Identification and Characterization of a Mitochondrial Carrier that Transports Glycolytic Intermediates in the Human Gut Parasite Blastocystis

Core Concepts

A mitochondrial carrier protein unique to stramenopiles transports glycolytic intermediates, providing a missing link between cytosolic and mitochondrial glycolysis in the human gut parasite Blastocystis.

Abstract

The content discusses the discovery and characterization of a mitochondrial carrier protein that is unique to stramenopiles, a diverse group of eukaryotic organisms including the human gut parasite Blastocystis. This carrier, named the glycolytic intermediate carrier (GIC), transports key glycolytic intermediates such as dihydroxyacetone phosphate, glyceraldehyde-3-phosphate, and phosphoenolpyruvate across the mitochondrial inner membrane, linking the cytosolic and mitochondrial branches of glycolysis in Blastocystis. The key highlights are: Phylogenetic analysis identified a new class of mitochondrial carboxylate carriers that is unique to stramenopiles and distinct from other eukaryotic carriers. Two Blastocystis GIC proteins, bGIC-1 and bGIC-2, were shown to localize to the mitochondria using immunofluorescence microscopy. Thermostability assays and transport experiments demonstrated that bGIC-2 can transport various glycolytic intermediates, but not the canonical substrates of other mitochondrial carriers. The presence of the glycolytic pay-off phase in the mitochondrial matrix of Blastocystis, along with the discovery of bGIC-2, provides a mechanism for linking cytosolic and mitochondrial glycolysis in this anaerobic parasite, which lacks key components of oxidative phosphorylation. The unique substrate specificity of the GIC carrier makes it a potential drug target against stramenopile pathogens, which are of great economic importance.

Stats

Blastocystis ST7-B has four copies of the putative glycolytic intermediate carrier (GIC) protein, but two of them are truncated and likely non-functional. The apparent melting temperatures (Tm) for the purified Blastocystis carriers are: bOGC (52.6 ± 0.5 °C), bGIC-1 (60.7 ± 0.4 °C) and bGIC-2 (59.8 ± 0.4 °C). The initial transport rates for bGIC-2 were 4.5 times above background for [33P]-phosphate/phosphate homo-exchange and 22 times above background for [35S]-sulphate/sulphate homo-exchange.

Quotes

"Blastocystis is an anaerobe (Zierdt, 1991) with highly divergent mitochondria (Stechmann et al., 2008). It has respiratory complexes I and II, but lacks the rest of the electron transport chain, as well as ATP synthase and mitochondrial ADP/ATP carriers (Gentekaki et al., 2017; Stechmann et al., 2008; Wawrzyniak et al., 2008)." "Understanding the unique aspects of parasite metabolism is crucial for the discovery of new drug targets."

Key Insights Distilled From

A mitochondrial carrier transports glycolytic intermediates to link cytosolic and mitochondrial glycolysis in the human gut parasite Blastocystis

by Pyrihova,E.,... at www.biorxiv.org 11-02-2023

https://www.biorxiv.org/content/10.1101/2023.11.02.565298v2

Deeper Inquiries

What other stramenopile pathogens could the glycolytic intermediate carrier be a potential drug target against?

The glycolytic intermediate carrier identified in Blastocystis could potentially be a drug target against other stramenopile pathogens that rely on mitochondrial glycolysis for their energy production. Some examples of stramenopile pathogens include Phytophthora infestans, which causes potato blight, and Saprolegnia parasitica, a pathogen of fish. These pathogens share similarities with Blastocystis in terms of their reliance on mitochondrial glycolysis, making them potential candidates for targeting the glycolytic intermediate carrier for therapeutic intervention.

How might the loss of certain mitochondrial carriers in Blastocystis, such as the ADP/ATP carrier, impact its overall metabolism and energy production?

The loss of key mitochondrial carriers in Blastocystis, such as the ADP/ATP carrier, can have significant implications for its metabolism and energy production. The ADP/ATP carrier is essential for the exchange of adenine nucleotides between the mitochondrial matrix and the cytosol, playing a crucial role in ATP synthesis and energy transfer within the cell. In the absence of the ADP/ATP carrier, Blastocystis may face challenges in maintaining adequate ATP levels, impacting various energy-dependent processes such as protein import, DNA replication, and mitochondrial protein synthesis. This loss may force Blastocystis to rely more heavily on alternative pathways for energy production, such as glycolysis and fermentation.

Could the unique substrate specificity of the glycolytic intermediate carrier be exploited to develop novel diagnostic or therapeutic approaches for Blastocystis infections?

The unique substrate specificity of the glycolytic intermediate carrier in Blastocystis opens up possibilities for developing novel diagnostic and therapeutic approaches for Blastocystis infections. By targeting this specific carrier, it may be possible to disrupt the transport of glycolytic intermediates essential for the parasite's energy production, leading to its inhibition or eradication. This targeted approach could potentially offer a more effective and specific treatment for Blastocystis infections, reducing the risk of resistance development and minimizing side effects associated with broad-spectrum treatments. Additionally, the identification of this carrier could also serve as a diagnostic marker for detecting Blastocystis infections, providing a more accurate and efficient means of diagnosis.