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Nitric oxide modulates intracellular translocation of pigment organelles in Xenopus laevis melanophores
Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Care, Pharmacology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
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2000 (English)In: Cell Motility and the Cytoskeleton, ISSN 0886-1544, E-ISSN 1097-0169, Vol. 47, no 3, 209-218 p.Article in journal (Refereed) Published
Abstract [en]

Pigment organelles in Xenopus laevis melanophores are used by the animal to change skin color, and they provide a good model for studying intracellular organelle transport. Movement of organelles and vesicles along the cytoskeleton is essential for many processes, such as axonal transport, endocytosis, and intercompartmental trafficking. Nitric oxide (NO) is a signaling molecule that plays a role in, among other things, relaxation of blood vessels, sperm motility, and polymerization of actin. Our study focused on the effect NO exerts on cytoskeleton-mediated transport, which has previously received little attention. We found that an inhibitor of NO synthesis, N-nitro-L-arginine methyl ester (L-NAME), reduced the melatonin-induced aggregation of the pigment organelles, melanosomes. Preaggregated melanosomes dispersed after treatment with L-NAME but not after exposure to the inactive stereoisomer (D-NAME) or the substrate for NO synthesis (L-arginine). Signal transduction by NO can be mediated through the activation of soluble guanylate cyclase (sGC), which leads to increased production of cGMP and activation of cGMP-dependent kinases (PKG). We found that both the sGC inhibitor 1H-(1,2,4) oxadiazolo(4,3-a)quinoxalin-1-one (ODQ) and the cGMP analogue 8-bromoguanosine 3′:5′-cyclic monophosphate (8-Br-cGMP) reduced melanosome aggregation, whereas the PKG inhibitor KT582 did not. Our results demonstrate that melanosome aggregation depends on synthesis of NO, and NO deprivation causes dispersion. It seems, thus, as if NO and cGMP are essential and can regulate melanosome translocation.

Place, publisher, year, edition, pages
2000. Vol. 47, no 3, 209-218 p.
Keyword [en]
melanosome, aggregation, cGMP, microtubules, actin, L-NAME
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-13570DOI: 10.1002/1097-0169(200011)47:3<209::AID-CM4>3.0.CO;2-WOAI: oai:DiVA.org:liu-13570DiVA: diva2:20972
Available from: 2001-03-14 Created: 2001-03-14 Last updated: 2017-12-13Bibliographically approved
In thesis
1. The role of nitric oxide in cytoskeleton-mediated organelle transport and cell adhesion
Open this publication in new window or tab >>The role of nitric oxide in cytoskeleton-mediated organelle transport and cell adhesion
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nitric oxide (NO) is a signaling molecule that is produced by many different kinds of cells, and it is known to mediate actions such as blood vessel dilation, communication between nerve cells, and killing of bacteria in infections. The cytoskeleton is involved in many important cellular functions, among them intracellular transport of organelles, migration, and cell division. The aim of the present studies was to examine the effects of NO on some of the indicated functions. Homotypic adhesion of human neutrophils, which is mediated by ß2 integrins, is an early step in the inflammatory process. Addition of L-argiriine (the substrate of NO production) to fMLP-stimulated neutrophils increased and prolonged aggregation of the cells. Stimulation of L-arginine-pretreated neutrophils by cross-linking of ß2 integrins attenuated the increase in F-actin, as compared to control cells. These results suggest that the aggregation is prolonged by activation of ß2 integrins and endogenous NO production, two events that together seem to inhibit actin polymerization, possibly via ADP ribosylation.

The effect of NO on intracellular translocation of organelles along the cytoskeleton was studied in Xenopus laevis pigment cells. Inhibition of NO production induced by the drug L-NAME was found to inhibit aggregation of the pigment organelles (melanosomes) and to induce dispersion. Activation of PKC, MEK, and ERKl, but not PKA, was associated with the dispersion, thus NO may negatively regulate these kinases, which, when activated, would induce movement of melanosomes. During melanosome aggregation, the cell center increases in height by approximately 30%. Experiments were performed to determine whether the cell membrane is pushed upwards by actin polymerization and water influx through HgCl2-sensitive aquaporins. The results gave no evidence that either two of these mechanisms affects the upward movement. However, L-NAME caused dispersion and a decrease in cell height, thus NO may play a role in maintaining an aggregated, elevated state. In conclusion, many factors regulate both homotypic aggregation and intracellular organelle transport, and NO seems to prolong homotypic aggregation of neutrophils and regulate melanosome transport by inhibiting PKC, MEK and ERKl.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2001. 48 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 660
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28614 (URN)13769 (Local ID)91-7219-761-7 (ISBN)13769 (Archive number)13769 (OAI)
Public defence
2001-03-02, Elsa Brändströmssalen, Universitetssjukhuset, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2015-09-18Bibliographically approved

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Nilsson, Harriet M.Karlsson, Annika M.Loitto, Vesa-MattiSvensson, Samuel P.S.Sundqvist, Tommy

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