Iron-Induced Changes in the Proteome of Trichomonas vaginalis Hydrogenosomes

Abstract

Iron plays a crucial role in metabolism as a key component of catalytic and redox cofactors, such as heme or iron-sulfur clusters in enzymes and electron-transporting or regulatory proteins. Limitation of iron availability by the host is also one of the mechanisms involved in immunity. Pathogens must regulate their protein expression according to the iron concentration in their environment and optimize their metabolic pathways in cases of limitation through the availability of respective cofactors. Trichomonas vaginalis, a sexually transmitted pathogen of humans, requires high iron levels for optimal growth. It is an anaerobe that possesses hydrogenosomes, mitochondrion-related organelles that harbor pathways of energy metabolism and iron-sulfur cluster assembly. We analyzed the proteomes of hydrogenosomes obtained from cells cultivated under iron-rich and iron-deficient conditions employing two-dimensional peptide separation combining IEF and nano-HPLC with quantitative MALDI-MS/MS. We identified 179 proteins, of which 58 were differentially expressed. Iron deficiency led to the upregulation of proteins involved in iron-sulfur cluster assembly and the downregulation of enzymes involved in carbohydrate metabolism. Interestingly, iron affected the expression of only some of multiple protein paralogues, whereas the expression of others was iron independent. This finding indicates a stringent regulation of differentially expressed multiple gene copies in response to changes in the availability of exogenous iron.

Novel Functions of an Iron-Sulfur Flavoprotein from Trichomonas vaginalis Hydrogenosomes

“…The TvIsf paralog herein named TvIsf3 was selected for our study because its presence in hydrogenosomes was confirmed by two independent proteomic studies (19,20) and because our previous analysis revealed that the mRNA of this gene was produced at the highest level of all seven TvIsf paralogs (unpublished data).…”

“…On the other hand, ferredoxin and not the pyridine nucleotide coenzyme was identified as an electron donor to Isf from Methanosarcina for the reduction of oxygen and hydrogen peroxide (6). T. vaginalis encodes seven paralogs of ferredoxin (18), and most of them, if not all, are expressed in the hydrogenosomes (19,20), where they serve as one-electron carriers that link the crucial reactions of hydrogenosomal metabolism (10). Ferredoxin is an electron donor to the oxygen-reducing and water-forming flavodiiron protein (17); in this work, we show that upon in vitro reduction by hydrogenosomal PFO, ferredoxin can also transfer electrons to TvIsf3.…”

“…Other proteins thus should be present that afford the protection against nitrosative stress. In addition to TvIsf3 and two other Isf paralogs present in the hydrogenosomes (19,20), among those to be considered are three other putative flavodiiron protein homologs, all lacking hydrogenosomal targeting signals (18). However, no experimental data on these proteins are currently available.…”

“…Among these were seven distinct paralogs of Isf; thus, T. vaginalis is the second eukaryote (in addition to Entamoeba histolytica) identified to possess otherwise strictly prokaryotic Isf proteins. The results of subsequent proteomic studies showed that three Isf paralogs are expressed in T. vaginalis hydrogenosomes under standard in vitro cultivation conditions (19,20).…”

Trichomonas vaginalis: Clinical relevance, pathogenicity and diagnosis

“…This is indicative of the self clearing nature of the infection in males, with the majority of persistent infections occurring in females (Van Der Pol, 2007). The higher likelihood of persistence in the female genital tract has been linked to the availability of iron, which increases during the menstrual cycle, providing the parasite with increased exposure to a major growth requirement (Beltrán et al, 2013). The expression of various adhesion proteins promoting cytoadherance is enhanced in response to increased iron concentration (Sehgal et al, 2012), and this is associated with increased virulence (Ryu et al, 2001).…”