Conformational Reorganization Coupled to the Ionization of Internal Lys Residues in Proteins.

Ionizable groups buried in the hydrophobic interior of proteins are essential for energy transduction and catalysis. Because the protein interior is usually neither as polar nor as polarizable as water, these groups tend to have anomalous pKa values, and their ionization tends to be coupled to conformational reorganization. To elucidate mechanisms of energy transduction in proteins, it is necessary to understand the structural determinants of the pKa values of these buried groups, including the range and character of the conformational reorganization that the ionization of these buried groups can elicit. The L25K and L125K variants of staphylococcal nuclease (SNase) were used to characterize the diverse types of structural reorganization that can be promoted by the ionization of buried groups. NMR relaxation dispersion and ZZ-exchange experiments were used to identify the locations and measure the time scales and extent of pH-dependent conformational exchange in these two proteins. The buried Lys-25 and Lys-125 residues titrate with pKa of 6.3 and 6.2, respectively. The L25K protein fluctuates between the native state and an ensemble of locally unfolded states on the 400 µs to 7 ms time scale. On the 100 to 500 ms time scale the native state exchanges with a subglobally unfolded state in which the ß-barrel is partially reorganized. The equilibrium between the native state and this alternative state is highly pH dependent; at pH values below the pKa of Lys-25 the state with the partially reorganized ß-barrel is the dominant state. In contrast, the L125K protein only exhibited pH-independent fluctuation in the microsecond to millisecond time scale in the region near Lys-125. The study illustrates how diverse and how localized the coupling between conformational reorganization and ionization of buried groups can be. The pH-sensitive exchange between the fully native and subglobally or locally unfolded states in time scales well into hundreds of milliseconds will challenge all computational methods for structure-based calculations of pKa values.

pH dependence of conformational fluctuations of the protein backbone.

Proton binding equilibria (pK(a) values) of ionizable groups in proteins are exquisitely sensitive to their microenvironments. Apparent pK(a) values measured for individual ionizable residues with NMR spectroscopy are actually population-weighted averages of the pK(a) in different conformational microstates. NMR spectroscopy experiments with staphylococcal nuclease were used to test the hypothesis that pK(a) values of surface Glu and Asp residues are affected by pH-sensitive fluctuations of the backbone between folded and locally unfolded conformations. (15)N spin relaxation studies showed that as the pH decreases from the neutral into the acidic range the amplitudes of backbone fluctuations in the ps-ns timescale increase near carboxylic residues. Hydrogen exchange experiments suggested that backbone conformational fluctuations promoted by decreasing pH also reflect slower local or sub-global unfolding near carboxylic groups. This study has implications for structure-based pKa calculations: (1) The timescale of the backbone's response to ionization events in proteins can range from ps to ms, and even longer; (2) pH-sensitive fluctuations of the backbone can be localized to both the segment the ionizable residue is attached to or the one that occludes the ionizable group; (3) Structural perturbations are not necessarily propagated through Coulomb interactions; instead, local fluctuations appear to be coupled through the co-operativity inherent to elements of secondary structure and to networks of hydrogen bonds. These results are consistent with the idea that local conformational fluctuations and stabilities are important determinants of apparent pK(a) values of ionizable residues in proteins.

Type 2 cytokines sensitize human sensory neurons to itch-associated stimuli.

Introduction: Chronic itch is a central symptom of atopic dermatitis. Cutaneous afferent neurons express receptors interleukins (IL)-4, IL-13, and IL-33, which are type 2 cytokines that are elevated in atopic dermatitis. These neuronal cytokine receptors were found to be required in several murine models of itch. Prior exposure of neurons to either IL-4 or IL-33 increased their response to subsequent chemical pruritogens in mice but has not been previously examined in humans. The objective of the present study was to determine if type 2 cytokine stimulation sensitizes sensory neurons to future itch stimuli in a fully human ex vivo system. Methods: We measured calcium flux from human dorsal root ganglia cultures from cadaveric donors in response to pruritogens following transient exposure to type 2 cytokines. We also measured their effect on neuronal calcium flux and changes in gene expression by RNA sequencing. Results: Type 2 cytokines (IL-4, IL-13, and IL-33) were capable of sensitizing human dorsal root ganglia neurons to both histaminergic and nonhistaminergic itch stimuli. Sensitization was observed after only 2 h of pruritogen incubation. We observed rapid neuronal calcium flux in a small subset of neurons directly in response to IL-4 and to IL-13, which was dependent on the presence of extracellular calcium. IL-4 and IL-13 induced a common signature of upregulated genes after 24 h of exposure that was unique from IL-33 and non-type 2 inflammatory stimuli. Discussion: This study provides evidence of peripheral neuron sensitization by type 2 cytokines as well as broad transcriptomic effects in human sensory ganglia. These studies identify both unique and overlapping roles of these cytokines in sensory neurons.

Sonographically guided cryoneurolysis: preliminary experience and clinical outcomes.

Chronic peripheral nerve pain is a common problem that can arise from numerous causes, for which neurolysis is a therapeutic option. It is postulated that cryotherapy will have less adverse events than other methods of nerve ablation. A retrospective case series review was performed in patients who had undergone sonographically guided cryoneurolysis for Morton neuromas, postsurgical and posttraumatic neuromas, and idiopathic neuralgia. Fifteen of 20 patients had a positive response to cryoneurolysis, as did 2 of 4 patients with borderline symptoms for chronic regional pain syndrome. In view of our positive results, we believe that cryoneurolysis should be considered a reasonable option in performing neurolytic therapy.

Baseline Demographics and Severity and Burden of Atopic Dermatitis in Adult Patients Initiating Dupilumab Treatment in a Real-World Registry (PROSE).

INTRODUCTION: Dupilumab was initially approved in 2017 as the first biologic therapy for atopic dermatitis (AD). We characterized adults with AD initiating dupilumab in a real-world setting in the USA/Canada. METHODS: PROSE is an ongoing, longitudinal, prospective, observational, multicenter registry of patients with AD initiating dupilumab per country-specific prescribing information. We report baseline data (day of first dupilumab injection) for patients enrolled from April 2018 through July 2019. RESULTS: Among 315 patients (mean age 42.5 years, 55.2% female), the median AD duration was 17.0 years; 65.4% reported a history of type 2 inflammatory comorbidities (e.g., allergic rhinitis, asthma), and 93.3% reported treatment(s) for AD in the previous year, including topical corticosteroids (90.8%), systemic corticosteroids (36.2%), and nonsteroidal systemic therapies (14.0%). In total, 89.2% had an Overall Disease Severity score of 3 (moderate) or 4 (severe). Other mean disease severity scores included the following: Eczema Area and Severity Index 16.9 (range 0-72), body surface area affected 26.8%, Patient-Oriented Eczema Measure 18.5 (range 0-28), Dermatology Life Quality Index 12.7 (range 0-30), and pruritus Numerical Rating Scale score 6.9 (range 0-10). CONCLUSION: Patients initiating dupilumab have longstanding moderate-to-severe AD with significant disease burden and frequent type 2 comorbidities. GOV IDENTIFIER: NCT03428646.

Enriching Peptide Libraries for Binding Affinity and Specificity Through Computationally Directed Library Design.

Peptide reagents with high affinity or specificity for their target protein interaction partner are of utility for many important applications. Optimization of peptide binding by screening large libraries is a proven and powerful approach. Libraries designed to be enriched in peptide sequences that are predicted to have desired affinity or specificity characteristics are more likely to yield success than random mutagenesis. We present a library optimization method in which the choice of amino acids to encode at each peptide position can be guided by available experimental data or structure-based predictions. We discuss how to use analysis of predicted library performance to inform rounds of library design. Finally, we include protocols for more complex library design procedures that consider the chemical diversity of the amino acids at each peptide position and optimize a library score based on a user-specified input model.

Epidural steroid injection for lumbar disc herniation in NFL athletes.

PURPOSE: To our knowledge, there is no published information on the efficacy of epidural steroid injections for the treatment of lumbar disc herniation in an athletic population. The purpose of this study was to evaluate the efficacy of epidural corticosteroid injection for treatment of lumbar disc herniation in a group of National Football League (NFL) players. METHODS: We retrospectively reviewed the records of all NFL players who underwent an epidural steroid injection at our institution for incapacitating pain secondary to an acute lumbar disc herniation (confirmed on magnetic resonance imaging) from 2003 to 2010. Our primary outcome was success of the injection, defined as return to play. The secondary outcome of the study was to evaluate risk factors for failure of this treatment approach. RESULTS: Seventeen players had a total of 37 injections for 27 distinct lumbar disc herniation episodes from 2003 to 2010. The success rate of returning an athlete to play for a given episode of disc herniation was 89% (24 of 27 episodes) with an average loss of 2.8 practices (range = 0-12) and 0.6 games (range = 0-2) after the injection. Four players required a repeat injection for the same episode. Three of these four players ultimately failed conservative management and required surgical intervention. Risk factors for failing injection therapy included sequestration of the disc herniation on magnetic resonance imaging (P = 0.01) and weakness on physical examination (P = 0.002). There were no complications reported. CONCLUSIONS: In this highly selective group of professional athletes, our results suggest that epidural steroid injections are a safe and effective therapeutic option in the treatment of symptomatic lumbar disc herniation.