Ancient Origin of the CARD–Coiled Coil/Bcl10/MALT1-Like Paracaspase Signaling Complex Indicates Unknown Critical Functions

Abstract

The CARD–coiled coil (CC)/Bcl10/MALT1-like paracaspase (CBM) signaling complexes composed of a CARD–CC family member (CARD-9, -10, -11, or -14), Bcl10, and the type 1 paracaspase MALT1 (PCASP1) play a pivotal role in immunity, inflammation, and cancer. Targeting MALT1 proteolytic activity is of potential therapeutic interest. However, little is known about the evolutionary origin and the original functions of the CBM complex. Type 1 paracaspases originated before the last common ancestor of planulozoa (bilaterians and cnidarians). Notably in bilaterians, Ecdysozoa (e.g., nematodes and insects) lacks Bcl10, whereas other lineages have a Bcl10 homolog. A survey of invertebrate CARD–CC homologs revealed such homologs only in species with Bcl10, indicating an ancient common origin of the entire CBM complex. Furthermore, vertebrate-like Syk/Zap70 tyrosine kinase homologs with the ITAM-binding SH2 domain were only found in invertebrate organisms with CARD–CC/Bcl10, indicating that this pathway might be related to the original function of the CBM complex. Moreover, the type 1 paracaspase sequences from invertebrate organisms that have CARD–CC/Bcl10 are more similar to vertebrate paracaspases. Functional analysis of protein–protein interactions, NF-κB signaling, and CYLD cleavage for selected invertebrate type 1 paracaspase and Bcl10 homologs supports this scenario and indicates an ancient origin of the CARD–CC/Bcl10/paracaspase signaling complex. By contrast, many of the known MALT1-associated activities evolved fairly recently, indicating that unknown functions are at the basis of the protein conservation. As a proof-of-concept, we provide initial evidence for a CBM- and NF-κB-independent neuronal function of the Caenorhabditis elegans type 1 paracaspase malt-1. In conclusion, this study shows how evolutionary insights may point at alternative functions of MALT1.

Defining the relevant combinatorial space of the PKC/CARD-CC signal transduction nodes

“…4D). CARD14 S250 nicely aligns with CARD9 T231 and the oncogenic CARD11 S250P mutation [11], indicating that this is a common and evolutionarily conserved activation site. To evaluate whether CARD14 S250 also would be responsible for PKCδ-mediated activation of CARD14, we evaluated the CARD14 S250A mutant both for spontaneous activity (Fig.…”

“…One class of such narrow-waist signaling nodes is represented by the CARD-CC/Bcl10/MALT1 (CBM) signaling complexes. Several different CBM signaling complexes exist, which are composed of Bcl10, MALT1 and specific CARD-CC family [11] proteins (CARD9 [12], CARD11 (also known as CARMA1) [13], CARD14 (also known as CARMA2) [14][15][16] and CARD10 (also known as CARMA3) [17] ; Fig. 1) and which are formed upon stimulation of distinct receptors in several immune and non-immune cells.…”

“…Receptor signaling via the ITAM (immunoreceptor tyrosine-based activation motif) binding one of the two related SH2 domain tyrosine kinases Zap70 or Syk activates PKC, leading to CARD-CC phosphorylation and the recruitment of a pre-existing Bcl10/MALT1 complex and TRAF6 ( Fig. 2A) [11,13,33,34]. An alternative CBM-dependent pathway upstream of PKC activation is represented by the Gα 12 /Gα 13 and RhoAdependent G protein coupled receptors (GPCRs) [35].…”

“…Recently, a novel CARD-CC-independent oncogenic Bcl10/MALT1 activation mechanism has also been described, where the Karposi's sarcoma-associated herpes virus (KSHV) virulence factors K15 and K13 engage directly with Bcl10/MALT1 in a " KBM" complex [43,44]. MALT1 can also be activated independently of Bcl10 and CARD-CC proteins, which is illustrated by that MALT1 homologs are present in species lacking Bcl10 and CARD-CC [11,45] and that MALT1 can be activated by TRAF6 overexpression in mammalian knock-out cells lacking Bcl10 or CARD-CC proteins [46]. However, in the context of the dominant CBM complex-mediated MALT1 activation pathway, studies on CARD11 have shown that phosphorylation leads to release of intramolecular auto-inhibition and aggregation of the CARD-CC protein together with the other CBM complex components in huge macromolecular filamentous structures that acts as a platform for downstream signaling [47][48][49].…”

“…It is very likely that there are more CBM-activating PKC isozymes, and that there are more PKC::CARD-CC kinase/substrate relationships in different cells and pathways. While the CARD-CC protein family is old and originated before the last common ancestor of planulozoa (cnidaria and bilateria) [11], the PKC family is however significantly older with origins in the last ancestor of opisthokonts (metazoa and fungi) [56], highlighting that PKCs also have many CBM-independent functions. In humans and mice, the PKC family consists of nine true members in the "conventional" (α, β, γ), "novel" (δ, ε, η, θ) and "atypical" (ζ, ι/λ) sub-classes [57,58].…”