Localization of the proteinase inhibitor activity in the fish cestode Eubothrium rugosum

Abstract

The mechanisms enabling fish tapeworms to avoid proteolytic attacks by digestive enzymes of their fish host have been studied in less detail compared with mammalian cestodes. This study aimed to assess the inhibitory ability towards trypsin and chymotrypsin in Eubothrium rugosum, an intestinal parasite of burbot Lota lota, and establish its localization in the tapeworm. To this end, the worms were treated with Triton X-100 followed by differential centrifugation to isolate the tegumental brush border membrane. The protease inhibitory abilities of the worms were mostly determined by their excretory/secretory products released into the incubation medium. These inhibitory abilities proved to be linked mainly with the brush border fractions. Notably, the per cent inhibition of both studied digestive enzymes (trypsin and chymotrypsin) hardly depended on the duration of the parasite exposure in the incubation medium, probably due to intermittent glycocalyx renewal. Improved knowledge on functions of the excretory/secretory proteins produced by fish tapeworms may contribute to a better understanding of host-parasite relations and development of new approaches to the treatment and prevention of diseases caused by pathogenic helminths.

The influence of parasite load on transcriptional activity and morphology of a cestode and its ant intermediate host

“…Ten highly expressed genes in this group are involved in the serine/glycine interconversion pathway. Serine proteinases are associated with multiple functions in cestodes, including defence against the host immune system (Izvekova et al, 2021; Patel, 2017) and lipid metabolism (Webb & Mettrick, 1975). In addition, we found overexpression of mitochondrial uncoupling protein 4, which is involved in the response to starvation in C. elegans (Figure 4a) and regulates the long-chain fatty acid metabolism, primarily in response to nutrient availability.…”

“…Ten serine proteases that are upregulated in cestodes living under crowded conditions provide more insights. Among other things, serine proteases are related to the ability of cestodes to evade the host immune system (Izvekova et al, 2021; Patel, 2017). Since infection with multiple parasites could trigger a stronger host immune response, this enhanced evasion of the host immune system might be necessary.…”

The influence of parasite load on transcriptional activity and morphology of a cestode and its ant intermediate host

“…Ten highly expressed genes in this group are involved in the serine/glycine interconversion pathway. Serine proteinases are associated with multiple functions in cestodes, including defence against the host immune system (Izvekova et al, 2021; Patel, 2017) and lipid metabolism (Webb & Mettrick, 1975). In addition, we found overexpression of mitochondrial uncoupling protein 4, which is involved in the response to starvation in Caenorhabditis elegans (Figure 4a) and regulates the long‐chain fatty acid metabolism, primarily in response to nutrient availability.…”

“…Ten serine proteases that are upregulated in cestodes living under crowded conditions provide more insights. Among other things, serine proteases are related to the ability of cestodes to evade the host immune system (Izvekova et al, 2021; Patel, 2017). Since infection with multiple parasites could trigger a stronger host immune response, this enhanced evasion of the host immune system might be necessary.…”

First insights into the activity of major digestive enzymes in the intestine of the European catfish Silurus glanis and protective anti‐enzymatic potential of its gut parasite Silurotaenia siluri

“…This can be explained by two factors: strictly local effect of the tapeworm's inhibitor and low parasitic load. The experiments with another cestode, Eubothrium rugosum (intestinal parasite of burbot Lota lota ), suggest that worm's antiproteases operate in close proximity to its surface, offering bioenergetically cost‐effective protection from the host enzymes (Izvekova et al, 2021). Otherwise, continuously releasing inhibitory substances and strongly suppressing the host proteases, the tapeworms would be left without a source of amino acids.…”