A newly-synthesized GPI-anchored protein, TAG-1/axonin-1, is inserted into axonal membranes along the entire length of the axon and not exclusively at the growth cone

Evidence exists that some newly-synthesized membrane components are inserted into the membrane of the growing axon at the growth cone. We now examine the site of insertion of a glycosylphosphatidylinositol-anchored protein, TAG-1/axonin-1. The protein was cleaved from the plasma membrane by phosphatidylinositol-specific phospholipase C. Newly-synthesized TAG-1/axonin-1 was subsequently detected along the entire length of the axonal membrane, with no evidence for preferential insertion at the distal end. These results raise the possibility that different subsets of proteins are inserted at different locations in axonal membranes.