Single-molecule analysis of diffusion and trapping of STIM1 and Orai1 at endoplasmic reticulum-plasma membrane junctions.

ABSTRACT: Following endoplasmic reticulum (ER) Ca(2+) depletion, STIM1 and Orai1 complexes assemble autonomously at ER-plasma membrane (PM) junctions to trigger store-operated Ca(2+) influx. One hypothesis to explain this process is a diffusion trap in which activated STIM1 diffusing in the ER becomes trapped at junctions through interactions with the PM, and STIM1 then traps Orai1 in the PM through binding of its calcium release-activated calcium activation domain. We tested this model by analyzing STIM1 and Orai1 diffusion using single-particle tracking, photoactivation of protein ensembles, and Monte Carlo simulations. In resting cells, STIM1 diffusion is Brownian, while Orai1 is slightly subdiffusive. After store depletion, both proteins slow to the same speeds, consistent with complex formation

SUBMITTER: Wu MM 

PROVIDER: S-EPMC4230625 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature