[No Title Available]

Abstract

In insects the importance of lipid metabolism has been widely recognized. Neutral lipids and fatty acids constitute the major lipids of insect hemolymph whereas phospholipids are the main lipid class found in the midgut. In insect hemolymph lipophorins are the molecules responsible for lipid transfer between the tissues involved in lipid absorption, storage and utilization. We have previously demonstrated that Rhodnius prolixus' midgut are able to take up 14 C-oleic acid from lipophorin preferentially at 10 th after a blood meal. The fatty acids are used to synthesizes neutral lipids (40%) and phospholipids (60%). The neutral lipids are released to hemolymph but phospholipids remained in the organ and are used to synthesizes midgut's membranes.When Rhodnius prolixus are infected with Trypanosoma cruzi these parasites multiplies and develops in intestine of insect attached to the membranes. Now we are studying the capacity of T. cruzi to incorporate phospholipids from R. prolixus' midguts membranes. The infection of Trypanosoma cruzi increases 2-fold the 3 H-palmitic acid incorporation by midgut from hemolymphatic lipophorin. The time course was linear up to 30 minutes. The 3 Hpalmitic acid was used to synthesizes mainly phospholipids membranes (70% from total lipids). In order to separate the parasites from membranes after 3 H-palmitic acid incorporation the luminal content was subject to a Percoll gradient. In the infected midguts the 3 H-phospholipids were found associated with T. cruzi. These data indicate that R. prolixus' midgut can provide essential lipids which will perhaps constitute parasite membranes. Advances in the biochemical and molecular biological knowledge of parasitic protozoa have shown that proteases play key roles in several aspects of their metabolism, differentiation, and infection of hosts. Taking advantage of a substrate containing the collagen motif "GPLGP" we have characterized a Trypanosoma cruzi-secreted 80 kDa prolyl-endopeptidase (Tc80) with specificity for native collagen. Its features suggest a role on T. cruzi-host cell infection. Supported by FAPERJ, PRONEX, PADCT and CNPq B-U-2 -SPECIFIC INHIBITORS OF THE TRYPANOSOMA CRUZI PROLYL-ENDOPEPTIDASE (TC 80) ARREST TRYPOMASTIGOTES ENTRY INTO HOST CELLSTo evaluate the possible role of the Tc80 activity on trypomastigotes entry into host cells we used available inhibitors of prolyl-endopeptidases, a specific Tc80 inhibitor that has been discovered by screening of a peptide combinatorial library, and others that have been synthesized based on the LGP sequence. Their specificity were assayed by comparing K i s for Tc80 and other T. cruzi proteases (oligopeptidase B or Tc120, cruzipain and cathepsin B-like) as well as for the human prolyl-endopeptidase, trypsin and chemotrypsin. The experiments consisted of the incubation of 5X10 5 trypomastigotes in DMEM containing 10% fetal calf serum with different concentrations of inhibitors during 1 h at 37 o C. The treated parasites were used to infect 5X10 4 rat myoblasts during 3 h at 37 o C. The...