Acidocalcisomes in Toxoplasma gondii tachyzoites

被引:133
作者
Moreno, SNJ
Zhong, L
机构
[1] Division of Parasitology, Department of Veterinary Pathobiology, University of Illinois at Urbana-Champaign, Urbana
关键词
D O I
10.1042/bj3130655
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Toxoplasma gondii tachyzoites were loaded with the fluorescent indicator fura 2 to investigate the transport mechanisms involved in maintaining their intracellular Ca2+ homoeostasis. The mitochondrial ATPase inhibitor oligomycin and the endoplasmic-reticulum Ca2+-ATPase inhibitor thapsigargin increased the intracellular Ca2+ concentration ([Ca2+](i)), thus indicating the requirement for ATP and the involvement of the endoplasmic reticulum in maintaining intracellular Ca2+ homoeostasis. The effect of thapsigargin was more accentuated in the presence of extracellular Ca2+, clearly showing that, as occurs with other eukaryotic cells, depletion of intracellular Ca2+ pools led to an increase in the uptake of Ca2+ from the extracellular medium. In addition to these results, we found evidence that, in contrast with what occurs in mammalian cells, T. gondii tachyzoites possess a significant amount of Ca2+ stored in an acidic compartment, termed the acidocalcisome, as indicated by: (1) the increase in [Ca2+](i) induced by bafilomycin A(1) (a specific inhibitor of H+-ATPases), nigericin (a K+/H+ exchanger) or the weak base NH4Cl, in the nominal absence of extracellular Ca2+ to preclude Ca2+ entry; and (2) the effect of ionomycin, a Ca2+-releasing ionophore that cannot take Ca2+ out of acidic organelles and that was more effective after alkalinization of these compartments by addition of bafilomycin A(1), nigericin or NH4Cl. Considering the relative importance of the ionomycin-releasable and the ionomycin + NH4Cl-releasable Ca2+ pools, it is apparent that T. gondii tachyzoites contain a significant amount of Ca2+ stored in acidocalcisomes.
引用
收藏
页码:655 / 659
页数:5
相关论文
共 35 条
[1]  
Araujo F G, 1992, Int J Antimicrob Agents, V1, P153, DOI 10.1016/0924-8579(92)90002-9
[2]   AN INVESTIGATION ON THE ROLE OF VACUOLAR-TYPE PROTON PUMPS AND LUMINAL ACIDITY IN CALCIUM SEQUESTRATION BY NONMITOCHONDRIAL AND INOSITOL-1,4,5-TRISPHOSPHATE-SENSITIVE INTRACELLULAR CALCIUM STORES IN CLONAL INSULIN-SECRETING CELLS [J].
BODE, HP ;
EDER, B ;
TRAUTMANN, M .
EUROPEAN JOURNAL OF BIOCHEMISTRY, 1994, 222 (03) :869-877
[3]   BAFILOMYCINS - A CLASS OF INHIBITORS OF MEMBRANE ATPASES FROM MICROORGANISMS, ANIMAL-CELLS, AND PLANT-CELLS [J].
BOWMAN, EJ ;
SIEBERS, A ;
ALTENDORF, K .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 1988, 85 (21) :7972-7976
[4]   METABOLIC-REGULATION VIA INTRACELLULAR PH [J].
BUSA, WB ;
NUCCITELLI, R .
AMERICAN JOURNAL OF PHYSIOLOGY, 1984, 246 (04) :R409-R438
[5]   INTRACELLULAR CALCIUM HOMEOSTASIS [J].
CARAFOLI, E .
ANNUAL REVIEW OF BIOCHEMISTRY, 1987, 56 :395-433
[6]   COMPARATIVE ACTIVITY OF MACROLIDES AGAINST TOXOPLASMA-GONDII DEMONSTRATING UTILITY OF AN INVITRO MICROASSAY [J].
CHAMBERLAND, S ;
KIRST, HA ;
CURRENT, WL .
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, 1991, 35 (05) :903-909
[7]   ROLE OF ACIDIC COMPARTMENTS IN TRYPANOSOMA-BRUCEI, WITH SPECIAL REFERENCE TO LOW-DENSITY-LIPOPROTEIN PROCESSING [J].
COPPENS, I ;
BAUDHUIN, P ;
OPPERDOES, FR ;
COURTOY, PJ .
MOLECULAR AND BIOCHEMICAL PARASITOLOGY, 1993, 58 (02) :223-232
[8]   CALCINEURIN-DEPENDENT GROWTH-CONTROL IN SACCHAROMYCES-CEREVISIAE MUTANTS LACKING PMC1, A HOMOLOG OF PLASMA-MEMBRANE CA2+ ATPASES [J].
CUNNINGHAM, KW ;
FINK, GR .
JOURNAL OF CELL BIOLOGY, 1994, 124 (03) :351-363
[9]   INTRACELLULAR CA2(+) STORAGE IN ACIDOCALCISOMES OF TRYPANOSOMA-CRUZI [J].
DOCAMPO, R ;
SCOTT, DA ;
VERCESI, AE ;
MORENO, SNJ .
BIOCHEMICAL JOURNAL, 1995, 310 :1005-1012
[10]  
Dubey J. P., 1988, TOXOPLASMOSIS ANIMAL