α2–6 sialylation of β
integrins in three ovarian carcinoma cell lines. A, Lysates from PA1, OV4, and SKOV3 cells were incubated with agarose-conjugated SNA, a lectin specific for α2–6 sialic acids. Glycoproteins were precipitated, resolved by SDS-PAGE and immunoblotted for the β1 integrin. B, Cell lysates were immunoblotted for the β1 integrin to control for total levels of protein expression. The top band in β1 immunoblots represents the functional receptor isoform ("mature β1"), whereas the bottom band represents a precursor, ER-resident, form of β1. Of note, OV4 cells do not appear to express a precursor isoform.