GRK2 suppresses lymphomagenesis by inhibiting the MALT1 proto-oncoprotein
Jing Cheng, … , Peter C. Lucas, Linda M. McAllister-Lucas
Jing Cheng, … , Peter C. Lucas, Linda M. McAllister-Lucas
Published January 21, 2020
Citation Information: J Clin Invest. 2020;130(2):1036-1051. https://doi.org/10.1172/JCI97040.
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Research Article Immunology Oncology

GRK2 suppresses lymphomagenesis by inhibiting the MALT1 proto-oncoprotein

Abstract

Antigen receptor–dependent (AgR-dependent) stimulation of the NF-κB transcription factor in lymphocytes is a required event during adaptive immune response, but dysregulated activation of this signaling pathway can lead to lymphoma. AgR stimulation promotes assembly of the CARMA1-BCL10-MALT1 complex, wherein MALT1 acts as (a) a scaffold to recruit components of the canonical NF-κB machinery and (b) a protease to cleave and inactivate specific substrates, including negative regulators of NF-κB. In multiple lymphoma subtypes, malignant B cells hijack AgR signaling pathways to promote their own growth and survival, and inhibiting MALT1 reduces the viability and growth of these tumors. As such, MALT1 has emerged as a potential pharmaceutical target. Here, we identified G protein–coupled receptor kinase 2 (GRK2) as a new MALT1-interacting protein. We demonstrated that GRK2 binds the death domain of MALT1 and inhibits MALT1 scaffolding and proteolytic activities. We found that lower GRK2 levels in activated B cell–type diffuse large B cell lymphoma (ABC-DLBCL) are associated with reduced survival, and that GRK2 knockdown enhances ABC-DLBCL tumor growth in vitro and in vivo. Together, our findings suggest that GRK2 can function as a tumor suppressor by inhibiting MALT1 and provide a roadmap for developing new strategies to inhibit MALT1-dependent lymphomagenesis.

Authors

Jing Cheng, Linda R. Klei, Nathaniel E. Hubel, Ming Zhang, Rebekka Schairer, Lisa M. Maurer, Hanna B. Klei, Heejae Kang, Vincent J. Concel, Phillip C. Delekta, Eric V. Dang, Michelle A. Mintz, Mathijs Baens, Jason G. Cyster, Narayanan Parameswaran, Margot Thome, Peter C. Lucas, Linda M. McAllister-Lucas

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Figure 4

GRK2 attenuates AgR stimulation–induced NF-κB activation, CBM complex formation, MALT1 activity, and IL-2 production in Jurkat T cells.

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GRK2 attenuates AgR stimulation–induced NF-κB activation, CBM complex fo...
(A) Expression of WT GRK2 or kinase-deficient (K220R) GRK2 mutant in Jurkat T cells inhibits PMA/ionomycin–induced (P/I-induced) (top) but not TNF-induced (bottom) NF-κB luciferase reporter activity (n = 3). (B) Knockdown of GRK2 in Jurkat T cells leads to enhanced P/I-induced CBM complex formation. Jurkat T cells were subjected to knockdown with either control or GRK2 shRNA lentivirus (GRK2 shRNA1) and then treated with or without P/I. Binding of BCL10 and CARMA1 to immunoprecipitated MALT1 and phosphorylation of IκB were examined. Blot is representative of 2 independent experiments. (C) GRK2 knockdown in Jurkat T cells leads to increased cleavage of CYLD in response to P/I stimulation. Quantification of the cleavage is shown below. Densitometric analysis was performed using AlphaView software (n = 3). (D) GRK2 knockdown in Jurkat T cells leads to increased cleavage of RELB in response to P/I (left) or anti-CD3/CD28 (right) stimulation. Blots are representative of 3 independent experiments. (E) GRK2 knockdown leads to enhanced IL-2 production in Jurkat T cells. Cells were treated with or without P/I (left) or anti-CD3/CD28 (right) for 24 hours, and IL-2 in supernatant was measured by ELISA (n = 3). All values are represented as mean ± SEM. *P < 0.05, ***P < 0.001, ****P < 0.0001. Data from A, C, and E were analyzed by 2-way ANOVA, followed by Tukey’s multiple-comparisons test.