Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Poster Abstracts

71-POS Board 36 Track STIM1 and Orai1 Molecules in Live Cells Xianan Qin 1 , Sangkwon Lee 3 , Kaitlin Chan 2 , Min Zhang 2 , Chenglong Yu 2 , Jun Chu 4 , Chan Young Park 3 , Hyokeun Park 1,2 . 1 The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China, 2 The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China, 3 Ulsan National Institute of Science and Technology, Ulsan, South Korea, 4 Shenzhen Institutes of Advanced Technology, Chinese Academy of Science, Shenzhen, Guangdong, China. Ca 2+ inside cells plays important roles in biological processesy. The store operated calcium entry (SOCE) can be regulated by STIM1 (a calcium sensor in the membrane of ER) and Orai1 (a calcium channel in the plasma membrane). STIM1 binds to Orai1 , and activates the Orai1 channel after the calcium depletion in ER. Although there are several reports about the molecular mechanism of Orai1 and STIM1, the detailed dynamics of STIM1 and Orai1 assembly is not clearly understood yet. We tracked STIM1 and Orai1 particles using our real time single-particle tracking setup. Using single-particle tracking, we calculated the diffusion coefficients of individual STIM1 and Orai1 particles. The diffusion coefficients of STIM1 and Orai1 particles were widely distributed when the ER calcium was at resting state. The depletion of ER calcium store after the treatment of Thapsigargin (TG) decreased the diffusion coefficients drastically. We further obtained the diffusion coefficient map and the potential energy landscape of STIM1 and Orai1 inside cells using Bayesian inference analysis. We also found that the potential energy landscapes of STIM1 and Orai1drastically changed after ER calcium depletion. These studies imply the diffusion-trapping of STIM1 and Orai1 in their assembly.

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