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Sialylation of glycoproteins, including integrins, is crucial in various cancers and diseases such as immune disorders. These modifications significantly impact cellular functions and are associated with cancer progression. Sialylation, catalyzed by specific sialyltransferases (STs), has traditionally been considered to be regulated at the mRNA level. Recent research has expanded our understanding of sialylation, revealing ST activity changes beyond mRNA level variations. This includes insights into COPI vesicle formation and Golgi apparatus maintenance and identifying specific target proteins of STs that are not predictable through recombinant enzyme assays. This review summarizes that Golgi-associated pathways largely influence the regulation of STs. GOLPH3, GORAB, PI4K, and FAK have become critical elements in sialylation regulation. Some STs have been revealed to possess specificity for specific target proteins, suggesting the presence of additional, enzyme-specific regulatory mechanisms. This study enhances our understanding of the molecular interplay in sialylation regulation, mainly focusing on the role of integrin and FAK. It proposes a bidirectional system where sialylations might influence integrins and vice versa. The diversity of STs and their specific linkages offer new perspectives in cancer research, potentially broadening our understanding of cellular mechanisms and opening avenues for new therapeutic approaches in targeting sialylation pathways. • Epigenetic and transcriptional factors influence ST gene expressions. • GOLPH3 and GORAB regulate sialylation through their roles in COPI vesicles. • FAK modulates the stability of PI4KIIα, influencing N-glycan sialylation. • ST6GAL1 and the ST3GAL family have distinct target substrates. [ABSTRACT FROM AUTHOR]

The epithelial cell adhesion molecule (EpCAM) is one of the most frequently and intensely expressed of tumor-associated antigens, but the role that EpCAM plays in the proliferation, adhesion and migration properties of cancer cells remains unclear. In the present study, we screened several tumor cell lines and found that colorectal cancer CW-2 and epidermoid carcinoma A431 cells expressed relatively higher levels of EpCAM. In order to assess the biological functions of EpCAM expression in cell adhesion and migration, we established a knock out (KO) of EpCAM genes in both of these types of cancer cells via a CRISPR/Cas9 system. The elongated cell morphology was converted to a rounded morphology in the EpCAM-KO cells. These cells showed decreases in cell proliferation and migration into extracellular matrix proteins, as well as decreases in cellular signaling elements such as phosphorylated focal adhesion kinase (FAK), AKT and ERK. Moreover, the cell growth and the colony formation abilities were significantly decreased in EpCAM-KO cells. Importantly, co-immunoprecipitation analysis revealed that EpCAM associated with integrin β1. Also, the expression levels of integrin α5 were decreased in EpCAM-KO cells, compared with that in the wild-type cells. Taken together, these data clearly demonstrate that EpCAM associates with integrin β1 to regulate FAK/ERK signaling pathways in controlling cell adhesion, migration and proliferation via extracellular matrix adhesion, which provides novel mechanisms for EpCAM-mediated biological functions and cancer phenotypes. • Screening of the EpCAM expression in different cancer cell lines helped establish EpCAM-knockout cell lines. • Reduction in EpCAM led to a decrease in cell-ECM adhesion and to a suppression of signaling by phospho-FAK, -ERK and -AKT. • A novel complex of EpCAM and integrin β1 could intervene in the signaling crosstalk between cell-cell and cell-ECM adhesion. [ABSTRACT FROM AUTHOR]

Transforming growth factor (TGF)-β1 is a significant stimulator of tumor invasion and metastasis. More recently, it has been found that TGF-β1 acts through microRNAs to regulate their target genes to promote cancer progresses. However, such similar regulation is rarely reported in colorectal cancer (CRC). Here, we observed a decrease in TGF-β1 expression in CRC specimens, compared with matched adjacent normal tissues. In parallel, there was an increase in miR-130b characterized in the same samples by microarray assay. Further, treatment of CRC cells with TGF-β1 caused a significant decrease in the expression of miR-130b and an increased CRC cell migration. Luciferase reporter assay revealed that miR-130b directly targeted the 3′ untranslated region (3′UTR) region of integrin α5 gene, which encodes a key molecule involved in cell motility. Subsequently, in the overexpression of miR-130b CRC cells, we observed a decreased level of integrin α5 protein. The regulation of integrin α5 by miR-130b was further shown using the miR-130b mimics and inhibitor of miR-130b. And, knockdown miR-130b with inhibitor in the overexpression of miR-130b CRC cells recovered integrin α5 expression and integrin α5-mediated cell motility. Moreover, the inverse relevance between miR-130b and integrin α5 was also observed in CRC specimens. At last, the enhancement of integrin α5 in TGF-β1-treated cells can be reversed partly when rescuing miR-130b expression. Together, our findings suggested that TGF-β1 acted through miR-130b to promote integrin α5 expression, resulting in the enhanced migration of CRC cells. [ABSTRACT FROM AUTHOR]

Glycosylation is one of the most common post-translational modifications, and approximately 50% of all proteins are presumed to be glycosylated in eukaryotes. Branched N-glycans, such as bisecting GlcNAc, β-1,6-GlcNAc and core fucose (α-1,6-fucose), are enzymatic products of N-acetylglucosaminyltransferase III, N-acetylglucosaminyltransferase V and α-1,6-fucosyltransferase, respectively. These branched structures are highly associated with various biological functions of cell adhesion molecules, including cell adhesion and cancer metastasis. E-cadherin and integrins, bearing N-glycans, are representative adhesion molecules. Typically, both are glycosylated by N-acetylglucosaminyltransferase III, which inhibits cell migration. In contrast, integrins glycosylated by N-acetylglucosaminyltransferase V promote cell migration. Core fucosylation is essential for integrin-mediated cell migration and signal transduction. Collectively, N-glycans on adhesion molecules, especially those on E-cadherin and integrins, play key roles in cell–cell and cell–extracellular matrix interactions, thereby affecting cancer metastasis. [ABSTRACT FROM AUTHOR]

The N -glycosylation of integrin α5β1 is involved in multiple cell biological functions. Our group previously reported that the N- glycosylation of the Calf-1,2 domain on α5 subunit (S3-5,10-14) was important for its inhibitory effect on EGFR signaling through regulating α5-EGFR complex formation. In this follow-up study, we provide evidence that the N -glycosylation on integrin β1 subunit suppress cell growth by promoting its association with EGFR under fibronectin (FN)-coated conditions. Expression of wild-type (WT) β1, but not the N -glycosylation mutant S4-6 β1, which contains fewer N -glycans, inhibited EGFR signaling and cell proliferation after cell adhesion to FN. Furthermore, consistent restoration of the N -glycans on sites 1-3 of β1 reinstated the inhibitory effects. Mechanistically, the N -glycosylation mutant of β1 (S4-6+1-3) inhibited the EGFR response upon EGF stimulation via facilitating the α5β1-EGFR complex formation. Moreover, we identified the N -glycosylation of sites 10-14 on α5 and 1-3 on β1 were most important for EGFR signaling. Taken together, these data indicate that α5S3-5+10-14β1S4-6+1-3 mutant represents the minimal N -glycosylation required for its regulation on EGFR signaling and cell proliferation, providing a plausible mechanism for the crosstalk between with α5β1 and EGFR. • No.1-3 N -glycosylation on integrin β1 suppress cell growth on fibronectin. • N -glycosylation on sites 1-3 of β1 mediate the interaction between integrin α5β1 and EGFR. • α5S3-5+10-14β1S4-6+1-3 is the minimal N -glycosylation mutant that required for its inhibitory effect on EGFR signaling. [ABSTRACT FROM AUTHOR]