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Laminin (green) uses gal-sulfatide (red) as its anchor.

Two decades ago researchers considered the possibility that glycolipids could link laminin and other extracellular matrix proteins to the cell, but once integrins were discovered the focus switched to protein–protein interactions. Now on page 179, Li et al. show that the glycolipid galactosyl-sulfatide (gal-sulfatide) is a crucial anchor for laminin in Schwann cells and is necessary for basement membrane assembly. However, intracellular signaling requires protein receptors, such as integrins and dystroglycan.Laminin was known to interact with sulfated glycolipids, but the significance of the interaction was not known. Li et al. found that laminin aggregated on the surface of Schwann cells in vitro only in the presence of gal-sulfatide. Treatment of the cells with an enzyme that removed the sulfate groups from the surface blocked laminin binding. Fibroblasts do not normally make a basement membrane, but when the team seeded them with gal-sulfatide, the cells bound laminin. In both cell types, basement membrane formation occurred only after laminin bound to the glycolipid. However, intracellular signaling was triggered when laminin had access to functional β1-integrins and dystroglycan, not because of the interaction with the glycolipid.

The team has started to look at other systems to see if this phenomenon is common. Already they have found hints that gal-sulfatide is used for the polymerization of laminins and basement membrane formation in embryoid bodies.