Metabolic pathways of vitellogenin and lipophorin, and their putative receptors in the oocytes of Panstrongylus megistus (Hemiptera: Reduviidae)

FRUTTERO LEONARDO; LEYRIA JIMENA; RUBIOLO EDILBERTO; CANAVOSO LILIÁN

Amsterdam

Congreso; The Seventh International Symposium on Molecular Insect Science; 2014

Elsevier

In insects, vitellogenesis is a central event of reproduction that elicits a massive synthesis of yolk protein precursors in the fat body. Yolk is composed of proteins, lipids and other minor components packed inside the oocyte. The main yolk protein precursor synthesized by the fat body is vitellogenin (Vg), a phospholipoglycoprotein which is taken up by developing oocytes by receptor mediated endocytosis and stored as vitellin in the yolk bodies. Lipophorin (Lp), the main hemolymphatic lipoprotein, is also a yolk protein precursor that contributes to the buildup of lipid and protein stores in vitellogenic oocytes. Vg and Lp receptors (VgR and LpR) have been poorly characterized in Triatominae. The aim of this work was to study VgR and LpR in vitellogenic follicles of the triatomine Panstrongylus megistus, a vector of Chagas? disease. The metabolic pathways of Vg and Lp in vitellogenic oocytes were evaluated in vivo, by injecting the females with fluorescently labelled lipoproteins to follow the entire particles or their lipid cargo. The results indicated that Lp and Vg were endocytosed by vitellogenic oocytes, co-localizing in yolk bodies. The convergence of endocytic and non-endocytic pathways for Lp in the oocytes was also shown. On the other hand, lipids stored in the oocyte lipid droplets also originated from endocytosed Vg. A putative VgR in the ovarian tissue that is overexpressed during vitellogenesis was identified by RT-qPCR. The β chain of ATP synthase (β-ATPase), a Lp binding protein in the midgut of P. megistus, was detected in enriched ovarian membrane preparations by western blot. Moreover, immunofluorescence allowed the detection of β-ATPase in the plasma membrane of oocytes and follicular cells. In summary, this preliminary study indicates that the putative ovarian VgR and β-ATPase can function as lipoprotein receptors in the oocytes, thus participating in the storage of nutritional resources during vitellogenesis.