann cells are known to be stimulated to divide by growth factors in media containing fetal bovine serum. The stimulation by glial growth factor (GGF) or platelet-derived growth factor-BB (PDGF-BB) is though to be through the PKC pathway, but not by the basic fibroblast growth factor (bFGF) or transforming growth factor-beta (TGF-beta). Thus, we tested responses of twi/twi and +/+ Schwann cells to these growth factors. Schwann cells were isolated from the dorsal root ganglia at 30 days of age and the experiments were carried out at 21 days in vitro. In media containing PDGF-BB or bovine pituitary extract (BPE), the mitotic rate of twi/twi Schwann cells was 76% or 69% of the +/+ value, respectively, while significant differences were detected between twi/twi and +/+ in cultures containing TGF-beta or bFGF. When phorbol 12,13-dibutyrylate, a specific activator of PKC, was added to the media containing PDGF-BB or BPE, the mitotic rate of twi/twi Schwann cells improved up to 90% of +/+ cells. Staurosporine, an inhibitor of PKC. suppressed the proliferation of both twi/twi and +/+ Schwann cells. However, proliferation of twi/twi Schwann cells was suppressed by one-tenth of the concentration required for +/+ Schwann cells. These results are consistent with an accumulation of psychosine, an inhibitor of PKC, and suggest that the signal transduction system through PKC is impaired in the twi/twi Schwann cells.
Yamada
H
H
Brain and Development Research Center, School of Medicine, University of North Carolina at Chapel Hill 27599-7525, USA.
Martin
P
P
Suzuki
K
K
D000818:Animals; D002417:Cattle; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D020904:Glia Maturation Factor; D006131:Growth Inhibitors / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008818:Mice, Neurologic Mutants; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010902:Pituitary Gland / Q000502:physiology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D012583:Schwann Cells / Q000187:drug effects / Q000201:enzymology*; D019311:Staurosporine / Q000494:pharmacology; D014020:Tissue Extracts / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D004791:Enzyme Inhibitors; D020904:Glia Maturation Factor; D006131:Growth Inhibitors; D009419:Nerve Tissue Proteins; D010982:Platelet-Derived Growth Factor; D011994:Recombinant Proteins; D014020:Tissue Extracts; D016212:Transforming Growth Factor beta; D016222:Fibroblast Growth Factor 2; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D019311:Staurosporine