Ca2+, Mg2+ and pH integrate novel regulatory mechanisms of structure and function of mitochondrial peroxiredoxins from Leishmania contributing to parasite survival

Author(s)

Mariana Abrahão Bueno de Morais

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2016-11-24

Examining board members

Mário Tyago Murakami; Jörg Kobarg; Igor Polikarpov; Shaker Chuck Farah; Anete Pereira de Souza

• Advisor: Mário Tyago Murakami

Abstract

2-Cys peroxiredoxins (Prxs) from Prx1 subfamily are Cys-based peroxidases that control intracellular levels of H2O2 besides being involved in cell signaling pathways and assuming chaperone function under specific conditions. The regulation of their functions involves changes in their quaternary structure which are induced by multiple factors, such as redox state, posttranslational modifications and pH. However, there is still a lack of information about the molecular basis for these phenomena. The mitochondrial 2-Cys peroxiredoxin (Prx1m) from Leishmania, for example, exhibits dual peroxidase and chaperone functions, but only the latter is crucial for the parasite survival in the mammalian host. Recent in vitro studies indicated that reduced Leishmania infantum Prx1m forms chaperone-active decamers, whereas the oxidized protein dissociates into chaperone-inactive dimers. Herein, we solved the crystal structures of Leishmania braziliensis Prx1m (LbPrx1m) in both dimeric and decameric forms, showing that conformational changes of the region I from the catalytic loop are associated with the decamerization process. We provided, for the first time to our knowledge, structural data of a Prx1 member in two different oligomeric states induced by pH variations. Based on these data, we unveiled the molecular mechanism of pH modulation in dimers/decamers conversion. This mechanism might be extended to other peroxiredoxins and seems to be physiologically relevant. Moreover, we demonstrated that the divalent cations Ca2+ and Mg2+ - which play key roles in mitochondrial metabolism ¿ activate the chaperone function of oxidized Prx1m and stimulate the catalytic activity via a novel and exclusive mechanism of decamer stabilization of mitochondrial Prxs from Leshmania. Using a dimeric mutant of LbPrx1m unable to decamerize by pH, cation influence, or redox state, we also demonstrated that decamer formation is a pre-requisite not only for the peroxidase function of Prx1m but also for the chaperone activity, being essential to provide to Leishmania infantum resistance against heat stress during the transition from insect to the mammalian hosts. Together, our results showed that basal concentrations of Ca2+ and Mg2+, found in the mitochondrial matrix, support the dual function of Prx1m from Leishmania, whereas small decreases in pH or increased Ca2+ levels regulate the mitochondrial reservoir of chaperone-active Prx1m. Our findings imply that the search for compounds that prevent Leishmania Prx1m decamerization represents a promising strategy to inhibit the crucial chaperone function of this attractive therapeutic target (AU)

• FAPESP's process: 12/24134-3 - Functional and structural studies of peroxiredoxin I from Leishmania braziliensis and Homo sapiens aiming to understand the oligomerization and catalysis mechanisms
• Grantee: Mariana Abrahão Bueno de Morais
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)