Abstract
Aberrant N-glycan sialylation of glycoproteins is closely associated with malignant phenotypes of cancer cells and metastatic potential, which includes cell adhesion, migration, and growth. Recently, phosphatidylinositol 4-kinase IIα (PI4KIIα), which is localized to the trans-Golgi network, was identified as a regulator of Golgi phosphoprotein 3 (GOLPH3) and of vesicle transport in the Golgi apparatus. GOLPH3 is a target of PI4KIIα and helps anchor sialyltransferases and thereby regulates sialylation of cell surface receptors. However, how PI4KIIα-mediated sialyation of cell surface proteins is regulated remains unclear. In this study, using several cell lines, CRISPR/Cas9-based gene knockout and short hairpin RNA-mediated silencing, RT-PCR, lentivirus-mediated overexpression, and immunoblotting methods, we confirmed that PI4KIIα knockdown suppresses the sialylation of N-glycans on the cell surface, in Akt phosphorylation and activation, and integrin α3-mediated cell migration of MDA-MB-231 breast cancer cells. Interestingly, both integrin α3β1 and PI4KIIα co-localized to the trans-Golgi network, where they physically interacted with each other, and PI4KIIα specifically associated with integrin α3 but not α5. Furthermore, overexpression of both integrin α3β1 and PI4KIIα induced hypersialylation. Conversely, integrin α3 knockout significantly inhibited the sialylation of membrane proteins, such as the epidermal growth factor receptor, as well as in total cell lysates. These findings suggest that the malignant phenotype of cancer cells is affected by a sialylation mechanism that is regulated by a complex between PI4KIIα and integrin α3β1.
Highlights
Aberrant N-glycan sialylation of glycoproteins is closely associated with malignant phenotypes of cancer cells and metastatic potential, which includes cell adhesion, migration, and growth
These findings suggest that the malignant phenotype of cancer cells is affected by a sialylation mechanism that is regulated by a complex between PI4KII␣ and integrin ␣31
We recently reported that the expression of Golgi phosphoprotein 3 (GOLPH3) upregulated cell surface sialylation and cell migration [11]
Summary
A complex between phosphatidylinositol 4-kinase II␣ and integrin ␣31 is required for N-glycan sialylation in cancer cells. In this study, using several cell lines, CRISPR/Cas9-based gene knockout and short hairpin RNA–mediated silencing, RT-PCR, lentivirus-mediated overexpression, and immunoblotting methods, we confirmed that PI4KII␣ knockdown suppresses the sialylation of N-glycans on the cell surface, in Akt phosphorylation and activation, and integrin ␣3-mediated cell migration of MDA-MB-231 breast cancer cells Both integrin ␣31 and PI4KII␣ co-localized to the trans-Golgi network, where they physically interacted with each other, and PI4KII␣ associated with integrin ␣3 but not ␣5. Integrin ␣3 knockout significantly inhibited the sialylation of membrane proteins, such as the epidermal growth factor receptor, as well as in total cell lysates These findings suggest that the malignant phenotype of cancer cells is affected by a sialylation mechanism that is regulated by a complex between PI4KII␣ and integrin ␣31. These findings suggest a novel mechanism for sialylation, which suggests a new concept for the regulation of glycosylation in cell biology
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