CCDC22 deficiency in humans blunts activation of proinflammatory NF-κB signaling
Petro Starokadomskyy, Nathan Gluck, Haiying Li, Baozhi Chen, Mathew Wallis, Gabriel N. Maine, Xicheng Mao, Iram W. Zaidi, Marco Y. Hein, Fiona J. McDonald, Steffen Lenzner, Agnes Zecha, Hans-Hilger Ropers, Andreas W. Kuss, Julie McGaughran, Jozef Gecz, Ezra Burstein
Petro Starokadomskyy, Nathan Gluck, Haiying Li, Baozhi Chen, Mathew Wallis, Gabriel N. Maine, Xicheng Mao, Iram W. Zaidi, Marco Y. Hein, Fiona J. McDonald, Steffen Lenzner, Agnes Zecha, Hans-Hilger Ropers, Andreas W. Kuss, Julie McGaughran, Jozef Gecz, Ezra Burstein
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Research Article Oncology

CCDC22 deficiency in humans blunts activation of proinflammatory NF-κB signaling

Abstract

NF-κB is a master regulator of inflammation and has been implicated in the pathogenesis of immune disorders and cancer. Its regulation involves a variety of steps, including the controlled degradation of inhibitory IκB proteins. In addition, the inactivation of DNA-bound NF-κB is essential for its regulation. This step requires a factor known as copper metabolism Murr1 domain–containing 1 (COMMD1), the prototype member of a conserved gene family. While COMMD proteins have been linked to the ubiquitination pathway, little else is known about other family members. Here we demonstrate that all COMMD proteins bind to CCDC22, a factor recently implicated in X-linked intellectual disability (XLID). We showed that an XLID-associated CCDC22 mutation decreased CCDC22 protein expression and impaired its binding to COMMD proteins. Moreover, some affected individuals displayed ectodermal dysplasia, a congenital condition that can result from developmental NF-κB blockade. Indeed, patient-derived cells demonstrated impaired NF-κB activation due to decreased IκB ubiquitination and degradation. In addition, we found that COMMD8 acted in conjunction with CCDC22 to direct the degradation of IκB proteins. Taken together, our results indicate that CCDC22 participates in NF-κB activation and that its deficiency leads to decreased IκB turnover in humans, highlighting an important regulatory component of this pathway.

Authors

Petro Starokadomskyy, Nathan Gluck, Haiying Li, Baozhi Chen, Mathew Wallis, Gabriel N. Maine, Xicheng Mao, Iram W. Zaidi, Marco Y. Hein, Fiona J. McDonald, Steffen Lenzner, Agnes Zecha, Hans-Hilger Ropers, Andreas W. Kuss, Julie McGaughran, Jozef Gecz, Ezra Burstein

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Figure 5

CCDC22 is required for RelA nuclear transport and IκB degradation.

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CCDC22 is required for RelA nuclear transport and IκB degradation. (A) C...
(A) CCDC22 deficiency resulted in depressed nuclear accumulation of active NF-κB. HEK 293 cells were transfected with the indicated siRNAs and stimulated with TNF. The presence of active NF-κB complexes in nuclear extracts was assessed by a DNA-protein coprecipitation assay (top) or by direct immunoblotting (input, bottom). RNA polymerase II (Pol II) served as a loading control. (B) TNF-induced degradation of classical IκB proteins was impaired in primary fibroblasts bearing the T17A mutation. Primary dermal fibroblasts from 2 patients demonstrate decreased TNF-induced degradation of IκB-α, IκB-β, and IκB-ε compared with fibroblasts from their mother, a heterozygote mutation carrier. (C) CCDC22 deficiency impaired TNF-induced IκB degradation. HEK 293 cells were transfected with the indicated siRNA oligonucleotides and treated with TNF. IκB degradation was determined by Western blot analysis. (D) CCDC22 deficiency affected IκB-β stability. Cells transfected with the indicated siRNA were subsequently treated with cycloheximide (CHX) to inhibit new protein synthesis. IκB-β stability after TNF stimulation was examined by immunoblotting. (E) IκB-α degradation was impaired in XLID-derived LCLs. LCLs derived from a healthy control subject and an XLID patient with the T17A mutation were stimulated with PMA, and IκB-α degradation was examined by immunoblotting. (F) IκB-α phosphorylation was not affected in XLID-derived LCLs. LCLs derived from a healthy control and an XLID patient were stimulated with PMA for indicated times. Phosphorylation of IκB-α at serines 32 and 36 was determined by immunoblotting using a phosphospecific antibody.