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Thumkeo D, Katsura Y, Nishimura Y, Kanchanawong P, Tohyama K, Ishizaki T, Kitajima S, Takahashi C, Hirata T, Watanabe N, Krummel MF, Narumiya S. mDia1/3-dependent actin polymerization spatiotemporally controls LAT phosphorylation by Zap70 at the immune synapse. Sci Adv 2020; 6:eaay2432. [PMID: 31911947 PMCID: PMC6938706 DOI: 10.1126/sciadv.aay2432] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 10/31/2019] [Indexed: 05/06/2023]
Abstract
The mechanism by which the cytosolic protein Zap70 physically interacts with and phosphorylates its substrate, the transmembrane protein LAT, upon T cell receptor (TCR) stimulation remains largely obscure. In this study, we found that the pharmacological inhibition of formins, a major class of actin nucleators, suppressed LAT phosphorylation by Zap70, despite TCR stimulation-dependent phosphorylation of Zap70 remaining intact. High-resolution imaging and three-dimensional image reconstruction revealed that localization of phosphorylated Zap70 to the immune synapse (IS) and subsequent LAT phosphorylation are critically dependent on formin-mediated actin polymerization. Using knockout mice, we identify mDia1 and mDia3, which are highly expressed in T cells and which localize to the IS upon TCR activation, as the critical formins mediating this process. Our findings therefore describe previously unsuspected roles for mDia1 and mDia3 in the spatiotemporal control of Zap70-dependent LAT phosphorylation at the IS through regulation of filamentous actin, and underscore their physiological importance in TCR signaling.
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Affiliation(s)
- D. Thumkeo
- Department of Drug Discovery Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Pathology, University of California, San Francisco, San Francisco, CA, USA
- Corresponding author. (D.T.); (S.N.)
| | - Y. Katsura
- Department of Drug Discovery Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Pharmacology, Kyoto University Faculty of Medicine, Kyoto, Japan
| | - Y. Nishimura
- Mechanobiology Institute, National University of Singapore, Singapore, Republic of Singapore
| | - P. Kanchanawong
- Mechanobiology Institute, National University of Singapore, Singapore, Republic of Singapore
- Department of Biomedical Engineering, National University of Singapore, Singapore, Republic of Singapore
| | - K. Tohyama
- Department of Drug Discovery Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Department of Pharmacology, Kyoto University Faculty of Medicine, Kyoto, Japan
| | - T. Ishizaki
- Department of Pharmacology, Oita University Graduate School of Medicine, Oita, Japan
| | - S. Kitajima
- Division of Oncology and Molecular Biology, Cancer Research Institute, Kanazawa University, Ishikawa, Japan
| | - C. Takahashi
- Division of Oncology and Molecular Biology, Cancer Research Institute, Kanazawa University, Ishikawa, Japan
| | - T. Hirata
- Department of Fundamental Biosciences, Shiga University of Medical Science, Shiga, Japan
| | - N. Watanabe
- Department of Pharmacology, Kyoto University Faculty of Medicine, Kyoto, Japan
- Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Kyoto, Japan
| | - M. F. Krummel
- Department of Pathology, University of California, San Francisco, San Francisco, CA, USA
| | - S. Narumiya
- Department of Drug Discovery Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
- Corresponding author. (D.T.); (S.N.)
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André G, Kanchanawong P, Palma R, Cho H, Deng X, Irwin D, Himmel ME, Wilson DB, Brady JW. Computational and experimental studies of the catalytic mechanism of Thermobifida fusca cellulase Cel6A (E2). Protein Eng Des Sel 2003; 16:125-34. [PMID: 12676981 DOI: 10.1093/proeng/gzg017] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mutagenesis experiments suggest that Asp79 in cellulase Cel6A (E2) from Thermobifida fusca has a catalytic role, in spite of the fact that this residue is more than 13 A from the scissile bond in models of the enzyme-substrate complex built upon the crystal structure of the protein. This suggests that there is a substantial conformational shift in the protein upon substrate binding. Molecular mechanics simulations were used to investigate possible alternate conformations of the protein bound to a tetrasaccharide substrate, primarily involving shifts of the loop containing Asp79, and to model the role of water in the active site complex for both the native conformation and alternative low-energy conformations. Several alternative conformations of reasonable energy have been identified, including one in which the overall energy of the enzyme-substrate complex in solution is lower than that of the conformation in the crystal structure. This conformation was found to be stable in molecular dynamics simulations with a cellotetraose substrate and water. In simulations of the substrate complexed with the native protein conformation, the sugar ring in the -1 binding site was observed to make a spontaneous transition from the (4)C(1) conformation to a twist-boat conformer, consistent with generally accepted glycosidase mechanisms. Also, from these simulations Tyr73 and Arg78 were found to have important roles in the active site. Based on the results of these various MD simulations, a new catalytic mechanism is proposed. Using this mechanism, predictions about the effects of changes in Arg78 were made which were confirmed by site-directed mutagenesis.
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Affiliation(s)
- G André
- Department of Food Science, Stocking Hall, Cornell University, Ithaca, NY 14853, USA
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