sample preparation for flow cytometry to measure phluorin2 fluorescence in living trypanosoma brucei

Développement d’une sonde à base de pHluorin2 pour le pH glycosomal chez Trypanosoma brucei

Parasitic kinetoplastids, like most living organisms, rely on glucose as a fundamental component of central carbon metabolism. This group includes medically important organisms, such as the African trypanosome, Trypanosoma brucei; the American trypanosome, T. cruzi; and parasites of the genus Leishmania. Glucose metabolism is critical to parasite growth in the pathogenic lifecycle stages. For example, when deprived of glucose, the bloodstream form (BSF) of the African trypanosome dies rapidly. Notably, glycolysis serves as the sole source of ATP during this stage of infection1. Leishmania&#160;parasites are likewise dependent on glucose in the human host, with the amastigote lifecycle stage that resides in host macrophages reliant on this carbon source for growth2.
While these parasites have distinct lifestyles involving different insect vectors, they share many commonalities in how they respond to and consume glucose. For example, these parasites localize most glycolytic enzymes into modified peroxisomes called glycosomes. This kinetoplastid-specific organelle is related to mammalian peroxisomes based on conserved biosynthetic mechanisms and morphology3,4,5,6.
The compartmentalization of most of the glycolytic pathway enzymes into the glycosome offers parasite-specific means of regulation of the pathway. Using a chemical pH probe, we established that nutrient deprivation triggers a rapid acidification of procyclic form (PF) parasite glycosomes that results in altered glycolytic enzyme activity through exposure of an allosteric regulator binding site on the key glycolytic enzyme hexokinase7,8. In our previous work, the chemical probe required constant delivery for use, limiting its utility in other applications. Additionally, challenges maintaining the probe distribution in the glycosome in the BSF limited the utility of the approach for investigating glycosomal pH in that life stage.
In this study, we have used the fluorescent protein biosensor pHluorin2 to monitor glycosomal pH change in BSF T. brucei in response to environmental cues including glucose starvation9 (Figure 1). Results from this work suggest that BSF T. brucei acidifies glycosomes rapidly in response to starvation in a reversible fashion, similar to responses we have observed in PF parasites. We expect this biosensor will improve our understanding of glycolytic regulation in T. brucei and related parasites.

Pleins feux sur l’auteur : Progrès dans la surveillance du pH glycosomal chez Trypanosoma brucei à l’aide du biocapteur pHluorin2

Mesure des changements dynamiques du pH glycosomal chez Trypanosoma brucei vivant

Préparation d’échantillons pour la cytométrie en flux afin de mesurer la fluorescence de la pHluorin2 chez Trypanosoma brucei vivant

Pour commencer, prenez des cellules de Trypanosoma brucei exprimant la pHluorine. Ajouter de la tétracycline ou de la doxycycline et incuber pendant la nuit pour induire l’expression de pHluorin. Transférez ensuite trois millilitres de chaque culture dans des tubes séparés de 15 millilitres.Ensuite, centrifugez les cellules à température ambiante pendant 10 minutes à 1000 xg. Retirez le surnageant et remettez les cellules en suspension dans un millilitre de PBS. Après avoir centrifugé les cellules pour la quatrième fois, retirez le surnageant et mettez à nouveau en suspension la pastille cellulaire dans du PBS avec des concentrations variables de glucose.Ajoutez de l’iodure de propidium ou du rouge de thiazole pour distinguer les cellules mortes des cellules vivantes. Transférez ensuite chaque échantillon dans des tubes de cinq millilitres compatibles avec le cytomètre en flux.

sample-preparation-for-flow-cytometry-to-measure-phluorin2

Research

JoVE Journal

Immunology and Infection

Sample Preparation for Flow Cytometry to Measure pHluorin2 Fluorescence in Living Trypanosoma brucei

47 vues. Pour commencer, prenez des cellules de Trypanosoma brucei exprimant la pHluorine. Ajouter de la tétracycline ou de la doxycycline et incuber pendant la nuit pour induire l’expression de pHluorin. Transférez ensuite trois millilitres de chaque culture dans des tubes séparés de 15 millilitres.Ensuite, centrifugez les cellules à température ambiante pendant 10 minutes à 1000 xg. Retirez le surnageant et remettez les cellules en suspension dans un millilitre de PBS. Après avoir c...

Vidéo: Préparation d’échantillons pour la cytométrie en flux afin de mesurer la fluorescence de la pHluorin2 chez Trypanosoma brucei vivant

Measuring Dynamic Glycosomal pH Changes in Living Trypanosoma brucei

Glucose metabolism is critical for the African trypanosome, Trypanosoma brucei, as an essential metabolic process and regulator of parasite development. Little is known about the cellular responses generated when environmental glucose levels change. In both bloodstream and procyclic form (insect stage) parasites, glycosomes house most of glycolysis. These organelles are rapidly acidified in response to glucose deprivation, which likely results in the allosteric regulation of glycolytic enzymes such as hexokinase. In previous work, localizing the chemical probe used to make pH measurements was challenging, limiting its utility in other applications.
This paper describes the development and use of parasites that express glycosomally localized pHluorin2, a heritable protein pH biosensor. pHluorin2 is a ratiometric pHluorin variant that displays a pH (acid)-dependent decrease in excitation at 395 nm while simultaneously yielding an increase in excitation at 475 nm. Transgenic parasites were generated by cloning the pHluorin2 open reading frame into the trypanosome expression vector pLEW100v5, enabling inducible protein expression in either lifecycle stage. Immunofluorescence was used to confirm the glycosomal localization of the pHluorin2 biosensor, comparing the localization of the biosensor to the glycosomal resident protein aldolase. The sensor responsiveness was calibrated at differing pH levels by incubating cells in a series of buffers that ranged in pH from 4 to 8, an approach we have previously used to calibrate a fluorescein-based pH sensor. We then measured pHluorin2 fluorescence at 405 nm and 488 nm using flow cytometry to determine glycosomal pH. We validated the performance of the live transgenic pHluorin2-expressing parasites, monitoring pH over time in response to glucose deprivation, a known trigger of glycosomal acidification in PF parasites. This tool has a range of potential applications, including potentially being used in high-throughput drug screening. Beyond glycosomal pH, the sensor could be adapted to other organelles or used in other trypanosomatids to understand pH dynamics&#160;in the live cell setting.

We describe a method to study how pH responds to environmental cues in the glycosomes of the bloodstream form of African trypanosomes. This approach involves a pH-sensitive heritable protein sensor in combination with flow cytometry to measure pH dynamics, both as a time-course assay and in a high-throughput screen format.

Glucose metabolism is critical for the African trypanosome, Trypanosoma brucei, as an essential metabolic process and regulator of parasite development. ...