Effect of a Lactococcus lactis culture supernatant on diarrhea and performance parameters of piglets in the post-weaning period and on expression of the faeG gene in vitro.

Objectives: To evaluate the effects of a cell-free supernatant from Lactococcus lactis (CFSM) on performance and diarrhearelated parameters and the presence of F4+ enterotoxigenic E. coli (ETEC) in piglets during post-weaning, and to evaluate the in vitro effect of the CFSM on faeG gene expression in an E. coli F4+. Animals and procedure: In 3 trials with 90 piglets per trial, pigs were assigned to receive a placebo or 1 of 2 CFSM treatments and observed for diarrhea and performance. Fecal swabs were taken to determine the presence of ETEC. Quantitative RT-PCR was used to assess faeG gene expression in E. coli 21259 after treatment with CFSM at 50 mg/mL. Results: The CFSM administered for 14 d at a dose of 24 mg/kg BW (2X) reduced diarrhea-related parameters compared to the placebo. Quantitative RT-PCR showed that, in E. coli 21259 treated with CFSM at 50 mg/mL, expression of the faeG gene was significantly repressed (P < 0.0001) relative to that in the untreated control. Conclusion: The evaluated CFSM reduced the frequency and prevalence of diarrhea in a field situation. The in vitro treatment had an inhibitory effect on the expression of the faeG gene in F4+ E. coli 21259.

Effet d'un surnageant de culture de Lactococcus lactis sur la diarrhée et les paramètres de performance des porcelets en période post-sevrage et sur l'expression du gène faeG in vitro. Objectifs: Évaluer les effets d'un surnageant acellulaire de Lactococcus lactis (CFSM) sur les paramètres de performance et de diarrhée et la présence d'E. coli entérotoxinogène F4+ (ETEC) chez les porcelets en post-sevrage, et évaluer l'effet in vitro du CFSM sur l'expression du gène faeG dans un E. coli F4+. Animaux et procédure: Dans 3 essais portant sur 90 porcelets par essai, les porcs ont reçu un placebo ou 1 des 2 traitements CFSM et ont été observés pour détecter la diarrhée et leurs performances. Des prélèvements fécaux ont été effectués pour déterminer la présence d'ETEC. La RT-PCR quantitative a été utilisée pour évaluer l'expression du gène faeG dans E. coli 21259 après traitement avec CFSM à 50 mg/mL. Résultats: Le CFSM administré pendant 14 jours à une dose de 24 mg/kg de poids corporel (2X) a réduit les paramètres liés à la diarrhée par rapport au placebo. La RT-PCR quantitative a montré que, chez E. coli 21259 traité avec CFSM à 50 mg/mL, l'expression du gène faeG était significativement réprimée (P < 0,0001) par rapport à celle du témoin non traité. Conclusion: Le CFSM évalué a réduit la fréquence et la prévalence de la diarrhée sur le terrain. Le traitement in vitro a eu un effet inhibiteur sur l'expression du gène faeG chez F4+ E. coli 21259.(Traduit par Dr Serge Messier).

Conformationally Restricted Glycopeptide Backbone Inhibits Gas-Phase H/D Scrambling between Glycan and Peptide Moieties.

Protein glycosylation is a common post-translational modification on extracellular proteins. The conformational dynamics of several glycoproteins have been characterized by hydrogen/deuterium exchange mass spectrometry (HDX-MS). However, it is, in most cases, not possible to extract information about glycan conformation and dynamics due to the general difficulty of separating the deuterium content of the glycan from that of the peptide (in particular, for O-linked glycans). Here, we investigate whether the fragmentation of protonated glycopeptides by collision-induced dissociation (CID) can be used to determine the solution-specific deuterium content of the glycan. Central to this concept is that glycopeptides can undergo a facile loss of glycans upon CID, thereby allowing for the determination of their masses. However, an essential prerequisite is that hydrogen and deuterium (H/D) scrambling can be kept in check. Therefore, we have measured the degree of scrambling upon glycosidic bond cleavage in glycopeptides that differ in the conformational flexibility of their backbone and glycosylation pattern. Our results show that complete scrambling precedes the glycosidic bond cleavage in normal glycopeptides derived from a glycoprotein; i.e., all labile hydrogens have undergone positional randomization prior to loss of the glycan. In contrast, the glycosidic bond cleavage occurs without any scrambling in the glycopeptide antibiotic vancomycin, reflecting that the glycan cannot interact with the peptide moiety due to a conformationally restricted backbone as revealed by molecular dynamics simulations. Scrambling is also inhibited, albeit to a lesser degree, in the conformationally restricted glycopeptides ristocetin and its pseudoaglycone, demonstrating that scrambling depends on an intricate interplay between the flexibility and proximity of the glycan and the peptide backbone.

Developmental origin underlies evolutionary rate variation across the placental skull.

The placental skull has evolved into myriad forms, from longirostrine whales to globular primates, and with a diverse array of appendages from antlers to tusks. This disparity has recently been studied from the perspective of the whole skull, but the skull is composed of numerous elements that have distinct developmental origins and varied functions. Here, we assess the evolution of the skull's major skeletal elements, decomposed into 17 individual regions. Using a high-dimensional morphometric approach for a dataset of 322 living and extinct eutherians (placental mammals and their stem relatives), we quantify patterns of variation and estimate phylogenetic, allometric and ecological signal across the skull. We further compare rates of evolution across ecological categories and ordinal-level clades and reconstruct rates of evolution along lineages and through time to assess whether developmental origin or function discriminate the evolutionary trajectories of individual cranial elements. Our results demonstrate distinct macroevolutionary patterns across cranial elements that reflect the ecological adaptations of major clades. Elements derived from neural crest show the fastest rates of evolution, but ecological signal is equally pronounced in bones derived from neural crest and paraxial mesoderm, suggesting that developmental origin may influence evolutionary tempo, but not capacity for specialisation. This article is part of the theme issue 'The mammalian skull: development, structure and function'.

Inverse effects of APOC2 and ANGPTL4 on the conformational dynamics of lid-anchoring structures in lipoprotein lipase.

The lipolytic processing of triglyceride-rich lipoproteins (TRLs) by lipoprotein lipase (LPL) is crucial for the delivery of dietary lipids to the heart, skeletal muscle, and adipose tissue. The processing of TRLs by LPL is regulated in a tissue-specific manner by a complex interplay between activators and inhibitors. Angiopoietin-like protein 4 (ANGPTL4) inhibits LPL by reducing its thermal stability and catalyzing the irreversible unfolding of LPL's α/ß-hydrolase domain. We previously mapped the ANGPTL4 binding site on LPL and defined the downstream unfolding events resulting in LPL inactivation. The binding of LPL to glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 protects against LPL unfolding. The binding site on LPL for an activating cofactor, apolipoprotein C2 (APOC2), and the mechanisms by which APOC2 activates LPL have been unclear and controversial. Using hydrogen-deuterium exchange/mass spectrometry, we now show that APOC2's C-terminal α-helix binds to regions of LPL surrounding the catalytic pocket. Remarkably, APOC2's binding site on LPL overlaps with that for ANGPTL4, but their effects on LPL conformation are distinct. In contrast to ANGPTL4, APOC2 increases the thermal stability of LPL and protects it from unfolding. Also, the regions of LPL that anchor the lid are stabilized by APOC2 but destabilized by ANGPTL4, providing a plausible explanation for why APOC2 is an activator of LPL, while ANGPTL4 is an inhibitor. Our studies provide fresh insights into the molecular mechanisms by which APOC2 binds and stabilizes LPL-and properties that we suspect are relevant to the conformational gating of LPL's active site.

Opioid prescribing practices and patient-requested refill patterns following laparoscopic inguinal hernia repair.

PURPOSE: Excessive post-operative opioid prescribing has led to efforts to match prescriptions with patient need after surgery. We investigated opioid prescribing practices, rate of patient-requested opioid refills, and associated factors after laparoscopic inguinal hernia repair (LIHR). METHODS: LIHRs at a single institution from 3/2019 to 3/2021 were queried from the Abdominal Core Health Quality Collaborative for demographics, perioperative details, and patient-reported opioid usage. Opioid prescriptions at discharge and opioid refills were extracted from the medical record. Univariate and multivariable regression were used to identify factors associated with opioid refills within 30-days of surgery. RESULTS: Four hundred and ninety LIHR patients were analyzed. The median number of opioid tablets prescribed was 12 [interquartile range (IQR) 10-15], and 4% requested a refill. On univariate analysis, patients who requested refills were younger [55 years (IQR 37-61) vs. 62 years (IQR 36.8-61), p = 0.012], more likely to have undergone transabdominal preperitoneal repair (75% vs. 26.4%, p < 0.001), have a scrotal component (30% vs. 11%, p = 0.022), and have permanent tacks used (80% vs. 49.4%, p = 0.014). There was a 12% increase in the odds of opioid refill for every 1 tablet of oxycodone prescribed at discharge (95% CI for OR 1.04-1.21, p = 0.003) after controlling for age and surgery type. Patient-reported opioid use was available for 289 (59%) patients. Post-operatively, 67% of patients used ≤ 4 opioid tablets, and 87% used no more than 10 opioid tablets. CONCLUSION: Most patients use fewer opioid tablets than prescribed. Requests for opioid refills are rare following LIHR (4%) and associated with higher opioid prescribing.

Ileus rate after abdominal wall reconstruction: a retrospective analysis of two clinical trials.

PURPOSE: Postoperative ileus (POI) is the paralytic disruption of gastrointestinal motility, a common complication following abdominal wall reconstruction that often leads to increased patient morbidity and length of stay (LOS). We reviewed two randomized clinical trials to determine POI rates, predictive factors, LOS, and associated cost. METHODS: Two randomized trials were performed from 2017-2019 with all patients receiving elective open abdominal wall reconstruction with retromuscular mesh. Using multivariate logistic regression, we performed a retrospective analysis including demographics and operative details from patients at a single site to determine predictive factors for POI. All medical costs encompassing surgery and the 30-day postoperative period were compared between ileus and non-ileus groups. RESULTS: Four hundred and seventy patients were reviewed with a POI rate of 13.0% (N = 61). There were no differences in age, body mass index (BMI), history of abdominal surgery, or comorbidities between patients with and without POI. Logistic regression showed no association with POI and age, BMI, hernia width, or operative time lasting longer than 4 h. Median LOS was 8 days for patients with POI compared to five for those without (p < 0.001). Relative median 30-day costs were 1.19 in patients with ileus and 1.0 in those without (p < 0.001). CONCLUSION: We identified a 13% rate of POI in patients undergoing open abdominal wall reconstruction with mesh with no clearly identified predisposing factors. This resulted in a 3 days increase in median LOS and 19% additional costs. Further efforts should be devoted to investigating interventions that may reduce postoperative ileus after abdominal wall reconstruction.

EGCG has Dual and Opposing Effects on the N-terminal Region of Self-associating α-synuclein Oligomers.

Oligomers of the protein α-synuclein (α-syn) are thought to be a major toxic species in Parkinson's disease, particularly through their ability to permeabilize cell membranes. The green tea polyphenol epigallocatechin gallate (EGCG) has been found to reduce this ability. We have analyzed α-syn oligomer dynamics and interconversion by H/D exchange monitored by mass spectrometry (HDX-MS). Our results show that the two oligomers OI and OII co-exist in equilibrium; OI is a multimer of OII and its dissociation can be followed by HDX-MS by virtue of the correlated exchange of the N-terminal region. Urea destabilizes the α-syn oligomers, dissociating OI to OII and monomers. Oligomers exposed to EGCG undergo Met oxidation. Intriguingly, EGCG induces an oxidation-dependent effect on the structure of the N-terminal region. For the non-oxidized N-terminal region, EGCG increases the stability of the folded structure as measured by a higher level of protection against H/D exchange. In contrast, protection is clearly abrogated in the Met oxidized N-terminal region. Having a non-oxidized and disordered N-terminal region is known to be essential for efficient membrane binding. Therefore, our results suggest that the combined effect of a structural stabilization of the non-oxidized N-terminal region and the presence of a disordered oxidized N-terminal region renders the oligomers less cytotoxic by decreasing the ability of the N-terminal region to bind to cell membranes and facilitate their permeabilization.

Attenuated evolution of mammals through the Cenozoic.

The Cenozoic diversification of placental mammals is the archetypal adaptive radiation. Yet, discrepancies between molecular divergence estimates and the fossil record fuel ongoing debate around the timing, tempo, and drivers of this radiation. Analysis of a three-dimensional skull dataset for living and extinct placental mammals demonstrates that evolutionary rates peak early and attenuate quickly. This long-term decline in tempo is punctuated by bursts of innovation that decreased in amplitude over the past 66 million years. Social, precocial, aquatic, and herbivorous species evolve fastest, especially whales, elephants, sirenians, and extinct ungulates. Slow rates in rodents and bats indicate dissociation of taxonomic and morphological diversification. Frustratingly, highly similar ancestral shape estimates for placental mammal superorders suggest that their earliest representatives may continue to elude unequivocal identification.

Structural Basis for Dityrosine-Mediated Inhibition of α-Synuclein Fibrillization.

α-Synuclein (α-Syn) is an intrinsically disordered protein which self-assembles into highly organized ß-sheet structures that accumulate in plaques in brains of Parkinson's disease patients. Oxidative stress influences α-Syn structure and self-assembly; however, the basis for this remains unclear. Here we characterize the chemical and physical effects of mild oxidation on monomeric α-Syn and its aggregation. Using a combination of biophysical methods, small-angle X-ray scattering, and native ion mobility mass spectrometry, we find that oxidation leads to formation of intramolecular dityrosine cross-linkages and a compaction of the α-Syn monomer by a factor of √2. Oxidation-induced compaction is shown to inhibit ordered self-assembly and amyloid formation by steric hindrance, suggesting an important role of mild oxidation in preventing amyloid formation.

Stopping molecular rotation using coherent ultra-low-energy magnetic manipulations.

Rotational motion lies at the heart of intermolecular, molecule-surface chemistry and cold molecule science, motivating the development of methods to excite and de-excite rotations. Existing schemes involve perturbing the molecules with photons or electrons which supply or remove energy comparable to the rotational level spacing. Here, we study the possibility of de-exciting the molecular rotation of a D2 molecule, from J = 2 to the non-rotating J = 0 state, without using an energy-matched perturbation. We show that passing the beam through a 1 m long magnetic field, which splits the rotational projection states by only 10-12 eV, can change the probability that a molecule-surface collision will stop a molecule from rotating and lose rotational energy which is 9 orders larger than that of the magnetic manipulation. Calculations confirm that different rotational orientations have different de-excitation probabilities but underestimate rotational flips (∆mJ[Formula: see text]0), highlighting the importance of the results as a sensitive benchmark for further developing theoretical models of molecule-surface interactions.

The effects of prenatal nicotine and THC E-cigarette exposure on motor development in rats.

RATIONALE: In the USA, nicotine and cannabis are the most common licit and illicit drugs used among pregnant women. Importantly, nicotine and cannabis are now being combined for consumption via e-cigarettes, an increasingly popular delivery device. Both nicotine and tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, cross the placenta barrier. However, the consequences of prenatal cannabis use are not well understood, and less is known about potential combination effects when consumed with nicotine, especially via e-cigarettes. OBJECTIVE: The present study used a rodent model to examine how prenatal e-cigarette exposure to nicotine, THC, and the combination impacts motor development among offspring. METHODS: Pregnant Sprague-Dawley rats were exposed to nicotine (36 mg/mL), THC (100 mg/mL), the combination, or vehicle via e-cigarette inhalation from gestational days (GD) 5-20. One sex pair per litter was tested on an early sensorimotor development task (postnatal days [PD] 12-20) and a parallel bar motor coordination task (PD 30-32). RESULTS: Combined prenatal exposure to nicotine and THC delayed sensorimotor development, even though neither drug produced impairments on their own. In contrast, prenatal exposure to either nicotine or THC impaired motor coordination, whereas combined exposure exacerbated these effects, particularly among females. CONCLUSIONS: These data illustrate that prenatal exposure to either nicotine or THC may alter motor development, and that the combination may produce more severe effects. These findings have important implications for pregnant women as we better understand the teratogenic effects of these drugs consumed via e-cigarettes.

The changing face of SDS denaturation: Complexes of Thermomyces lanuginosus lipase with SDS at pH 4.0, 6.0 and 8.0.

HYPOTHESIS: Lipases are widely used in the detergent industry and must withstand harsh conditions involving both anionic and zwitterionic surfactants at alkaline pH. Thermomyces lanuginosus lipase (TlL) is often used and stays active at high concentrations of the anionic surfactant sodium dodecyl sulfate (SDS) at pH 8.0, but is sensitive to SDS at pH 6.0 and below. We propose that enhanced stability at pH 8.0 results from a structurally distinct complex formation with SDS. EXPERIMENTS: We use small-angle X-ray scattering (SAXS) to elucidate structures of TlL:SDS at pH 4.0, 6.0, and 8.0 and further investigate the complexes at pH 8.0 using hydrogen/deuterium exchange mass spectrometry (HDX-MS). FINDINGS: At pH 4.0, large dense aggregates are formed at low [SDS], which become gradually less dense at higher [SDS], resulting in a core-shell structure. At pH 6.0, SDS induces a TlL dimer and forms a hemi-micelle along the side of the dimer. At higher [SDS], TlL adopts a core-shell structure. At pH 8.0, TlL forms a dimer with a SDS hemi-micelle but avoids a core-shell structure and maintains activity. Three helices are identified as SDS anchor points. This study provides important structural insight into the stability of TlL towards SDS under alkaline conditions.

Comparing rates of bowel injury for laparoscopic and robotic ventral hernia repair: a retrospective analysis of the abdominal core health quality collaborative.

PURPOSE: Bowel injury during laparoscopic and robotic ventral hernia repair is a rare but potentially serious complication. We sought to compare bowel injury rates during minimally invasive approaches to ventral hernia repair using a national hernia registry. METHODS: Patients undergoing elective laparoscopic and robotic ventral hernia repair (including cases converted-to-open) between 2013 and 2021 were retrospectively identified in the Abdominal Core Health Quality Collaborative registry. The primary outcome was bowel injury, which included partial- and full-thickness injuries and re-operations for missed enterotomies. Statistical analysis was performed using multivariate logistic regression. RESULTS: Overall, 10,660 patients were included (4116 laparoscopic, 6544 robotic). The laparoscopic group included more incisional hernias (68% vs 62%, p < 0.001) and similar rates of recurrent hernias (23% vs 22%, p = 0.26). A total of 109 bowel injuries were identified, with more occurring in the laparoscopic group (55 [1.3%] laparoscopic vs. 54 [0.8%] robotic; p = 0.01). Specifically, there were more full-thickness and missed enterotomies in the laparoscopic group (29 laparoscopic vs. 20 robotic; p = 0.012). Bowel injury resulted in higher rates of wound morbidity and major post-operative complications including sepsis, re-admission, and re-operation. Following adjustment for recurrent and incisional hernias, prior mesh, patient age, and hernia width, bowel injury during laparoscopic repair remained significantly more likely than bowel injury during robotic repair (OR 1.669 [95% C.I.: 1.141-2.440]; p = 0.008). CONCLUSION: In a large registry, laparoscopic ventral hernia repair is associated with an increased risk of bowel injury compared to repairs utilizing the robotic platform. Knowing the limitations of retrospective research, large national registries are well suited to explore rare outcomes which cannot be feasibly assessed with randomized controlled trials.

Lipid Peroxidation Products HNE and ONE Promote and Stabilize Alpha-Synuclein Oligomers by Chemical Modifications.

The aggregation of α-synuclein (αSN) and increased oxidative stress leading to lipid peroxidation are pathological characteristics of Parkinson's disease (PD). Here, we report that aggregation of αSN in the presence of lipid peroxidation products 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) increases the stability and the yield of αSN oligomers (αSO). Further, we show that ONE is more efficient than HNE at inducing αSO. In addition, we demonstrate that the two αSO differ in both size and shape. ONE-αSO are smaller in size than HNE-αSO, except when they are formed at a high molar excess of aldehyde. In both monomeric and oligomeric αSN, His50 is the main target of HNE modification, and HNE-induced oligomerization is severely retarded in the mutant His50Ala αSN. In contrast, ONE-induced aggregation of His50Ala αSN occurs readily, demonstrating the different pathways for inducing αSN aggregation by HNE and ONE. Our results show different morphologies of the HNE-treated and ONE-treated αSO and different roles of His50 in their modification of αSN, but we also observe structural similarities between these αSO and the non-treated αSO, e.g., flexible C-terminus, a folded core composed of the N-terminal and NAC region. Furthermore, HNE-αSO show a similar deuterium uptake as a previously characterized oligomer formed by non-treated αSO, suggesting that the backbone conformational dynamics of their folded cores resemble one another.

Outcomes of redo-transversus abdominis release for abdominal wall reconstruction.

BACKGROUND: Transversus abdominis release (TAR) is increasingly used to address complex ventral hernias; consequently, associated complications are seen more frequently. Our hernia center has a growing experience with redo-transversus abdominis release (redo-TAR) to address large, complex hernia recurrences after failed TAR. Here, we describe our outcomes after abdominal wall reconstruction with redo-TAR. STUDY DESIGN: Adults undergoing elective open, redo-TAR at our institution from January 2015 to February 2021 were queried from a prospectively collected database in the Abdominal Core Health Quality Collaborative. The primary outcome was 30-day wound morbidity. Secondary outcomes were long-term composite hernia recurrence and patient-reported quality of life. RESULTS: Sixty-five patients underwent redo-TAR. Median age was 60 years, 50.8% were female, and median BMI 31.8 kg/m2. Median recurrent hernias were 16 cm wide by 25 cm long. Frequent mechanisms of recurrence included linea semilunaris injury (27.7%), mesh fracture (18.5%), infection (16.9%), and posterior sheath disruption (15.4%). Wound complications occurred in 33.8% and 16.9% required procedural intervention. With median clinical and PRO follow-up of 12 and 19 months, respectively, the composite hernia recurrence rate was 22.5% and patients reported significantly improved quality of life (HerQLes: median + 36.7, PROMIS: median - 9.5). CONCLUSION: Redo-TAR may be performed as a salvage procedure to reconstruct complex defects after failed TAR, however, in our center, it is associated with increased wound morbidity and fairly high composite recurrence rates. Despite this, patients report improvements in quality of life and pain. Tracking outcomes after TAR will facilitate understanding how to manage its failures.

An economic analysis comparing health care resource use and cost of dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin versus gemcitabine and cisplatin as neoadjuvant therapy for muscle invasive bladder cancer.

PURPOSE: To compare healthcare resource utilization (HRU) and costs associated with dose-dense methotrexate, vinblastine, doxorubicin, cisplatin (ddMVAC) and gemcitabine, cisplatin (GC) as neoadjuvant chemotherapy for muscle-invasive bladder cancer (MIBC). METHODS: Patient treated at Dana-Farber Cancer Institute from 2010 to 2019 were identified. HRU data on chemotherapy administered, supportive medications, patient monitoring, clinic, infusion, emergency department (ED) visits and hospitalization were collected retrospectively. Unit costs for HRU components were obtained from the Centers for Medicare and Medicaid Website and HRU was compared between groups using quantile regression analysis. RESULTS: 137 patients were included; 51 received ddMVAC and 86 GC. Baseline characteristics were similar, except lower mean age (P < 0.001) and higher proportion of ECOG-PS = 0 (P < 0.001) for ddMVAC. ddMVAC required more granulocyte-colony stimulating factor support (P < 0.001), central line placement (P = 0.017), cardiac imaging (P < 0.001), and infusion visits (P < 0.001), whereas GC required more clinic visits. ED visits were higher for ddMVAC (P = 0.048), while chemotherapy cycle delays and hospitalization days were higher for GC (P = 0.008). After adjusting for ECOG-PS and age, the cost per patient was approximately 41% lower (95%CI: 28% to 52%; P < 0.001) for GC vs. ddMVAC, which translated to a median adjusted cost savings of $7,410 (95%CI: $5,474-$9,347) per patient. CONCLUSIONS: Although excess HRU did not clearly favor one regimen, adjusting for PS and age indicated lower costs with GC vs. ddMVAC. Given the similar cumulative cisplatin delivery with both regimens, the associated values and costs supports the preferential selection of GC in the neoadjuvant setting of MIBC.

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 intrinsic instability of the hydrolase domain of lipoprotein lipase facilitates its inactivation by ANGPTL4-catalyzed unfolding.

The complex between lipoprotein lipase (LPL) and its endothelial receptor (GPIHBP1) is responsible for the lipolytic processing of triglyceride-rich lipoproteins (TRLs) along the capillary lumen, a physiologic process that releases lipid nutrients for vital organs such as heart and skeletal muscle. LPL activity is regulated in a tissue-specific manner by endogenous inhibitors (angiopoietin-like [ANGPTL] proteins 3, 4, and 8), but the molecular mechanisms are incompletely understood. ANGPTL4 catalyzes the inactivation of LPL monomers by triggering the irreversible unfolding of LPL's α/ß-hydrolase domain. Here, we show that this unfolding is initiated by the binding of ANGPTL4 to sequences near LPL's catalytic site, including ß2, ß3-α3, and the lid. Using pulse-labeling hydrogen‒deuterium exchange mass spectrometry, we found that ANGPTL4 binding initiates conformational changes that are nucleated on ß3-α3 and progress to ß5 and ß4-α4, ultimately leading to the irreversible unfolding of regions that form LPL's catalytic pocket. LPL unfolding is context dependent and varies with the thermal stability of LPL's α/ß-hydrolase domain (Tm of 34.8 °C). GPIHBP1 binding dramatically increases LPL stability (Tm of 57.6 °C), while ANGPTL4 lowers the onset of LPL unfolding by ∼20 °C, both for LPL and LPL•GPIHBP1 complexes. These observations explain why the binding of GPIHBP1 to LPL retards the kinetics of ANGPTL4-mediated LPL inactivation at 37 °C but does not fully suppress inactivation. The allosteric mechanism by which ANGPTL4 catalyzes the irreversible unfolding and inactivation of LPL is an unprecedented pathway for regulating intravascular lipid metabolism.

The Wilms Tumor Gene wt1a Contributes to Blood-Cerebrospinal Fluid Barrier Function in Zebrafish.

The Wilms tumor suppressor gene Wt1 encodes a zinc finger transcription factor, which is highly conserved among vertebrates. It is a key regulator of urogenital development and homeostasis but also plays a role in other organs including the spleen and the heart. More recently additional functions for Wt1 in the mammalian central nervous system have been described. In contrast to mammals, bony fish possess two paralogous Wt1 genes, namely wt1a and wt1b. By performing detailed in situ hybridization analyses during zebrafish development, we discovered new expression domains for wt1a in the dorsal hindbrain, the caudal medulla and the spinal cord. Marker analysis identified wt1a expressing cells of the dorsal hindbrain as ependymal cells of the choroid plexus in the myelencephalic ventricle. The choroid plexus acts as a blood-cerebrospinal fluid barrier and thus is crucial for brain homeostasis. By employing wt1a mutant larvae and a dye accumulation assay with fluorescent tracers we demonstrate that Wt1a is required for proper choroid plexus formation and function. Thus, Wt1a contributes to the barrier properties of the choroid plexus in zebrafish, revealing an unexpected role for Wt1 in the zebrafish brain.