Diminished degradation of myelin basic protein by anti-sulfatide antibody and interferon-γ in myelin from glia maturation factor-deficient mice

Abstract

In this study we show the effect of anti-sulfatide (RmAb) antibodies and inflammatory cytokines, TNF-α and IFN-γ in inducing myelin basic protein (MBP) degradation in myelin isolated from control wild type (WT) and glia maturation factor (GMF)-deficient (GMF-KO) mice. GMF was not detected in isolated myelin from WT and GMF-KO mice although it is present in brains of WT mice. Our results show that calcium-dependent neutral protease activity caused significantly elevated degradation of 18.5 and/or 17.5 kDa isoforms of MBP in WT myelin treated with RmAb or IFN-γ. In contrast, MBP degradation in isolated myelin from GMF-KO mice remained unaffected following treatment with RmAb, IFN-γ, or GM-CSF. Neither the 14 kDa isoform of MBP nor proteolipid protein (PLP) showed an elevated degradation compared to controls. A virtual absence of GM-CSF, TNF-α and IFN-γ in GMF-KO brain compared to WT was also evident when the animals were challenged with MOG 35-55. Additionally, the myelin from GMF-KO mice showed difference in distribution of myelin oligodendrocyte glycoprotein (MOG) and β-tubulin in a sucrose density gradient myelin–axolemmal fractions compared to WT. Taken together, our data suggests a role for GMF in the biochemical organization of myelin and thereby its effect on MBP degradation induced by RmAb and IFN-γ.