In type 1 diabetes (T1D), proinsulin is a major autoantigen and the insulin B:9–23 peptide contains epitopes for CD4 T cells in both mice and humans. This peptide requires C-terminal mutations for uniform binding in the proper position within the mouse IAg7 or human DQ8 MHCII peptide grooves and for strong CD4 T cell stimulation. Here we present structures showing how these mutations control CD4 T cell receptor (TCR) binding to these MHCII-peptide complexes. Our data reveal striking similarities between mouse and human CD4 TCRs in their interactions with these ligands. We also show how fusions between fragments of B:9–23 and of proinsulin C-peptide create chimeric peptides with activities as strong or stronger than the mutated insulin peptides. We propose transpeptidation in the lysosome as a mechanism that could accomplish these fusions in vivo, similar to the creation fused peptide epitopes for MHCI presentation shown to occur by transpeptidation in the proteasome. Were this mechanism unique to the pancreas and absent in the thymus, it could provide an explanation for how diabetogenic T cells escape negative selection during development but find their modified target antigens in the pancreas to cause T1D.

Ca2+-binding human S100A1 protein is a type of S100 protein. S100A1 is a significant mediator during inflammation when Ca2+ binds to its EF-hand motifs. Receptors for advanced glycation end products (RAGE) correspond to 5 domains: the cytoplasmic, transmembrane, C2, C1, and V domains. The V domain of RAGE is one of the most important target proteins for S100A1. It binds to the hydrophobic surface and triggers signaling transduction cascades that induce cell growth, cell proliferation, and tumorigenesis. We used nuclear magnetic resonance (NMR) spectroscopy to characterize the interaction between S100A1 and the RAGE V domain. We found that S100B could interact with S100A1 via NMR 1H-15N HSQC titrations. We used the HADDOCK program to generate the following two binary complexes based on the NMR titration results: S100A1-RAGE V domain and S100A1-S100B. After overlapping these two complex structures, we found that S100B plays a crucial role in blocking the interaction site between RAGE V domain and S100A1. A cell proliferation assay WST-1 also supported our results. This report could potentially be useful for new protein development for cancer treatment.

Background Recanalization of cerebral large‐vessel occlusions (LVOs) by intravenous thrombolysis is infrequent but has been relatively unexplored with ultraearly treatment. We evaluated prehospital treatment with tissue plasminogen activator (tPA) in a mobile stroke unit to explore the recanalization rate in patients with LVOs and its effect on early clinical improvement and long‐term disability. Methods Prospectively collected data were analyzed from Houston mobile stroke unit patients who were treated with tPA and had LVOs identified by either hyperdense arteries on computed tomography or arterial occlusion on computed tomography angiography while on board the mobile stroke unit. The primary outcome was immediate recanalization (IRC), categorized as resolution of LVO on repeat vascular imaging in the emergency department (ED) or on emergent angiography. The secondary outcome was change in National Institutes of Health Stroke Scale from baseline and modified Rankin score at 90 days. Results Sixty‐nine patients with anterior or posterior circulation LVOs were enrolled; the median time from last known normal to tPA bolus was 64.0 minutes (interquartile range, 52.0–89.0). Nineteen patients (28%) had IRC, with 11 based on computed tomography angiography on ED arrival and 8 based on first run of emergent angiography. Median time from tPA bolus to documentation of IRC was 61.0 minutes (interquartile range, 42.0–111.0). IRC was associated with improvement in median National Institutes of Health Stroke Scale from baseline (17.0 [14.0–22.0]) to ED arrival (10.0 [5.5–16.5]) and to 24 hours (4.0 [0.5–10.5]). Of the non‐IRC patients, 41 had recanalization after endovascular thrombectomy and 9 did not receive recanalization. The IRC group, earlier last known normal to tPA bolus, greater baseline National Institutes of Health Stroke Scale, and M1 and M2 middle cerebral artery occlusion locations were independently associated with greater improvement in National Institutes of Health Stroke Scale from baseline to ED arrival. The 90‐day modified Rankin score distribution was best in the IRC group, followed by the delayed recanalization group, and both had significantly less disability than the no recanalization group ( P =0.002). Conclusions Recanalization by ED arrival occured in 28% of patients with LVO who received tPA treatment in a mobile stroke unit and results in early clinical improvement and less disability at 90 days.

Motivation Quaternary structure determination for transmembrane/soluble proteins requires a reliable computational protocol that leverages observed distance restraints and/or cyclic symmetry (Cn symmetry) found in most homo-oligomeric transmembrane proteins. Results We survey 118 X-ray crystallographically solved structures of homo-oligomeric transmembrane proteins (HoTPs) and find that ∼97% are Cn symmetric. Given the prevalence of Cn symmetric HoTPs and the benefits of incorporating geometry restraints in aiding quaternary structure determination, we introduce two new filters, the distance-restraints (DR) and the Symmetry-Imposed Packing (SIP) filters. SIP relies on a new method that can rebuild the closest ideal Cn symmetric complex from docking poses containing a homo-dimer without prior knowledge of the number (n) of monomers. Using only the geometrical filter, SIP, near-native poses of 7 HoTPs in their monomeric states can be correctly identified in the top-10 for 71% of all cases, or 29% among 31 HoTP structures obtained through homology modeling, while ZDOCK alone returns 14 and 3%, respectively. When the n is given, the optional n-mer filter is applied with SIP and returns the near-native poses for 76% of the test set within the top-10, outperforming M-ZDOCK’s 55% and Sam’s 47%. While applying only SIP to three HoTPs that comes with distance restraints, we found the near-native poses were ranked 1st, 1st and 10th among 54 000 possible decoys. The results are further improved to 1st, 1st and 3rd when both DR and SIP filters are used. By applying only DR, a soluble system with distance restraints is recovered at the 1st-ranked pose. Availability and implementation https://github.com/capslockwizard/drsip. Supplementary information Supplementary data are available at Bioinformatics online.