Tag: Roberto Docampo

The mitochondrial Ca²⁺ uptake, which is important to regulate bioenergetics, cell death and cytoplasmic Ca²⁺ signaling, is mediated via the calcium uniporter complex (MCUC). In animal cells the MCUC is regulated by the mitochondrial calcium uptake 1 and 2 dimer (MICU1/MICU2), which has been proposed to act as gatekeeper preventing mitochondrial Ca²⁺ overload at low cytosolic Ca²⁺ levels. In contrast to animal cells, knockout of either MICU1 or MICU2 in Trypanosoma cruzi, the etiologic agent of Chagas disease, did not allow Ca²⁺ uptake at low extramitochondrial Ca²⁺ concentrations ([Ca²⁺]_ext) and it was though that in the absence of one MICU the other would replace its role. However, previous attempts to knockout both genes were unsuccessful. Here, we designed a strategy to generate TcMICU1/TcMICU2 double knockout cell lines using CRISPR/Cas9 genome editing. Ablation of both genes was confirmed by PCR and Southern blot analyses. The absence of both proteins did not allow Ca²⁺ uptake at low [Ca²⁺]_ext, significantly decreased the mitochondrial Ca²⁺ uptake at different [Ca²⁺]_ext, without dissipation of the mitochondrial membrane potential, and increased the [Ca²⁺]_ext set point needed for Ca²⁺ uptake, as we have seen with TcMICU1-KO and TcMICU2-KO cells. Mg²⁺ was found to be a negative regulator of MCUC-mediated mitochondrial Ca²⁺ uptake at different [Ca²⁺]_ext. Occlusion of the MCUC pore by Mg²⁺ could partially explain the lack of mitochondrial Ca²⁺ uptake at low [Ca²⁺]_ext in TcMICU1/TcMICU2-KO cells. In addition, TcMICU1/TcMICU2-KO epimastigotes had a lower growth rate, while infective trypomastigotes have a reduced capacity to invade host cells and to replicate within them as amastigotes.

Mayara S Bertolini, Roberto Docampo. Cell Calcium. 2022 Sep 21;107:102654. doi: 10.1016/j.ceca.2022.102654.

Trypanosoma cruzi is a unicellular parasite that causes Chagas disease, which is endemic in the American continent but also worldwide, distributed by migratory movements. A striking feature of trypanosomatids is the polycistronic transcription associated with post-transcriptional mechanisms that regulate the levels of translatable mRNA. In this context, epigenetic regulatory mechanisms have been revealed to be of great importance, since they are the only ones that would control the access of RNA polymerases to chromatin. Bromodomains are epigenetic protein readers that recognize and specifically bind to acetylated lysine residues, mostly at histone proteins. There are seven coding sequences for BD-containing proteins in trypanosomatids, named TcBDF1 to TcBDF7, and a putative new protein containing a bromodomain was recently described. Using the Tet-regulated overexpression plasmid pTcINDEX-GW and CRISPR/Cas9 genome editing, we were able to demonstrate the essentiality of TcBDF2 in T. cruzi. This bromodomain is located in the nucleus, through a bipartite nuclear localization signal. TcBDF2 was shown to be important for host cell invasion, amastigote replication, and differentiation from amastigotes to trypomastigotes. Overexpression of TcBDF2 diminished epimastigote replication. Also, some processes involved in pathogenesis were altered in these parasites, such as infection of mammalian cells, replication of amastigotes, and the number of trypomastigotes released from host cells. In in vitro studies, TcBDF2 was also able to bind inhibitors showing a specificity profile different from that of the previously characterized TcBDF3. These results point to TcBDF2 as a druggable target against T. cruzi.

Alejandro Pezza, Luis E Tavernelli, Victoria L Alonso, Virginia Perdomo, Raquel Gabarro, Rab Prinjha, Elvio Rodríguez Araya, Inmaculada Rioja, Roberto Docampo, Felix Calderón, Julio Martin, Esteban Serra. ACS Infect Dis. 2022 Apr 28. doi: 10.1021/acsinfecdis.2c00057.

Trypanosoma cruzi, the agent of Chagas disease, accumulates polyphosphate (polyP) and Ca²⁺ inside acidocalcisomes. The alkalinization of this organelle stimulates polyP hydrolysis and Ca²⁺ release. Here, we report that histidine ammonia lyase (HAL), an enzyme that catalyzes histidine deamination with production of ammonia (NH₃) and urocanate, is responsible for acidocalcisome alkalinization. Histidine addition to live parasites expressing HAL fused to the pH-sensitive emission biosensor green fluorescent protein (GFP) variant pHluorin induced alkalinization of acidocalcisomes. PolyP decreased HAL activity of epimastigote lysates or the recombinant protein but did not cause its polyphosphorylation, as determined by the lack of HAL electrophoretic shift on NuPAGE gels using both in vitro and in vivo conditions. We demonstrate that HAL binds strongly to polyP and localizes to the acidocalcisomes and cytosol of the parasite. Four lysine residues localized in the HAL C-terminal region are instrumental for its polyP binding, its inhibition by polyP, its function inside acidocalcisomes, and parasite survival under starvation conditions. Expression of HAL in yeast deficient in polyP degradation decreased cell fitness. This effect was enhanced by histidine and decreased when the lysine-rich C-terminal region was deleted. In conclusion, this study highlights a mechanism for stimulation of acidocalcisome alkalinization linked to amino acid metabolism.

IMPORTANCE Trypanosoma cruzi is the etiologic agent of Chagas disease and is characterized by the presence of acidocalcisomes, organelles rich in phosphate and calcium. Release of these molecules, which are necessary for growth and cell signaling, is induced by alkalinization, but a physiological mechanism for acidocalcisome alkalinization was unknown. In this work, we demonstrate that a histidine ammonia lyase localizes to acidocalcisomes and is responsible for their alkalinization.

Brian S Mantilla, Cristina Azevedo, Paul W Denny, Adolfo Saiardi, Roberto Docampo. mBio. 2021 Nov 2;e0198121. doi: 10.1128/mBio.01981-21.