Galectin-3 binding to
cell surface glycoproteins, including branched N-
glycans generated by
N-acetylglucosaminyltransferase V (Mgat5) activity, forms a multivalent, heterogeneous, and dynamic lattice. This lattice has been shown to regulate
integrin and
receptor tyrosine kinase signaling promoting
tumor cell migration.
N-cadherin is a homotypic cell-cell adhesion receptor commonly overexpressed in
tumor cells that contributes to cell motility. Here we show that
galectin-3 and
N-cadherin interact and colocalize with the
lipid raft marker
GM1 ganglioside in cell-cell junctions of mammary epithelial
cancer cells. Disruption of the lattice by deletion of Mgat5,
siRNA depletion of
galectin-3, or competitive inhibition with
lactose stabilizes cell-cell junctions. It also reduces, in a p120-catenin-dependent manner, the dynamic pool of junctional
N-cadherin. Proteomic analysis of
detergent-resistant membranes (DRMs) revealed that the
galectin lattice opposes entry of many
proteins into DRM rafts.
N-cadherin and
catenins are present in DRMs; however, their DRM distribution is not significantly affected by lattice disruption.
Galectin lattice integrity increases the mobile fraction of the raft marker,
GM1 ganglioside binding
cholera toxin B subunit Ctb, at cell-cell contacts in a p120-catenin-independent manner, but does not affect the mobility of either Ctb-labeled GM1 or GFP-coupled
N-cadherin in nonjunctional regions. Our results suggest that the
galectin lattice independently enhances lateral molecular diffusion by direct interaction with specific
glycoconjugates within the adherens junction. By promoting exchange between raft and non-raft microdomains as well as molecular dynamics within junction-specific raft microdomains, the lattice may enhance turnover of
N-cadherin and other
glycoconjugates that determine junctional stability and rates of cell migration.