Ginster, Stefanie, Bardet, Maureen, Unterreiner, Adeline, Malinverni, Claire, Renner, Florian, Lam, Stephen, Freuler, Felix, Gerrits, Bertran, Voshol, Johannes, Calzascia, Thomas, Regnier, Catherine, Renatus, Martin, Nikolay, Rainer, Israel, Laura and Bornancin, Frederic (2017) Two antagonistic MALT1 auto-cleavage mechanisms reveal a role for TRAF6 to unleash MALT1 activation. PLoS ONE, 12 (1). e0169026. ISSN 1932-6203

Abstract

The paracaspase MALT1 has arginine-directed proteolytic activity triggered by engagement of immune receptors. Recruitment of MALT1 into activation complexes is required for MALT1 proteolytic function. Here, co-expression of MALT1 in HEK293 cells, either with activated CARD11 and BCL10 or with TRAF6, was used to explore the mechanism of MALT1 activation at the molecular level. This work identified a novel self-cleavage site of MALT1 isoform A at R781 (R770 in isoform B) and revealed that TRAF6 can activate MALT1 independently of the CBM. Intramolecular cleavage at R781/R770 removes a C-terminal TRAF6-binding site in both MALT1 isoforms, leaving isoform B devoid of the two key interaction sites with TRAF6. A previously identified auto-proteolysis site of MALT1 at R149 leads to deletion of the death-domain, thereby abolishing interaction with BCL10. By using MALT1 isoforms and cleaved fragments thereof as well as TRAF6 WT and mutant forms, this work shows that interaction with TRAF6 is essential for auto-proteolytic cleavage of MALT1 at R149. The corresponding MALT1 auto-cleaved fragment displayed enhanced signaling properties shown to correlate with increased steady-state levels of ubiquitination. Conversely, C-terminal self-cleavage at R781/R770 hampered the ability for self-cleavage at R149. C-terminal self-cleavage had limited impact on MALT1 isoform A but abrogated MALT1 isoform B proteolytic and signaling functions. Altogether, this study provides further insights into mechanisms that regulate the scaffolding and activation cycle of MALT1. It also emphasizes the reduced functional capacity of MALT1 isoform B as compared to isoform A.

Item Type:	Article
Date Deposited:	28 Jan 2017 00:45
Last Modified:	28 Jan 2017 00:45
URI:	https://oak.novartis.com/id/eprint/30740