Perimicrovillar membrane assembly: the fate of phospholipids synthesised by the midgut of Rhodnius prolixus

Abstract

In this study, we describe the fate of fatty acids that are incorporated from the lumen by the posterior midgut epithelium of Rhodnius prolixus and the biosynthesis of lipids. We also demonstrate that neutral lipids (NL) are transferred to the haemolymphatic lipophorin (Lp) and that phospholipids remain in the tissue in which they are organised into perimicrovillar membranes (PMMs). 3H-palmitic acid added at the luminal side of isolated midguts of R. prolixus females was readily absorbed and was used to synthesise phospholipids (80%) and NL (20%). The highest incorporation of 3H-palmitic acid was on the first day after a blood meal. The amounts of diacylglycerol (DG) and triacylglycerol synthesised by the tissue decreased in the presence of Lp in the incubation medium. The metabolic fates of 3H-lipids synthesised by the posterior midgut were followed and it was observed that DG was the major lipid released to Lp particles. However, the majority of phospholipids were not transferred to Lp, but remained in the tissue. The phospholipids that were synthesised and accumulated in the posterior midgut were found to be associated with Rhodnius luminal contents as structural components of PMMs.

Ironing out the Details: Exploring the Role of Iron and Heme in Blood-Sucking Arthropods

“…This suggests that uPE and uPC (to lesser extent) play integral roles in the determination of crystal morphology for hemozoin in the midgut of R. prolixus . This is in agreement with previous findings, which reported 1,2-dilinoleoyl-sn-glycero-3-phosphoethanolamine as the major phospholipid synthesized by R. prolixus midgut epithelium (Bittencourt-Cunha et al, 2013 ). A similar involvement of lipids in hemozoin formation has been well documented in the parasites Plasmodium and Schistosoma mansoni (blood fluke) (Oliveira et al, 2004 ; Corrêa Soares et al, 2007 ; Stiebler et al, 2010 , 2014 ).…”

Unsaturated Glycerophospholipids Mediate Heme Crystallization: Biological Implications for Hemozoin Formation in the Kissing Bug Rhodnius prolixus

“…Another possibility to consider is that these two kinetically distinct components of uPC were related to the way by which heme interacts with the exposed CH 3 groups at the surface of uPC vesicles [46]. Interestingly, β-hematin formation induced by the phospholipid blend was revealed to be as fast as the uPE-mediated heme crystallization, suggesting that beyond representing the dominant phospholipid synthesized by R. prolixus midgut epithelia [52] uPE is able to produce crystals very similar in shape to those found biologically (Figure 2), mediating fast and efficient β-hematin formation (about 60% of heme conversion) (Figure 4). Regardless of the catalyst, we can observe that all reactions were essentially completed after 8 h (∼500 minutes) and all exhibited two kinetically distinct components: one very fast, making a major contribution to β-hematin conversion (54% to 100%), and the other a slow one.…”

“…In the midgut of the triatomine insect Rhodnius prolixus , Hz formation is mediated by perimicrovillar membranes (PMVM) [34] , phospholipid bilayers that cover the epithelial cells of the midgut [50] , [51] , with fewer integral proteins [15] , [16] and with phosphaditylethanolamine (PE) being the most abundant phospholipid synthesized by the midgut [52] . Hz crystals have also been observed in close association with PMVM [35] , [20] .…”

Long-chain acyl-CoA synthetase 2 knockdown leads to decreased fatty acid oxidation in fat body and reduced reproductive capacity in the insect Rhodnius prolixus

“…This structure also allows anchoring of digestive enzymes [65]. It is likely that RhoprACSL2 activates and channels dietary fatty acids into pathways of intracellular PL synthesis that constitute the perimicrovillar membranes [66], thereby directly affecting digestion rates.…”