Interactions of asymmetric forms of acetylcholinesterase with basement membrane components.

Previous studies have indicated that the asymmetric form of acetylcholinesterase is localized in the basement membrane zone of the neuromuscular junction. We find that the collagenous subunit of the enzyme is required for interactions with basement membrane components. Acetylcholinesterase (the A12 form) binds best to the basement membrane heparan sulfate proteoglycan and type V collagen, to a lesser extent to laminin, fibronectin, and type I collagen, but not to type IV collagen. In addition, the purified A12 enzyme as prepared from electric eel is associated with a heparan sulfate-like component which appears to be responsible for the aggregation of the enzyme at low ionic strength. We observed that the purified form of the enzyme reacted with antibodies to type V collagen, and to a lesser extent with anti-type I collagen antibody, but not with anti-type IV collagen antibody. These data suggest that the collagenous subunit of the enzyme may have some similarity to type V collagen and that the interaction of the collagenous subunit with a heparan sulfate proteoglycan may be involved in its binding to basement membrane in the neuromuscular junction.