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First published online 2 September 2008
doi: 10.1242/jcs.034496


Journal of Cell Science 121, 3133-3139 (2008)
Published by The Company of Biologists 2008
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Short Report

Cytosolic Ca2+ prevents the subplasmalemmal clustering of STIM1: an intrinsic mechanism to avoid Ca2+ overload

Roland Malli1, Shamim Naghdi1, Christoph Romanin2 and Wolfgang F. Graier1,*

1 Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Graz, Austria
2 Institute of Biophysics, University of Linz, Linz, Austria

* Author for correspondence (e-mail: wolfgang.graier{at}meduni-graz.at)

Accepted 3 July 2008

Summary

The stromal interacting molecule (STIM1) is pivotal for store-operated Ca2+ entry (SOC). STIM1 proteins sense the Ca2+ concentration within the lumen of the endoplasmic reticulum (ER) via an EF-hand domain. Dissociation of Ca2+ from this domain allows fast oligomerization of STIM1 and the formation of spatially discrete clusters close to the plasma membrane. By lifetime-imaging of STIM1 interaction, the rearrangement of STIM1, ER Ca2+ concentration ([Ca2+]ER) and cytosolic Ca2+ signals ([Ca2+]cyto) we show that [Ca2+]cyto affects the subcellular distribution of STIM1 oligomers and prevents subplasmalemmal STIM clustering, even if the ER is depleted. These data indicate that [Ca2+]cyto, independently of the ER Ca2+ filling state, crucially tunes the formation and disassembly of subplasmalemmal STIM1 clusters, and, thus, protects cells against Ca2+ overload resulting from excessive SOC activity.

Key words: ER Ca2+ dynamics, FRET, STIM1 oligomerization, Store-operated Ca2+ entry







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