Endosomal association of a protein phosphatase with high dephosphorylating activity against a coronavirus nucleocapsid protein

FEBS Letters

Mohandas, Devaki V.¹  Dales, Samuel¹ 

[1] Cytobiology Group, Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada N6A 5C1

关键词: Phosphoprotein phosphatase;    Endosome;    Coronavirus;    Nucleocapsid protein;    EDTA;    Ethylenediaminetetraacetate;    disodium salt;    EGTA;    Ethyleneglycol-bis(β-aminoethyl ether)-N;    N;    N′;    N′-tetraacetic acid;    PMSF;    phenyl methyl sulfonyl fluoride;    pNPP;    p-nitrophenyl phosphate;   

DOI  :  10.1016/0014-5793(91)80528-B

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

On the assumption that dephosphorylation of the neurotropic coronavirus JHM (JHMV) nucleocapsid protein (N) may be connected with initiation of the infectious cycle we searched for a relevant host enzyme activity. Analysis of subcellular fractions from L-2 murine fibroblasts, separated by dual Percoll density gradients, revealed the presence of a phosphoprotein phosphatase (PPPase), co-sedimenting with the endososomal/prelysosomal material, which possesses high activity against N. With purified [²²P]N as substrate it was demonstrated that this PPPase, distinguishable from acid and alkaline phosphatases, acts optimally at neutral pH in the presence of Mn²⁺ following treatment with a detergent. Complete inhibition with okadaic acid at 0.9–4.5 μM but not at 1–10 nM relegates this PPase to a type I protein phosphatase. Similar PPPase activity for N was present in the endosome fraction of a rat Roc-1 astrocytoma-oligodendrocyte cell line and in homogenates of brain and cultured oligodendrocytes. Our data suggest that the phosphorylated N of the inoculum may be modified by the endosomal PPPase in host cells, including those from the CNS so as to facilitate the JHMV infectious process.

【 授权许可】

Unknown