“Malt1 Paracaspace-mediated Crosstalk of TGF-β and NF-κB Signaling Pathways”
Assoc. Prof. Şerif Şentürk
Functional Cancer Genomics Group
Biomedicine and Genom Center, Dokuz Eylül University,Izmir
Time: April 27, 2022 03:30 PM
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Host : Işık Yuluğ
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Abstract
Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (Malt1) is a paracaspase known for its role in the regulation of receptor-stimulated nuclear factor kappa B (NF-κB) pathway activation. Transforming growth factor-β (TGF-β) and NF-κB pathways are two fundamental signaling cascades with key functions in cancer cell proliferation and survival. It is widely recognized that these pathways crosstalk at multiple levels, yet the function of Malt1in this crosstalk has not been addressed. This talk will summarize our recent findings on the interplay between Malt1, and TGF-β and NF-κB signaling crosstalk in cancer cells. Experiments were conducted in two TGF-β -responsive cell lines, a NSCLC cell line (A549) and an HCC cell line (Huh7). The role of canonical TGF-β signaling in Malt1 gene expression was studied by suppressing the pathway using shRNA- and CRISPR/Cas9-mediated perturbations. The regulation of Malt1 gene expression by TGF-β was examined using luciferase reporter assay with Malt1 promoter constructs. TGF-β and NF-κB crosstalk was analyzed by immunofluorescence staining of NF-κB subunit p65 (RelA) nuclear translocation as well as p65 reporter assays.
Collectively, we showed that Malt1 expression was upregulated by TGF-β in a dose- and timedependent manner, both at the transcript and protein levels. shRNA-mediated silencing of TGFBR1 or Smad3 and Smad4 genes abolished TGF-β -induced Malt1 expression, stressing the positive transcriptional regulatory role of canonical TGF-β signaling. Furthermore, reporter experiments with Malt1 promoter plasmids as well as CRISPR/Cas9-based genetic ablation studies and rescue experiments identified the Malt1 gene as a direct target of Smad3. Finally, shRNA knockdown of Malt1 gene inhibited TGF-β -induced nuclear translocation of p65 and NF-κB target gene expressions, suggesting that Malt1 is a key mediator of TGF-β and NF-κB signaling crosstalk. Further studies may provide mechanistic insights into how Malt1 facilitates the activation of NF-κB signaling by the TGF-β pathway.