No abstract

Background: Inhibition of Abl kinases has an ameliorating effect on the rodent model for multiple sclerosis, experimental autoimmune encephalomyelitis, and arrests lymphocyte activation. The family of Abl kinases consists of the Abl1/Abl and Abl2/Arg tyrosine kinases. While the Abl kinase has been extensively studied in immune activation, roles for Arg are incompletely characterized. To investigate the role for Arg in experimental autoimmune encephalomyelitis, we studied disease development in Arg −/− mice. Methods: Arg −/− and Arg +/+ mice were generated from breeding of Arg +/− mice on the C57BL/6 background. Mice were immunized with the myelin oligodendrocyte glycoprotein (MOG)35–55 peptide and disease development recorded. Lymphocyte phenotypes of wild type Arg +/+ and Arg −/− mice were studied by in vitro stimulation assays and flow cytometry. Results: The breeding of Arg +/+ and Arg −/− mice showed skewing in the frequency of born Arg −/− mice. Loss of Arg function did not affect development of experimental autoimmune encephalomyelitis, but reduced the number of splenic B-cells in Arg −/− mice following immunization with MOG peptide. Conclusions: Development of MOG-induced experimental autoimmune encephalomyelitis is not dependent on Arg, but Arg plays a role for the number of B cells in immunized mice. This might suggest a novel role for the Arg kinase in B-cell trafficking or regulation. Furthermore, the results suggest that Arg is important for normal embryonic development.

Multiple sclerosis is a neuroinflammatory degenerative disease, caused by activated immune cells infiltrating the CNS. The disease etiology involves both genetic and environmental factors. The mouse genetic locus, Eae27, linked to disease development in the experimental autoimmune encephalomyelitis (EAE) model for multiple sclerosis, was studied in order to identify contributing disease susceptibility factors and potential drug targets for multiple sclerosis. Studies of an Eae27 congenic mouse strain, revealed that genetic variation within Eae27 influences EAE development. The Abl2 gene, encoding the non-receptor tyrosine kinase Arg, is located in the 4,1 megabase pair long Eae27 region. The Arg protein plays an important role in cellular regulation and is, in addition, involved in signaling through the B- and T-cell receptors, important for the autoimmune response. The presence of a single nucleotide polymorphism causing an amino acid change in a near actin-interacting domain of Arg, in addition to altered lymphocyte activation in the congenic mice upon immunization with myelin antigen, makes Abl2/Arg a candidate gene for EAE. Here we demonstrate that the non-synonymous SNP does not change Arg’s binding affinity for F-actin but suggest a role for Abl kinases in CNS inflammation pathogenesis by showing that pharmacological inhibition of Abl kinases ameliorates EAE, but not experimental arthritis.

The Abelson non-receptor tyrosine kinases, c-Abl and Arg, are important regulators of cellular processes in cancer, inflammation, infection, and neuronal dynamics. Recent research on the role for these kinases in processes involving interactions with the cytoskeleton or signaling molecules, may lead to further insight into the pathogenesis of a variety of disorders, including chronic inflammatory diseases. In a mouse model for multiple sclerosis, we recently reported that Arg deficient mice develop T-cell mediated autoimmune neuro-inflammation with the same severity as littermate controls, but display a different B-cell phenotype upon immunization. Here we comment on these results and discuss the role for Arg in B-cell activation and homeostasis.