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Published on: October 4, 2017
Gain-of-function mutations in CARD11 promote enhanced aggregation and idiosyncratic signalosome assembly
Jeffrey R Stinson1, Batsukh Dorjbal1, Dennis P McDaniel2
1Department of Pharmacology & Molecular Therapeutics, Uniformed Services University of Health Sciences, Bethesda, MD, United States.
Insights
Gain-of-function mutations in CARD11 cause B cell Expansion with NF-κB and T cell Anergy (BENTA) and some lymphomas. These mutant CARD11 proteins form aggregates called mCADS, which signal constitutively, suggesting a new therapeutic target.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- B cell Expansion with NF-κB and T cell Anergy (BENTA) is a lymphoproliferative disorder.
- Germline, gain-of-function (GOF) mutations in CARD11 cause BENTA.
- Somatic CARD11 mutations are implicated in diffuse large B cell lymphoma (DLBCL).
Purpose of the Study:
- To investigate the molecular mechanism of GOF CARD11 mutations.
- To identify novel therapeutic targets for BENTA and DLBCL.
Main Methods:
- Studied wild-type and mutant CARD11 protein aggregation.
- Utilized immunofluorescence microscopy to detect protein aggregates (mCADS).
- Assessed colocalization of signaling molecules (MALT1, phospho-IKK) with mCADS.
Main Results:
- GOF CARD11 mutants form unique cytosolic aggregates termed mCADS.
- MALT1 and phospho-IKK are localized to mCADS, indicating active signaling.
- Endogenous mCADS are present in ABC-DLBCL cell lines with GOF CARD11 mutations.
Conclusions:
- GOF CARD11 mutations lead to constitutive NF-κB activity via mCADS formation.
- mCADS represent a potential therapeutic target for BENTA and DLBCL.
- The aggregation propensity of mutant CARD11 is a key pathogenic feature.
Abstract:
BENTA (B cell Expansion with NF-κB and T cell Anergy) is a novel lymphoproliferative disorder caused by germline, gain-of-function (GOF) mutations in the lymphocyte-restricted scaffolding protein CARD11. Similar somatic CARD11 mutations are found in lymphoid malignancies such as diffuse large B cell lymphoma (DLBCL). Normally, antigen receptor (AgR) engagement converts CARD11 into an active conformation that nucleates a signalosome required for IκB kinase (IKK) activation and NF-κB nuclear translocation. However, GOF CARD11 mutants drive constitutive NF-κB activity without AgR stimulation. Here we show that unlike wild-type CARD11, GOF CARD11 mutants can form large, peculiar cytosolic protein aggregates we term mCADS (mutant CARD11 dependent shells). MALT1 and phospho-IKK are reliably colocalized with mCADS, indicative of active signaling. Moreover, endogenous mCADS are detectable in ABC-DLBCL lines harboring similar GOF CARD11 mutations. The unique aggregation potential of GOF CARD11 mutants may represent a novel therapeutic target for treating BENTA or DLBCL.
