Functional Characterization of Contractile Vacuole Isolated from Amoeba proteus

Nishihara, Eri; Shimmen, Teruo; Sato, Seiji

doi:10.1247/csf.29.85

Cited by 9 publications

(11 citation statements)

References 19 publications

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“…Second, it suggests that aquaporins play an important role in contractile vacuole physiology. Aquaporin research in protozoa is underdeveloped, but one recent study in Paramecium supports our assertion that aquaporin involvement is not limited to the trypanosomatids, since isolated contractile vacuoles from this organism were found to have a very high water permeability coefficient suggestive of the presence of an aquaporin (Nishihara et al, 2004). Cell swelling causes activation of an adenylyl cyclase which results in a spike of intracellular cAMP, resulting in activation of protein kinase, amino acid release, and microtubule-dependent fusion of acidocalcisomes with the contractile vacuole with translocation of an aquaporin.…”

Section: Model For the Involvement Of The Contractile Vacuole And Acisupporting

confidence: 78%

supporting

confidence: 80%

“…cruzi ) Previously a water channel was postulated to be involved in contractile vacuole function (Allen and Naitoh, 2002), and calculations of water permeability in the contractile vacuole of Amoeba proteus suggested that their membrane was equipped with water channels (Nishihara et al, 2004). Interestingly, vacuoles besides the contractile vacuole have been observed to take up water when protozoa are placed in hyposmotic media (Cronkite et al, 1991;Temesvari et al, 1996), and they have been suggested to play a role in volume homeostasis (Van Rossum, 1987).…”

Section: Adaptation To Hyposmotic Stress In Protozoa: the Contractilementioning

confidence: 99%

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A contractile vacuole complex is involved in osmoregulation in Trypanosoma cruzi

Rohloff

Docampo

2008

Experimental Parasitology

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Acidocalcisomes are dense, acidic organelles with a high concentration of phosphorus present as pyrophosphate and polyphosphate complexed with calcium and other cations. Acidocalcisomes have been linked to the contractile vacuole complex in Chlamydomonas reinhardtii, Dictyostelium discoideum, and Trypanosoma cruzi. A microtubule-and cyclic AMP-mediated fusion of acidocalcisomes to the contractile vacuole complex in T. cruzi results in translocation of aquaporin and the resulting water movement which, in addition to swelling of acidocalcisomes, is responsible for the volume reversal not accounted for by efflux of osmolytes. Polyphosphate hydrolysis occurs during hyposmotic stress, probably increasing the osmotic pressure of the contractile vacuole and facilitating water movement. Index DescriptorsChlamydomonas reinhardtii; Dictyostelium discoideum; Trypanosoma cruzi; Kinetoplastida; acidocalcisomes; contractile vacuole Need for osmoregulation in Trypanosoma cruziTrypanosoma cruzi has a complex life cycle involving several morphological and functionally different stages. As T. cruzi progresses through its life cycle, it encounters diverse environmental stressors to which it must successfully adapt. Of particular interest is the parasite's ability to cope with extreme fluctuations in osmolarity that occur within the gut of the vector (Kollien et al., 2001;Kollien and Schaub, 2002) and also as the parasite moves from the insect gut through the acidic phagolysosome to the cytosol of the host cell. The infective form of the parasite passes out of the vector in the highly concentrated excreta (600-700 mOsm) (Kollien et al., 2001) and rapidly encounters the interstitial fluid of the mammalian host with a much lower osmolarity (300 mOsm). Clearly the parasite must have mechanisms that allow it to adapt both to hyperosmotic and hyposmotic stresses. In this review we limit our discussion to the response of T. cruzi to hyposmotic stress. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Adaptation to hyposmotic stress in vertebrate cellsPhysiological adaptations to hyposmotic stress have been studied extensively in a wide range of vertebrate cell types. Upon exposure to a reduction in external osmolarity, cells initially swell but soon regain nearly normal cell volume by a process that has been termed the Regulatory Volume Decrease (RVD; reviewed in (Lang et al., 1998a; Lang et al., 1998b), which is accomplished by the efflux of various inorganic ions (such as Na + and K + ) and organic osmolytes to the extracellular environment. Vertebrate cells maintain hig...

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Section: Model For the Involvement Of The Contractile Vacuole And Acisupporting

confidence: 78%

supporting

confidence: 80%

Section: Adaptation To Hyposmotic Stress In Protozoa: the Contractilementioning

confidence: 99%

See 1 more Smart Citation

A contractile vacuole complex is involved in osmoregulation in Trypanosoma cruzi

Rohloff

Docampo

2008

Experimental Parasitology

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“…A water channel had been previously postulated to be involved in the CVC function (Allen and Naitoh, 2002) and calculations of water permeability in the CVC of Amoeba proteus suggested that their membrane was equipped with water channels (Nishihara et al, 2004). Experiments in T. cruzi clearly established a role for the CVC-located aquaporin, TcAQP1, in the cellular response to both hyposmotic and hyperosmotic stresses (Li et al, 2011).…”

Section: The Contractile Vacuolementioning

confidence: 99%

New Insights into Roles of Acidocalcisomes and Contractile Vacuole Complex in Osmoregulation in Protists

Docampo

Jiménez

Lander

et al. 2013

International Review of Cell and Molecular Biology

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While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking.

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“…Recently Nishihara et al (2004) estimated the water permeability coefficient of the CV membrane in a freshwater amoeba Amoeba proteus, based on the rate of shrinkage of the isolated CV in a hyperosmotic solution of 3.8ϫ10 -7 ·m·s -1 ·Pa -1 . This value is strikingly similar to our value for the water permeability coefficient of the CVC of Paramecium.…”

Section: The Cvc Membrane Is Water Permeablementioning

confidence: 99%

Electrical properties and fusion dynamics ofin vitromembrane vesicles derived from separate parts of the contractile vacuole complex ofParamecium multimicronucleatum

Sugino

Tominaga

Allen

et al. 2005

Journal of Experimental Biology

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SUMMARY The contractile vacuole complex of Paramecium multimicronucleatumtransforms into membrane-bound vesicles on excision from the cell. The I–V relationship was linear in a voltage range of–80 to +80 mV in all vesicles, despite being derived from different parts of the contractile vacuole complex. No voltage-gated unit currents were observed in membrane patches from the vesicles. Vesicles derived from the radial arm showed a membrane potential of >10 mV, positive with reference to the cytosol, while those derived from the contractile vacuole showed a residual (<5 mV) membrane potential. The electrogenic V-ATPases in the decorated spongiome are responsible for the positive potential, and Cl– leakage channels are responsible for the residual potential. The specific resistance of the vesicle membrane (∼6 kΩcm2) increased, while the membrane potential shifted in a negative direction when the vesicle rounded. An increase in the membrane tension (to∼5×10–3 N m–1) is assumed to reduce the Cl– leakage conductance. It is concluded that neither voltage- nor mechano-sensitive ion channels are involved in the control of the fluid segregation and membrane dynamics that govern fluid discharge cycles in the contractile vacuole complex. The membrane vesicles shrank when the external osmolarity was increased,and swelled when the osmolarity was decreased, implying that the contractile vacuole complex membrane is water permeable. The water permeability of the membrane was 4–20×10–7 μm s–1Pa–1. The vesicles containing radial arm membrane swelled after initially shrinking when exposed to higher external osmolarity, implying that the V-ATPases energize osmolyte transport mechanisms that remain functional in the vesicle membrane. The vesicles showed an abrupt (<30 ms),slight, slackening after rounding to the maximum extent. Similar slackening was also observed in the contractile vacuoles in situ before the opening of the contractile vacuole pore. A slight membrane slackening seems to be an indispensable requirement for the contractile vacuole membrane to fuse with the plasma membrane at the pore. The contractile vacuole complex-derived membrane vesicle is a useful tool for understanding not only the biological significance of the contractile vacuole complex but also the molecular mechanisms of V-ATPase activity.

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Functional Characterization of Contractile Vacuole Isolated from Amoeba proteus

Cited by 9 publications

References 19 publications

A contractile vacuole complex is involved in osmoregulation in Trypanosoma cruzi

A contractile vacuole complex is involved in osmoregulation in Trypanosoma cruzi

New Insights into Roles of Acidocalcisomes and Contractile Vacuole Complex in Osmoregulation in Protists

Electrical properties and fusion dynamics ofin vitromembrane vesicles derived from separate parts of the contractile vacuole complex ofParamecium multimicronucleatum

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