Interaction of lipophorin with Rhodnius prolixus oocytes: biochemical properties and the importance of blood feeding

Abstract

Lipophorin (Lp) is the main haemolymphatic lipoprotein in insects and transports lipids between different organs. In adult females, lipophorin delivers lipids to growing oocytes. In this study, the interaction of this lipoprotein with the ovaries of Rhodnius prolixus was characterised using an oocyte membrane preparation and purified radiolabelled Lp (125I-Lp). Lp-specific binding to the oocyte membrane reached equilibrium after 40-60 min and when 125I-Lp was incubated with increasing amounts of membrane protein, corresponding increases in Lp binding were observed. The specific binding of Lp to the membrane preparation was a saturable process, with a Kdof 7.1 ± 0.9 x 10-8M and a maximal binding capacity of 430 ± 40 ng 125I-Lp/µg of membrane protein. The binding was calcium independent and pH sensitive, reaching its maximum at pH 5.2-5.7. Suramin inhibited the binding interaction between Lp and the oocyte membranes, which was completely abolished at 0.5 mM suramin. The oocyte membrane preparation from R. prolixus also showed binding to Lp from Manduca sexta. When Lp was fluorescently labelled and injected into vitellogenic females, the level of Lp-oocyte binding was much higher in females that were fed whole blood than in those fed blood plasma.

OVARIAN NUTRITIONAL RESOURCES DURING THE REPRODUCTIVE CYCLE OF THE HEMATOPHAGOUSDIPETALOGASTER MAXIMA(HEMIPTERA: REDUVIIDAE): FOCUS ON LIPID METABOLISM

“…In Triatominae, studies about Lp‐mediated lipid delivery to developing oocytes were undertaken only in R. prolixus and Panstrongylus megistus . In R. prolixus , Lp proved to be an important source of phospholipids and fatty acids for developing oocytes, although in vitro and immunohistochemistry studies indicated that endocytosis of Lp was not operative in this species (Gondim et al., ; Machado et al., ; Santos et al., , Entringer et al., ). On the other hand, in vivo assays using fluorescently labeled Lp and Vg probes demonstrated that vitellogenic oocytes of P. megistus were able to take up lipids by both a major, nonendocytic pathway, and by an endocytic pathway (Fruttero et al., ).…”

The Fate of Dietary Cholesterol in the Kissing Bug Rhodnius prolixus

“…Lp also transferred cholesterol to the ovaries, which reached maximal accumulation of radioactivity at 4 h 30 min after injection ( Figure 7C ). In both organs, radioactivity association was very fast and detected at the first time point (10 min), probably due to the binding of labeled Lp to cell surface, which is a very fast event ( Gondim et al, 1989 ; Pontes et al, 2002 ; Entringer et al, 2013 ). As previously observed for diacylglycerol, phospholipids, and fatty acids ( Gondim et al, 1989 ; Pontes et al, 2008 ; Santos et al, 2011 ), keeping the insects at 4°C inhibited cholesterol transfer from Lp to the tissues.…”

“…Rhodnius prolixus is an important vector of Chagas disease in South and Central Americas ( de Fuentes-Vicente et al, 2018 ), and it is a model for insect physiology and biochemistry studies ( Nunes-da-Fonseca et al, 2017 ), including lipid metabolism ( Gondim et al, 2018 ). Our group has already characterized various aspects of R. prolixus lipid metabolism, including TAG digestion, absorption, and distribution ( Grillo et al, 2007 ); the interaction of Lp with different organs ( Pontes et al, 2002 ; Grillo et al, 2003 ; Entringer et al, 2013 ); and the synthesis and dynamics of TAG in the fat body ( Pontes et al, 2008 ; Alves-Bezerra and Gondim, 2012 ; Alves-Bezerra et al, 2017 ) and ovaries ( Santos et al, 2011 ). However, cholesterol metabolism remains a gap in the knowledge of this insect physiology.…”