Compartmentalization of phosphatidylinositol 4,5-bisphosphate in low-density membrane domains in the absence of caveolin.
In cells that exhibit caveolae, the hormone-sensitive pool of PtdIns 4,5-P2 is localized in a low density, caveolin-enriched membrane fraction (1). Neuro 2a cells do not express caveolin. Nonetheless, the PtdIns 4,5-P2 in these cells is compartmentalized in a low density, detergent-insoluble domain that also contains other signaling-related molecules. Compartmentalization of PtdIns 4,5-P2 was observed regardless of whether Triton X-100-containing or detergent-free methods were used to prepare the membranes. However, the partitioning of receptor tyrosine kinases and GPI-anchored proteins into the low density domains was dependent upon the method of membrane preparation. Treatment of Neuro 2a cells with cyclodextrin delocalized the PtdIns 4,5-P2 and inhibited hormone-stimulated PtdIns turnover. These results suggest that compartmentalization of PtdIns 4,5-P2 does not require caveolin but is necessary for the proper functioning of phosphoinositide-based signaling.
Liu
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Y
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Casey
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Pike
L J
LJ
D000818:Animals; D015153:Blotting, Western; D051242:Caveolin 1; D022461:Caveolins; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003505:Cyclodextrins / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D017830:Octoxynol / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*
D051242:Caveolin 1; D022461:Caveolins; D003505:Cyclodextrins; D008565:Membrane Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D017830:Octoxynol