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      Ca 2+ influx and phosphoinositide signalling are essential for the establishment and maintenance of cell polarity in monospores from the red alga Porphyra yezoensis

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          Abstract

          The asymmetrical distribution of F-actin directed by cell polarity has been observed during the migration of monospores from the red alga Porphyra yezoensis. The significance of Ca 2+ influx and phosphoinositide signalling during the formation of cell polarity in migrating monospores was analysed pharmacologically. The results indicate that the inhibition of the establishment of cell polarity, as judged by the ability of F-actin to localize asymmetrically, cell wall synthesis, and development into germlings, occurred when monospores were treated with inhibitors of the Ca 2+ permeable channel, phospholipase C (PLC), diacylglycerol kinase, and inositol-1,4,5-trisphosphate receptor. Moreover, it was also found that light triggered the establishment of cell polarity via photosynthetic activity but not its direction, indicating that the Ca 2+ influx and PLC activation required for the establishment of cell polarity are light dependent. By contrast, inhibition of phospholipase D (PLD) prevented the migration of monospores but not the asymmetrical localization of F-actin. Taken together, these findings suggest that there is functional diversity between the PLC and PLD signalling systems in terms of the formation of cell polarity; the former being critical for the light-dependent establishment of cell polarity and the latter playing a role in the maintenance of established cell polarity.

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          PTEN-mediated apical segregation of phosphoinositides controls epithelial morphogenesis through Cdc42.

          Formation of the apical surface and lumen is a fundamental, yet poorly understood, step in epithelial organ development. We show that PTEN localizes to the apical plasma membrane during epithelial morphogenesis to mediate the enrichment of PtdIns(4,5)P2 at this domain during cyst development in three-dimensional culture. Ectopic PtdIns(4,5)P2 at the basolateral surface causes apical proteins to relocalize to the basolateral surface. Annexin 2 (Anx2) binds PtdIns(4,5)P2 and is recruited to the apical surface. Anx2 binds Cdc42, recruiting it to the apical surface. Cdc42 recruits aPKC to the apical surface. Loss of function of PTEN, Anx2, Cdc42, or aPKC prevents normal development of the apical surface and lumen. We conclude that the mechanism of PTEN, PtdIns(4,5)P2, Anx2, Cdc42, and aPKC controls apical plasma membrane and lumen formation.
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            Spatial and temporal regulation of 3-phosphoinositides by PI 3-kinase and PTEN mediates chemotaxis.

            We have investigated the mechanisms of leading edge formation in chemotaxing Dictyostelium cells. We demonstrate that while phosphatidylinositol 3-kinase (PI3K) transiently translocates to the plasma membrane in response to chemoattractant stimulation and to the leading edge in chemotaxing cells, PTEN, a negative regulator of PI3K pathways, exhibits a reciprocal pattern of localization. By uniformly localizing PI3K along the plasma membrane, we show that chemotaxis pathways are activated along the lateral sides of cells and PI3K can initiate pseudopod formation, providing evidence for a direct instructional role of PI3K in leading edge formation. These findings provide evidence that differential subcellular localization and activation of PI3K and PTEN is required for proper chemotaxis.
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              Signaling by distinct classes of phosphoinositide 3-kinases.

              Many signaling pathways converge on and regulate phosphoinositide 3-kinase (PI3K) enzymes whose inositol lipid products are key mediators of intracellular signaling. Different PI3K isoforms generate specific lipids that bind to FYVE and pleckstrin homology (PH) domains in a variety of proteins, affecting their localization, conformation, and activities. Here we review the activation mechanisms of the different types of PI3Ks and their downstream actions, with focus on the PI3Ks that are acutely triggered by extracellular stimulation. Copyright 1999 Academic Press.
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                Author and article information

                Journal
                J Exp Bot
                jexbot
                exbotj
                Journal of Experimental Botany
                Oxford University Press
                0022-0957
                1460-2431
                August 2009
                16 June 2009
                16 June 2009
                : 60
                : 12
                : 3477-3489
                Affiliations
                [1 ]Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan
                [2 ]Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan
                Author notes
                [* ]To whom correspondence should be addressed. E-mail: komikami@ 123456fish.hokudai.ac.jp
                Article
                10.1093/jxb/erp183
                2724695
                19531546
                ad88db6a-efda-49fd-9cd2-15feaae0efae
                © 2009 The Author(s).

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

                Categories
                Research Papers

                Plant science & Botany
                phosphatidylinositol,monospore,porphyra yezoensis,f-actin,phospholipase d,cell polarity,phospholipase c,cell wall,ca2+ influx

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