title: Role of H(+)-pyrophosphatase activity in the regulation of intracellular pH in a scuticociliate parasite of turbot: Physiological effects.
abstract: The scuticociliatosis is a very serious disease that affects the cultured turbot, and whose causal agent is the anphizoic and marine euryhaline ciliate Philasterides dicentrarchi. Several protozoans possess acidic organelles that contain high concentrations of pyrophosphate (PPi), Ca(2+) and other elements with essential roles in vesicular trafficking, pH homeostasis and osmoregulation. P. dicentrarchi possesses a pyrophosphatase (H(+)-PPase) that pumps H(+) through the membranes of vacuolar and alveolar sacs. These compartments share common features with the acidocalcisomes described in other parasitic protozoa (e.g. acid content and Ca(2+) storage). We evaluated the effects of Ca(2+) and ATP on H (+)-PPase activity in this ciliate and analyzed their role in maintaining intracellular pH homeostasis and osmoregulation, by the addition of PPi and inorganic molecules that affect osmolarity. Addition of PPi led to acidification of the intracellular compartments, while the addition of ATP, CaCl2 and bisphosphonates analogous of PPi and Ca(2+) metabolism regulators led to alkalinization and a decrease in H(+)-PPase expression in trophozoites. Addition of NaCl led to proton release, intracellular Ca(2+) accumulation and downregulation of H(+)-PPase expression. We conclude that the regulation of the acidification of intracellular compartments may be essential for maintaining the intracellular pH homeostasis necessary for survival of ciliates and their adaptation to salt stress, which they will presumably face during the endoparasitic phase, in which the salinity levels are lower than in their natural environment.
authors.affiliation: Laboratorio de Parasitología, Instituto de Investigación y Análisis Alimentarios, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: Natalia
authors.initials: N
authors.lastname: Mallo
authors.affiliation: Departamento de Biología Celular y Ecología e Instituto de Acuicultura, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Lamas
authors.affiliation: Laboratorio de Parasitología, Instituto de Investigación y Análisis Alimentarios, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: Ana-Paula
authors.initials: AP
authors.lastname: de Felipe
authors.affiliation: Laboratorio de Parasitología, Instituto de Investigación y Análisis Alimentarios, Universidad de Santiago de Compostela, Santiago de Compostela, Spain; Departamento de Biología Celular y Ecología e Instituto de Acuicultura, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: Rosa-Ana
authors.initials: RA
authors.lastname: Sueiro
authors.affiliation: Departamento de Biología Celular y Ecología e Instituto de Acuicultura, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Fontenla
authors.affiliation: Laboratorio de Parasitología, Instituto de Investigación y Análisis Alimentarios, Universidad de Santiago de Compostela, Santiago de Compostela, Spain. Electronic address: josemanuel.leiro@usc.es.
authors.forename: José-Manuel
authors.initials: JM
authors.lastname: Leiro
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000502:physiology; D016770:Ciliophora Infections / Q000378:metabolism / Q000469:parasitology / Q000662:veterinary*; D005393:Fish Diseases / Q000201:enzymology / Q000378:metabolism / Q000469:parasitology*; D005412:Flatfishes / Q000469:parasitology*; D005455:Fluorescent Antibody Technique; D006863:Hydrogen-Ion Concentration; D043564:Inorganic Pyrophosphatase / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D046529:Microscopy, Electron, Transmission; D016802:Oligohymenophorea / Q000201:enzymology* / Q000502:physiology / Q000648:ultrastructure; D009994:Osmolar Concentration; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D054712:Salinity
chemical_list: D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D043564:Inorganic Pyrophosphatase; D002118:Calcium
keywords: ATP; Calcium; H(+)-PPase; Intracellular pH; Osmoregulation; Philasterides dicentrarchi