TY - JOUR
T1 - Mutations in the zinc finger domain of IKKγ block the activation of NF-κB and the induction of IL-2 in stimulated T lymphocytes
AU - Shifera, Amde Selassie
AU - Horwitz, Marshall S.
N1 - Funding Information:
The authors express their gratitude to Dr. Shao-Cong Sun (Pennsylvania State University) for the parental IKKγ-positive (SVT35) and IKKγ-null (SVT26) Jurkat cell lines and to Dr. Dean W. Ballard (Vanderbilt University, Nashville, TN) for the IκBα expressing plasmid. The authors also appreciate very much the help obtained from Noemi Soto-Nieves (Albert Einstein College of Medicine) in performing the IL-2 ELISA, the EMSA and the quantitative RT-PCR experiments. The authors are very thankful to Dr. Joan W. Berman and Dr. Elena Mashalova (both at Albert Einstein College of Medicine) for providing helpful comments during the preparation of the manuscript. This work was supported by National Institutes of Health grants 1RO1 CA72963, 1RO1 AI42295, 1PO1 DK-52956, and P30-CA13330 (to MSH). ASS was a recipient of NIH Training Program in Cellular and Molecular Biology and Genetics Grant (NIGMS) T32 07491.
PY - 2008/3
Y1 - 2008/3
N2 - Mutations in the zinc finger of IκB kinase gamma (IKKγ) are associated with hypohidrotic ectodermal dysplasia-immune deficiency (HED-ID) in which the major immune deficit is the inability to switch Ab heavy chain class. However, the pathophysiologic role of the mutations has not been fully delineated. Since help from activated Th cells is essential in Ab class switching, we sought to examine how these mutations affect T cell activation. Using a human T cell line that was null for IKKγ, we generated cells stably expressing two of the reported mutations, namely, D406V and C417R. Cells expressing either mutation failed to induce IL-2 following stimulation with PMA/ionomycin while the induction of IL-2 was restored in cells reconstituted with the wild type IKKγ. The lack of IL-2 upregulation correlated with the lack of NF-κB activation as evidenced by the inability to induce IκBα degradation, NF-κB binding to DNA and the expression of a reporter gene. However, both mutations did not prevent the incorporation of IKKγ into the IKK complex and, interestingly, the induced phosphorylation of IκBα at S32 and S36 and its subsequent ubiquitination were not affected. The suppression of IL-2 induction was solely due to the inhibition of NF-κB activation as the mutations did not impair the activation of AP-1 and NFAT. Our data indicated that the failure of T cells to undergo activation in response to TCR stimuli may play a role in the pathophysiology of HED-ID and also showed that IKKγ has a role in the post-ubiquitination processing of IκBα.
AB - Mutations in the zinc finger of IκB kinase gamma (IKKγ) are associated with hypohidrotic ectodermal dysplasia-immune deficiency (HED-ID) in which the major immune deficit is the inability to switch Ab heavy chain class. However, the pathophysiologic role of the mutations has not been fully delineated. Since help from activated Th cells is essential in Ab class switching, we sought to examine how these mutations affect T cell activation. Using a human T cell line that was null for IKKγ, we generated cells stably expressing two of the reported mutations, namely, D406V and C417R. Cells expressing either mutation failed to induce IL-2 following stimulation with PMA/ionomycin while the induction of IL-2 was restored in cells reconstituted with the wild type IKKγ. The lack of IL-2 upregulation correlated with the lack of NF-κB activation as evidenced by the inability to induce IκBα degradation, NF-κB binding to DNA and the expression of a reporter gene. However, both mutations did not prevent the incorporation of IKKγ into the IKK complex and, interestingly, the induced phosphorylation of IκBα at S32 and S36 and its subsequent ubiquitination were not affected. The suppression of IL-2 induction was solely due to the inhibition of NF-κB activation as the mutations did not impair the activation of AP-1 and NFAT. Our data indicated that the failure of T cells to undergo activation in response to TCR stimuli may play a role in the pathophysiology of HED-ID and also showed that IKKγ has a role in the post-ubiquitination processing of IκBα.
KW - Cell activation
KW - Cytokines
KW - Immunodeficiency diseases
KW - T Cells
KW - T cell receptors
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U2 - 10.1016/j.molimm.2007.09.036
DO - 10.1016/j.molimm.2007.09.036
M3 - Article
C2 - 18207244
AN - SCOPUS:39149094918
SN - 0161-5890
VL - 45
SP - 1633
EP - 1645
JO - Molecular Immunology
JF - Molecular Immunology
IS - 6
ER -