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MBC in Press, published online ahead of print April 30, 2008
Mol. Biol. Cell 10.1091/mbc.E08-02-0146

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Submitted on February 13, 2008
Revised on April 8, 2008
Accepted on April 17, 2008

Dynamic Movement of the Calcium Sensor STIM1 and the Calcium Channel Orai1 in Activated T Cells: Puncta and Distal Caps

Valarie A. Barr,* Kelsie M. Bernot,* Sonal Srikanth,{dagger}{ddagger} Yousang Gwack,{dagger}{ddagger} Lakshmi Balagopalan,* Carole K. Regan,* Daniel J. Helman,* Connie L. Sommers,* Masatsugu Oh-hora,{dagger} Anjana Rao,{dagger} and Lawrence E. Samelson*

*Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD 20892-4256; {dagger}Department of Pathology, Harvard Medical School and the Immune Disease Institute, Boston, MA 02115

Monitoring Editor: Carl-Henrik Heldin

The proteins STIM1 and Orai1are the long sought components of the store-operated channels required in T-cell activation. However, little is known about the interaction of these proteins in T-cells following engagement of the T-cell receptor. We found that T-cell receptor engagement caused STIM1 and Orai1 to colocalize in puncta near the site of stimulation and accumulate in a dense structure on the opposite side of the T-cell. FRET measurements showed a close interaction between STIM1 and Orai1 both in the puncta and in the dense cap-like structure. The formation of cap-like structures did not entail rearrangement of the entire endoplasmic reticulum (ER). Cap formation depended on TCR engagement and tyrosine phosphorylation, but not on channel activity or Ca+2 influx. These caps were very dynamic in T-cells activated by contact with superantigen pulsed B cells and could move from the distal pole to an existing or a newly forming immunological synapse. One function of this cap may be to provide preassembled Ca+2 channel components to existing and newly forming immunological synapses.

{ddagger}Present Address: Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1751.

Address correspondence to: Lawrence E. Samelson (samelson{at}helix.nih.gov)






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