title: Calmidazolium evokes high calcium fluctuations in Plasmodium falciparum.
abstract: Calcium and calmodulin (CaM) are important players in eukaryote cell signaling. In the present study, by using a knockin approach, we demonstrated the expression and localization of CaM in all erythrocytic stages of Plasmodium falciparum. Under extracellular Ca(2+)-free conditions, calmidazolium (CZ), a potent CaM inhibitor, promoted a transient cytosolic calcium ([Ca(2+)]cyt) increase in isolated trophozoites, indicating that CZ mobilizes intracellular sources of calcium. In the same extracellular Ca(2+)-free conditions, the [Ca(2+)]cyt rise elicited by CZ treatment was ~3.5 fold higher when the endoplasmic reticulum (ER) calcium store was previously depleted ruling out the mobilization of calcium from the ER by CZ. The effects of the Ca(2+)/H(+) ionophore ionomycin (ION) and the Na(+)/H(+) ionophore monensin (MON) suggest that the [Ca(2+)]cyt-increasing effect of CZ is driven by the removal of Ca(2+) from at least one Ca(2+)-CaM-related (CaMR) protein as well as by the mobilization of Ca(2+) from intracellular acidic calcium stores. Moreover, we showed that the mitochondrion participates in the sequestration of the cytosolic Ca(2+) elicited by CZ. Finally, the modulation of membrane Ca(2+) channels by CZ and thapsigargin (THG) was demonstrated. The opened channels were blocked by the unspecific calcium channel blocker Co(2+) but not by 2-APB (capacitative calcium entry inhibitor) or nifedipine (L-type Ca(2+) channel inhibitor). Taken together, the results suggested that one CaMR protein is an important modulator of calcium signaling and homeostasis during the Plasmodium intraerythrocytic cell cycle, working as a relevant intracellular Ca(2+) reservoir in the parasite.
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Budu
authors.affiliation: Departamento de Biociências, Universidade Federal de São Paulo, Santos, SP, Brazil.
authors.forename: Mayrim M
authors.initials: MM
authors.lastname: Gomes
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Pollyana M
authors.initials: PM
authors.lastname: Melo
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Sarah
authors.initials: S
authors.lastname: El Chamy Maluf
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
authors.forename: Piero
authors.initials: P
authors.lastname: Bagnaresi
authors.affiliation: Instituto de Ciências Biomédicas, Universidade de São Paulo, SP, Brazil.
authors.forename: Mauro F
authors.initials: MF
authors.lastname: Azevedo
authors.affiliation: Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil. Electronic address: ak.carmona@unifesp.br.
authors.forename: Adriana K
authors.initials: AK
authors.lastname: Carmona
authors.affiliation: Departamento de Biociências, Universidade Federal de São Paulo, Santos, SP, Brazil. Electronic address: marcos.gazarini@unifesp.br.
authors.forename: Marcos L
authors.initials: ML
authors.lastname: Gazarini
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D055879:Gene Knock-In Techniques; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D018613:Microscopy, Confocal; D010963:Plasmodium falciparum / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D053058:Trophozoites / Q000187:drug effects / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002147:Calmodulin; D005456:Fluorescent Dyes; D007093:Imidazoles; C031938:calmidazolium; D019284:Thapsigargin; D002118:Calcium
keywords: Calcium channels; Calcium signaling; Calmidazolium; Calmodulin; Malaria; Plasmodium falciparum