Aberrant expression of the NF-kappaB and IkappaB proteins in B cells from viable motheaten mice.

In viable motheaten mice, a mutation in the gene encoding the phosphatase, SHP1, causes severe immunodeficiency and autoimmunity. A defective phosphatase may result in modified phosphorylation of proteins involved in gene regulation. Since the NF kappa B/I kappa B proteins are regulated through phosphorylation, we wished to understand if the expression of these proteins,vas altered by the SHP1 defect. Splenic B cells from viable motheaten mice were isolated and assessed for purity by flow cytometry. Levels of each protein in isolated B cells were examined by Western blot analyses. Measurement of RNA levels for each protein was assessed by semi-quantitative RT-PCR. Western blots revealed that, in me(v) whole cell lysates, there were reduced levels of RelA and RelB proteins and increased levels of p50 and c-Rel. Furthermore, we analyzed the protein levels of I kappa B alpha and found that, in me(v), this inhibitor was significantly reduced, while the level of another member of the I kappa B family, I kappa B beta, was not. To determine if these findings in me(v) were secondary to the autoimmune process, we evaluated NF-kappa B/I kappa B expression in the BXSB murine model of autoimmunity. Unlike me(v), B cells from BXSB/Yaa mice had NF-kappa B complexes composed of the ReM submit, and I kappa B alpha was readily detected. In addition, RNA for the RelA and I kappa B alpha proteins in me(v) and control littermates was detected by RT-PCR, indicating that the reduced amounts of these proteins was not exclusively due to transcriptional defects. We conclude that the differences in NF-kappa B/I kappa B proteins that we have described in me(v) are likely a consequences of the SHP1 defect and could contribute to the clinical disorder that characterizes me(v) mice.