The Social Life of African Trypanosomes

The unicellular parasite Trypanosoma brucei shuttles between its definitive host, the tsetse fly, and various mammals including humans. In the fly digestive tract, T. brucei must first migrate to the ectoperitrophic space, establish a persistent infection of the midgut and then migrate to the salivary glands before being transmitted to a new mammalian host. In 2010, it was shown that insect stages of the parasite (procyclic forms) exhibit social motility (SoMo) when cultured on a semi-solid surface, and it was postulated that this behaviour might reflect a migration step in the tsetse fly. Now, almost 5 years after the initial report, several new publications shed some light on the biological function of SoMo and provide insights into the underlying signalling pathways.

The Psychological Outcome of Religious Coping with Stressful Life Events in a Swiss Sample of Church Attendees

Background: Recent research suggested thatreligious coping, based on dispositional religiousness and spirituality (R/S), is an important modulating factor in the process of dealing with adversity. In contrast to the United States, the effect of R/S on psychological adjustment to stress is a widely unexplored area in Europe. Methods: We examined a Swiss sample of 328 church attendees in the aftermath of stressful life events to explore associations of positive or negative religious coping with the psychological outcome. Applying a cross-sectional design, we used Huber’s Centrality Scale to specify religiousness and Pargament’s measure of religious coping (RCOPE) for the assessment of positive and negative religious coping. Depressive symptoms and anxiety as outcome variables were examined by the Brief Symptom Inventory. The Stress-Related Growth Scale and the Marburg questionnaire for the assessment of well-being were used to assess positive outcome aspects. We conducted Mann-Whitney tests for group comparisons and cumulative logit analysis for the assessmentof associations of religious coping with our outcome variables. Results: Both forms of religious coping were positively associated with stress-related growth (p < 0.01). However, negative religious coping additionally reduced well-being (p = 0.05, β = 0.52, 95% CI = 0.27–0.99) and increased anxiety (p = 0.02, β = 1.94, 95% CI = 1.10–3.39) and depressive symptoms (p = 0.01, β = 2.27, 95% CI = 1.27–4.06). Conclusions: The effects of religious coping on the psychological adjustment to stressful life events seem relevant. These findings should be confirmed in prospective studies.

Trypanosoma brucei Bloodstream Forms Depend upon Uptake of myo-Inositol for Golgi Complex Phosphatidylinositol Synthesis and Normal Cell Growth

myo-Inositol is a building block for all inositol-containing phospholipids in eukaryotes. It can be synthesized de novo from glucose-6-phosphate in the cytosol and endoplasmic reticulum. Alternatively, it can be taken up from the environment via Na(+)- or H(+)-linked myo-inositol transporters. While Na(+)-coupled myo-inositol transporters are found exclusively in the plasma membrane, H(+)-linked myo-inositol transporters are detected in intracellular organelles. In Trypanosoma brucei, the causative agent of human African sleeping sickness, myo-inositol metabolism is compartmentalized. De novo-synthesized myo-inositol is used for glycosylphosphatidylinositol production in the endoplasmic reticulum, whereas the myo-inositol taken up from the environment is used for bulk phosphatidylinositol synthesis in the Golgi complex. We now provide evidence that the Golgi complex-localized T. brucei H(+)-linked myo-inositol transporter (TbHMIT) is essential in bloodstream-form T. brucei. Downregulation of TbHMIT expression by RNA interference blocked phosphatidylinositol production and inhibited growth of parasites in culture. Characterization of the transporter in a heterologous expression system demonstrated a remarkable selectivity of TbHMIT for myo-inositol. It tolerates only a single modification on the inositol ring, such as the removal of a hydroxyl group or the inversion of stereochemistry at a single hydroxyl group relative to myo-inositol.