In vivo and in vitro models of demyelinating disease: a phosphoprotein phosphatase in host cell endosomes dephosphorylating the nucleocapsid protein of coronavirus JHM.

We have identified a phosphoprotein phosphatase which dephosphorylates efficiently the NC protein of coronavirus JHM. The activity was found in L-2 murine fibroblasts, Wistar Furth rat neonatal brain extracts, Wistar Furth rat oligodendrocyte primary cells and in Roc-1 cells, an oligodendrocytic hybrid cell line. In both L-2 cells and Roc-1 cells the enzyme was found to be localized predominantly in the endosomal fraction. The enzyme is optimally active at pH 7.0 and has a requirement for Mn++ ions. This PPPase activity is distinguishable from acidic and alkaline phosphatases. In view of the specificity of the endosomal PPPase for the phosphory-lated NC protein it is hypothesized that this enzyme may have a function during early stages of coronavirus infection.