Effects of intracellular calcium and actin cytoskeleton on TCR mobility measured by fluorescence recovery.
BACKGROUND
The activation of T lymphocytes by specific antigen is accompanied by the formation of a specialized signaling region termed the immunological synapse, characterized by the clustering and segregation of surface molecules and, in particular, by T cell receptor (TCR) clustering.


RESULTS
To better understand TCR motion during cellular activation, we used confocal microscopy and photo-bleaching recovery techniques to investigate the lateral mobility of TCR on the surface of human T lymphocytes under various pharmacological treatments. Using drugs that cause an increase in intracellular calcium, we observed a decrease in TCR mobility that was dependent on a functional actin cytoskeleton. In parallel experiments measurement of filamentous actin by FACS analysis showed that raising intracellular calcium also causes increased polymerization of the actin cytoskeleton. These in vitro results were analyzed using a mathematical model that revealed effective binding parameters between TCR and the actin cytoskeleton.


CONCLUSIONS
We propose, based on our results, that increase in intracellular calcium levels leads to actin polymerization and increases TCR/cytoskeleton interactions that reduce the overall mobility of the TCR. In a physiological setting, this may contribute to TCR re-positioning at the immunological synapse.
Dushek
Omer
O
Department of Mathematics and Institute of Applied Mathematics, University of British Columbia, Vancouver, British Columbia, Canada.
Mueller
Sabina
S
Soubies
Sebastien
S
Depoil
David
D
Caramalho
Iris
I
Coombs
Daniel
D
Valitutti
Salvatore
S
D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D004058:Diffusion; D005434:Flow Cytometry; D036681:Fluorescence Recovery After Photobleaching; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D008213:Lymphocyte Activation; D008954:Models, Biological; D021381:Protein Transport; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology
D000199:Actins; D011948:Receptors, Antigen, T-Cell; D002118:Calcium