Chlorovirus Glycoproteins and SOD1G93A Significantly Enhance, While Cellular Proteins IRF3 and ERK MAP-kinase Significantly Dampen, Production of ALS-associated Inflammatory Factors from Murine Macrophages
Gary Pattee1, Petro Thomas2, Ahmed Esmael3, Irina Agarkova3, David Dunigan3, Fabrizio Chiodo4, Cristina de castro5, James Van Etten3
1Neurology Associates PC, 2UNMC, 3UNL, 4Institute of Biomolecular Chemistry (ICB), 5DIPARTIMENTO DI SCIENZE CHIMICHE
Objective:
Human SOD1G93A influences the response of macrophages to chloroviruses or the major glycoproteins of chloroviruses.
Background:
Compared with PBCV-1 chlorovirus, ATCV-1 chlorovirus accelerates the onset of motor neuron disease in ALS model SOD1G93A mice and induces an ALS-associated inflammatory cytokine response from macrophages that is composed of high levels of Nitric oxide (NO) and IL-6.
Design/Methods:
We developed murine RAW264.7 macrophage cell lines that express human wtSOD1 or SOD1G93A. We isolated the major glycoproteins (gp) from chloroviruses PBCV-1, ATCV-1, OSy-NE5, and variants of PBCV-1 and then stimulated RAW cells with each. Because the protein IRF3 drives ISRE activity and along with ERK MAPKs induce innate anti-viral immune responses, we stimulated wtRAW cells and IRF3KO RAW cells with ATCV-1gp and P1L6gp in the presence or absence of the ERK MAPK inhibitor, U0126.
Results:
RAW cells expressing wtSOD1 exhibited reduced inflammatory factors to ATCV-1 compared with cells expressing SOD1G93A. PBCV-1-gp failed to stimulate activity of Interferon stimulated Response Elements (ISRE), IL-6, and NO from RAW cells. Interestingly, the PBCV-1 variant P1L6, which produces a truncated glycan on its gp, stimulated very high levels of ISRE activity, IL-6 and NO. As with ATCV-1 virus, RAW cells expressing wtSOD1 exhibited reduced IL-6 and NO response to ATCV-1gp, P1L6gp, and OSy-NE5gp, compared with high responses of RAW cells with G93ASOD1. In the absence of IRF3 or ERK activity, the induction of IL-6 by ATCV-1gp and P1L6gp from RAW cells was significantly higher than wt RAW cells with ERK activity. In contrast, without IRF3 the production of NO was significantly lower, while the absence of ERK activity significantly increased NO induction.
Conclusions:
The results show that SOD1G93A in macrophages responding to certain chlorovirus glycoproteins enhances production of inflammatory factors associated with development of ALS. Moreover, IRF3 and ERK MAP kinases likely regulate the responses of macrophages to those chlorovirus glycoproteins.