QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 15 August 2006
doi: 10.1242/jcs.03075

This Article Figures Only Full Text Full Text (PDF) Supplementary Material All Versions of this Article: jcs.03075v1 119/17/3705    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ladenburger, E.-M. Articles by Plattner, H. Search for Related Content PubMed PubMed Citation Articles by Ladenburger, E.-M. Articles by Plattner, H. Social Bookmarking                         What's this?

An Ins(1,4,5)P₃ receptor in Paramecium is associated with the osmoregulatory system

Department of Biology, University of Konstanz, 78457 Konstanz, Germany

^* Author for correspondence (e-mail: Eva.Ladenburger{at}uni-konstanz.de)

Accepted 1 June 2006

In the ciliate Paramecium, a variety of well characterized processes are regulated by Ca²⁺, e.g. exocytosis, endocytosis and ciliary beat. Therefore, among protozoa, Paramecium is considered a model organism for Ca²⁺ signaling, although the molecular identity of the channels responsible for the Ca²⁺ signals remains largely unknown. We have cloned - for the first time in a protozoan - the full sequence of the gene encoding a putative inositol (1,4,5)-trisphosphate (Ins(1,4,5)P₃) receptor from Paramecium tetraurelia cells showing molecular characteristics of higher eukaryotic cells. The homologously expressed Ins(1,4,5)P₃-binding domain binds [³H]Ins(1,4,5)P₃, whereas antibodies unexpectedly localize this protein to the osmoregulatory system. The level of Ins(1,4,5)P₃-receptor expression was reduced, as shown on a transcriptional level and by immuno-staining, by decreasing the concentration of extracellular Ca²⁺ (Paramecium cells rapidly adjust their Ca²⁺ level to that in the outside medium). Fluorochromes reveal spontaneous fluctuations in cytosolic Ca²⁺ levels along the osmoregulatory system and these signals change upon activation of caged Ins(1,4,5)P₃. Considering the ongoing expulsion of substantial amounts of Ca²⁺ by the osmoregulatory system, we propose here that Ins(1,4,5)P₃ receptors serve a new function, i.e. a latent, graded reflux of Ca²⁺ to fine-tune [Ca²⁺] homeostasis.

Key words: Ca²⁺, Calcium, Inositol 1,4,5-trisphosphate, IP₃, Osmoregulation, Paramecium

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				E.-M. Ladenburger, I. M. Sehring, I. Korn, and H. Plattner Novel Types of Ca2+ Release Channels Participate in the Secretory Cycle of Paramecium Cells Mol. Cell. Biol., July 1, 2009; 29(13): 3605 - 3622. [Abstract] [Full Text] [PDF]

				X. Cai Unicellular Ca2+ Signaling 'Toolkit' at the Origin of Metazoa Mol. Biol. Evol., July 1, 2008; 25(7): 1357 - 1361. [Abstract] [Full Text] [PDF]