Chaperone-directed ribosome repair after oxidative damage.

Because of the central role ribosomes play for protein translation and ribosome-mediated mRNA and protein quality control (RQC), the ribosome pool is surveyed and dysfunctional ribosomes degraded both during assembly, as well as the functional cycle. Oxidative stress downregulates translation and damages mRNAs and ribosomal proteins (RPs). Although damaged mRNAs are detected and degraded via RQC, how cells mitigate damage to RPs is not known. Here, we show that cysteines in Rps26 and Rpl10 are readily oxidized, rendering the proteins non-functional. Oxidized Rps26 and Rpl10 are released from ribosomes by their chaperones, Tsr2 and Sqt1, and the damaged ribosomes are subsequently repaired with newly made proteins. Ablation of this pathway impairs growth, which is exacerbated under oxidative stress. These findings reveal an unanticipated mechanism for chaperone-mediated ribosome repair, augment our understanding of ribosome quality control, and explain previous observations of protein exchange in ribosomes from dendrites, with broad implications for aging and health.

Chemical approaches to discovery and study of sources and targets of hydrogen peroxide redox signaling through NADPH oxidase proteins.

Hydrogen peroxide (H2O2) is a prime member of the reactive oxygen species (ROS) family of molecules produced during normal cell function and in response to various stimuli, but if left unchecked, it can inflict oxidative damage on all types of biological macromolecules and lead to cell death. In this context, a major source of H2O2 for redox signaling purposes is the NADPH oxidase (Nox) family of enzymes, which were classically studied for their roles in phagocytic immune response but have now been found to exist in virtually all mammalian cell types in various isoforms with distinct tissue and subcellular localizations. Downstream of this tightly regulated ROS generation, site-specific, reversible covalent modification of proteins, particularly oxidation of cysteine thiols to sulfenic acids, represents a prominent posttranslational modification akin to phosphorylation as an emerging molecular mechanism for transforming an oxidant signal into a dynamic biological response. We review two complementary types of chemical tools that enable (a) specific detection of H2O2 generated at its sources and (b) mapping of sulfenic acid posttranslational modification targets that mediate its signaling functions, which can be used to study this important chemical signal in biological systems.

Ocular Gene Therapy in a Patient with Dystrophic Epidermolysis Bullosa.

Dystrophic epidermolysis bullosa is a rare genetic disease caused by damaging variants in COL7A1, which encodes type VII collagen. Blistering and scarring of the ocular surface develop, potentially leading to blindness. Beremagene geperpavec (B-VEC) is a replication-deficient herpes simplex virus type 1-based gene therapy engineered to deliver functional human type VII collagen. Here, we report the case of a patient with cicatrizing conjunctivitis in both eyes caused by dystrophic epidermolysis bullosa who received ophthalmic administration of B-VEC, which was associated with improved visual acuity after surgery.

Nucleophilic covalent ligand discovery for the cysteine redoxome.

With an eye toward expanding chemistries used for covalent ligand discovery, we elaborated an umpolung strategy that exploits the 'polarity reversal' of sulfur when cysteine is oxidized to sulfenic acid, a widespread post-translational modification, for selective bioconjugation with C-nucleophiles. Here we present a global map of a human sulfenome that is susceptible to covalent modification by members of a nucleophilic fragment library. More than 500 liganded sulfenic acids were identified on proteins across diverse functional classes, and, of these, more than 80% were not targeted by electrophilic fragment analogs. We further show that members of our nucleophilic fragment library can impair functional protein-protein interactions involved in nuclear oncoprotein transport and DNA damage repair. Our findings reveal a vast expanse of ligandable sulfenic acids in the human proteome and highlight the utility of nucleophilic small molecules in the fragment-based covalent ligand discovery pipeline, presaging further opportunities using non-traditional chemistries for targeting proteins.

Thiol-based chemical probes exhibit antiviral activity against SARS-CoV-2 via allosteric disulfide disruption in the spike glycoprotein.

The development of small-molecules targeting different components of SARS-CoV-2 is a key strategy to complement antibody-based treatments and vaccination campaigns in managing the COVID-19 pandemic. Here, we show that two thiol-based chemical probes that act as reducing agents, P2119 and P2165, inhibit infection by human coronaviruses, including SARS-CoV-2, and decrease the binding of spike glycoprotein to its receptor, the angiotensin-converting enzyme 2 (ACE2). Proteomics and reactive cysteine profiling link the antiviral activity to the reduction of key disulfides, specifically by disruption of the Cys379-Cys432 and Cys391-Cys525 pairs distal to the receptor binding motif in the receptor binding domain (RBD) of the spike glycoprotein. Computational analyses provide insight into conformation changes that occur when these disulfides break or form, consistent with an allosteric role, and indicate that P2119/P2165 target a conserved hydrophobic binding pocket in the RBD with the benzyl thiol-reducing moiety pointed directly toward Cys432. These collective findings establish the vulnerability of human coronaviruses to thiol-based chemical probes and lay the groundwork for developing compounds of this class, as a strategy to inhibit the SARS-CoV-2 infection by shifting the spike glycoprotein redox scaffold.

Pilot study of a virtual weight management program for Duchenne muscular dystrophy.

INTRODUCTION/AIMS: Young people with Duchenne muscular dystrophy (DMD) are at increased risk of obesity. Weight management is important to families; however, several barriers exist. This pilot study aimed to investigate the feasibility and acceptability of a co-designed weight management program for DMD. METHODS: The Supporting Nutrition and Optimizing Wellbeing Program (SNOW-P) was a single-arm diet and behavior weight management intervention delivered via weekly telehealth/phone visits over 6 weeks to young people with DMD and obesity (body mass index (BMI) ≥95th percentile) and their caregivers. Using an online survey, caregivers of boys with DMD were consulted on the structure and topics delivered in SNOW-P. Primary outcomes were feasibility and acceptability; secondary outcomes were weight, physical function, and quality of life at 6- and 12-weeks follow-up. RESULTS: Of nineteen eligible participants, eight were enrolled (median age 11.4 years, range 4.9-15.8), and seven completed the program. Visit attendance was high (88%-100%); most participants reported high satisfaction and that participation was easy. Suggested changes included online and visual DMD-specific resources. At 6-weeks, median change in weight z-scores was -0.01 (IQR: -0.23, 0.17) indicating that on average, weight gain tracked as expected for age. Waist circumference measured by caregivers lacked accuracy and the completion rate of caregiver-reported secondary outcome measures (e.g., food diaries) was low. DISCUSSION: A co-designed, telehealth/phone weight management program appeared to be feasible and acceptable in a small group of boys with DMD. An adapted, hybrid telehealth and face-to-face program is recommended for efficacy testing.

Exploring caregivers' attitudes and beliefs about nutrition and weight management for young people with Duchenne muscular dystrophy.

INTRODUCTION/AIMS: Obesity disproportionately affects children and adolescents with Duchenne muscular dystrophy (DMD) and with adverse consequences for disease progression. This study aims to: explore barriers, enablers, attitudes, and beliefs about nutrition and weight management; and to obtain caregiver preferences for the design of a weight management program for DMD. METHODS: We surveyed caregivers of young people with DMD from four Australian pediatric neuromuscular clinics. Survey questions were informed by the Theoretical Domains Framework and purposefully designed to explore barriers and enablers to food and weight management. Caregivers were asked to identify their preferred features in a weight management program for families living with DMD. RESULTS: Fifty-three caregivers completed the survey. Almost half (48%) perceived their son as above healthy weight. Consequences for those children were perceived to be self-consciousness (71%), a negative impact on self-esteem (64%) and movement (57%). Preventing weight gain was a common reason for providing healthy food and healthy eating was a high priority for families. Barriers to that intention included: time constraints, selective food preferences, and insufficient nutrition information. Caregivers preferred an intensive six-week weight management program addressing appetite management and screen time. DISCUSSION: Managing weight is an important issue for caregivers of sons with DMD; yet several barriers exist. Individualized 6 week programs are preferred by caregivers to improve weight management for DMD.

Fracture risk and impact in boys with Duchenne muscular dystrophy: A retrospective cohort study.

INTRODUCTION/AIMS: Boys with Duchenne muscular dystrophy (DMD) are at increased risk of fracture. This study investigated the incidence of fractures, factors contributing to risk of first fracture with emphasis on body mass index (BMI), and the impact of fractures on functional capacity in an Australian cohort of boys with DMD. METHODS: A retrospective cohort study included boys with DMD who attended a pediatric neuromuscular clinic from 2011 to 2018. Information regarding fractures, anthropometry measurements, body composition and functional assessment was collected. Factors associated with first fracture risk were analyzed with Cox-proportional hazards. Longitudinal analysis of function post-fracture was also conducted. RESULTS: This study included 155 boys with DMD. At least one fracture occurred in 71 (45%) boys; overall incidence of fractures was 399-per-10,000 persons-years. The first fracture was vertebral in 55%; 41% had non-vertebral fractures and 4% had both. Vertebral fractures occurred in significantly older (12.28 vs 9.28 y) boys with longer exposure to glucocorticoids (5.45 vs 2.50 y) compared to non-vertebral fractures. Boys with a history of fracture(s) had a steeper rate of functional decline (measured by Northstar Ambulatory Assessment score) than those with no recorded fractures. DISCUSSION: A high fracture burden was observed in a large Australian cohort of boys with DMD. Further investigation is required to understand preventative strategies and modifiable risk factors to reduce the incidence of fractures in DMD. The impact on fractures on ambulatory capacity should be closely monitored.

Development of a Clinical Framework for the Assessment of Dyskinesia and Function in the Upper Limb in Children with Cerebral Palsy.

OBJECTIVE: Dyskinesia in cerebral palsy (CP) is a complex movement disorder that can significantly impact upper limb function. Despite a range of available tools, there is no consensus on best practice assessment of upper limb function in children with CP and dyskinesia. This study aimed to develop a clinical framework for the assessment of the impact of dyskinesia on upper limb function in children with CP. DESIGN: Modified Delphi study using expert consensus. METHODS: An expert panel of six highly experienced Australian therapists ranked assessment tools sourced from existing evidence-based literature using a five-point Likert scale. Tools rated as important for use "most" or "all" of the time, by 80% of respondents were accepted into the framework following two survey rounds and a third stage discussion. RESULTS: Of 21 tools, 12 were included in the framework under five categories: (i) screening for dyskinesia; (ii) measuring the severity of dyskinesia; (iii) Classifying upper limb functional ability; (iv) measuring upper limb functional ability; and (v) measuring upper limb movement. CONCLUSIONS: The framework for assessing the impact of dyskinesia on upper limb function in CP aims to guide clinicians to improve assessment consistency and facilitate individualized goal-directed management. Further studies with a larger number of expert clinicians and researchers will further strengthen the utility of the framework.

Delivering multidisciplinary neuromuscular care for children via telehealth.

INTRODUCTION/AIMS: In response to coronavirus disease 2019 (COVID-19) pandemic restrictions int 2020, our face-to-face (F2F) multidisciplinary neuromuscular clinic (NMC) transitioned to widespread use of telehealth (TH). This study aimed to (1) understand parent/guardian, child, and clinician perceptions of TH; (2) examine TH-related changes in clinical activity; and (3) use these findings to inform a future model of care for the NMC. METHODS: A clinical audit was undertaken to examine clinical activity throughout 2018-2020. Online surveys were distributed to clinicians and parents of children attending the NMC via TH in 2020. A working group of clinicians created a checklist to guide a future hybrid model of TH and F2F care. RESULTS: Total clinical activity in 2020 was maintained from previous years; 62.8% of all appointments occurred via TH, and 82.3% of patients attended NMC by TH at least once. Ninety-nine parents (30.6% response rate), 52 children, and 17 clinicians (77% response rate) responded to the survey. All groups reported better interaction when F2F compared to TH. Eighty percent of parents identified advantages of TH and reported lower levels of stress. A lack of "hands-on" physical assessment was identified by parents and clinicians as a TH limitation. Most families (68.1% of parents; 58.8% of children) and all clinicians indicated a preference for a mix of TH and F2F NMC appointments in the future. DISCUSSION: This study has informed a checklist to guide future TH use in a new hybrid model of care. Further investigation is required to assess health impacts of TH use in pediatric neuromuscular care.

Early ambulation after transfemoral diagnostic cerebral angiography: a pilot study.

BACKGROUND: A significant proportion of transfemoral cerebral angiography complications are related to the access site, with no clear consensus concerning the optimal closure technique. In this study, we examined the usefulness of a shortened closure protocol for transfemoral diagnostic cerebral angiography. METHODS: We performed a retrospective review of patients who underwent transfemoral (4Fr sheath) diagnostic cerebral angiography procedures at our institution. We included patients > 18 years old who underwent the shortened closure protocol to achieve hemostasis at the access site. The shortened protocol entailed the use of nonocclusive manual compression for 15 min followed by 2 h of bed rest, with additional 10-15 min of compression for new hematoma. We collected and analyzed the patients' demographics, use of antiplatelet and anticoagulation medications, sheath size, and others. RESULTS: The study cohort comprised 119 patients with a mean age was 54 years with (88%) females. Forty-one patients (34%) were on antiplatelet medications, with 12 (10%) on dual antiplatelet therapy (DAPT). Four patients (3%) (two on DAPT, one on Aspirin alone, and one was not on any antiplatelet medication) had access site hematoma that required additional compression. Subgroup analysis showed that within the DAPT, Aspirin alone, and no antiplatelet medications groups, (17%), (3%), and (1%) of patients developed access site hematoma, respectively. CONCLUSION: This pilot study demonstrates that our closure protocol for transfemoral angiograms is safe and effective. There was a trend toward higher access-site complications in patients on DAPT. Further studies are required to expand on and validate our results.

Mining for protein S-sulfenylation in Arabidopsis uncovers redox-sensitive sites.

Hydrogen peroxide (H2O2) is an important messenger molecule for diverse cellular processes. H2O2 oxidizes proteinaceous cysteinyl thiols to sulfenic acid, also known as S-sulfenylation, thereby affecting the protein conformation and functionality. Although many proteins have been identified as S-sulfenylation targets in plants, site-specific mapping and quantification remain largely unexplored. By means of a peptide-centric chemoproteomics approach, we mapped 1,537 S-sulfenylated sites on more than 1,000 proteins in Arabidopsis thaliana cells. Proteins involved in RNA homeostasis and metabolism were identified as hotspots for S-sulfenylation. Moreover, S-sulfenylation frequently occurred on cysteines located at catalytic sites of enzymes or on cysteines involved in metal binding, hinting at a direct mode of action for redox regulation. Comparison of human and Arabidopsis S-sulfenylation datasets provided 155 conserved S-sulfenylated cysteines, including Cys181 of the Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE4 (AtMAPK4) that corresponds to Cys161 in the human MAPK1, which has been identified previously as being S-sulfenylated. We show that, by replacing Cys181 of recombinant AtMAPK4 by a redox-insensitive serine residue, the kinase activity decreased, indicating the importance of this noncatalytic cysteine for the kinase mechanism. Altogether, we quantitatively mapped the S-sulfenylated cysteines in Arabidopsis cells under H2O2 stress and thereby generated a comprehensive view on the S-sulfenylation landscape that will facilitate downstream plant redox studies.

Differential Expression of Immune Checkpoint Molecules on CD8+ T Cells Specific for Immunodominant and Subdominant Herpes Simplex Virus 1 Epitopes.

Herpes simplex virus 1 (HSV-1) causes a lifelong infection of neurons that innervate barrier sites like the skin and mucosal surfaces like the eye. After primary infection of the cornea, the virus enters latency within the trigeminal ganglion (TG), from which it can reactivate throughout the life of the host. Viral latency is maintained, in part, by virus-specific CD8+ T cells that nonlethally interact with infected neurons. When CD8+ T cell responses are inhibited, HSV-1 can reactivate, and these recurrent reactivation events can lead to blinding scarring of the cornea. In the C57BL/6 mouse, CD8+ T cells specific for the immunodominant epitope from glycoprotein B maintain functionality throughout latency, while CD8+ T cells specific for subdominant epitopes undergo functional impairment that is associated with the expression of the inhibitory checkpoint molecule programmed death 1 (PD-1). Here, we investigate the checkpoint molecule T cell immunoglobulin and mucin domain-containing 3 (Tim-3), which has traditionally been associated with CD8+ T cell exhaustion. Unexpectedly, we found that Tim-3 was preferentially expressed on highly functional ganglionic CD8+ T cells during acute and latent HSV-1 infection. This, paired with data that show that Tim-3 expression on CD8+ T cells in the latently infected TG is influenced by viral gene expression, suggests that Tim-3 is an indicator of recent T cell stimulation, rather than functional compromise, in this model. We conclude that Tim-3 expression is not sufficient to define functional compromise during latency; however, it may be useful in identifying activated cells within the TG during HSV-1 infection.IMPORTANCE Without an effective means of eliminating HSV-1 from latently infected neurons, efforts to control the virus have centered on preventing viral reactivation from latency. Virus-specific CD8+ T cells within the infected TG have been shown to play a crucial role in inhibiting viral reactivation, and with a portion of these cells exhibiting functional impairment, checkpoint molecule immunotherapies have presented a potential solution to enhancing the antiviral response of these cells. In pursuing this potential treatment strategy, we found that Tim-3 (often associated with CD8+ T cell functional exhaustion) is not upregulated on impaired cells but instead is upregulated on highly functional cells that have recently received antigenic stimulation. These findings support a role for Tim-3 as a marker of activation rather than exhaustion in this model, and we provide additional evidence for the hypothesis that there is persistent viral gene expression in the HSV-1 latently infected TG.

Activity-Based Sensing for Site-Specific Proteomic Analysis of Cysteine Oxidation.

Oxidative post-translational modifications (OxiPTMs) of cysteine residues are the molecular foundation of thiol-based redox regulation that modulates physiological events such as cell proliferation, differentiation, and migration and, when dysregulated, can lead to biomolecule damage and cell death. Common OxiPTMs of cysteine thiols (-SH) include reversible modifications such as S-sulfenylation (-SOH), S-glutathionylation (-SSG), disulfide formation (-SSR), S-nitrosylation (-SNO), and S-sulfhydration (-SSH) as well as more biologically stable modifications like S-sulfinylation (-SO2H) and S-sulfonylation (-SO3H). In the past decade, our laboratory has developed first-in-class chemistry-based tools and proteomic methods to advance the field of thiol-based redox biology and oxidative stress. In this Account, we take the reader through the historical aspects of probe development and application in our laboratory, highlighting key advances in our understanding of sulfur chemistry, in the test tube and in living systems. Offering superior resolution, throughput, accuracy, and reproducibility, mass spectrometry (MS)-based proteomics coupled to chemoselective "activity-based" small-molecule probes is the most rigorous technique for global mapping of cysteine OxiPTMs. Herein, we describe the evolution of this field from indirect detection to state-of-the-art site-centric quantitative chemoproteomic approaches that enable mapping of physiological and pathological changes in cysteine oxidation. These methods enable protein and site-level identification, mechanistic studies, mapping fold-changes, and modification stoichiometry. In particular, this Account focuses on activity-based methods for profiling S-sulfenylation, S-sulfinylation, and S-sulfhydration with an eye toward new reactions and methodologies developed in our group as well as their applications that have shed new light on fundamental processes of redox biology. Among several classes of sulfenic acid probes, dimedone-based C-nucleophiles possess superior chemical selectivity and compatibility with tandem MS. Cell-permeable dimedone derivatives with a bioconjugation handle are capable of detecting of S-sulfenylation in living cells. In-depth screening of a C-nucleophile library has yielded several entities with significantly enhanced reactivity over dimedone while maintaining selectivity, and reversible linear C-nucleophiles that enable controlled target release. C-Nucleophiles have also been implemented in tag-switch methods to detect S-sulfhydration. Most recently, activity-based detection of protein S-sulfinylation with electrophilic nitrogen species (ENS), such as C-nitroso compounds and electron deficient diazines, offers significant advantages in simplicity-of-use and target specificity compared to label-free methods. When feasible, the rich information provided by site-centric quantitative proteomics should not be tainted by oxidation artifacts from cell lysis. Therefore, chemoselective probes that function in a native environment with low cytotoxicity, good cell-permeability, and competitive kinetics are desired in modern redox chemoproteomics approaches. As our understanding of sulfur chemistry and redox signaling evolves, newly discovered cysteine OxiPTMs in microorganisms, plants, cells, tissues, and disease models should innovatively promote mechanistic and therapeutic research.

Cumulative Intracranial Tumor Volume as a Prognostic Factor in Patients with Brain Metastases Undergoing Stereotactic Radiosurgery.

Approximately 25-35% of all cancer patients suffer from brain metastases (BM), and many of them-in particular, those with a limited number of intracranial tumors-are treated with stereotactic radiosurgery (SRS). Accurate prediction of survival remains a key clinical challenge in this population. Several prognostic scales have been developed to facilitate this prognostication, including the Recursive Partitioning Analysis (RPA) classification, the modified Recursive Partitioning Analysis (mRPA) subclassifications, the Basic Score for Brain Metastases (BS-BM), the Score Index for Radiosurgery (SIR), the Graded Prognostic Assessment (GPA), and the diagnosis-specific Graded Prognostic Assessment (dsGPA). However, none of these scales include consideration of the cumulative intracranial tumor volume (CITV), which is defined as the sum of all intracranial tumor volumes. Since there is mounting evidence that the CITV carries significant prognostic value in SRS-treated patients with BM, this variable should be considered during survival prognostication, along with other pertinent clinical, pathological, and molecular characteristics.

Chemical proteomics reveals new targets of cysteine sulfinic acid reductase.

Cysteine sulfinic acid or S-sulfinylation is an oxidative post-translational modification (OxiPTM) that is known to be involved in redox-dependent regulation of protein function but has been historically difficult to analyze biochemically. To facilitate the detection of S-sulfinylated proteins, we demonstrate that a clickable, electrophilic diazene probe (DiaAlk) enables capture and site-centric proteomic analysis of this OxiPTM. Using this workflow, we revealed a striking difference between sulfenic acid modification (S-sulfenylation) and the S-sulfinylation dynamic response to oxidative stress, which is indicative of different roles for these OxiPTMs in redox regulation. We also identified >55 heretofore-unknown protein substrates of the cysteine sulfinic acid reductase sulfiredoxin, extending its function well beyond those of 2-cysteine peroxiredoxins (2-Cys PRDX1-4) and offering new insights into the role of this unique oxidoreductase as a central mediator of reactive oxygen species-associated diseases, particularly cancer. DiaAlk therefore provides a novel tool to profile S-sulfinylated proteins and study their regulatory mechanisms in cells.

PD-L1/B7-H1 Inhibits Viral Clearance by Macrophages in HSV-1-Infected Corneas.

Immune privilege helps protect the cornea from damaging inflammation but can also impair pathogen clearance from this mucosal surface. Programmed death-ligand 1 (PD-L1 or B7-H1) contributes to corneal immune privilege by inhibiting the function of a variety of immune cells. We asked whether programmed death-1 (PD-1)/PD-L1 interaction regulates HSV-1 clearance from infected corneas. We show that PD-L1 is constitutively expressed in the corneal epithelium and is upregulated upon HSV-1 corneal infection, with peak expression on CD45+ cells NK cells, dendritic cells, neutrophils, and macrophages and CD45- corneal epithelial cells at 4 d postinfection (dpi). As early as 1 dpi, HSV-1-infected corneas of B7-H1-/- mice as compared with wild-type mice showed increased chemokine expression and this correlated with increased migration of inflammatory cells into the viral lesions and decreased HSV-1 corneal titers. Local PD-L1 blockade caused a similar increase in viral clearance, suggesting a local effect of PD-1/PD-L1 in the cornea. The enhanced HSV-1 clearance at 2 dpi resulting from PD-1/PD-L1 blockade is mediated primarily by a monocyte/macrophage population. Studies in bone marrow chimeras demonstrated enhanced viral clearance when PD-L1 was absent only from nonhematopoietic cells. We conclude that PD-L1 expression on corneal cells negatively impacts the ability of the innate immune system to clear HSV-1 from infected corneas.

The Expanding Landscape of the Thiol Redox Proteome.

Cysteine occupies a unique place in protein chemistry. The nucleophilic thiol group allows cysteine to undergo a broad range of redox modifications beyond classical thiol-disulfide redox equilibria, including S-sulfenylation (-SOH), S-sulfinylation (-SO(2)H), S-sulfonylation (-SO(3)H), S-nitrosylation (-SNO), S-sulfhydration (-SSH), S-glutathionylation (-SSG), and others. Emerging evidence suggests that these post-translational modifications (PTM) are important in cellular redox regulation and protection against oxidative damage. Identification of protein targets of thiol redox modifications is crucial to understanding their roles in biology and disease. However, analysis of these highly labile and dynamic modifications poses challenges. Recent advances in the design of probes for thiol redox forms, together with innovative mass spectrometry based chemoproteomics methods make it possible to perform global, site-specific, and quantitative analyses of thiol redox modifications in complex proteomes. Here, we review chemical proteomic strategies used to expand the landscape of thiol redox modifications.

A universal entropy-driven mechanism for thioredoxin-target recognition.

Cysteine residues in cytosolic proteins are maintained in their reduced state, but can undergo oxidation owing to posttranslational modification during redox signaling or under conditions of oxidative stress. In large part, the reduction of oxidized protein cysteines is mediated by a small 12-kDa thiol oxidoreductase, thioredoxin (Trx). Trx provides reducing equivalents for central metabolic enzymes and is implicated in redox regulation of a wide number of target proteins, including transcription factors. Despite its importance in cellular redox homeostasis, the precise mechanism by which Trx recognizes target proteins, especially in the absence of any apparent signature binding sequence or motif, remains unknown. Knowledge of the forces associated with the molecular recognition that governs Trx-protein interactions is fundamental to our understanding of target specificity. To gain insight into Trx-target recognition, we have thermodynamically characterized the noncovalent interactions between Trx and target proteins before S-S reduction using isothermal titration calorimetry (ITC). Our findings indicate that Trx recognizes the oxidized form of its target proteins with exquisite selectivity, compared with their reduced counterparts. Furthermore, we show that recognition is dependent on the conformational restriction inherent to oxidized targets. Significantly, the thermodynamic signatures for multiple Trx targets reveal favorable entropic contributions as the major recognition force dictating these protein-protein interactions. Taken together, our data afford significant new insight into the molecular forces responsible for Trx-target recognition and should aid the design of new strategies for thiol oxidoreductase inhibition.

Evaluation of Serial Casting for Boys with Duchenne Muscular Dystrophy: A Case Report.

AIM: To report the effects of below-knee serial casting in two boys with Duchenne muscular dystrophy who presented with well-preserved strength and calf shortening. METHODS: Bilateral below-knee serial casts were applied over two weeks with follow-up of daily stretching and wearing of customized night splints. Outcome measures were performed at baseline, 1, 3, 6, and 12 months post-casting. These included measures of calf length, leg strength, motor function, endurance, and spatio-temporal gait parameters. RESULTS: Both boys completed serial casting with gains in muscle length. No adverse effects on strength or motor function were observed over a 12-month follow-up period.