Clustering of CARMA1 through SH3-GUK domain interactions is required for its activation of NF-κB signalling.

Hiromitsu Hara,Takashi Saito,Masanori Yamazaki,Chitose Ishihara,Hideki Hirakawa,Shinsuke Yasukawa,Tadashi Yokosuka,Hiroki Yoshida,Haruhiko Koseki

doi:10.1038/ncomms6555

Abstract

CARMA1-mediated NF-κB activation controls lymphocyte activation through antigen receptors and survival of some malignant lymphomas. CARMA1 clusters are formed on physiological receptor-mediated activation or by its oncogenic mutation in activated B-cell-diffuse large B-cell lymphomas (ABC-DLBCLs) with constitutive NF-κB activation. However, regulatory mechanisms and relevance of CARMA1 clusters in the NF-κB pathway are unclear. Here we show that SH3 and GUK domain interactions of CARMA1 link CARMA1 clustering to signal activation. SH3 and GUK domains of CARMA1 interact by either intra- or intermolecular mechanisms, which are required for activation-induced assembly of CARMA1. Disruption of these interactions abolishes the formation of CARMA1 microclusters at the immunological synapse, CARMA-regulated signal activation following antigen receptor stimulation as well as spontaneous CARMA1 clustering and NF-κB activation by the oncogenic CARMA1 mutation in ABC-DLBCLs. Thus, the SH3-GUK interactions that regulate CARMA1 cluster formations are promising therapeutic targets for ABC-DLBCLs.

Highlights

CARMA1-mediated Nuclear factor kB (NF-kB) activation controls lymphocyte activation through antigen receptors and survival of some malignant lymphomas
The molecular mechanisms by which the Src homology 3 (SH3) and GUK domains of CARMA1 contribute to its function are unclear and some controversy exists between T- and B-cell data
Previous studies have suggested that the intra- and intermolecular interactions of the SH3–GUK module are conserved among related membrane-associated guanylate kinase (MAGUK) proteins and have a crucial role in regulating the formation and function of signalling complexes at cell–cell junctions in polarized tissues such as epithelia and synapses

Summary

Introduction

CARMA1-mediated NF-kB activation controls lymphocyte activation through antigen receptors and survival of some malignant lymphomas. SH3 and GUK domains of CARMA1 interact by either intra- or intermolecular mechanisms, which are required for activation-induced assembly of CARMA1 Disruption of these interactions abolishes the formation of CARMA1 microclusters at the immunological synapse, CARMA-regulated signal activation following antigen receptor stimulation as well as spontaneous CARMA1 clustering and NF-kB activation by the oncogenic CARMA1 mutation in ABC-DLBCLs. the SH3–GUK interactions that regulate CARMA1 cluster formations are promising therapeutic targets for ABC-DLBCLs. Nuclear factor kB (NF-kB) controls the activation and survival of lymphocytes. The importance of the SH3–GUK domain interaction for MAGUK function was demonstrated by genetic studies in invertebrates that identified numerous loss-of-function mutations in the SH3 and GUK domains of disc large (dlg) in Drosophila[13] and lin-2 in Caenorhabditis elegans[14], all of which could disrupt SH3–GUK interactions[6] It is unknown whether such mechanisms regulate CARMA1 function. Selective interference with L-CBM signalling is a promising strategy for ABC-DLBCL treatment and the suppression of CARMA1 cluster formation might be a therapeutic target

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Results

Conclusion