title: Two Antagonistic MALT1 Auto-Cleavage Mechanisms Reveal a Role for TRAF6 to Unleash MALT1 Activation.
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 prominent self-cleavage site of MALT1 isoform A (MALT1A) at R781 (R770 in MALT1B) 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 MALT1B 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 TRAF6 induces N-terminal auto-proteolytic cleavage of MALT1 at R149 and accelerates MALT1 protein turnover. The MALT1 fragment generated by N-terminal self-cleavage at R149 was labile and displayed enhanced signaling properties that required an intact K644 residue, previously shown to be a site for mono-ubiquitination of MALT1. Conversely, C-terminal self-cleavage at R781/R770 hampered the ability for self-cleavage at R149 and stabilized MALT1 by hindering interaction with TRAF6. C-terminal self-cleavage had limited impact on MALT1A but severely reduced MALT1B proteolytic and signaling functions. It also abrogated NF-κB activation by N-terminally cleaved MALT1A. 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 MALT1B as compared to MALT1A.
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ginster
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Maureen
authors.initials: M
authors.lastname: Bardet
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Adeline
authors.initials: A
authors.lastname: Unterreiner
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Claire
authors.initials: C
authors.lastname: Malinverni
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Renner
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Stephen
authors.initials: S
authors.lastname: Lam
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Felix
authors.initials: F
authors.lastname: Freuler
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Bertran
authors.initials: B
authors.lastname: Gerrits
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Voshol
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Calzascia
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Catherine H
authors.initials: CH
authors.lastname: Régnier
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Renatus
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Rainer
authors.initials: R
authors.lastname: Nikolay
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Laura
authors.initials: L
authors.lastname: Israël
authors.affiliation: Novartis Institutes for BioMedical Research, Novartis Campus, Basel, Switzerland.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bornancin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000074018:B-Cell CLL-Lymphoma 10 Protein; D015153:Blotting, Western; D053468:CARD Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015151:Immunoblotting; D019169:Jurkat Cells; D008214:Lymphocytes / Q000378:metabolism; D000074884:Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein; D016296:Mutagenesis; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013601:T-Lymphocytes / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000235:genetics / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000074018:B-Cell CLL-Lymphoma 10 Protein; C118591:BCL10 protein, human; D053468:CARD Signaling Adaptor Proteins; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D048029:TNF Receptor-Associated Factor 6; D020169:Caspases; C400109:MALT1 protein, human; D000074884:Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein; C426242:CARD11 protein, human; D006162:Guanylate Cyclase