Lipophorin, the main
lipoprotein in the circulation of the insects, cycles among peripheral tissues to exchange its
lipid cargo at the plasma membrane of target cells, without synthesis or degradation of its
apolipoprotein matrix. Currently, there are few characterized candidates supporting the functioning of the docking mechanism of
lipophorin-mediated
lipid transfer. In this work we combined
ligand blotting assays and tandem mass spectrometry to characterize
proteins with the property to bind
lipophorin at the midgut membrane of Panstrongylus megistus, a vector of
Chagas' disease. We further evaluated the role of
lipophorin binding proteins in the transfer of
lipids between the midgut and
lipophorin. The β subunit of the
ATP synthase complex (β-
ATPase) was identified as a
lipophorin binding protein. β-
ATPase was detected in enriched midgut membrane preparations free of mitochondria. It was shown that β-
ATPase partially co-localizes with
lipophorin at the plasma membrane of isolated enterocytes and in the sub-epithelial region of the midgut tissue. The interaction of endogenous
lipophorin and β-
ATPase was also demonstrated by co-immunoprecipitation assays. Blocking of β-
ATPase significantly diminished the binding of
lipophorin to the isolated enterocytes and to the midgut tissue. In vivo assays injecting the β-
ATPase antibody significantly reduced the transfer of [(3)H]-
diacylglycerol from the midgut to the hemolymph in insects fed with [9,10-(3)H]-
oleic acid, supporting the involvement of
lipophorin-β-
ATPase association in the transfer of
lipids. In addition, the β-
ATPase antibody partially impaired the transfer of
fatty acids from
lipophorin to the midgut, a less important route of
lipid delivery to this tissue. Taken together, the findings strongly suggest that β-
ATPase plays a role as a docking
lipophorin receptor at the midgut of P. megistus.