Essential role of Ca2+/Calmodulin in Early Endosome Antigen-1 Localization
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Published:2003-07
Issue:7
Volume:14
Page:2935-2945
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ISSN:1059-1524
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Container-title:Molecular Biology of the Cell
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language:en
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Short-container-title:MBoC
Author:
Lawe Deirdre C.1, Sitouah Nachida1, Hayes Susan2, Chawla Anil13, Virbasius Joseph V.13, Tuft Richard4, Fogarty Kevin4, Lifshitz Lawrence4, Lambright David123, Corvera Silvia12
Affiliation:
1. Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 10615 2. Interdisciplinary Graduate Program, University of Massachusetts Medical School, Worcester, Massachusetts 10615 3. Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 10615 4. Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 10615
Abstract
Ca2+is an essential requirement in membrane fusion, acting through binding proteins such as calmodulin (CaM). Ca2+/CaM is required for early endosome fusion in vitro, however, the molecular basis for this requirement is unknown. An additional requirement for endosome fusion is the protein Early Endosome Antigen 1 (EEA1), and its recruitment to the endosome depends on phosphatidylinositol 3-phosphate [PI(3)P] and the Rab5 GTPase. Herein, we demonstrate that inhibition of Ca2+/CaM, by using either chemical inhibitors or specific antibodies directed to CaM, results in a profound inhibition of EEA1 binding to endosomal membranes both in live cells and in vitro. The concentration of Ca2+/CaM inhibitors required for a full dissociation of EEA1 from endosomal membranes had no effect on the activity of phosphatidylinositol 3-kinases or on endogenous levels of PI(3)P. However, the interaction of EEA1 with liposomes containing PI(3)P was decreased by Ca2+/CaM inhibitors. Thus, Ca2+/CaM seems to be required for the stable interaction of EEA1 with endosomal PI(3)P, perhaps by directly or indirectly stabilizing the quaternary organization of the C-terminal FYVE domain of EEA1. This requirement is likely to underlie at least in part the essential role of Ca2+/CaM in endosome fusion.
Publisher
American Society for Cell Biology (ASCB)
Subject
Cell Biology,Molecular Biology
Reference37 articles.
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