Peptidases compartmentalized to the Ascaris suum intestinal lumen and apical intestinal membrane.

John Pius Dalton,Douglas P Jasmer,Makedonka Mitreva,Bruce A Rosa

doi:10.1371/journal.pntd.0003375

John Pius Dalton, Douglas P Jasmer + Show 2 more

Open Access

https://doi.org/10.1371/journal.pntd.0003375

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Abstract

The nematode intestine is a tissue of interest for developing new methods of therapy and control of parasitic nematodes. However, biological details of intestinal cell functions remain obscure, as do the proteins and molecular functions located on the apical intestinal membrane (AIM), and within the intestinal lumen (IL) of nematodes. Accordingly, methods were developed to gain a comprehensive identification of peptidases that function in the intestinal tract of adult female Ascaris suum. Peptidase activity was detected in multiple fractions of the A. suum intestine under pH conditions ranging from 5.0 to 8.0. Peptidase class inhibitors were used to characterize these activities. The fractions included whole lysates, membrane enriched fractions, and physiological- and 4 molar urea-perfusates of the intestinal lumen. Concanavalin A (ConA) was confirmed to bind to the AIM, and intestinal proteins affinity isolated on ConA-beads were compared to proteins from membrane and perfusate fractions by mass spectrometry. Twenty-nine predicted peptidases were identified including aspartic, cysteine, and serine peptidases, and an unexpectedly high number (16) of metallopeptidases. Many of these proteins co-localized to multiple fractions, providing independent support for localization to specific intestinal compartments, including the IL and AIM. This unique perfusion model produced the most comprehensive view of likely digestive peptidases that function in these intestinal compartments of A. suum, or any nematode. This model offers a means to directly determine functions of these proteins in the A. suum intestine and, more generally, deduce the wide array functions that exist in these cellular compartments of the nematode intestine.

Highlights

Parasitic nematodes cause major diseases of humans, directly affecting more than two billion people on a global scale [1]
Past research has demonstrated that the nematode intestine has value for developing new methods of therapy and control of parasitic nematodes, as related to both vaccines and other anthelmintics
Research progress reported here moves towards the comprehensive identification of proteins, and functions, that are sited on the apical intestinal membrane and within the intestinal lumen of adult female Ascaris suum

Summary

Introduction

Parasitic nematodes cause major diseases of humans, directly affecting more than two billion people on a global scale [1]. Diseases they cause in food animal species pose significant constraints to agricultural production and indirectly impact human health in regions of the world where nutritional resources are limited. The apical intestinal membrane (AIM) forms an intestinal lumen (IL), and both the AIM and IL are accessible from the outside host environment In combination, these two intestinal cell compartments form a major parasite interface with the host that performs a wide range of biochemical and cellular functions essential for survival of these pathogens

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