Lipid metabolism in the hematophagous Panstrongylus megistus (Hemiptera: Reduviidae): interaction lipophorin-midgut membrane

FRUTTERO, LL; STARIOLO, R; RUBIOLO, ER; CANAVOSO, LE

Journal of Insect Science

University of Wisconsin

Lugar: Wisconsin, USA; Año: 2006 vol. 6 p. 21 - 22

1536-2442

Lipid metabolism in the hematophagous Panstrongylus megistus (Hemiptera:Reduviidae): interaction lipophorin-midgut membrane.   L.L. Fruttero1, R. Stariolo2, E.R. Rubiolo1 and L.E. Canavoso1. 1Departamento de Bioquímica Clínica, CIBICI-Conicet. Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Córdoba, Argentina. 2Coordinacion Nacional de Control de Vectores. Córdoba, Argentina, CP 5000.   In insects, the transfer of midgut lipids to the hemolymph is a remarkable event mediated by lipophorin (Lp), the main insect lipoprotein. In order to understand the regulation of this process in hematophagous insects, we have analyzed the transfer of diacylglycerol into circulation and the interaction Lp and the midgut membrane using a solid-phase binding assay. In addition, the sites of interaction of Lp with the midgut cells were localized by immunofluorescence assays. This study was performed employing Panstrongylus megistus, an important vector of Chagas’ disease. This insect takes large blood meals, containing a substantial amount of lipids. Lp was isolated from hemolymph of fifth instar nymphs by a KBr gradient and the membranes were obtained by ultracentrifugation of midgut homogenates. Thereafter, the membranes were suspended by mild sonification, adsorbed in plates, and the amount of bound Lp was quantified by ELISA. Among the factors analyzed included the effect of ionic strength on binding, the effect of pH, the requirement of divalent cations, and the effect of suramin. The saturation kinetics most likely fit a ligand-binding model for a single binding site. The interaction between Lp and the membrane showed a strong dependence with the pH and, in contrast with LDL receptor family, did not required Ca+2 or Mg+2. Like other lipoprotein receptors, suramin significantly inhibited the interaction between Lp and the membrane. The effect of ionic strength suggested that Lp binding is optimal at low NaCl concentration. In addition, the partial effect on binding after membranes were treated with proteases or changes in temperature strongly indicated that such interaction needs proteins in addition to other components of the membrane. Finally, the immunofluorescence assays showed that the interaction of Lp with midgut cells mainly occurred at the basolateral region of the membrane cells. Supported by Secyt-UNC (E.R.R) and CONICET-Argentina (L.E.C). L.L. Fruttero is a research fellow from CONICET-Argentina.