Structural dynamics and signal conduction of the inner segment of the TCR complex.

On March 24, cell Research, an international academic journal, published online the latest research results by Xu Wei, a researcher at the Institute of Biochemistry and Cell Biology of the Shanghai Institute of Life Sciences of the Chinese Academy of Sciences, in collaboration with Cao Yi, a professor at Nanjing University.
the study reveals the structural dynamics of the inner cell segments of TCR complexes and provides a structural basis for TCR complexes to conduct different stimulus signals.
in the accessible immune system, T cells are able to remove pathogens and infected lesions.
T-cell antigen receptor (T-cell receptor, TCR) is the primary receptor for T-cell recognition of "self" and "non-I" substances and can be combined with a specific peptide-MHC complex (pMHC) on the surface of antigen delivery cells (APC).
ab TCR complex consists of TCRab heterogeneity djubo, CD3eg, CD3ed, and CD3zz.
TCR is combined with pMHC, it causes phosphorylation of tyrosine residues in the CD3 molecule in the TCR complex in the intracellumatic immune tyrosine sequence (immunoreceptor tyrosine-activation motifs, ITAMs), and then turns on the downstream signal.
this process can be divided into two stages, the first stage is the TCR from the structure off to the structure open conversion, the second stage is opened by the TCR structure to THETAMs phosphate activation state.
Previous work has shown that the intracerviral segments of CD3e and CD3z contain alkaline amino acid abunding zones (Basic Rich Sequences, BRS, positively charged), which interact with the lining of cell membranes rich in acidic phospholipids (negatively charged) through charge interaction, so that their ITATM is protected from phospholipids and is protected from downstream kinase phosphate (Xu et al.Cell, 2008).
Then they found that, in the early stages of T-cellization, the internal flow of Ca2 plus could help the intracertic segments of the non-antigen-binding TCR complex to be removed from the cell membrane by neutralizing the negative charge of acidic phospholipids on the inside of the cell membrane, which would phosphate and amplify the initial TCR signal (Shi et al., Nature, 2013).
these studies demonstrate the important regulatory role of cell membrane phospholipids in TCR signal transduction.
addition, the TCR complex produces different downstream signals when stimulated by different antigens, causing different T-cell immune responses, but the structural basis for this functional diversity is still not clear.
In order to explore the scientific problem, under the joint guidance of Xu Wei and Cao Yi, postdoctoral student Guo Xingdong, doctoral student Yu Chengsong, associate researcher Li Hua, doctoral student Huang Wenmao and others used a variety of technical means to analyze the structural dynamics of the binding of the cell membrane phospholipids in the cell cell cells of the TCR complex.
, they used a single-molecule atomic force microscope (AFM) to detect the mesothystological characteristics of the interaction between the CD3e intrinsic segment (CD3eCD) and the inner cell membrane.
study found that CD3eCD produces a specific force spectrum during the dissosis of the cell membrane, and in addition to single-peak events, there is a certain percentage of Twin Peaks events, suggesting that there are likely to be two points in CD3eCD that bind to the cell membrane.
the calculations, the researchers found that in addition to the previously identified BRS region, there was a weaker secondary membrane binding site in the proline Rich Collection Area (PRS) and the first half of ITAM.
to test this hypothesy, they then used an mron Magnetic (NMR), combined with the solution PRE resonant TEMPOL, to determine the dynamic characteristics of the composition of CD3eCD, which binds to phospholipids.
results show that the amino acid residue PRE effect in the subfilm binding bit area is relatively low, which further verifies the existence of the secondary membrane binding bit.
the alkaline and hydrophobic residue mutations in the binding point were found that the first half of CD3eCD was still combined with phospholipids and the second half was removed from phospholipids.
Finally, using the full-reflection fluorescence microscope (TIRFM) and fluorescent resonance energy transfer (FRET) technology, they detected the degree to which CD3eCD was dissociate from the cell membrane under different intensity antigen stimulation, and found that cd3eCD did dissociate from the cell membrane at different intensity of antigen stimulation.
suggests that antigens of different strengths can indeed make CD3eCDs in different morphological states.
these experiments show that the dynamic characteristics of the structure of the TCR complex on which membrane lipids depend are likely to be the structural basis for the transmission of different stimulus signals by the TCR complex.
The study was greatly assisted by Liu Wanli, Professor of Tsinghua University, Huang Chaolan, Researcher of the Institute of Biochemistry and Cells of the Shanghai Academy of Health Sciences, Tang Wei, Researcher of Wuhan Institute of Physics and Mathematics of the Chinese Academy of Sciences, Wang Hongda, Researcher of the Institute of Applied Chemistry of the Dean of Chinese Academy of Sciences, and Zhang Xiaohui, Professor of Lehigh University of the United States, and supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Chinese Academy of Sciences and the Shanghai Science and Technology Commission.
The research work has also been supported by the National Protein Science Facility (Shanghai) Nuclear Magnetic Resonance System, Mass Spectrometry System, Composite Laser Microscope System, Molecular Imaging System, Biochemistry and Cell Analysis Technology Platform, Molecular Biology Technology Platform, and Animal Experimental Technology Platform.
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