Differential glycosylation of tractin and LeechCAM, two novel Ig superfamily members, regulates neurite extension and fascicle formation.

By immunoaffinity purification with the mAb Lan3-2, we have identified two novel Ig superfamily members, Tractin and LeechCAM. LeechCAM is an NCAM/FasII/ApCAM homologue, whereas Tractin is a cleaved protein with several unique features that include a PG/YG repeat domain that may be part of or interact with the extracellular matrix. Tractin and LeechCAM are widely expressed neural proteins that are differentially glycosylated in sets and subsets of peripheral sensory neurons that form specific fascicles in the central nervous system. In vivo antibody perturbation of the Lan3-2 glycoepitope demonstrates that it can selectively regulate extension of neurites and filopodia. Thus, these experiments provide evidence that differential glycosylation can confer functional diversity and specificity to widely expressed neural proteins.