Dynamic movement of the calcium sensor STIM1 and the calcium channel Orai1 in activated T-cells: puncta and distal caps.
The proteins STIM1 and Orai1 are 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 after 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. 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.
Barr
Valarie A
VA
Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD 20892-4256, USA.
Bernot
Kelsie M
KM
Srikanth
Sonal
S
Gwack
Yousang
Y
Balagopalan
Lakshmi
L
Regan
Carole K
CK
Helman
Daniel J
DJ
Sommers
Connie L
CL
Oh-Hora
Masatsugu
M
Rao
Anjana
A
Samelson
Lawrence E
LE
D001402:B-Lymphocytes / Q000378:metabolism; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D054992:Immunological Synapses / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000378:metabolism*; D000071740:ORAI1 Protein; D010766:Phosphorylation; D000071737:Stromal Interaction Molecule 1; D013601:T-Lymphocytes / Q000378:metabolism*
D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D002118:Calcium