ppGalNAc-T4-catalyzed O-Glycosylation of TGF-β type Ⅱ receptor regulates breast cancer cells metastasis potential

Abstract

GalNAc-type O-glycosylation, initially catalyzed by polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts), is one of the most abundant and complex post-translational modifications of proteins. Emerging evidence has proven that aberrant ppGalNAc-Ts are involved in malignant tumor transformation. However, the exact molecular functions of ppGalNAc-Ts are still unclear. Here, the role of one isoform, ppGalNAc-T4, in breast cancer cell lines was investigated. The expression of ppGalNAc-T4 was found to be negatively associated with migration of breast cancer cells. Loss-of function studies revealed that ppGalNAc-T4 attenuated the migration and invasion of breast cancer cells by inhibiting the epithelial-mesenchymal transition (EMT) process. Correspondingly, transforming growth factor beta (TGF-β) signaling, which is the upstream pathway of EMT, was impaired by ppGalNAc-T4 expression. ppGalNAc-T4 knock-out decreased O-GalNAc modification of TGF-β type Ⅰ and Ⅱ receptor (TβR Ⅰ and Ⅱ) and led to the elevation of TGF-β receptor dimerization and activity. Importantly, a peptide from TβR Ⅱ was first identified as the naked peptide substrate of ppGalNAc-T4 with a higher affinity than ppGalNAc-T2. Further, Ser31, corresponding to the extracellular domain of TβR Ⅱ, was identified as the O-GalNAcylation site upon in vitro glycosylation by ppGalNAc-T4. The O-GalNAc-deficient S31A mutation enhanced TGF-β signaling activity and EMT in breast cancer cells. Together, these results identified a novel mechanism of ppGalNAc-T4-catalyzed TGF-β receptors O-GalNAcylation that suppresses breast cancer cell migration and invasion via the EMT process. Targeting ppGalNAc-T4 may be a potential therapeutic strategy for breast cancer treatment.

GALNTs: master regulators of metastasis-associated epithelial-mesenchymal transition (EMT)?

“…It is interesting that Wu et al (2021b) reported converse findings when they examined the relationship between GALNT4 and EMT in breast cancer cells. Having demonstrated that GALNT4 was upregulated in good prognosis, luminal type breast cancer and associated with favourable recurrence free survival, they showed that knockdown of GALNT4 was associated with mesenchymal cell morphology and over-expression with an epithelial phenotype.…”

“…Altered levels of GALNT expression or distribution, determined by molecular approaches and by immunohistochemistry, respectively, have also been extensively reported in a broad range of cancers. These include colorectal (Kohsaki et al, 2000;Shibao et al, 2002;Guo et al, 2004;Guda et al, 2009;Abulí et al, 2011;Clarke et al, 2012;Lavrsen et al, 2018;Ubillos et al, 2018;Tang et al, 2021), gastric (Onitsuka et al, 2003;Gomes et al, 2009;Gao et al, 2013;He et al ., 2014;Xu et al, 2020b;Liu et al, 2016), renal (Kitada et al, 2013), breast (Berois et al, 2006a;Freire et al, 2006;Patani et al, 2008;2021a;2021b;Park et al, 2010;Liu et al, 2020;Huang et al, 2022), pancreatic (Li et al, 2011;Taniuchi et al, 2011;Tarhan et al, 2016;Caffrey et al, 2019), gallbladder (Miyahara et al, 2004), prostate (Landers et al, 2005), oesophageal (Ishikawa et al, 2005), lung adenocarcinoma (Gu et al, 2004;Song et al, 2020;Wang et al, 2021) and non small cell lung cancer (Dosaka-Akita et al, 2002), cervical (Peng et al, 2012;Cao et al, 2020), bladder (Ding et al, 2012), liver (Wu et al, 2011;Huang et al, 2015), oral …”

Role of Glycans on Key Cell Surface Receptors That Regulate Cell Proliferation and Cell Death

“…TGFR may also be O -glycosylated. Wu et al [ 146 ] showed that TGFR II from breast cancer cells was O -glycosylated at Ser31 and possibly also at Thr39. GALNT4 was shown to be the enzyme that transfers GalNAc to both TGFR I and II and blocks heterodimer formation.…”

“…This suggests that GalNAc residues of TGFR control receptor function. Depending on the cell type and the GTs expressed, GalNAc could be further modified to more complex O -glycans that would potentially regulate dimerization and signaling [ 146 ].…”

GALNT12 suppresses the bone-specific prostate cancer metastasis by activating BMP pathway via the O-glycosylation of BMPR1A

“…For instance, GALNT8 could suppress the metastasis of breast cancer via suppressing the EGFR signaling pathway [15]. GALNT4 promoted the O-GalNAc modification of TGF-β type Ⅰ and Ⅱ receptor in breast cancer and then suppressed the dimerization and activity of TGF-β receptor restraining the migration and invasion of cancer cells [16]. GALNT2 promoted the invasion of colorectal cancer cells via mediating the O-GalNAcylation of AXL [17].…”