CARD10 cleavage by MALT1 restricts lung carcinoma growth in vivo

Abstract

CARD-CC complexes involving BCL10 and MALT1 are major cellular signaling hubs. They govern NF-κB activation through their scaffolding properties as well as MALT1 paracaspase function, which cleaves substrates involved in NF-κB regulation. In human lymphocytes, gain-of-function defects in this pathway lead to lymphoproliferative disorders. CARD10, the prototypical CARD-CC protein in non-hematopoietic cells, is overexpressed in several cancers and has been associated with poor prognosis. However, regulation of CARD10 remains poorly understood. Here, we identified CARD10 as the first MALT1 substrate in non-hematopoietic cells and showed that CARD10 cleavage by MALT1 at R587 dampens its capacity to activate NF-κB. Preventing CARD10 cleavage in the lung tumor A549 cell line increased basal levels of IL-6 and extracellular matrix components in vitro, and led to increased tumor growth in a mouse xenograft model, suggesting that CARD10 cleavage by MALT1 might be a built-in mechanism controlling tumorigenicity.

MALT1-Dependent Cleavage of HOIL1 Modulates Canonical NF-κB Signaling and Inflammatory Responsiveness

“…MALT1 paracaspase was recently identified as a novel negative regulator of LUBAC-mediated signaling, whereby it cleaves HOIL1 to destabilize LUBAC assembly (37)(38)(39). As MALT1 has 12 substrates reported to date, and each regulates NF-kB or other signaling pathways differently (41)(42)(43), it is difficult to study the specific effects of cleavage of individual substrates by simply inhibiting MALT1 protease activity or genetically knocking-out/ down MALT1. To directly investigate the role of MALT1dependent cleavage of HOIL1 in immunity and physiology, we generated a non-cleavable version of HOIL1 (HOIL1-R/K) and stably expressed this construct in primary HOIL1-deficient patient fibroblasts.…”

Integrating knowledge of protein sequence with protein function for the prediction and validation of new MALT1 substrates

“…With 18 untested candidates in the top 40 proteins ranked by GO-2-Substrates (Supplementary Table 1 ), we predict that approximately 50 % will likely be new MALT1 substrates, a notable success rate. Indeed, during the preparation of this manuscript, CARD10 (rank 14) was validated as a novel MALT1 substrate [42] . To our knowledge, our work represents the first method to rank human proteins as potential MALT1 substrates by proteome-wide analysis.…”

“…During the preparation of this manuscript, Israël and coworkers [42] described the MALT1 cleavage of CARD10. Despite an unusual Ala at P 2 in its MALT1 cleavage site (Leu-Leu- Ala -Arg 587 ↓Gly), GO-2-Substrates correctly ranked CARD10 as an exceptionally strong candidate substrate—mainly due to its functional similarity to known substrates.…”

The Paracaspase MALT1 in Cancer

“…Whereas most studies describe a tumor-promoting role for MALT1, a recent study suggests that MALT1 can also act as a tumor suppressor. In the lung cancer cell line A549, MALT1 cleaves the C10BM complex member CARD10 after the arginine residue at position 587, thereby dampening its capacity to activate NF-κB [ 95 ]. In this manner, the cleavage of CARD10 by MALT1 acts as a negative feedback mechanism that limits the signaling potential and pro-tumorigenic role of CARD10.…”

“…This is also reflected in the observation that A549 knock-in (KI) cells expressing the cleavage-deficient R587A CARD10 variant exhibit a growth advantage, increased angiogenesis, and tumorigenic potential upon i.v. injection in mice [ 95 ]. The authors identified IL-6 as the main cytokine upregulated in the A549-KI cells, suggesting that cleavage of CARD10 by MALT1 is important to limit IL-6 signaling and to suppress tumorigenesis.…”