Aberrant Expression of the NF-κB and IκB Proteins in B Cells from Viable Motheaten Mice

Abstract

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 NFκB/IκB proteins are regulated through phosphorylation, we wished to understand if the expression of these proteins was 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 Re1A and Re1B proteins and increased levels of p50 and c-Re1. Furthermore, we analyzed the protein levels of IκBU and found that, in me^v, this inhibitor was significantly reduced, while the level of another member of the IκB family, IκBβ, was not. To determine if these findings in me^v were secondary to the autoimmune process, we evaluated NF-KB/IKB expression in the BXSB murine model of autoimmunity. Unlike me^v, B cells from BXSB/Yaa mice had NF-κB complexes composed of the Re1A submit, and IκBα was readily detected. In addition, RNA for the Re1A and IκBα 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-κB/IκB 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.

Key Words:

• NF-κB
• Viable motheaten
• Phosphatase
• Autoimmunity