Essential role of Ca2+/calmodulin in Early Endosome Antigen-1 localization
Graduate School of Biomedical Sciences; Program in Molecular Medicine; Department of Physiology
Life Sciences | Medicine and Health Sciences
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.
DOI of Published Version
Mol Biol Cell. 2003 Jul;14(7):2935-45. Epub 2003 Mar 20. Link to article on publisher's site
Molecular biology of the cell
Lawe DC, Sitouah N, Hayes S, Chawla A, Virbasius JV, Tuft RA, Fogarty KE, Lifshitz LM, Lambright DG, Corvera S. (2003). Essential role of Ca2+/calmodulin in Early Endosome Antigen-1 localization. Morningside Graduate School of Biomedical Sciences Student Publications. https://doi.org/10.1091/mbc.E02-09-0591. Retrieved from https://escholarship.umassmed.edu/gsbs_sp/651