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Cell Rep. 2016 Aug 23;16(8):2156-2168. doi: 10.1016/j.celrep.2016.07.047. Epub 2016 Aug 11.

Cortical Polarity of the RING Protein PAR-2 Is Maintained by Exchange Rate Kinetics at the Cortical-Cytoplasmic Boundary.

Author information

1
Cellular Informatics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan. Electronic address: arata@riken.jp.
2
Cellular Informatics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan; Laboratory for Cell Signaling Dynamics, Quantitative Biology Center (QBiC), RIKEN, Suita, Osaka 565-0874, Japan.
3
Cellular Informatics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan; Asan Institute for Life Sciences, University of Ulsan, College of Medicine, Asan Medical Center, Seoul 138-736, Republic of Korea.
4
Temasek Life Sciences Laboratory, Mechanobiology Institute, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore.
5
Theoretical Biology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
6
Cellular Informatics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
7
Department of Physics, McGill University, Montréal, QC H3A 2T8, Canada; Department of Chemistry, McGill University, Montréal, QC H3A 0B8, Canada.
8
Multicellular Organization Laboratory, National Institute of Genetics, Mishima 411-8540, Japan.
9
Institute of Industrial Science, University of Tokyo, Tokyo 153-8505, Japan.
10
Department of Physics, McGill University, Montréal, QC H3A 2T8, Canada; Graduate Program in Biophysics, Harvard University, Boston, MA 02115, USA.
11
Laboratory for Physical Biology, RIKEN Center for Developmental Biology (CDB), Chuo-ku Kobe, Hyogo 650-0047, Japan.
12
Cellular Informatics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan. Electronic address: sako@riken.jp.

Abstract

Cell polarity arises through the spatial segregation of polarity regulators. PAR proteins are polarity regulators that localize asymmetrically to two opposing cortical domains. However, it is unclear how the spatially segregated PAR proteins interact to maintain their mutually exclusive partitioning. Here, single-molecule detection analysis in Caenorhabditis elegans embryos reveals that cortical PAR-2 diffuses only short distances, and, as a result, most PAR-2 molecules associate and dissociate from the cortex without crossing into the opposing domain. Our results show that cortical PAR-2 asymmetry is maintained by the local exchange reactions that occur at the cortical-cytoplasmic boundary. Additionally, we demonstrate that local exchange reactions are sufficient to maintain cortical asymmetry in a parameter-free mathematical model. These findings suggest that anterior and posterior PAR proteins primarily interact through the cytoplasmic pool and not via cortical diffusion.

PMID:
27524610
DOI:
10.1016/j.celrep.2016.07.047
[Indexed for MEDLINE]
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