Probing the Conformational Dynamics of Affinity-Enhanced T Cell Receptor Variants upon Binding the Peptide-Bound Major Histocompatibility Complex by Hydrogen/Deuterium Exchange Mass Spectrometry.

Binding of the T cell receptor (TCR) to its cognate, peptide antigen-loaded major histocompatibility complex (pMHC) is a key interaction for triggering T cell activation and ultimately elimination of the target cell. Despite the importance of this interaction for cellular immunity, a comprehensive molecular understanding of TCR specificity and affinity is lacking. We conducted hydrogen/deuterium exchange mass spectrometry (HDX-MS) analyses of individual affinity-enhanced TCR variants and clinically relevant pMHC class I molecules (HLA-A*0201/NY-ESO-1157-165) to investigate the causality between increased binding affinity and conformational dynamics in TCR-pMHC complexes. Differential HDX-MS analyses of TCR variants revealed that mutations for affinity enhancement in TCR CDRs altered the conformational response of TCR to pMHC ligation. Improved pMHC binding affinity was in general observed to correlate with greater differences in HDX upon pMHC binding in modified TCR CDR loops, thereby providing new insights into the TCR-pMHC interaction. Furthermore, a specific point mutation in the ß-CDR3 loop of the NY-ESO-1 TCR associated with a substantial increase in binding affinity resulted in a substantial change in pMHC binding kinetics (i.e., very slow kon, revealed by the detection of EX1 HDX kinetics), thus providing experimental evidence for a slow induced-fit binding mode. We also examined the conformational impact of pMHC binding on an unrelated TRAV12-2 gene-encoded TCR directed against the immunodominant MART-126-35 cancer antigen restricted by HLA-A*0201. Our findings provide a molecular basis for the observed TRAV12-2 gene bias in natural CD8+ T cell-based immune responses against the MART-1 antigen, with potential implications for general ligand discrimination and TCR cross-reactivity processes.

The feasibility and efficacy of total laparoscopic radical cystectomy with intracorporeal Xing's orthotopic neobladder / 中华泌尿外科杂志

Objective To explore the feasibility and clinical effect of laparoscopic radical cystectomy with intracorporeal Xing's orthotopic neobladder.Methods Forty-one patients who underwent laparoscopic radical cystectomy with intracorporeal Xing's orthotopic neobladder from July 2013 to August 2019.There were 31 cases performed in Beijing Chaoyang hospital and 10 cases in National Cancer Center.Mean age was 59 (range 44-78) years,mean BMI was 25.3 (range 20.1-34.7) kg/m2,and mean CCI was 3 (range 2-6).No urethral stricture or urinary incontinence was found by preoperative examination.No distant metastasis was identified by bone scans,chest X-ray and sonography.Cystoscopy or TURBT was performed on all patients and biopsy was taken to confirm the diagnosis.Preoperative pathology showed 30 cases (73.2％) of MIBC,9 cases of NMIBC (22.0％) and 2 cases (4.9％) of in-situ cancer.Laparoscopic radical cystectomy and lymphadenectomy were performed under general anesthesia.Urinary diversion was completed in the peritoneal cavity,by intercepting the terminal ileum about 60 cm,and taking the proximal ileum 10 cm as input loop on the right side with proximal to distal way,and the middle 40 cm ileum was detubated.After u-shaped suture,the ileum was folded back and stitched into a sphere building a novd orthotopic neobladder with bilateral isoperistaltic afferent limbs.The prognosis of perioperative data and postoperative satisfaction regarding continence were analyzed,continence was defined as 0-1 pad/day.The 41 patients were divided into two groups to compare the difference in term of operation time and blood loss between the first 21 patients and the last 20 patients.Results Mean total operative time was 324.9 mins (range 210-480) mins,and mean estimated blood loss was 177.6(range 50-700) ml.There were significant statistical differences in term of total operation time,construction time and blood loss between the first 21 patients and the next 20 patients (P ＜ 0.05).Postoperative pathological results were urothelial carcinoma in 40 cases (2 in situ carcinoma) and small cell carcinoma in 1 case.Mean number of dissected lymph nodes was 19 (range 11-58),with 7 cases(17.1％)of positive lymph nodes,and 3 cases(7.3％) had positive surgical margin.At a mean follow up of 17.6 (range 2-64) months,36 patients (87.8％) survived,including 2 patients (4.9％) with metastasis and 1 patient (2.4％) with recurrence,and 5 cases (12.2％)died.All patients were able to urinate without catheterization.Thirty-seven patients (90.2％) were satisfied with voiding control during the daytime (0-1 urinal pad),and 29 patients (70.7％) were satisfied with voiding control at nighttime (0-1 urinal pad) by the follow-up 12 months after the operation.Conclusions Total laparoscopic radical cystectomy combined with Xing's orthotopic ileum neobladder is a simple method with fewer postoperative complications and a satisfactory continence rate.

The T-Cell Receptor Can Bind to the Peptide-Bound Major Histocompatibility Complex and Uncomplexed ß2-Microglobulin through Distinct Binding Sites.

T-Cell receptor (TCR)-mediated recognition of the peptide-bound major histocompatibility complex (pMHC) initiates an adaptive immune response against antigen-presenting target cells. The recognition events take place at the TCR-pMHC interface, and their effects on TCR conformation and dynamics are controversial. Here, we have measured the time-resolved hydrogen/deuterium exchange (HDX) of a soluble TCR in the presence and absence of its cognate pMHC by mass spectrometry to delineate the impact of pMHC binding on solution-phase structural dynamics in the TCR. Our results demonstrate that while TCR-pMHC complex formation significantly stabilizes distinct CDR loops of the TCR, it does not trigger structural changes in receptor segments remote from the binding interface. Intriguingly, our HDX measurements reveal that the TCR α-constant domain (C- and F-strand) directly interacts with the unbound MHC light chain, ß2-microglobulin (ß2m). Surface plasmon resonance measurements corroborated a binding event between TCR and ß2m with a dissociation constant of 167 ± 20 µM. We propose a model structure for the TCR-ß2m complex based on a refined protein-protein docking approach driven by HDX data and information from molecular dynamics simulations. Using a biological assay based on TCR gene-engineered primary human T cells, we did not observe a significant effect of ß2m on T-cell cytotoxicity, suggesting an alternate role for ß2m binding. Overall, we show that binding of ß2m to the TCR occurs in vitro and, as such, not only should be considered in structure-function studies of the TCR-pMHC complex but also could play a hitherto unidentified role in T-cell function in vivo.