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He L, Lee GT, Zhou H, Buhimschi IA, Buhimschi CS, Weiner CP, Mason CW. Expression, Regulation, and Function of the Calmodulin Accessory Protein PCP4/PEP-19 in Myometrium. Reprod Sci 2019; 26:1650-1660. [PMID: 30744532 DOI: 10.1177/1933719119828072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Calmodulin (CaM) plays a key role in the orchestration of Ca2+ signaling events, and its regulation is considered an important component of cellular homeostasis. The control of uterine smooth muscle function is largely dependent on the regulation of Ca2+ and CaM signaling. The objective of this study was to investigate the expression, function, and regulation of CaM regulatory proteins in myometrium during pregnancy. STUDY DESIGN Myometrium was obtained from nonpregnant women and 4 groups of pregnant women at the time their primary cesarean delivery: (i) preterm not in labor, (ii) preterm in labor with clinical and/or histological diagnosis of chorioamnionitis, (3) term not in labor; and (4) term in labor. The effect of perinatal inflammation on pcp4/pep-19 expression was evaluated in a mouse model of Ureaplasma parvum-induced chorioamnionitis. Human myometrial cells stably expressing wild-type and mutant forms of PCP4/PEP-19 were used in the evaluation of agonist-induced intracellular Ca2+ mobilization. RESULTS Compared to other CaM regulatory proteins, PCP4/PEP-19 transcripts were more abundant in human myometrium. The expression of PCP4/PEP-19 was lowest in myometrium of women with preterm pregnancy and chorioamnionitis. In the mouse uterus, pcp4/pep-19 expression was lower in late compared to mid-gestation and decreased in mice injected intra-amniotic with Ureaplasma parvum. In myometrial smooth muscle cells, tumor necrosis factor alpha and progesterone decreased and PCP4/PEP-19 promoter activity increased. Finally, the overexpression of PCP4/PEP-19 reduced agonist-induced intracellular Ca2+ levels in myometrial cells. CONCLUSION The decreased expression of PCP4/PEP-19 in myometrium contributes to a loss of quiescence in response to infection-induced inflammation at preterm pregnancy.
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Affiliation(s)
- Lily He
- Department of Obstetrics and Gynecology, Division of Research, University of Kansas School of Medicine, Kansas City, KS, USA
| | - Gene T Lee
- Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of Kansas School of Medicine, Kansas City, KS, USA.,The Center for Perinatal Research, University of Kansas School of Medicine, Kansas City, KS, USA
| | - Helen Zhou
- Department of Obstetrics and Gynecology, Division of Research, University of Kansas School of Medicine, Kansas City, KS, USA
| | - Irina A Buhimschi
- Department of Obstetrics and Gynecology, The Ohio State University, Columbus, OH, USA.,Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital and Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Catalin S Buhimschi
- Department of Obstetrics and Gynecology, The Ohio State University, Columbus, OH, USA.,Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital and Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Carl P Weiner
- Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of Kansas School of Medicine, Kansas City, KS, USA
| | - Clifford W Mason
- Department of Obstetrics and Gynecology, Division of Research, University of Kansas School of Medicine, Kansas City, KS, USA.,The Center for Perinatal Research, University of Kansas School of Medicine, Kansas City, KS, USA
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Xu W, Vebrosky EN, Richards ML, Armbrust KL. Evaluation of dicloran phototoxicity using primary cardiomyocyte culture from Crassostrea virginica. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 628-629:1-10. [PMID: 29432924 DOI: 10.1016/j.scitotenv.2018.02.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 01/30/2018] [Accepted: 02/02/2018] [Indexed: 06/08/2023]
Abstract
Dicloran is a commonly used fungicide throughout the Southern and Western United States. Runoff of dicloran from agriculture systems to nearby waterbodies can accumulate in the organisms that inhabit those areas. Although severe damage of dicloran to ecological systems has not been reported, its toxicity has been modified by photodegradation. The objective of this study is to assess the changes of dicloran toxicities during photo exposure using a reliable in vitro biological model. In the present investigation, the photodegradation of dicloran in vitro showed over 90% of dicloran was degraded within 24h of UV exposure in water. Two major intermediate degradation products, 2-chloro-1,4-benzoquinone (CBQ) and 1,4-benzoquinone (BQ), were detected upon UV exposure of dicloran; however, they were rapidly degraded via photolysis. To estimate the impact of the phototoxicity of dicloran to aquatic organisms, we developed an in vitro cell culture system using the C. virginica cardiomyoctes (CvCMs) which were isolated from heart tissues and formed beating cell clusters. The CvCM clusters were treated with irradiated dicloran or the two intermediate standards, CBQ and BQ, and they showed up to 41% decrease in beating rates compared to control cell clusters. Expression levels of selected genes: def, hsp70, and cam, were upregulated in response to stimulations of UV irradiated dicloran and the two standard intermediates. The four-hour irradiated dicloran also resulted in more significant inhibition in the proliferation and small cardioactive peptide β production of CvCMs than other treatment. Tested solutions of photolyzed dicloran showed elevated toxicities opposed to the standard intermediates, CBQ and BQ, suggesting additive toxicity of these dicloran products or toxicity due to other unidentified degradation products. Results of this study supported our hypothesis that the degradation of dicloran caused by photo irradiation results in an elevated toxicity which can be evaluated by the in vitro CvCM model.
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Affiliation(s)
- Wei Xu
- School of Renewable Natural Resources, Louisiana State University, Baton Rouge, LA 70803, United States; Agricultural Center, Louisiana State University, Baton Rouge, LA 70803, United States.
| | - Emily N Vebrosky
- Department of Environmental Sciences, College of the Coast & Environment, Louisiana State University, Baton Rouge, LA 70803, United States
| | - Mackenzie L Richards
- School of Renewable Natural Resources, Louisiana State University, Baton Rouge, LA 70803, United States; Agricultural Center, Louisiana State University, Baton Rouge, LA 70803, United States
| | - Kevin L Armbrust
- Department of Environmental Sciences, College of the Coast & Environment, Louisiana State University, Baton Rouge, LA 70803, United States
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Sherwin JC, Kokavec J, Thornton SN. Hydration, fluid regulation and the eye: in health and disease. Clin Exp Ophthalmol 2015; 43:749-64. [DOI: 10.1111/ceo.12546] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 04/30/2015] [Indexed: 12/01/2022]
Affiliation(s)
- Justin C Sherwin
- Royal Victorian Eye and Ear Hospital; Melbourne Victoria Australia
- Lions Eye Institute; University of Western Australia; Centre for Ophthalmology and Visual Science; Perth Western Australia Australia
| | - Jan Kokavec
- South Australian Institute of Ophthalmology; Royal Adelaide Hospital; Adelaide South Australia Australia
| | - Simon N Thornton
- Université de Lorraine; Nancy France
- INSERM U1116; Vandoeuvre les Nancy France
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Navarro A, Campos B, Barata C, Piña B. Transcriptomic seasonal variations in a natural population of zebra mussel (Dreissena polymorpha). THE SCIENCE OF THE TOTAL ENVIRONMENT 2013; 454-455:482-489. [PMID: 23567168 DOI: 10.1016/j.scitotenv.2013.03.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 03/01/2013] [Accepted: 03/13/2013] [Indexed: 06/02/2023]
Abstract
The zebra mussel Dreissena polymorpha is a Caspian Sea bivalve that colonized freshwater bodies worldwide during the XX century. To analyze the impact of seasonal and environmental variations on the physiology and metabolism of this invasive species, we developed a custom microarray using 4057 publicly available DNA sequences from Dreissena and other related genera. Transcriptome profiles were analyzed using half-body samples from a relatively clean site (Riba-Roja, low Ebro River, N.E. Spain), at three different stages of the annual cycle: Pre-spawning (February), spawning (June), and gonad resorption (September). Transcripts from a total of 745 unique sequences showed significant changes among these three groups of samples. Functional characterization of these transcripts based on their closest known homologues showed that genes involved in stress defense (oxidative and infection) were overrepresented in September, whereas genes related to reproductive functions were overrepresented in the spawning and pre-spawning periods. This transcriptomic information can help to identify developmental stages at which the organism is more vulnerable for future control strategies. These data will also contribute to the implementation of gene expression-based assays for pollution monitoring in water bodies harboring stable zebra mussel populations.
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Affiliation(s)
- Anna Navarro
- Department of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18, 08034 Barcelona, Spain
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Gossypol affects ion transport in the isolated intestine of the seawater adapted eel, Anguilla anguilla. Comp Biochem Physiol A Mol Integr Physiol 2008; 151:139-43. [PMID: 18606239 DOI: 10.1016/j.cbpa.2008.06.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Revised: 06/12/2008] [Accepted: 06/12/2008] [Indexed: 11/23/2022]
Abstract
Cottonseed (Gossypium sp.) meals are protein rich and inexpensive, but the presence of the polyphenolic dialdehyde, gossypol, is responsible of many toxic effects in animals including fishes. Recently an effect on the transepithelial ion transport in rat colon has been demonstrated. In this study we investigated the effect of gossypol on the transepithelial electrical parameters of the isolated intestine of seawater adapted eel, Anguilla anguilla, by employing a Ussing chamber technique. We showed that the addition of gossypol to the perfusion media reduced short circuit current (I(sc)), a measure of Cl- active absorption in this tissue, and increased tissue conductance (g(t)). The observation that the effect of gossypol on both I(sc) and g(t) was modified by the pretreatment with TFP, a calmodulin inhibitor, suggests that the substance acts via a Ca2+ calmodulin pathway and excludes the possibility that the observed effects were due to a cytotoxic action. In addition, experiments performed in the presence of verapamil suggest that the polyphenolic pigment increases Ca2+ influx. It is likely that gossypol stimulates a basolateral quinine sensitive K+ conductance producing a K+ flux in absorptive direction that explains the reduction of I(sc). In addition dilution potential experiments showed that the polyphenolic aldehyde increases the anion conductance of the paracellular pathway. In conclusion our study suggests that gossypol alters ion transport in eel intestine by acting on both transcellular and paracellular pathways. Since the intestine is an important organ for maintaining the water and ion balance in seawater adapted fish, it is conceivable that gossypol could impair the ability of the animals to adapt to the environment.
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Li G, Liu Y, Olson JE. Calcium/calmodulin-modulated chloride and taurine conductances in cultured rat astrocytes. Brain Res 2002; 925:1-8. [PMID: 11755895 DOI: 10.1016/s0006-8993(01)03235-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Osmotically swollen rat cerebral astrocytes develop an increased anion conductance which can mediate chloride and taurine release. We used whole cell patch clamp to study mechanisms that modulate this conductance. Astrocyte chloride conductance increased within 4 min of exposure to 200 mOsm medium and was 670+/-123% of its initial value after 15 min (mean+/-S.E.M.). This conductance was substantially reduced in 0.1 mM extracellular calcium with 20 mM BAPTA added to the electrode solution and was completely inhibited with calcium-free perfusion solution containing 1 mM EDTA (n=4). The conductance increase in 200 mOsm medium also was inhibited in a dose-dependent manner by nimodipine with a calculated K(i) of 0.31+/-0.4 microM and mean+/-S.E.M. inhibition of 84.4+/-4% at 100 microM nimodipine. In the presence of 100 microM W-7, a calmodulin antagonist, the mean+/-S.E.M. conductance increase after 15 min was 223+/-40% of the initial value while 300 microM W-7 or 100 microM trifluoperazine inhibited the conductance increase completely (n=6). With taurine as the major anion in electrode and perfusion solutions, a significant conductance increase was observed in 200 mOsm medium. This conductance increase was inhibited by 300 microM W-7 or 100 microM nimodipine. We conclude extracellular calcium influx via L-type calcium channels leads to increased astrocyte anion conductance in 200 mOsm conditions via calmodulin-dependent activation of anion channels. Efflux of anionic taurine from swollen astrocytes also may be affected by calcium influx through a similar calcium/calmodulin-dependent process.
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Affiliation(s)
- Guangze Li
- Department of Emergency Medicine, Wright State University School of Medicine, Dayton, OH, USA.
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Pierce SK, Warren JW. The Taurine Efflux Portal Used to Regulate Cell Volume in Response to Hypoosmotic Stress Seems to Be Similar in Many Cell Types: Lessons to Be Learned from Molluscan Red Blood Cells1. ACTA ACUST UNITED AC 2001. [DOI: 10.1668/0003-1569(2001)041[0710:tteput]2.0.co;2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
The use of a method to follow changes in endogenous peptide production, as they occur in biological studies, is an excellent complement to other molecular techniques. It has the unique ability to characterize peptides that have been produced from protein precursors, and instrumentation is available that provides high resolution peptide separations that are quantitative, sensitive, and amenable to automation. All tissues express a large number of peptide species that can be visualized, or profiled, on chromatographic separations using reverse-phase high-performance liquid chromatography. This large number of peptides offers many potential molecules that can be used to identify biological mechanisms associated with experimental paradigms. Peptide analysis has been used successfully in many types of studies. In this review, we outline our experience in using peptides as biological markers and provide a description of the evolution of peptide profiling in our laboratories. Peptide expression has been used in studies ranging from how brain regions develop to identifying changes in disease processes including Alzheimer's disease and models of stroke. Some of the findings provided by these studies have been new pathways of peptide processing and the identification of accelerated proteolysis on proteins such as hemoglobin as a function of Alzheimer's disease and brain insult. Peptide profiling has also proven to be an excellent technique for studying many well-known nervous system proteins including calmodulin, PEP-19, myelin basic protein, cytoskeletal proteins, and others. It is the purpose of this review to describe our experience using the technique and to highlight improvements that have added to the power of the approach. Peptide analysis and the expansion in the instrumentation that can detect peptides will no doubt make these types of studies a powerful addition to our molecular armamentarium for conducting biological studies.
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Affiliation(s)
- J R Slemmon
- Department of Biochemistry, University of Rochester Medical Center, NY 14642, USA
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9
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Abstract
PEP-19 is a 6 kDa polypeptide that is highly expressed in select populations of neurons that sometimes demonstrate resistance to degeneration. These include the granule cells of the hippocampus and the Purkinje cells of the cerebellum. Its only identified activity to date is that of binding apo-calmodulin. As a consequence, it has been demonstrated to act as an inhibitor of calmodulin-dependent neuronal nitric oxide synthase in vitro, although PEP-19 regulation of calmodulin-dependent enzymes has never been characterized in intact cells. The activation of the calmodulin-dependent enzyme calmodulin kinase II (CaM kinase II) was studied in PC12 cells that had been transfected so as to express physiological levels of PEP-19. The expression of PEP-19 yielded a stable phenotype that failed to activate CaM kinase II upon depolarization in high K(+). However, CaM kinase II could be fully activated when calcium influx was achieved with ATP. The effect of PEP-19 on CaM kinase II activation was not attributable to changes in the cellular expression of calmodulin. The cellular permeability of the transfected cells to calcium ions also appeared essentially unchanged. The results of this study demonstrated that PEP-19 can regulate CaM kinase II in situ in a manner that was dependent on the stimulus used to mobilize calcium. The selective nature of the regulation by PEP-19 suggests that its function is not to globally suppress calmodulin activity but rather change the manner in which different stimuli can access this activity.
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Cruzblanca H, Gamiño SM, Bernal J, Alvarez-Leefmans FJ. Trifluoperazine enhancement of Ca2+-dependent inactivation of L-type Ca2+ currents in Helix aspersa neurons. INVERTEBRATE NEUROSCIENCE : IN 1998; 3:269-78. [PMID: 10212396 DOI: 10.1007/bf02577687] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The effects of trifluoperazine hydrochloride (TFP), a calmodulin antagonist, on L-type Ca2+ currents (L-type ICa2+) and their Ca(2+)-dependent inactivation, were studied in identified Helix aspersa neurons, using two microelectrode voltage clamp. Changes in [Ca2+]i were measured in unclamped fura-2 loaded neurons. Bath applied TFP produced a reversible and dose-dependent reduction in amplitude of L-type ICa2+ (IC50 = 28 microM). Using a double-pulse protocol, we found that TFP enhances the efficacy of Ca(2+)-dependent inactivation of L-type ICa2+. Trifluoperazine sulfoxide (50 microM), a TFP derivative with low calmodulin-antagonist activity, did not have any effects on either amplitude or inactivation of L-type ICa2+. TFP (20 microM) increased basal [Ca2+]i from 147 +/- 37 nM to 650 +/- 40 nM (N = 7). The increase in [Ca2+]i was prevented by removal of external Ca2+ and curtailed by depletion of caffeine-sensitive intracellular Ca2+ stores. Since TFP may also block protein kinase C (PKC), we tested the effect of a PKC activator (12-C-tetradecanoyl-phorbol-13-acetate) on L-type Ca2+ currents. This compound produced an increase in L-type ICa2+ without enhancing Ca(2+)-dependent inactivation. The results show that 1) TFP reduces L-type ICa2+ while enhancing the efficacy of Ca(2+)-dependent inactivation. 2) TFP produces an increase in basal [Ca2+]i which may contribute to the enhancement of Ca(2+)-dependent inactivation. 3) PKC up-regulates L-type ICa2+ without altering the efficacy of Ca(2+)-dependent inactivation. 4) The TFP effects cannot be attributed to its action as PKC blocker.
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Affiliation(s)
- H Cruzblanca
- Departamento de Neurobiología, Instituto Mexicano de Psiquiatría, México
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Abstract
Bovine spermatozoa were shown to exhibit rapid regulatory volume decrease (RVD) when exposed to hypotonic saline media. This quinine- and quinidine-sensitive regulatory volume decrease was coincident with K+ release due to stretch-activation of inhibitor-specific presumptive K+ channels. The regulatory volume decrease response was much faster than a similar phenomenon observed in human peripheral blood lymphocytes. Studies on volume changes in different electrolyte and nonelectrolyte media suggested that: (1) this inhibitor-specific channel could also be a nonspecific pore in the spermatozoal membrane for nonelectrolytes below 150 daltons; (2) subpopulations (of nearly equal size) of the spermatozoa differ in the expression of the pore; (3) capacitation abolishes this distinction between subpopulations of spermatozoa; and (4) the general case of RVD for other mammalian spermatozoa was also established.
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Affiliation(s)
- S B Kulkarni
- Department of Biotechnology, University of Pune, Ganeshkhind, India
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Basavappa S, Ellory JC. The role of swelling-induced anion channels during neuronal volume regulation. Mol Neurobiol 1996; 13:137-53. [PMID: 8938648 DOI: 10.1007/bf02740638] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Regulation of cell volume is an essential function of most mammalian cells. In the cells of the central nervous system, maintenance of cell osmolarity and, hence, volume, is particularly crucial because of the restrictive nature of the skull. Cell volume regulation involves a variety of pathways, with considerable differences between cell types. One common pathway activated during hypo-osmotic stress involves chloride (Cl-) channels. However, hypo-osmotically stimulated anion permeability can be regulated by a diverse array of second messengers. Although neuronal swelling can occur in a number of pathological and nonpathological conditions, our understanding of neuronal volume regulation is limited. This article summarizes our current understanding of the role of anion channels during neuronal volume regulation.
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Affiliation(s)
- S Basavappa
- University Laboratory of Physiology, University of Oxford, UK
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Hoffmann EK, Dunham PB. Membrane mechanisms and intracellular signalling in cell volume regulation. INTERNATIONAL REVIEW OF CYTOLOGY 1995; 161:173-262. [PMID: 7558691 DOI: 10.1016/s0074-7696(08)62498-5] [Citation(s) in RCA: 337] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Recent work on selected aspects of the cellular and molecular physiology of cell volume regulation is reviewed. First, the physiological significance of the regulation of cell volume is discussed. Membrane transporters involved in cell volume regulation are reviewed, including volume-sensitive K+ and Cl- channels, K+, Cl- and Na+, K+, 2Cl- cotransporters, and the Na+, H+, Cl-, HCO3-, and K+, H+ exchangers. The role of amino acids, particularly taurine, as cellular osmolytes is discussed. Possible mechanisms by which cells sense their volumes, along with the sensors of these signals, are discussed. The signals are mechanical changes in the membrane and changes in macromolecular crowding. Sensors of these signals include stretch-activated channels, the cytoskeleton, and specific membrane or cytoplasmic enzymes. Mechanisms for transduction of the signal from sensors to transporters are reviewed. These include the Ca(2+)-calmodulin system, phospholipases, polyphosphoinositide metabolism, eicosanoid metabolism, and protein kinases and phosphatases. A detailed model is presented for the swelling-initiated signal transduction pathway in Ehrlich ascites tumor cells. Finally, the coordinated control of volume-regulatory transport processes and changes in the expression of organic osmolyte transporters with long-term adaptation to osmotic stress are reviewed briefly.
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Affiliation(s)
- E K Hoffmann
- Biochemical Department, August Krogh Institute, University of Copenhagen, Denmark
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Deaton LE. Hypoosmotic volume regulation in bivalves: Protein kinase C and amino acid release. ACTA ACUST UNITED AC 1994. [DOI: 10.1002/jez.1402680212] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Deaton LE, Pierce SK. Introduction: cellular volume regulation--mechanisms and control. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1994; 268:77-9. [PMID: 8301254 DOI: 10.1002/jez.1402680202] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- L E Deaton
- Department of Biology, University of Southwestern Louisiana, Lafayette 70504
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Osmolyte permeability in molluscan red cells is regulated by Ca2+ and membrane protein phosphorylation: The present perspective. ACTA ACUST UNITED AC 1994. [DOI: 10.1002/jez.1402680215] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Cronkite DL, Diekman AB, Lewallen B, Phillips L. Aminotransferase and the production of alanine during hyperosmotic stress in Paramecium calkinsi. J Eukaryot Microbiol 1993; 40:796-800. [PMID: 8292998 DOI: 10.1111/j.1550-7408.1993.tb04477.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
When Paramecium calkinsi encounter hyperosmotic stress, intracellular free alanine increases. In vivo assays indicate that the reaction catalyzed by alanine aminotransferase contributes to the build up of alanine in response to hyperosmotic shock. 14C-pyruvate is converted to 14C-alanine in cells grown axenically at 200 mosm. When shifted to 600 mosm, the rate of conversion of pyruvate to alanine increases, and conversion at either 200 or 600 mosm is blocked by 1 mM aminooxyacetic acid (AOA), an inhibitor of aminotransferase. Intracellular free alanine increase is partially inhibited by AOA, and AOA prevents cells living in fresh water from acclimating to higher salinities, an indication that the increase in intracellular alanine is physiologically significant.
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Affiliation(s)
- D L Cronkite
- Biology Department, Hope College, Holland, Michigan 49422-9000
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Pierce SK, Rowland-Faux LM. Ionomycin produces an improved volume recovery by an increased efflux of taurine from hypoosmotically stressed molluscan red blood cells. Cell Calcium 1992; 13:321-7. [PMID: 1623502 DOI: 10.1016/0143-4160(92)90067-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nucleated erythrocytes of the blood clam, Noetia ponderosa, recover cell volume after a hypoosmotic stress by an efflux of K+, Cl- and taurine. When the cells are exposed to ionomycin followed by hypoosmotic stress, swelling is less and volume recovery is both faster and more complete than in control cells without the ionophore. The improved volume recovery is caused by a large increase in the efflux of taurine. The taurine efflux is altered by changing Ca2+ concentrations in the presence of the ionophore. Potassium regulation by the osmotically stressed erythrocytes is also increased in the presence of ionomycin, but only by a small amount, perhaps accounting for the initial decrease in swelling. Variation of Ca2+ in the presence of ionomycin without osmotic stress produces no change in the regulation of either osmolyte. These results indicate that both the osmotic stress and an increase in [Ca2+]i are required for the permeability change that produces taurine efflux.
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Affiliation(s)
- S K Pierce
- Department of Zoology, University of Maryland, College Park
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19
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Politis AD, Pierce SK. Specific protein phosphorylation occurs in molluscan red blood cell ghosts in response to hypoosmotic stress. J Membr Biol 1991; 124:169-77. [PMID: 1762142 DOI: 10.1007/bf01870461] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The regulation of cellular volume upon exposure to hypoosmotic stress is accomplished by specific plasma membrane permeability changes that allow the efflux of certain intracellular solutes (osmolytes). The mechanism of this membrane permeability regulation is not understood; however, previous data implicate Ca2+ as an important component in the response. The regulation of protein phosphorylation is a pervasive aspect of cellular physiology that is often Ca2+ dependent. Therefore, we tested for osmotically induced protein phosphorylation as a possible mechanism by which Ca2+ may mediate osmotically dependent osmolyte efflux. We have found a rapid increase in 32Pi incorporation into two proteins in clam blood cell ghosts after exposure of the intact cells to a hypoosmotic medium. The osmotic component of the stress, not the ionic dilution, was the stimulus for the phosphorylations. The osmotically induced phosphorylation of both proteins was significantly inhibited when Ca2+ was omitted from the medium, or by the calmodulin antagonist, chlorpromazine. These results correlate temporally with cell volume recovery and osmolyte (specifically free amino acid) efflux. The two proteins that become phosphorylated in response to hypoosmotic stress may be involved in the regulation of plasma membrane permeability to organic solutes, and thus, contribute to hypoosmotic cell volume regulation.
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Affiliation(s)
- A D Politis
- Department of Zoology, University of Maryland, College Park 20742
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Edmonds BT, Koenig E. Volume regulation in response to hypo-osmotic stress in goldfish retinal ganglion cell axons regenerating in vitro. Brain Res 1990; 520:159-65. [PMID: 2207628 DOI: 10.1016/0006-8993(90)91701-h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Goldfish retinal ganglion cell (RGC) axons regenerating in vitro were used to investigate the volume regulatory response to hypo-osmotic stress. Reducing the tonicity of the bathing medium to half strength caused an immediate swelling of axons; however, within 1 min a progressive volume reduction ensued which stabilized at near control volume over a period of 10 min. This regulatory volume decrease (RVD) was attenuated by elevated [K+]o, Ca2(+)-activated K+ channel antagonists, and calmidazolium, a potent calmodulin inhibitor. Inclusion of ATP-gamma S in the hypotonic bathing medium led to a loading of stressed axons which resulted in an excessive volume reduction that reflected an overshooting of the RVD response. The latter suggested the importance of phosphorylation/dephosphorylation reactions in the RVD response pathway. Cytochalasin D and colchicine had no effect on the development of the typical RVD response, providing no evidence of involvement of actin or microtubule cytoskeletons in the volume reduction mechanism of the immature axons. The results are consistent with the hypothesis that hypo-osmotic stress activates a calcium/calmodulin dependent membrane pathway, which probably involves transient phosphorylation, leading to a loss of cellular K+ and osmotically obligated water which restorates normal axonal volume.
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Affiliation(s)
- B T Edmonds
- Department of Physiology, State University of New York, Buffalo 14214
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Edmonds BT, Koenig E. Calcium-dependent volume reduction in regenerating ganglion cell axons in vitro. J Neurosci Res 1990; 26:168-80. [PMID: 2164108 DOI: 10.1002/jnr.490260206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effects of increasing [Ca2+]i on volume regulatory behavior was investigated by phase-contrast videomicroscopy in immature axons regenerating from goldfish retinal explants in vitro. Elevating [Ca2+]i by using EGTA-buffered, ionomycin-containing bathing media with either greater than or equal to 100 microM [Ca2+]o or 1 microM [Ca2+]o with N-methylglucamine substituted for Na+ caused axons to undergo a "syneresis." The syneresis was characterized by a marked loss in volume and condensation of axoplasm, accompanied by a proliferation of lateral processes, which resulted ultimately in an arrest of visible particle transport. The random appearance of dynamic phase-lucent axial protrusions in the distal axon, apparently caused by microtubules, was a frequent early manifestation. Syneresis was also produced by increasing the tonicity of the Cortland saline with sorbitol or treating axons with either valinomycin or with permeant cyclic AMP analogs in normal Cortland saline. In the latter case, extracellular Ca2+ was required. Preterminal axons showed an increase in phalloidin fluorescence after syneresis, suggesting polymerization and/or rearrangement of the actin cytoskeleton. Digitonin-permeabilized axonal field models, which maintained good morphology and particle transport, failed to develop a syneresis even when [Ca2+]o was increased to 250 microM. Cytochalasin D did not interfere with the development of a syneresis, but did suppress the proliferation of lateral processes. Syneresis could be blocked by high [K+]o, putative antagonists of Ca2(+)-activated K+ channels, or by calmidazolium, a calmodulin antagonist. The experimental findings suggest that cytoskeletal changes associated with volume reduction in growing retinal ganglion cell axons are secondary to a loss of cell water and that calcium/calmodulin-activated K+ channels very likely play a primary role in dehydration through the loss of K+ and osmotically obligated water.
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Affiliation(s)
- B T Edmonds
- Department of Physiology, State University of New York, Buffalo
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