Characterization and role of Helix contactin-related proteins in cultured Helix pomatia neurons

We report on the structural and functional properties of the Helix contactin-related proteins (HCRPs), a family of closely related glycoproteins previously identified in the nervous system of the land snail Helix pomatia through antibodies against the mouse F3/contactin glycoprotein. We focus on HCRP1 and HCRP2, soluble FNIII domains-containing proteins of 90 and 45 kD bearing consensus motifs for both N- and O-glycosylation. Using the anti-HCRPs serum, we find secreted HCRPs in Helix nervous tissue isotonic extracts and in culture medium conditioned by Helix ganglia. In addition, we demonstrate expression of HCRPs on neuronal soma and on neurite extensions. Functionally, in Helix neurons, the antisense HCRP2 mRNA counteracts neurite elongation, and the recombinant HCRP2 protein exerts a strong positive effect on neurite growth when used as substrate. These data point to HCRPs as novel neurite growth-promoting molecules expressed in invertebrate nervous tissue.