GABARAPL1 Inhibits EMT Signaling through SMAD-Tageted Negative Feedback

Abstract

The pathway of selective autophagy, leading to a targeted elimination of specific intracellular components, is mediated by the ATG8 proteins, and has been previously suggested to be involved in the regulation of the Epithelial–mesenchymal transition (EMT) during cancer’s etiology. However, the molecular factors and steps of selective autophagy occurring during EMT remain unclear. We therefore analyzed a cohort of lung adenocarcinoma tumors using transcriptome analysis and immunohistochemistry, and found that the expression of ATG8 genes is correlated with that of EMT-related genes, and that GABARAPL1 protein levels are increased in EMT+ tumors compared to EMT- ones. Similarly, the induction of EMT in the A549 lung adenocarcinoma cell line using TGF-β/TNF-α led to a high increase in GABARAPL1 expression mediated by the EMT-related transcription factors of the SMAD family, whereas the other ATG8 genes were less modified. To determine the role of GABARAPL1 during EMT, we used the CRISPR/Cas9 technology in A549 and ACHN kidney adenocarcinoma cell lines to deplete GABARAPL1. We then observed that GABARAPL1 knockout induced EMT linked to a defect of GABARAPL1-mediated degradation of the SMAD proteins. These findings suggest that, during EMT, GABARAPL1 might intervene in an EMT-regulatory loop. Indeed, induction of EMT led to an increase in GABARAPL1 levels through the activation of the SMAD signaling pathway, and then GABARAPL1 induced the autophagy-selective degradation of SMAD proteins, leading to EMT inhibition.

Revealing the impact of autophagy-related genes in rheumatoid arthritis: Insights from bioinformatics

“…By interacting with SMAD2/3 proteins, GABARAPL1 can block the EMT signaling pathway that is activated by transforming growth factor-beta (TGF-B)/tumor necrosis factor-alpha (TNF-A). GABARAPL1 regulates autophagy to degrade SMAD and GABARAPL1 proteins, further inhibiting the EMT signaling pathway [ 66 ]. Furthermore, knockdown of GABARAPL1 inhibits the growth of androgen receptor (AR)-positive prostate cancer cells LNCaP and CWR22rv1, as well as reduces the transcriptional activity and nuclear translocation of AR/ Androgen Receptor Variants (ARV).…”

TGF-β as Predictive Marker and Pharmacological Target in Lung Cancer Approach

“…Recently, CRISPR/Cas9 technology has been used to explore the possible role of different proteins in TGF-β-induced EMT events in LC [ 80 , 81 ]. For instance, the depletion of Ras Association Domain Family 10 (RASSF10) in TGF-β-induced EMT in different cell lines (e.g., small, non-small and squamous cell LC) induces cell growth and invasiveness after TGF-β treatment [ 80 ].…”

“…For instance, the depletion of Ras Association Domain Family 10 (RASSF10) in TGF-β-induced EMT in different cell lines (e.g., small, non-small and squamous cell LC) induces cell growth and invasiveness after TGF-β treatment [ 80 ]. Similarly, CRISPR/Cas9 technology has been used to study the role of GABARAPL1, an autophagy-related gene, during TGF-β/TNF-α-triggered EMT in LC and kidney adenocarcinoma cell lines [ 81 ]; in LC cells, KO GABARAPL1 occurred during the induction of EMT via a defective GABARAPL1-mediated autophagic degradation of the SMAD proteins, proposing the possible role of GABARAPL1in a negative EMT-regulatory loop [ 81 ]. This evidence suggests that the loss of RASSF10 or GABARAPL1 could contribute to lung tumor progression by supporting TGF-β-induced EMT [ 80 , 81 ].…”

A New Era of Integration between Multiomics and Spatio-Temporal Analysis for the Translation of EMT towards Clinical Applications in Cancer

“…Negative regulatory processes may include the suppression of EMT-promoting signaling pathways through the expression of inhibitory proteins, some of which are induced by these signaling pathways themselves as a negative feedback mechanism [25][26][27][28][29]. Otherwise, extracellular autocrine or paracrine signals inducing a mesenchymal-epithelial transition (MET) can also balance this process [24,30,31]. Restoring the levels of epithelial and mesenchymal proteins during MET facilitates the re-establishment of an epithelial cell phenotype [31,32].…”