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Expression of JC virus agnoprotein in progressive multifocal leukoencephalopathy brain
Yuki Okada1, Hirofumi Sawa, Shuichi Endo
1Laboratory of Comparative Pathology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
Abstract:
To examine the function of JC virus (JCV) agnoprotein, we examined the brains of cases of progressive multifocal leukoencephalopathy (PML), which is caused by JCV infection, using a newly generated antibody. The antibody reacted with 8 kDa protein specific for JCV agnoprotein by Western blotting. In vitro analyses showed that JCV capsid protein VP1 and large T antigen (T-Ag) were localized in the nuclei, but that agnoprotein was mainly detected in the cytoplasm of JCV-infected cells with an occasional nuclear staining. In the PML brain, an immunoreactive signal for agnoprotein was distributed in the perinuclear areas and cytoplasmic processes with occasional punctate staining in demyelinating lesions as well as adjacent myelinated areas. Agnoprotein presented mostly in the infected oligodendrocytes and partly in the astrocytes. Using double immunostaining, agnoprotein was seen to be expressed in the cytoplasmic processes of the cells, the nuclei of which were labeled with VP1 and T-Ag, where virus particles existed. Thus, JCV agnoprotein was mostly expressed in the infected oligodendrocytes and mainly localized in the cytoplasmic processes apart from virus particles in the demyelinated lesions.
Insights
JC virus (JCV) agnoprotein is primarily found in the cytoplasm of infected oligodendrocytes within brain lesions. This study reveals its localization in cytoplasmic processes, separate from viral particles, in progressive multifocal leukoencephalopathy.
Area of Science:
- Neurovirology
- Molecular Biology
- Cell Biology
Background:
- Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by JC virus (JCV) infection.
- The function of JCV agnoprotein, a key viral protein, remains incompletely understood, particularly its cellular localization during infection.
Purpose of the Study:
- To investigate the cellular and subcellular localization of JC virus (JCV) agnoprotein in the context of progressive multifocal leukoencephalopathy (PML).
- To elucidate the role of agnoprotein in JCV-infected cells, specifically in oligodendrocytes and astrocytes within the brain.
Main Methods:
- Western blotting using a newly generated antibody specific for JCV agnoprotein.
- In vitro analysis of JCV-infected cells to determine protein localization (VP1, T-Ag, agnoprotein).
- Immunohistochemistry and double immunostaining on PML brain tissues to visualize agnoprotein distribution in situ.
Main Results:
- A specific 8 kDa JCV agnoprotein was detected by Western blotting.
- In vitro, agnoprotein was predominantly cytoplasmic, with some nuclear staining, while VP1 and T-Ag were nuclear.
- In PML brains, agnoprotein localized to perinuclear areas and cytoplasmic processes in demyelinating lesions, mainly in infected oligodendrocytes and some astrocytes.
- Agnoprotein was observed in cytoplasmic processes of cells containing viral proteins (VP1, T-Ag) and particles.
Conclusions:
- JC virus (JCV) agnoprotein is primarily localized in the cytoplasm and cytoplasmic processes of infected oligodendrocytes within demyelinating lesions of PML brains.
- Agnoprotein's localization is distinct from the sites of viral particle assembly, suggesting a role independent of virion formation.
- These findings contribute to understanding the pathobiology of JCV infection and the function of its non-structural proteins.