Mucosa-associated Lymphoid Tissue 1 Research Articles

Blood MALT1 expression could help predict treatment outcomes in psoriasis patients, especially in those receiving biologics.

Mucosa-associated lymphoid tissue 1 (MALT1) modulates T helper cell differentiation, pro-inflammatory cytokine production, and epidermal hyperplasia to participate in the pathology of psoriasis. This study aimed to explore the correlation of blood MALT1 with treatment outcomes in psoriasis patients. MALT1 was detected in peripheral blood mononuclear cells by reverse transcription-quantitative polymerase chain reaction in 210 psoriasis patients before starting or converting to a new therapy, 50 disease controls, and 50 healthy controls. The psoriasis area severity index (PASI) score was evaluated at month (M)1, M3, and M6 in psoriasis patients. MALT1 was increased in psoriasis patients versus disease controls and healthy controls (both p < .001); and positively related to body mass index (p = .019) and PASI score (p < .001) in psoriasis patients. PASI75 rate at M1, M3, and M6 was 22.9%, 46.2%, and 71.0%, respectively; while PASI90 rate at M1, M3, and M6 was 3.8%, 29.0%, and 50.5%, respectively, in psoriasis patients. PASI75/90 rates at M1, M3, and M6 were increased in psoriasis patients receiving biologics versus those without (all p < .05). Pretreatment MALT1 was higher in psoriasis patients who achieved PASI75 (p = .001) and PASI90 (p < .001) at M6 compared to those who did not achieve that. Subgroup analyses discovered that pretreatment MALT1 had a stronger ability to predict PASI75 and 90 realizations in psoriasis patients receiving biologics (area under the curve [AUC]: 0.723 and 0.808) versus those without (AUC: 0.594 and 0.675). Blood MALT1 measurement may assist in predicting outcomes in psoriasis patients, especially in those receiving biologics.

Androgen Receptor Upregulates Mucosa-Associated Lymphoid Tissue 1 to Induce NF-κB Activity via Androgen-Dependent and -Independent Pathways in Prostate Carcinoma Cells.

The androgen-dependent or -independent pathways are regarded as primary therapeutic targets for the neoplasm of the prostate. Mucosa-associated lymphoid tissue 1 (MALT1) acting as a paracaspase in the regulation of nuclear factor κB (NF-κB) signal transduction plays a central role in inflammation and oncogenesis in cancers. This study confirmed the potential linkages between androgen and NF-κB activation by inducing MALT1 in the androgen receptor-full length (ARFL)-positive LNCaP and 22Rv1 prostate cancer cells. Although androgen did not stimulate MALT1 expression in AR-null or ectopic ARFL-overexpressed PC-3 cells, the ectopic overexpression of the AR splicing variant 7 (ARv7) upregulated MALT1 to activate NF-κB activities in 22Rv1 and PC-3 cells. Since the nuclear translocation of p50 and p65 was facilitated by ARv7 to motivate NF-κB activity, the expressions of MALT1, prostate-specific antigen (PSA), and N-myc downstream regulated 1 (NDRG1) were therefore induced in ectopic ARv7-overexpressed prostate cancer cells. Ectopic ARv7 overexpression not only enhanced 22Rv1 or PC-3 cell growth and invasion in vitro but also the tumor growth of PC-3 cells in vivo. These results indicate that an androgen receptor induces MALT1 expression androgen-dependently and -independently in ARFL- or ARv7-overexpressed prostate cancer cells, suggesting a novel ARv7/MALT1/NF-κB-signaling pathway may exist in the cells of prostate cancer.

MALT1-dependent cleavage of CYLD promotes NF-κB signaling and growth of aggressive B-cell receptor-dependent lymphomas

The paracaspase mucosa-associated lymphoid tissue 1 (MALT1) is a protease and scaffold protein essential in propagating B-cell receptor (BCR) signaling to NF-κB. The deubiquitinating enzyme cylindromatosis (CYLD) is a recently discovered MALT1 target that can negatively regulate NF-κB activation. Here, we show that low expression of CYLD is associated with inferior prognosis of diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) patients, and that chronic BCR signaling propagates MALT1-mediated cleavage and, consequently, inactivation and rapid proteasomal degradation of CYLD. Ectopic overexpression of WT CYLD or a MALT1-cleavage resistant mutant of CYLD reduced phosphorylation of IκBα, repressed transcription of canonical NF-κB target genes and impaired growth of BCR-dependent lymphoma cell lines. Furthermore, silencing of CYLD expression rendered BCR-dependent lymphoma cell lines less sensitive to inhibition of NF-κΒ signaling and cell proliferation by BCR pathway inhibitors, e.g., the BTK inhibitor ibrutinib, indicating that these effects are partially mediated by CYLD. Taken together, our findings identify an important role for MALT1-mediated CYLD cleavage in BCR signaling, NF-κB activation and cell proliferation, which provides novel insights into the underlying molecular mechanisms and clinical potential of inhibitors of MALT1 and ubiquitination enzymes as promising therapeutics for DLBCL, MCL and potentially other B-cell malignancies.

MALT1 Positively Relates to T Helper 1 and T Helper 17 cells, and Serves as a Potential Biomarker for Predicting 30-Day Mortality in Stanford Type A Aortic Dissection Patients.

Mucosa-associated lymphoid tissue 1 (MALT1) regulates inflammation and T helper (Th) cell differentiation, which may participate in the progression of Stanford type A aortic dissection (TAAD). This study intended to assess the association of MALT1 expression with prognosis in TAAD patients. In this prospective study, MALT1 expression was measured by reverse transcription-quantitative polymerase chain reaction assay from peripheral blood samples in 100 TAAD patients and 100 non-AD controls (non-AD patients with chest pain) before treatment. Besides, Th1, Th2, and Th17 cells of TAAD patients before treatment were measured by flow cytometry assay, and their 30-day mortality was recorded. MALT1 expression was ascended in TAAD patients vs. non-AD controls (P < 0.001). In TAAD patients, elevated MALT1 expression was linked with hypertension complication (P = 0.009), increased systolic blood pressure (r = 0.291, P = 0.003), C-reactive protein (CRP) (r = 0.286, P = 0.004), and D-dimer (r = 0.359, P < 0.001). Additionally, MALT1 expression was positively correlated with Th1 cells (r = 0.312, P = 0.002) and Th17 cells (r = 0.397, P < 0.001), but not linked with Th2 cells (r = -0.166, P = 0.098). Notably, the 30-day mortality of TAAD patients was 28.0%. MALT1 expression [odds ratio (OR) = 1.936, P = 0.004], CRP (OR = 1.108, P = 0.002), D-dimer (OR = 1.094, P = 0.003), and surgery timing (emergency vs. selective) (OR = 8.721, P = 0.024) independently predicted increased risk of death within 30 days in TAAD patients. Furthermore, the combination of the above-mentioned independent factors had an excellent ability in predicting 30-day mortality with the area under curve of 0.949 (95% confidence interval: 0.909-0.989). MALT1 expression relates to increased Th1 cells, Th17 cells, and 30-day mortality risk in TAAD patients.

HECTD3 promotes NLRP3 inflammasome and pyroptosis to exacerbate diabetes-related cognitive impairment by stabilising MALT1 to regulate JNK pathway

Background HECTD3 (HECT domain E3 ubiquitin protein ligase 3) exerts biological activities in neuroinflammation of distinct diseases, such as autoimmune encephalomyelitis and donations after heart death. However, the effect of HECTD3 on diabetes-associated cognitive decline (DACD) remains unclear. Methods Wild-type or HECTD3-knockout rats were administered with streptozotocin to establish diabetic model. Pathological changes in the hippocampus were assessed by NISSL and haematoxylin and eosin staining. Morris water maze test was used to assess cognitive function. Neuronal survival and inflammation were investigated by immunofluorescence staining and ELISA assay. NLRP3 inflammasome and pyroptosis were assessed by western blot, immunofluorescence and flow cytometry assays. Results HECTD3 was up-regulated in hippocampus of streptozotocin-induced diabetic rats and high glucose-induced PC12 cells. Knockout of HECTD3 increased the number of neurons and improved the learning and memory function. Moreover, knockout of HECTD3 promoted in vivo neuronal survival, and reduced levels of IL-1β, TNF-α, and IL-6 in the hippocampus. Silencing of HECTD3 increased cell viability, and reduced IL-1β, TNF-α, and IL-6 in high glucose-induced PC12 cells. Fluorescence intensities of NLRP3, GSDMD-N and caspase-1 were reduced in HECTD3-knockout diabetic rats, and knockdown of HECTD3 down-regulated protein expression of NLRP3, GSDMD-N, caspase-1, IL-1β, and IL-18 in high glucose-induced PC12 cells to suppress the pyroptosis. HECTD3 promoted the stability of mucosa-associated lymphoid tissue 1 (MALT1) through up-regulation of c-JUN and phospho (p)-JNK in high glucose-induced PC12 cells. Over-expression of MALT1 attenuated neuroprotective effects of HECTD3 silencing on high glucose-induced PC12 cells. Conclusion HECTD3 silencing exerted neuroprotective effect against DACD through MALT1-mediated JNK signalling. Highlights HECTD3 was up-regulated in hippocampus of streptozotocin-induced diabetic rats and high glucose-induced PC12. Knockout of HECTD3 promoted in vivo neuronal survival, reduced inflammation and pyroptosis, and improved the learning and memory function in diabetic rats. Knockout of HECTD3 suppressed the activation of NLRP3 inflammasome in diabetic rats. Silencing of HECTD3 exerted neuroprotective effects through MALT1-mediated JNK signalling.

TRAF6 prevents fatal inflammation by homeostatic suppression of MALT1 protease.

Balanced control of T cell signaling is critical for adaptive immunity and protection from autoimmunity. By combining genetically engineered mouse models, biochemical analyses and pharmacological interventions, we describe an unexpected dual role of the tumor necrosis factor receptor–associated factor 6 (TRAF6) E3 ligase as both a positive and negative regulator of mucosa-associated lymphoid tissue 1 (MALT1) paracaspase. Although MALT1-TRAF6 recruitment is indispensable for nuclear factor κB signaling in activated T cells, TRAF6 counteracts basal MALT1 protease activity in resting T cells. In mice, loss of TRAF6-mediated homeostatic suppression of MALT1 protease leads to severe autoimmune inflammation, which is completely reverted by genetic or therapeutic inactivation of MALT1 protease function. Thus, TRAF6 functions as a molecular brake for MALT1 protease in resting T cells and a signaling accelerator for MALT1 scaffolding in activated T cells, revealing that TRAF6 controls T cell activation in a switch-like manner. Our findings have important implications for development and treatment of autoimmune diseases.

Mucosa-Associated Lymphoid Tissue 1 Is an Oncogene Inducing Cell Proliferation, Invasion, and Tumor Growth via the Upregulation of NF-κB Activity in Human Prostate Carcinoma Cells.

Prostate cancer is one of the most common seen malignancies and the leading cause of cancer-related death among men. Given the importance of early diagnosis and treatment, it is worth to identify a potential novel therapeutic target for prostate cancer. Mucosa-associated lymphoid tissue 1 (MALT1) is a novel gene involved in nuclear factor κB (NF-κB) signal transduction by acting as an adaptor protein and paracaspase, with an essential role in inflammation and tumorigenesis in many cancers. This study investigated the functions and the potential regulatory mechanisms of MALT1 in the human prostate cancer cells. We found that MALT1 is abundant in prostate cancer tissues. MALT1 facilitated NF-κB subunits (p50 and p65) nuclear translocation to induce gene expression of interleukin 6 (IL-6) and C-X-C motif chemokine 5 (CXCL5) in prostate carcinoma cells. MALT1 promoted cell proliferation, invasion, and tumor growth in vitro and in vivo. MALT1 enhanced NF-κB activity in prostate carcinoma cells; moreover, NF-κB induced MALT1 expression determined by reporter and immunoblot assays, implying there is a positive feedback loop between MALT1 and NF-κB. In conclusion, MALT1 is a NF-κB-induced oncogene in the human prostate carcinoma cells.

MALT1 proteolytic activity is necessary for FcɛRI-mediated cytokine production in mast cells

Abstract IgE mediated mast cell activation triggered by multivalent antigen crosslinking of FcɛRI receptors leads to the release of a wide range of inflammatory mediators. Recent studies revealed that B cell lymphoma 10 (Bcl10) and mucosa-associated lymphoid tissue 1 (MALT1) are required for IgE-induced nuclear factor κB (NF-κB)-induced proinflammatory cytokine production, while dispensible for mast cell degranulation and leukotriene synthesis. MALT1, a cytoplasmic signaling protein, possesses at least two functions: scaffolding activity and proteolytic activity. The contribution of MALT1 proteolytic activity to mast cell function has not yet been evaluated. We hypothesize that MALT1 proteolytic activity is necessary for FcɛRI-dependent proinflammatory cytokine production. In order to test our hypothesis, we compared the activation of bone marrow derived mast cells (BMMC) from wild type mice, MALT1 knockout mice (MALT1−/−), and mice harboring a mutant, proteolytically inactive MALT1 (MALT1PD/PD). We find MALT1 protease is active in wild-type BMMCs as evidenced by RelB cleavage, and is absent, as expected, in MALT1−/− and MALT1PD/PD BMMCs. Cytokine gene expression and production in response to IgE mediated FcɛRI crosslinking is equivalently abrogated in both MALT1−/− and MALT1PD/PD BMMCs as compared to wild type. These findings suggest that the contribution of MALT1 to IgE mediated responses can be largely attributed to its protease activity. The MALT1 protease has been shown to be drugable, and pharmaceutically targeting the MALT1 protease activity may represent a promising approach to abrogating late phase pathologic mast cell activation.

Regnase-1, a rapid response ribonuclease regulating inflammation and stress responses.

RNA-binding proteins (RBPs) are central players in post-transcriptional regulation and immune homeostasis. The ribonuclease and RBP Regnase-1 exerts critical roles in both immune cells and non-immune cells. Its expression is rapidly induced under diverse conditions including microbial infections, treatment with inflammatory cytokines and chemical or mechanical stimulation. Regnase-1 activation is transient and is subject to negative feedback mechanisms including proteasome-mediated degradation or mucosa-associated lymphoid tissue 1 (MALT1) mediated cleavage. The major function of Regnase-1 is promoting mRNA decay via its ribonuclease activity by specifically targeting a subset of genes in different cell types. In monocytes, Regnase-1 downregulates IL-6 and IL-12B mRNAs, thus mitigating inflammation, whereas in T cells, it restricts T-cell activation by targeting c-Rel, Ox40 and Il-2 transcripts. In cancer cells, Regnase-1 promotes apoptosis by inhibiting anti-apoptotic genes including Bcl2L1, Bcl2A1, RelB and Bcl3. Together with up-frameshift protein-1 (UPF1), Regnase-1 specifically cleaves mRNAs that are active during translation by recognizing a stem-loop (SL) structure within the 3'UTRs of these genes in endoplasmic reticulum-bound ribosomes. Through this mechanism, Regnase-1 rapidly shapes mRNA profiles and associated protein expression, restricts inflammation and maintains immune homeostasis. Dysregulation of Regnase-1 has been described in a multitude of pathological states including autoimmune diseases, cancer and cardiovascular diseases. Here, we provide a comprehensive update on the function, regulation and molecular mechanisms of Regnase-1, and we propose that Regnase-1 may function as a master rapid response gene for cellular adaption triggered by microenvironmental changes.

MALT1 Inhibition of Oral Carcinoma Cell Invasion and ERK/MAPK Activation

The expression of mucosa-associated lymphoid tissue 1 (MALT1) that activates nuclear factor (NF)–κB in lymphocyte lineages is rapidly inactivated in oral carcinoma cells at the invasive front and the patients with worst prognosis. However, its mechanism to accelerate carcinoma progression remains unknown, and this study was carried out to examine the role in invasion. HSC2 oral carcinoma cells stably expressing wild-type MALT1 (wtMALT1) reduced the invasion of basement membrane matrices and collagen gels, and the dominant-negative form (∆MALT1)–expressing cells aggressively invaded into collagen gels. MALT1 decelerated proliferation and migration of cells and downregulated expression of matrix metalloproteinase 2 and 9, which were confirmed by short interfering RNA transfections. Reporter assays and immunoblot analysis showed that MALT1 does not affect the NF-κB pathway but inhibits ERK/MAPK activation. This was confirmed by endogenous MALT1 expression in oral carcinoma cell lines. Orthotopic implantation of ∆MALT1-expressing HSC2 cells in mice grew rapid expansive and invasive tongue tumors in contrast to an absence of tumor formation by wtMALT1-expressing cells. These results demonstrate that MALT1 suppresses oral carcinoma invasion by inhibiting proliferation, migration, and extracellular matrix degradation and that the ERK/MAPK pathway is a target of MALT1 and further suggests a role as a suppressor of carcinoma progression.

MALT1 is required for EGFR-induced NF-κB activation and contributes to EGFR-driven lung cancer progression.

The transcription factor NF-κB has been implicated in playing a crucial role in the tumorigenesis of many types of human cancers. Although Epidermal Growth Factor Receptor (EGFR) can directly activate NF-κB, the mechanism by which EGFR induces NF-κB activation and the role of NF-κB in EGFR-associated tumor progression is still not fully defined. Herein, we found that Mucosa-Associated Lymphoid Tissue 1 (MALT1) is involved in EGFR-induced NF-κB activation in cancer cells, and MALT1 deficiency impaired EGFR-induced NF-κB activation. MALT1 mainly functions as a scaffold protein by recruiting E3 ligase TRAF6 to IKK complex to activate NF-κB in response to EGF stimulation. Functionally, MALT1 inhibition shows significant defects in EGFR-associated tumor malignancy, including cell migration, metastasis and anchorage independent growth. To further access a physiological role of MALT1-dependent NF-κB activation in EGFR-driven tumor progression, we generated triple transgenic mouse model (tetO-EGFRL858R; CCSP-rtTA; Malt1−/−), in which mutant EGFR-driven lung cancer was developed in the absence of MALT1 expression. MALT1-deficient mice show significantly less lung tumor burden when compared to its heterozygous controls, suggesting that MALT1 is required for the progression of EGFR-induced lung cancer. Mechanistically, MALT1 deficiency abolished both NF-κB and STAT3 activation in vivo, which is a result of a defect of IL-6 production. In comparison, MALT1 deficiency does not affect tumor progression in a mouse model (LSL-K-rasG12D; CCSP-Cre; Malt1−/−) in which lung cancer is induced by expressing a K-ras mutant. Thus, our study has provided the cellular and genetic evidence that suggests MALT1-dependent NF-κB activation is important in EGFR-associated solid tumor progression.

MALT1 induced immune response is governed by miR-2909 RNomics

The paracaspase mucosa-associated lymphoid tissue 1 (MALT1) has been widely recognized to play crucial role in lymphocyte activation, development and the generation of lymphomas through the modulation of innate and adaptive immune responses. Our results reported here provide evidence for the first time to support the view that MALT1 exerts its effect upon immune response involving genes coding for retinoic acid-inducible gene 1 (RIG1); interferon-β (IFN-β); apo-lipoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3G (APOBEC3G); IFN-γ; chemokine (C–C motif) ligand 5 (CCL5) and interleukin-17 (IL-17) through the initiation of cellular miR-2909 RNomics. This ensures sustained expression of specificity protein 1 (SP1)-dependent regulation of genes that in-turn governs MALT1 induced immune response. Based upon these results, a mechanistic-pathway is proposed that links the epigenomic-interplay between MALT1 and miR-2909.

MALT1 auto-proteolysis is essential for NF-κB-dependent gene transcription in activated lymphocytes.

Mucosa-associated lymphoid tissue 1 (MALT1) controls antigen receptor–mediated signalling to nuclear factor κB (NF-κB) through both its adaptor and protease function. Upon antigen stimulation, MALT1 forms a complex with BCL10 and CARMA1, which is essential for initial IκBα phosphorylation and NF-κB nuclear translocation. Parallel induction of MALT1 protease activity serves to inactivate negative regulators of NF-κB signalling, such as A20 and RELB. Here we demonstrate a key role for auto-proteolytic MALT1 cleavage in B- and T-cell receptor signalling. MALT1 cleavage occurred after Arginine 149, between the N-terminal death domain and the first immunoglobulin-like region, and did not affect its proteolytic activity. Jurkat T cells expressing an un-cleavable MALT1-R149A mutant showed unaltered initial IκBα phosphorylation and normal nuclear accumulation of NF-κB subunits. Nevertheless, MALT1 cleavage was required for optimal activation of NF-κB reporter genes and expression of the NF-κB targets IL-2 and CSF2. Transcriptome analysis confirmed that MALT1 cleavage after R149 was required to induce NF-κB transcriptional activity in Jurkat T cells. Collectively, these data demonstrate that auto-proteolytic MALT1 cleavage controls antigen receptor-induced expression of NF-κB target genes downstream of nuclear NF-κB accumulation.

Proteomic identification of keratin alterations with enhanced proliferation of oral carcinoma cells by loss of mucosa-associated lymphoid tissue 1 expression

Progression of oral carcinomas associates with aberrant activation and inactivation of molecules that work in established or unknown pathways. Although mucosa‑associated lymphoid tissue 1 (MALT1) expressed in normal oral epithelium is inactivated in the aggressive subset of carcinomas with worse prognosis, phenotypic changes of carcinoma cells upon the loss of expression is unknown. We performed a proteomic analysis to identify MALT1‑regulated proteins in oral carcinoma cells. Four different keratins were included in the ten most abundantly changed proteins. K8/18 were upregulated in MALT1 stably‑expressing carcinoma cells and K5/14 in MALT1‑marginal control cells. K8/18 upregulation and K5/14 downregulation were MALT1 dose‑dependent and observed in a series of oral carcinoma cells. MALT1 suppressed cell proliferation (0.52-fold, P<0.01) and its dominant-negative form stimulated it (1.33-fold, P<0.01). The decreased proliferation associated with reduction of cyclin D1, which was recovered by the short interfering RNA against MALT1. Taken together, loss of MALT1 expression alters keratin expression and enhances proliferation of carcinoma cells, and may progress oral carcinomas into the advanced state.

Inhibition of TGF-β and EGF pathway gene expression and migration of oral carcinoma cells by mucosa-associated lymphoid tissue 1

Background:Expression of mucosa-associated lymphoid tissue 1 (MALT1) is inactivated in oral carcinoma patients with worse prognosis. However, the role in carcinoma progression is unknown. Unveiling genes under the control of MALT1 is necessary to understand the pathology of carcinomas.Methods:Gene data set differentially transcribed in MALT1-stably expressing and -marginally expressing oral carcinoma cells was profiled by the microarray analysis and subjected to the pathway analysis. Migratory abilities of cells in response to MALT1 were determined by wound-healing assay and time-lapse analysis.Results:Totally, 2933 genes upregulated or downregulated in MALT1-expressing cells were identified. The subsequent pathway analysis implicated the inhibition of epidermal growth factor and transforming growth factor-β signalling gene expression, and highlighted the involvement in the cellular movement. Wound closure was suppressed by wild-type MALT1 (66.4%) and accelerated by dominant-negative MALT1 (218.6%), and the velocities of cell migration were increased 0.2-fold and 3.0-fold by wild-type and dominant-negative MALT1, respectively.Conclusion:These observations demonstrate that MALT1 represses genes activating the aggressive phenotype of carcinoma cells, and suggest that MALT1 acts as a tumour suppressor and that the loss of expression stimulates oral carcinoma progression.

A homozygous mucosa-associated lymphoid tissue 1 (MALT1) mutation in a family with combined immunodeficiency

Combined immunodeficiency (CID) is characterized by severe recurrent infections with normal numbers of T and B lymphocytes but with deficient cellular and humoral immunity. Most cases are sporadic, but autosomal recessive inheritance has been described. In most cases, the cause of CID remains unknown. We wanted to identify the genetic cause of CID in 2 siblings, the products of a first-cousin marriage, who experienced recurrent bacterial and candidal infections with bronchiectasis, growth delay, and early death. We performed immunologic, genetic, and biochemical studies in the 2 siblings, their family members, and healthy controls. Reconstitution studies were performed with T cells from mucosa-associated lymphoid tissue lymphoma-translocation gene 1-deficient (Malt1(-/-)) mice. The numbers of circulating T and B lymphocytes were normal, but T-cell proliferation to antigens and antibody responses to vaccination were severely impaired in both patients. Whole genome sequencing of 1 patient and her parents, followed by DNA sequencing of family members and healthy controls, showed the presence in both patients of a homozygous missense mutation in MALT1 that resulted in loss of protein expression. Analysis of T cells that were available on one of the patients showed severely impaired IκBα degradation and IL-2 production after activation, 2 events that depend on MALT1. In contrast to wild-type human MALT1, the patients' MALT1 mutant failed to correct defective nuclear factor-κB activation and IL-2 production in MALT1-deficient mouse T cells. An autosomal recessive form of CID is associated with homozygous mutations in MALT1. If future patients are found to be similarly affected, they should be considered as candidates for allogeneic hematopoietic cell transplantation.

The HECTD3 E3 Ubiquitin Ligase Suppresses Cisplatin-Induced Apoptosis via Stabilizing MALT1

Homologous to the E6-associated protein carboxyl terminus domain containing 3 (HECTD3) is an E3 ubiquitin ligase with unknown functions. Here, we show that HECTD3 confers cancer cell resistance to cisplatin. To understand the molecular mechanisms, we performed a yeast two-hybrid analysis and identified mucosa-associated lymphoid tissue 1 (MALT1) as an HECTD3-interacting protein. HECTD3 promotes MALT1 ubiquitination with non-degradative polyubiquitin chains by direct interacting with the MALT1 through its N-terminal destruction of cyclin domain. HECTD3 does not target MALT1 for degradation but stabilize it. HECTD3 depletion dramatically decreases the levels of MALT1 in MCF7 and HeLa cells treated with cisplatin, which is correlated to an increase in apoptosis. Knockdown of MALT1 likewise increases cisplatin-induced apoptosis in these cancer cells. However, HECTD3 overexpression leads to a decreased cisplatin-induced apoptosis, whereas overexpression of MALT1 partially rescues HECTD3 depletion–induced apoptosis. These findings suggest that HECTD3 promotes cell survival through stabilizing MALT1. Our data have important implications in cancer therapy by providing novel molecular targets.

BCL10GFP fusion protein as a substrate for analysis of determinants required for Mucosa-Associated Lymphoid Tissue 1 (MALT1)-mediated cleavage

BackgroundMALT1 belongs to a family of paracaspase and modulates NF-κB signaling pathways through its scaffolding function and proteolytic activity. MALT1 cleaves protein substrates after a positively charged Arginine residue. BCL10, a 233 amino acids polypeptide, is identified as one of the MALT1 proteolytic substrates. MALT1 cleaves BCL10 at the C-terminal end of Arg228. A mere 5 amino acids difference between the substrate and the proteolytic product made it difficult to tell whether the cleavage event took place by using a simple western blot analysis. Here, BCL10GFP was constructed and utilized to examine the specificity and domain determinants for MALT1 cleavage in cells.MethodsVarious BCL10GFP constructs were transfected into HEK293T cell with MALT1 construct by using calcium phosphate-DNA precipitation method. Lysates of transfectants were resolved by SDS/PAGE and analyzed by western blot analysis.ResultsBCL10GFP was proteolytically processed by MALT1 as BCL10. The integrity of caspase recruitment domain (CARD) and MALT1-interacting domain on BCL10 were required for MALT1 proteolytic activity. Besides the invariant P1 cleavage site Arg228, P4 Leu225 played a role in defining BCL10 as a good substrate for MALT1.ConclusionsWe offered a way of monitoring the catalytic activity of MALT1 in HEK293T cells using BCL10GFP as a substrate. BCL10GFP can be utilized as a convenient tool for studying the determinants for efficient MALT1 cleavage in HEK293T cells

Single nucleotide polymorphisms of mucosa-associated lymphoid tissue 1 in oral carcinoma cells and gingival fibroblasts

Oral carcinoma patients with inactivation of mucosa-associated lymphoid tissue 1 (MALT1) expression worsen their prognoses. Although the genetic mutation could be responsible for the inactivation, no information is available at present. In the present study, genomic DNA of oral carcinoma cells (HOC313, TSU, HSC2, HSC3, KOSC2, KOSC3, SCCKN, OSC19, Ca9.22, and Ho1u1 cells) and normal gingival fibroblasts (GF12 cells) derived from a Japanese population were amplified by polymerase chain reaction using primer sets spanning MALT1 exons, and nucleotide substitutions were analyzed by the single strand conformation polymorphism analysis. The substitutions were commonly observed in all cells, which express MALT1 at various levels. The substitutions at exons 1 and 9 were located at the 5' untranslated region and replaced (336)Asp to Asn, respectively, and others were positioned at the introns. Among the intronic substitutions, four were matched with the single nucleotide polymorphisms (SNPs) registered at the database. Since all cells were derived from a Japanese population, all substitutions detected are the SNPs. Absence of the carcinoma cell-specific mutation suggests that the inactivation of MALT1 expression but not the mutation promotes oral carcinoma progression.

Chlamydia psittaci-negative ocular adnexal marginal zone B-cell lymphomas have biased VH4-34 immunoglobulin gene expression and proliferate in a distinct inflammatory environment

Ocular adnexal marginal zone B-cell lymphomas (OAMZLs) arise in the connective tissues of the orbit or in the mucosa-associated lymphoid tissue of the conjunctiva. Here, we present the immunological and genetic analyses of 20 primary Chlamydia psittaci (Cp)-negative OAMZLs. Analysis of the immunoglobulin variable heavy chain (IgV(H)) gene usage demonstrated a significant preference for V(H)4-34. A combined analysis across all previously published OAMZLs confirmed that this is a general feature of OAMZL, in particular of the Cp-negative group. Our series of OAMZLs did not express the characteristic rheumatoid factor V(H)DJ(H) rearrangements that were previously found in salivary gland- and gastric-marginal zone B-cell lymphomas (MZBCLs). We did not detect the MZBCL-specific chromosomal translocations, t(11;18) API2-MALT1 (mucosa-associated lymphoid tissue1) and t(14;18) IgH/MALT1. Two cases contained a premature stop codon in the A20 gene (TNFAIP3) and one case harbored the activating MYD88 hotspot mutation L265P. Variable nuclear expression of BCL10, NFκB1 (p50) and NFκB2 (p52) suggests that other additional genetic abnormalities affecting the NFκB pathway exist within this group of lymphomas. OAMZL showed variable expression of the chemokine receptor CXCR3 and integrin α4β7 by the tumor B cells, and low interferon-γ and interlukin-4 mRNA levels in the tissue, indicative of an inflammatory environment with features in between those previously found in cutaneous and other extranodal MZBCL. The strongly biased usage of V(H)4-34 in Cp-negative OAMZLs suggests involvement of a particular stimulatory (auto-) antigen in their development.