© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ditlev, J. A., Vega, A. R., Köster, D. V., Su, X., Tani, T., Lakoduk, A. M., Vale, R. D., Mayor, S., Jaqaman, K., & Rosen, M. K. A composition-dependent molecular clutch between T cell signaling condensates and actin. Elife, 8, (2019): e42695, doi:10.7554/eLife.42695.
During T cell activation, biomolecular condensates form at the immunological synapse (IS) through multivalency-driven phase separation of LAT, Grb2, Sos1, SLP-76, Nck, and WASP. These condensates move radially at the IS, traversing successive radially-oriented and concentric actin networks. To understand this movement, we biochemically reconstituted LAT condensates with actomyosin filaments. We found that basic regions of Nck and N-WASP/WASP promote association and co-movement of LAT condensates with actin, indicating conversion of weak individual affinities to high collective affinity upon phase separation. Condensates lacking these components were propelled differently, without strong actin adhesion. In cells, LAT condensates lost Nck as radial actin transitioned to the concentric network, and engineered condensates constitutively binding actin moved aberrantly. Our data show that Nck and WASP form a clutch between LAT condensates and actin in vitro and suggest that compositional changes may enable condensate movement by distinct actin networks in different regions of the IS.
We thank L Rice, J Hammer III, and our fellow HCIA Summer Institute scientists for stimulating discussions about this study. This work was supported by a Howard Hughes Medical Institute Collaborative Innovation Award, the Welch Foundation (I-1544 to MKR), a JC Bose Fellowship from the Department of Science and Technology, government of India (SM), a Margadarshi Fellowship from the Wellcome Trust – Department of Biotechnology, India Alliance (IA/M/15/1/502018 to SM), NIH (R01 GM100160 to TT) (R35 GM119619 to KJ), a CPRIT Recruitment Award (R1216 to KJ), and the UT Southwestern Endowed Scholars Program (KJ). Research in the Rosen lab is supported by the Howard Hughes Medical Institute. JAD was supported by a National Research Service Award F32 (F32 DK101188). ARV was supported by a CPRIT Training Grant (RP140110, PI: Michael White). DVK was supported by fellowships of the AXA Research Fund and the National Centre for Biological Sciences, Tata Institute for Fundamental Research. XS was supported by a Cancer Research Institute Irvington postdoctoral fellowship.
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