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.