Schistosoma mansoniglyceraldehyde-3-phosphate dehydrogenase enhances formation of the blood-clot lysis protein plasmin

Abstract

Schistosomes are intravascular blood flukes that cause the parasitic disease schistosomiasis. In agreement with Schistosoma mansoni (Sm) proteomic analysis, we show here that the normally intracellular glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is also found at the parasite surface; live worms from all intravascular life stages display GAPDH activity. Suppressing GAPDH gene expression using RNA interference significantly lowers this live worm surface activity. Medium in which the worms are cultured overnight displays essentially no activity, showing that the enzyme is not shed or excreted but remains associated with the worm surface. Immunolocalization experiments confirm that the enzyme is highly expressed in the parasite tegument (skin). Surface activity in schistosomula amounts to ∼8% of that displayed by equivalent parasite lysates. To address the functional role of SmGAPDH, we purified the protein following its expression in Escherichia coli strain DS113. The recombinant protein displays optimal enzymatic activity at pH 9.2, shows robust activity at the temperature of the parasite's hosts, and has a Michaelis-Menten constant for glyceraldehyde-3-phosphate (GAP) of 1.4 mM±0.24. We show that recombinant SmGAPDH binds plasminogen (PLMG) and promotes PLMG conversion to its active form (plasmin) in a dose response in the presence of tissue plasminogen activator. Since plasmin is a key mediator of thrombolysis, our results support the hypothesis that SmGAPDH, a host-interactive tegumental protein that can enhance PLMG activation, could help degrade blood clots around the worms in the vascular microenvironment and thus promote parasite survival in vivo. This article has an associated First Person interview with the first author of the paper.

Schistosome immunomodulators

“…While it is initially surprising to find these conserved, classically cytosolic enzymes in the extracellular environment, it is now clear that such proteins can have “moonlighting” functions that are unrelated to glycolysis [ 119 ]. For instance, extracellular forms of schistosome enolase and GAPDH can bind to mammalian plasminogen and promote its conversion to the active form—plasmin [ 122 , 123 ]. In other systems, several glycolytic enzymes have been shown capable of modulating immunity by, e.g., blocking complement action or impeding B cell function [ 119 , 123 ].…”

“…For instance, extracellular forms of schistosome enolase and GAPDH can bind to mammalian plasminogen and promote its conversion to the active form—plasmin [ 122 , 123 ]. In other systems, several glycolytic enzymes have been shown capable of modulating immunity by, e.g., blocking complement action or impeding B cell function [ 119 , 123 ].…”

Comparative Proteomic Analysis of Taenia solium Cysticercus and Adult Stages

“…Plasmodium glyceraldehyde-3-phosphate dehydrogenase acted as a glycolytic enzyme and also as a host plasminogen-binding protein, thereby interacting with the host's brinolytic system to establish an important mechanism for that parasite invasion, growth, and development. At the same time, it could be used as a potential diagnostic biomarker for a variety of parasites, such as Plasmodium, T. solium, E. granulosus, and those causing lariasis, as well as S. mansoni, and Babesia microti [47][48][49][50][51]. Proliferating cell nuclear antigen (PCNA)was a protein that acted as a processivity factor for DNA polymerase δ in eukaryotic cells.…”

Multifunctional Fructose 1,6-Bisphosphate Aldolase as a Therapeutic Target

“…Figure 2 lists the wide variety of organisms that have been demonstrated to possess an extracellular aldolase (left) and instances in which the enzyme has been shown to bind to plasminogen, promoting its activation (right). Pathogens have been reported to use a number of other glycolytic enzymes, including triosephosphate isomerase (TPI), GAPDH, phosphoglycerate mutase (PGM) and enolase, to bind and activate plasminogen ( Pirovich et al, 2019 ; Pirovich et al, 2020 ).…”