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Asymmetric localization of flotillins/reggies in preassembled platforms confers inherent polarity to hematopoietic cells

  • Hematopoietic cells have long been defined as round, nonpolar cells that show uniform distribution of cell surface-associated molecules. However, recent analyses of the immunological synapse and the importance of lipid microdomains in signaling have shed new light on the aspect of lymphocyte polarization during the activation processes, but none of the molecules implicated so far in either the activation process or the microdomain residency are known to have a preferential localization in nonactivated cells. Chemical crosslinking and fluorescence resonance energy transfer methods have allowed the visualization of certain glycosylphosphatidylinositol-anchored proteins in lipid rafts but so far no microdomain resident protein has been shown to exist as visible stable platforms in the membrane. We report here that two lipid microdomain resident proteins, flotillins/reggies, form preassembled platforms in hematopoietic cells. These platforms recruit signaling molecules upon activation through lipid rafts. The preassembled platforms significantly differ from the canonical cholesterol-dependent "lipid rafts," as they are resistant to cholesterol-disrupting agents. Most evidence for the functional relevance of microdomains in living cells remains indirect. Using laser scanning confocal microscopy, we show that these proteins exist as stable, microscopically patent domains localizing asymmetrically to one pole of the cell. We present evidence that the asymmetric concentration of these microdomain resident proteins is built up during cytokinesis.

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Document Type:Article
Author:Lawrence Rajendran, Madhan Masilamani, Samuel Solomon, Ritva Tikkanen, Claudia A. O. Stuermer, Helmut Plattner, Harald Illges
Parent Title (English):Proc Natl Acad Sci USA (Proceedings of the National Academy of Sciences of the United States of America)
First Page:8241
Last Page:8246
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=12826615
Publisher:National Academy of Sciences
Date of first publication:2003/06/25
Departments, institutes and facilities:Institut für funktionale Gen-Analytik (IFGA)
Dewey Decimal Classification (DDC):6 Technik, Medizin, angewandte Wissenschaften / 61 Medizin und Gesundheit / 610 Medizin und Gesundheit
Entry in this database:2018/07/25