TRANSGLUTAMINASE-CATALYZED REACTION IS IMPORTANT FOR MOLTING OF ONCHOCERA-VOLVULUS 3RD-STAGE LARVAE

Highly insoluble proteins, which are probably cross-linked, are common in the cuticle and epicuticle of filarial parasites and other nematod e species. We have investigated the possible involvement of transgluta minase (TGase)-catalyzed reactions in the development of Onchocerca vo lvulus fourth-stage larvae (L4) by testing the effects of TGase inhibi tors on the survival of third-stage larvae (L3) and the molting of L3 to L4 in vitro. The larvae were cultured in the presence of three spec ific TGase inhibitors: monodansylcadaverine, cystamine, and ,L-beta-(3 -bromo-4,5-dihydroisoxazol-5-yl)-alanine benzylamide. None of the inhi bitors reduced the viability of either L3 or L4, However, the inhibito rs reduced, in a time- and dose-dependent manner, the number of L3 tha t molted to L4 in vitro. Molting was completely inhibited in the prese nce of 100 to 200 mu M inhibitors. Ultrastructural examination of L3 t hat did not molt in the presence of monodansylcadaverine or cystamine indicated that the new L3 cuticle was synthesized, but there was an in complete separation between the L3 cuticle and the L4 epicuticle. The product of the TGase-catalyzed reaction was localized in molting L3 to cuticle regions where the separation between the old and new cuticles occurs and in the amphids of L3 by a monoclonal antibody that reacts specifically with the isopeptide epsilon-(gamma-glutamyl)lysine. These studies suggest that molting and successful development of L4 also de pends on TGase-catalyzed reactions.