Biochemical and biophysical characterization of Dr-DLP-1, the major pseudocoelomic lipid binding protein of the giant kidney worm Dioctophyme renale

Abstract

Adults of the parasitic nematode Dioctophyme renale locate in the renal pelvis of one (usually the right) kidney ofmammals, destroying its parenchyma and function. The unaffected kidney compensates and hypertrophies suchthat, in most cases, there are no clear clinical signs of infection. It has recently been shown that the pseudocelomicbody fluid of D. renale contains a highly abundant protein of 44 kDa in both males and females, heredubbed “dorylipophorin” (Dr-DLP-1), that binds lipids in highly apolar sites. Orthologues of this protein arespecific to Clade I (Dorylaimia) of the Phylum Nematoda, initially described as the poly-cysteine and histidinetailedproteins of unknown function of Trichinella spiralis, and one that is the immunomodulatory secreted p43protein from Trichuris muris. We here present a biochemical and biophysical characterization of Dr-DLP-1,demonstrating that it is N-glycosylated, is more stable when bound to a fatty acid, and can be detected in thefluid surrounding the parasite in parasitized kidneys. The analysis of Dr-DLP-1 lipid binding activity showed Kdvalues of 2.1 ± 0.2 μM and 2.2 ± 0.4 μM for the fluorescent probes 11-(dansylamino) undecanoic acid (DAUDA)and 8-anilinonaphthalene-1-sulfonic acid (ANS) respectively. Moreover, the apparent affinity constants for oleicacid (Kdapp 6.9 ± 0.5 μM) and cholesterol (Kdapp 27.6 ± 2 μM) were estimated by competition assays. As a whole,these results indicate that Dr-DLP-1 binds fatty acids with an affinity appropriate for a transporter. This novelnematode protein likely has a role in mass distribution of lipids within the parasites and could be functionallyreplacing the nematode polyprotein allergens (NPAs) found in other nematode clades.