The hydrogenosome peripheral vesicle: similarities with the endoplasmic reticulum.

Abstract

Hydrogenosomes are anaerobic organelles that generate molecular hydrogen and ATP through pyruvate or malate oxidation, sharing several features with mitochondria. In the cattle parasite Tritrichomonas foetus, the hydrogenosome is a spherical structure bearing a peripheral vesicle whose origin and dynamics remain poorly characterized. This study applied energy-dispersive X-ray microanalysis, three-dimensional reconstruction, and cytochemical approaches to examine the peripheral vesicle and compare it with the endoplasmic reticulum (ER) and nuclear envelope of T. foetus. Multiple lines of evidence—including detection of ER-associated enzymes (glucose-6-phosphatase, IDPase, acid phosphatase, Ca2+-ATPase), elemental mapping of calcium, phosphorus, and oxygen, freeze-fracture analysis, high-pressure freezing and freeze-substitution transmission electron microscopy, monoclonal anti-ER antibody labeling, and ZIO/lectin cytochemistry—revealed compositional and structural parallels between the peripheral vesicle and the ER. The findings indicate that, analogous to mitochondria, hydrogenosomes maintain a functional relationship with the ER, particularly through this peripheral vesicle compartment.

Mechanism

The hydrogenosome peripheral vesicle shares ER-associated enzyme activities (glucose-6-phosphatase, Ca2+-ATPase, IDPase) and elemental composition (calcium, phosphorus) with the endoplasmic reticulum, suggesting a structural and functional relationship analogous to that observed between mitochondria and the ER.