Mapping interactions of calmodulin and neuronal NO synthase by crosslinking and mass spectrometry

Neuronal nitric oxide synthase (nNOS) is a homodimeric cytochrome P450-like enzyme that catalyzes the conversion of L-arginine to nitric oxide in the presence of NADPH and molecular oxygen. The binding of calmodulin (CaM) to a linker region between the FAD/FMN-containing reductase domain, and the heme-containing oxygenase domain is needed for electron transfer reactions, reduction of the heme, and NO synthesis. Due to the dynamic nature of the reductase domain and low resolution of available full-length structures, the exact conformation of the CaM-bound active complex during heme reduction is still unresolved. Interestingly, hydrogen-deuterium exchange and mass spectrometry studies revealed interactions of the FMN domain and CaM with the oxygenase domain for iNOS, but not nNOS. This finding prompted us to utilize covalent crosslinking and mass spectrometry to clarify interactions of CaM with nNOS. Specifically, MS-cleavable bifunctional crosslinker disuccinimidyl dibutyric urea was used to identify thirteen unique crosslinks between CaM and nNOS as well as 61 crosslinks within the nNOS. The crosslinks provided evidence for CaM interaction with the oxygenase and reductase domain residues as well as interactions of the FMN domain with the oxygenase dimer. Cryo-EM studies, which gave a high-resolution model of the oxygenase domain, along with crosslink-guided docking provided a model of nNOS that brings the FMN within 15 Å of the heme in support for a more compact conformation than previously observed. These studies also point to the utility of covalent crosslinking and mass spectrometry in capturing transient dynamic conformations that may not be captured by hydrogen-deuterium exchange and mass spectrometry experiments.

Preventing Teen Pregnancy: A Qualitative Study of the Perspectives of Parenting and Expecting Latino Adolescents

STUDY OBJECTIVE

Latino youths in the United States experience disproportionately high rates of teen pregnancy. The aim of this study was to obtain expecting and parenting Latino adolescents' perspectives regarding factors contributing to teen pregnancy and pregnancy prevention.

METHODS

Expecting/parenting Latino adolescents were recruited from high schools with high proportions of Latino youths and teen pregnancy. Participants completed a questionnaire on sociodemographic and background characteristics. Focus groups were stratified by age and gender and audio recorded. Grounded theory was used to identify themes from the transcribed audio recordings.

RESULTS

Thirty-two expecting/parenting Latino adolescents (20 females, 12 males) 14-19 years old participated in four focus groups. Quantitative results revealed that two-thirds of participants at birth had adolescent mothers. Over three-quarters of participants reported that their pregnancies had occurred too soon. Qualitative themes for factors contributing to teen pregnancy included lack of contraceptive knowledge/access, belief of invincibility, influence within relationships, male decisions on contraceptive use, desire to belong among peers, lack of parental support for contraceptive use, lack of parental attention, rebellion, normalization of adolescent parenthood in Latino culture, and media. Themes for pregnancy prevention included time alone with physicians, parenting teens as mentors, reproductive health education, and community pregnancy-prevention programs.

CONCLUSION

Multiple factors contribute to teen pregnancy in Latino youth, including influences from Latino culture, family, peers, partners, and social determinants of health. Pregnancy prevention should incorporate interventions to address these aspects, including disseminating culturally sensitive education materials, providing parenting teens as peer mentors, encouraging time alone with health care providers, and addressing various social determinants of health.

Observational study on the neonatal outcome during the COVID-19 pandemic in Germany

AIM

We aimed to determine stillbirth, preterm birth, perinatal complications, and the developmental outcome of children born preterm during the COVID-19 pandemic in Germany.

METHODS

National data from the perinatal survey of preterm and term infants born in 2017-2020 between 22 March and 31 December were evaluated. Neurodevelopment of preterm infants at 2 years corrected age was tested with the Parent Report of Children's Abilities-Revised questionnaire and by clinical testing with Bayley scales, either before or during the COVID-19 pandemic. Statistical significance was calculated using a Pearson's chi-square-independence test and a linear regression model.

RESULTS

In 2020, there was an increase of stillbirths of 0.02% (p = 0.01) and a decrease in preterm births by 0.38% (p < 0.001). No changes were found in a representative subgroup of infants with regard to neurodevelopmental scores (mental developmental index and psychomotor developmental index) or in parent survey data (non-verbal cognition scale and language development scale).

CONCLUSION

Increasing rates of stillbirths and decreasing preterm births in Germany were observed. Existing networks might stabilise neurodevelopment of preterm infants during the COVID-19 pandemic.

Dynamic cycling with a unique Hsp90/Hsp70-dependent chaperone machinery and GAPDH is needed for heme insertion and activation of neuronal NO synthase

Heat shock protein 90 (Hsp90) is known to mediate heme insertion and activation of heme-deficient neuronal nitric oxide (NO) synthase (apo-nNOS) in cells by a highly dynamic interaction that has been extremely difficult to study mechanistically with the use of subcellular systems. In that the heme content of many critical hemeproteins is regulated by Hsp90 and the heme chaperone GAPDH, the development of an in vitro system for the study of this chaperone-mediated heme regulation would be extremely useful. Here, we show that use of an antibody-immobilized apo-nNOS led not only to successful assembly of chaperone complexes but the ability to show a clear dependence on Hsp90 and GAPDH for heme-mediated activation of apo-nNOS. The kinetics of binding for Hsp70 and Hsp90, the ATP and K⁺ dependence, and the absolute requirement for Hsp70 in assembly of Hsp90•apo-nNOS heterocomplexes all point to a similar chaperone machinery to the well-established canonical machine regulating steroid hormone receptors. However, unlike steroid receptors, the use of a purified protein system containing Hsp90, Hsp70, Hsp40, Hop, and p23 is unable to activate apo-nNOS. Thus, heme insertion requires a unique Hsp90-chaperone complex. With this newly developed in vitro system, which recapitulates the cellular process requiring GAPDH as well as Hsp90, further mechanistic studies are now possible to better understand the components of the Hsp90-based chaperone system as well as how this heterocomplex works with GAPDH to regulate nNOS and possibly other hemeproteins.

Mapping protein-protein interactions in homodimeric CYP102A1 by crosslinking and mass spectrometry

Covalent crosslinking and mass spectrometry techniques hold great potential in the study of multiprotein complexes, but a major challenge is the inability to differentiate intra- and inter- protein crosslinks in homomeric complexes. In the current study we use CYP102A1, a well-characterized homodimeric P450, to examine a subtractive method that utilizes limited crosslinking with disuccinimidyl dibutyric urea (DSBU) and isolation of the monomer, in addition to the crosslinked dimer, to identify inter-monomer crosslinks. The utility of this approach was examined with the use of MS-cleavable crosslinker DSBU and recently published cryo-EM based structures of the CYP102A1 homodimer. Of the 31 unique crosslinks found, 26 could be fit to the reported structures whereas 5 exceeded the spatial constraints. Not only did these crosslinks validate the cryo-EM structure, they point to new conformations of CYP102A1 that bring the flavins in closer proximity to the heme.

Gender-affirming hormone therapy in cystic fibrosis - A case of new Pseudomonas infection

Background

Little is known about the impact of hormone therapy on transgender youth with Cystic Fibrosis (CF). This case report describes an 18-year-old affirmed female with CF who was treated with hormone therapy associated in timing with new growth of Pseudomonas aeruginosa in her sputum culture.

Discussion

We highlight important considerations, including the impact of gender-affirming hormone therapy on overall CF disease course. Evidence supports that females with CF have worse outcomes than males, which are partly attributed to estrogen effects. Pseudomonas aeruginosa is one of the most prevalent pathogens in people with CF. Here, we highlight a transfemale who grows Pseudomonas aeruginosa for the first time since her youth, nearly 1 year after starting estrogen therapy. This is consistent with previous literature of an association between high estrogen levels and Pseudomonas aeruginosa prevalence, but has never been evaluated in a transgender population.

Conclusion

Through this case, we demonstrate the need for additional research to understand the relationship between gender-affirmative hormone transition and CF care and management.

Hsp70:CHIP Ubiquitinates Dysfunctional but Not Native Neuronal NO Synthase

Heat shock protein (Hsp) 70 modulators are being developed to enhance the removal of toxic proteins in a variety of protein misfolding diseases. In the course of our studies on neuronal nitric oxide synthase (nNOS), a client of the Hsp90 and Hsp70 chaperone system, we have established that inactivation of nNOS by heme or tetrahydrobiopterin (BH₄) alteration and loss triggers ubiquitination by the Hsp70-associated E3 ligase c-terminus of Hsp70-interacting protein (CHIP) and subsequent degradation in cells. Although in cells Hsp90 and Hsp70 work together to maintain protein quality control, in this study, we specifically developed an assay to assess the selectivity of the Hsp70:CHIP complex for inactivated nNOS. We developed a highly sensitive ELISA to measure Hsp70:CHIP-dependent nNOS ubiquitination without interference from direct ubiquitination by CHIP, as evidenced by Bcl-2 associated athanogene 1-M completely abolishing ubiquitination. To further validate the assay we demonstrated, JG-98, a rhodocyanin compound that acts on Hsp70 but not its inactive structural analog JG-258, enhances the ubiquitination of nNOS 3-fold. Utilizing this assay, we have shown that the Hsp70:CHIP complex preferentially ubiquitinates heme-deficient nNOS (apo-nNOS) over heme-containing nNOS (holo-nNOS). Moreover, depletion of nNOS-bound BH₄ triggers ubiquitination of holo-nNOS by the Hsp70:CHIP complex. Most importantly, JG-98 was shown to enhance the ubiquitination of only dysfunctional nNOS while leaving the native functional nNOS untouched. Thus, the finding that enhancing Hsp70:CHIP-mediated ubiquitination does not affect native proteins has important pharmacological implications. Moreover, development of a facile in vitro method for Hsp70:CHIP-mediated ubiquitination will be beneficial for testing other Hsp70 modulators. SIGNIFICANCE STATEMENT: The heat shock protein 70 (Hsp70):c-terminus of Hsp70-interacting protein (CHIP) complex facilitates the ubiquitination and subsequent degradation of several hundred-client proteins, and activation of Hsp70 has been suggested as a therapeutic strategy to enhance the degradation of disease-causing proteins. The current study shows that the pharmacological activation of Hsp70 enhances the ubiquitination of dysfunctional but not native nNOS, and it suggests that this therapeutic strategy will likely be highly selective.

Evaluation of the effectiveness of the Family Nurse Partnership home visiting programme in first time young mothers in Scotland: a protocol for a natural experiment

Introduction

Individual, social and economic circumstances faced by young mothers (19 years or under) can challenge a successful start in life for their children. Intervening early might enhance life chances for both mother and child. The Family Nurse Partnership (FNP) is an intensive nurse-led home visiting programme developed in the US which aims to improve prenatal health behaviours, birth outcomes, child development and health outcomes, and maternal life course. Establishing evidence of effectiveness beyond the original US setting is important to understand where further adaptation is required within a country specific context.

Objective

This study will form one strand of the Scottish Government’s plan to evaluate the effectiveness of FNP as compared to usual care for mothers and their children in Scotland and will focus only on outcomes that can be identified using routine administrative data systems.

Methods

This study is a natural experiment with a case-cohort design using linked anonymised routine health, educational and social care data. Cases will be women enrolled as FNP Clients in ten NHS Health Boards in Scotland and Controls will be women who met FNP eligibility criteria but were pregnant at a time when the programme was not recruiting. Outcomes are mapped to the Scottish FNP logic model. All comparative analyses will be pre-specified, conducted on an intention to treat basis and will use multilevel regression models to compare outcomes between groups.

Discussion

The study protocol is based upon the specification of FNP commissioned by the Scottish Government. This study design is novel for the evaluation of the FNP/NFP programmes which are primarily evaluated with an RCT. Outcomes included within the study have been selected on the basis that they are outcomes FNP aims to influence and where there is routine data available to assess the outcome

Chaperone Activity and Dimerization Properties of Hsp90α and Hsp90β in Glucocorticoid Receptor Activation by the Multiprotein Hsp90/Hsp70-Dependent Chaperone Machinery

Several hundred proteins cycle into heterocomplexes with a dimer of the chaperone heat shock protein 90 (Hsp90), regulating their activity and turnover. There are two isoforms of Hsp90, Hsp90α and Hsp90β, and their relative chaperone activities and composition in these client protein•Hsp90 heterocomplexes has not been determined. Here, we examined the activity of human Hsp90α and Hsp90β in a purified five-protein chaperone machinery that assembles glucocorticoid receptor (GR)•Hsp90 heterocomplexes to generate high-affinity steroid-binding activity. We found that human Hsp90α and Hsp90β have equivalent chaperone activities, and when mixed together in this assay, they formed only GR•Hsp90αα and GR•Hsp90ββ homodimers and no GR•Hsp90αβ heterodimers. In contrast, GR•Hsp90 heterocomplexes formed in human embryonic kidney (HEK) cells also contain GR•Hsp90αβ heterodimers. The formation of GR•Hsp90αβ heterodimers in HEK cells probably reflects the longer time permitted for exchange to form Hsp90αβ heterodimers in the cell versus in the cell-free assembly conditions. This purified GR-activating chaperone machinery can be used to determine how modifications of Hsp90 affect its chaperone activity. To that effect, we have tested whether the unique phosphorylation of Hsp90α at threonines 5 and 7 that occurs during DNA damage repair affects its chaperone activity. We showed that the phosphomimetic mutant Hsp90α T5/7D has the same intrinsic chaperone activity as wild-type human Hsp90α in activation of GR steroid-binding activity by the five-protein machinery, supporting the conclusion that T5/7 phosphorylation does not affect Hsp90α chaperone activity.

Quantifying Qualitative Probabilties: A Cross-Cultural Examination

Language is a powerful tool and essential for human communication. Despite this criticality, linguistic terms often produce different percepts across differing individuals. Such variations can, and do lead to miscommunication and confusion. To assess the qualitative degree of such ambiguity, we look to quantify how different probability terms were characterized based upon an individual’s personality and culture. Thus, we evaluated the probability ratings of 35 participants in the United States and 50 participant in Germany on sixty-four terms such as “always,” “certain,” “unusual” etc. Participants rated the likelihood of these descriptions on a 0-100 scale. Additionally, participants were asked to rate the strength of statements that included terms such as “safety,” “guarantee,” “health” etc. Results indicated that there is a wide range of these probability ratings between participants. Additionally, cultural differences were found: German participants score higher on low-probability ratings, whereas Americans score higher on high-probability ratings. The implications of these findings for communications between individuals and between humans and machines are discussed.

IABP: history-evolution-pathophysiology-indications: what we need to know

Treatment with the intraaortic balloon pump (IABP) is the most common form of mechanical support for the failing heart. Augmentation of diastolic pressure during balloon inflation contributes to the coronary circulation and the presystolic deflation of the balloon reduces the resistance to systolic output. Consequently, the myocardial work is reduced. The overall effect of the IABP therapy is an increase in the myocardial oxygen supply/demand ratio and thus in endocardial viability.

This is an overall synopsis of what we need to know regarding IABP. Furthermore, this review article attempts to systematically delineate the pathophysiology linked with the hemodynamic consequences of IABP therapy. The authors also look at the future of the use of the balloon pump and conclude that the positive multi-systemic hemodynamic regulation during IABP treatment should further justify its use.

Changing trends in the UK management of upper GI bleeding: is there evidence of reduced UK training experience?

OBJECTIVE

The aim of this study was to evaluate UK trainee experience in endoscopy for acute upper gastrointestinal bleeding (AUGIB).

METHODS

Data was prospectively collected from all patients presenting to South Yorkshire Hospitals with AUGIB from September 2011 to December 2011 and compared with data from 1996. Concurrently, all gastroenterology trainees registered with the British Society of Gastroenterology were invited to respond to a web-based questionnaire regarding their experience in AUGIB management.

RESULTS

77% (589/766) of the patient cohort underwent endoscopy for AUGIB; 15% (90/589) were performed by trainees. 7.2% (9/125) of the out of hours endoscopy case load was performed by trainees; all were low-risk or medium-risk cases (pre-endoscopy Rockall score ≤4). During the study period, dual therapy was delivered by a trainee on only four occasions. Comparison with the 1996 cohort demonstrated a marked reduction in the number of trainee performed endoscopies (76% vs 15%; p<0.001). Questionnaires were returned by 51% (245/478) of British Society of Gastroenterology trainees. 81% (198/245) thought that <10% of the gastroscopies they had performed involved therapeutic intervention. 23% (57/245) felt they would not be competent in AUGIB endoscopy by completion of specialty training.

CONCLUSIONS

This study demonstrates the decline over time in trainee experience in AUGIB endoscopy. It also highlights a lack of trainee exposure to more challenging cases, out of hours endoscopy and therapeutic procedures. Furthermore, trainees are concerned that a level of competency may not be attained during specialty training. We advocate reviewing UK endoscopic training provision for AUGIB to ensure that experienced endoscopists are produced to meet future service needs.

Sinonasal Lymphoma Presenting as a Probable Sanctuary Site for Relapsed B Acute Lymphoblastic Leukaemia: A Case Report and Review of the Literature

Sinonasal lymphoma is a non-Hodgkin lymphoma (NHL) representing 1.5% of all lymphomas. It presents as an unremitting ulceration with progressive destruction of midline sinonasal and surrounding structures. Poor prognosis warrants early treatment although diagnosis is challenging and frequently delayed. It is usually primary in origin and to our knowledge the sinonasal region has never been reported as a sanctuary site in leukaemia/lymphoma relapse. We present a unique case of B-cell ALL (acute lymphoblastic leukaemia) with late relapse to the nasal septum as a sinonasal lymphoblastic lymphoma and with genetic support for this as a sanctuary site.

Architecture of the nitric-oxide synthase holoenzyme reveals large conformational changes and a calmodulin-driven release of the FMN domain

Nitric-oxide synthase (NOS) is required in mammals to generate NO for regulating blood pressure, synaptic response, and immune defense. NOS is a large homodimer with well characterized reductase and oxygenase domains that coordinate a multistep, interdomain electron transfer mechanism to oxidize l-arginine and generate NO. Ca(2+)-calmodulin (CaM) binds between the reductase and oxygenase domains to activate NO synthesis. Although NOS has long been proposed to adopt distinct conformations that alternate between interflavin and FMN-heme electron transfer steps, structures of the holoenzyme have remained elusive and the CaM-bound arrangement is unknown. Here we have applied single particle electron microscopy (EM) methods to characterize the full-length of the neuronal isoform (nNOS) complex and determine the structural mechanism of CaM activation. We have identified that nNOS adopts an ensemble of open and closed conformational states and that CaM binding induces a dramatic rearrangement of the reductase domain. Our three-dimensional reconstruction of the intact nNOS-CaM complex reveals a closed conformation and a cross-monomer arrangement with the FMN domain rotated away from the NADPH-FAD center, toward the oxygenase dimer. This work captures, for the first time, the reductase-oxygenase structural arrangement and the CaM-dependent release of the FMN domain that coordinates to drive electron transfer across the domains during catalysis.

Fibre from pumpkin (Cucurbita pepo L.) seeds and rinds: physico-chemical properties, antioxidant capacity and application as bakery product ingredients

INTRODUCTION

The aims of this study were to determine the proximate composition, functional properties and antioxidant activity of pumpkin seeds and rind. Besides, the effects of dietary fibre in pumpkin seeds and rinds on bread qualities and properties were evaluated.

METHODS

Formulations for bread substituted with 0%, 5% and 10% pumpkin seed and rind, respectively were produced. Sensory evaluation of the prepared bread samples for such attributes as appearance, aroma, flavour, texture and overall acceptability was undertaken. The physical properties of the bread samples, including dough expansion, loaf volume, crumb colour and bread texture, were determined. Proximate analysis and determination of antioxidant activity of the bread samples were also conducted.

RESULTS

Crude fibre of the pumpkin seeds and pumpkin rinds was high at 31.48% and 14.83%, respectively. The total phenolic compound (TPC) and DPPH radical scavenging activity for the pumpkin rinds were 38.60 mg GAE/100 g dry weight and 69.38%, respectively, which were higher than those of pumpkin seeds. A 5% level of pumpkin rind bread gave the best overall acceptability and sensory attributes, followed by 5% pumpkin seed bread. Total dietary fibre, total phenolic compound and DPPH radical scavenging activity in breads substituted with 5% pumpkin seed and 5% pumpkin rind flour were higher than the values in control bread.

CONCLUSION

Pumpkin seeds and rinds can be used as dietary fibre sources in bakery.

Ubiquitination of neuronal nitric-oxide synthase in the calmodulin-binding site triggers proteasomal degradation of the protein

Nitric-oxide synthase, a cytochrome P450-like hemoprotein enzyme, catalyzes the synthesis of nitric oxide, a critical signaling molecule in a variety of physiological processes. Our laboratory has discovered that certain drugs suicide-inactivate neuronal nitric-oxide synthase (nNOS) and lead to the preferential ubiquitination of the inactivated nNOS by an Hsp70- and CHIP (C terminus of Hsc70-interacting protein)-dependent process. To further understand the process by which altered nNOS is recognized, ubiquitinated, and proteasomally degraded, we examined the sites of ubiquitination on nNOS. We utilized an in vitro ubiquitination system containing purified E1, E2 (UbcH5a), Hsp70, and CHIP that recapitulates the ability of the cells to selectively recognize and ubiquitinate the altered forms of nNOS. LC-MS/MS analysis of the tryptic peptides obtained from the in vitro ubiquitinated nNOS identified 12 ubiquitination sites. Nine of the sites were within the oxygenase domain and two were in the calmodulin-binding site, which links the oxygenase and reductase domains, and one site was in the reductase domain. Mutational analysis of the lysines in the calmodulin-binding site revealed that Lys-739 is a major site for poly-ubiquitination of nNOS in vitro and regulates, in large part, the CHIP-dependent degradation of nNOS in HEK293 cells, as well as in in vitro studies with fraction II. Elucidating the exact site of ubiquitination is an important step in understanding how chaperones recognize and trigger degradation of nNOS.

Can sharing experiences in groups reduce the burden of living with diabetes, regardless of glycaemic control?

AIMS

To test whether patients with Type 1 diabetes would join support groups and benefit by improving psychosocial functioning, regardless of their HbA1c levels.

METHODS

A pre-post test with follow-up after 6 and 12 months was conducted as a concurrent mixed-method study. The convenience sample included patients with Type 1 diabetes aged ≥21 years, having been diagnosed ≥1 year earlier. Primary outcome was diabetes-related distress (using the Problem Areas in Diabetes scale). Secondary outcomes were psychological distress and depressive symptoms (Symptom Check List -90-R/Global Severity Index and depression subscale), well-being (World Health Organization 5) and HbA1c .

RESULTS

Equal numbers of patients with HbA1c above and below 64 mmol/mol (8%) joined the support groups (n = 54). Focus group interviews revealed that major benefits were feeling less alone and being intuitively understood among peers. The patients perceived the support groups as a safe environment for sharing experiences. Problem Areas in Diabetes, Global Severity Index and depression subscale scores were significantly reduced post-intervention and maintained at 1-year follow-up. Well-being increased insignificantly. HbA1c was unchanged.

CONCLUSIONS

Support groups are able to reduce diabetes-related and psychological distress 1 year after the intervention for patients with both good and poor glycaemic control displaying high levels of distress. Although patients with severely high levels of diabetes-related distress might need more extensive therapeutic interventions to further reduce their level of distress. Further, interventions that target specific self-management problems are needed for patients with poor glycaemic control to help them accomplish lower levels of HbA1c. Moreover, healthcare providers must be aware that patients with good glycaemic control might have an unacknowledged psychosocial burden of living with the illness.