MOLECULAR-CLONING AND CHARACTERIZATION OF THE 78-KILODALTON GLUCOSE-REGULATED PROTEIN OF TRYPANOSOMA-CRUZI

The protozoan Trypansoma cruzi is the etiologic agent of Chagas' disea se, an illness responsible for morbidity and death among millions of L atin Americans. Mice also develop this disease when infected with T. c ruzi and are a useful model organism for the study of parasite-specifi c immune responses. To identify immunogenic T. cruzi antigens, serum f rom an infected mouse was used to isolate clones from a T. cruzi epima stigote cDNA expression library. One of these clones was found to enco de the 78-kDa glucose-regulated protein (grp78), the endoplasmic retic ular member of the 70-kDa heat shock protein (bsp70) family. Like the mammalian and yeast grp78s, the T. cruzi protein contains an endoplasm ic reticular leader peptide and a carboxyl-terminal endoplasmic reticu lar retention sequence. T. cruzi grp78 is encoded by a tandemly arrang ed family of three genes located on a chromosome of 1.6 Mb. The effect s on grp78 expression of heat shock and tunicamycin treatment, the lat ter of which specifically stimulates mammalian grp78, were investigate d. While the level of the grp78 protein remained constant under all ci rcumstances, grp78 mRNA was unaffected by heat shock but induced fivef old by tunicamycin. Finally, we found that grp78 is the most immunogen ic of the T. cruzi heat shock proteins we have characterized, reacting strongly in immunoblots,vith sera from infected mice.