Structural insights into the activation mechanism of antimicrobial GBP1.

The dynamin-related human guanylate-binding protein 1 (GBP1) mediates host defenses against microbial pathogens. Upon GTP binding and hydrolysis, auto-inhibited GBP1 monomers dimerize and assemble into soluble and membrane-bound oligomers, which are crucial for innate immune responses. How higher-order GBP1 oligomers are built from dimers, and how assembly is coordinated with nucleotide-dependent conformational changes, has remained elusive. Here, we present cryo-electron microscopy-based structural data of soluble and membrane-bound GBP1 oligomers, which show that GBP1 assembles in an outstretched dimeric conformation. We identify a surface-exposed helix in the large GTPase domain that contributes to the oligomerization interface, and we probe its nucleotide- and dimerization-dependent movements that facilitate the formation of an antimicrobial protein coat on a gram-negative bacterial pathogen. Our results reveal a sophisticated activation mechanism for GBP1, in which nucleotide-dependent structural changes coordinate dimerization, oligomerization, and membrane binding to allow encapsulation of pathogens within an antimicrobial protein coat.

STIC2 selectively binds ribosome-nascent chain complexes in the cotranslational sorting of Arabidopsis thylakoid proteins.

Chloroplast-encoded multi-span thylakoid membrane proteins are crucial for photosynthetic complexes, yet the coordination of their biogenesis remains poorly understood. To identify factors that specifically support the cotranslational biogenesis of the reaction center protein D1 of photosystem (PS) II, we generated and affinity-purified stalled ribosome-nascent chain complexes (RNCs) bearing D1 nascent chains. Stalled RNCs translating the soluble ribosomal subunit uS2c were used for comparison. Quantitative tandem-mass spectrometry of the purified RNCs identified around 140 proteins specifically associated with D1 RNCs, mainly involved in protein and cofactor biogenesis, including chlorophyll biosynthesis, and other metabolic pathways. Functional analysis of STIC2, a newly identified D1 RNC interactor, revealed its cooperation with chloroplast protein SRP54 in the de novo biogenesis and repair of D1, and potentially other cotranslationally-targeted reaction center subunits of PSII and PSI. The primary binding interface between STIC2 and the thylakoid insertase Alb3 and its homolog Alb4 was mapped to STIC2's ß-sheet region, and the conserved Motif III in the C-terminal regions of Alb3/4.

LPS-aggregating proteins GBP1 and GBP2 are each sufficient to enhance caspase-4 activation both in cellulo and in vitro.

The gamma-interferon (IFNγ)-inducible guanylate-binding proteins (GBPs) promote host defense against gram-negative cytosolic bacteria in part through the induction of an inflammatory cell death pathway called pyroptosis. To activate pyroptosis, GBPs facilitate sensing of the gram-negative bacterial outer membrane component lipopolysaccharide (LPS) by the noncanonical caspase-4 inflammasome. There are seven human GBP paralogs, and it is unclear how each GBP contributes to LPS sensing and pyroptosis induction. GBP1 forms a multimeric microcapsule on the surface of cytosolic bacteria through direct interactions with LPS. The GBP1 microcapsule recruits caspase-4 to bacteria, a process deemed essential for caspase-4 activation. In contrast to GBP1, closely related paralog GBP2 is unable to bind bacteria on its own but requires GBP1 for direct bacterial binding. Unexpectedly, we find that GBP2 overexpression can restore gram-negative-induced pyroptosis in GBP1KO cells, without GBP2 binding to the bacterial surface. A mutant of GBP1 that lacks the triple arginine motif required for microcapsule formation also rescues pyroptosis in GBP1KO cells, showing that binding to bacteria is dispensable for GBPs to promote pyroptosis. Instead, we find that GBP2, like GBP1, directly binds and aggregates "free" LPS through protein polymerization. We demonstrate that supplementation of either recombinant polymerized GBP1 or GBP2 to an in vitro reaction is sufficient to enhance LPS-induced caspase-4 activation. This provides a revised mechanistic framework for noncanonical inflammasome activation where GBP1 or GBP2 assembles cytosol-contaminating LPS into a protein-LPS interface for caspase-4 activation as part of a coordinated host response to gram-negative bacterial infections.

Direct binding of polymeric GBP1 to LPS disrupts bacterial cell envelope functions.

In the outer membrane of gram-negative bacteria, O-antigen segments of lipopolysaccharide (LPS) form a chemomechanical barrier, whereas lipid A moieties anchor LPS molecules. Upon infection, human guanylate binding protein-1 (hGBP1) colocalizes with intracellular gram-negative bacterial pathogens, facilitates bacterial killing, promotes activation of the lipid A sensor caspase-4, and blocks actin-driven dissemination of the enteric pathogen Shigella. The underlying molecular mechanism for hGBP1's diverse antimicrobial functions is unknown. Here, we demonstrate that hGBP1 binds directly to LPS and induces "detergent-like" LPS clustering through protein polymerization. Binding of polymerizing hGBP1 to the bacterial surface disrupts the O-antigen barrier, thereby unmasking lipid A, eliciting caspase-4 recruitment, enhancing antibacterial activity of polymyxin B, and blocking the function of the Shigella outer membrane actin motility factor IcsA. These findings characterize hGBP1 as an LPS-binding surfactant that destabilizes the rigidity of the outer membrane to exert pleiotropic effects on the functionality of gram-negative bacterial cell envelopes.

The intramolecular allostery of GRB2 governing its interaction with SOS1 is modulated by phosphotyrosine ligands.

Growth factor receptor-bound protein 2 (GRB2) is a trivalent adaptor protein and a key element in signal transduction. It interacts via its flanking nSH3 and cSH3 domains with the proline-rich domain (PRD) of the RAS activator SOS1 and via its central SH2 domain with phosphorylated tyrosine residues of receptor tyrosine kinases (RTKs; e.g. HER2). The elucidation of structural organization and mechanistic insights into GRB2 interactions, however, remain challenging due to their inherent flexibility. This study represents an important advance in our mechanistic understanding of how GRB2 links RTKs to SOS1. Accordingly, it can be proposed that (1) HER2 pYP-bound SH2 potentiates GRB2 SH3 domain interactions with SOS1 (an allosteric mechanism); (2) the SH2 domain blocks cSH3, enabling nSH3 to bind SOS1 first before cSH3 follows (an avidity-based mechanism); and (3) the allosteric behavior of cSH3 to other domains appears to be unidirectional, although there is an allosteric effect between the SH2 and SH3 domains.

Screening is associated with lower mastectomy rates in eastern Switzerland beyond stage effects.

BACKGROUND: A recent study found an influence of organized mammography screening programmes (MSPs) on geographical and temporal variation of mastectomy rates. We aimed to quantify the effect on the example of one of the cantonal programmes in Switzerland. METHODS: We used incidence data for the years 2010-2017 from the cancer registry of Eastern Switzerland. We included women with invasive-non-metastatic breast cancer (BC) in the screening age group 50-69-year-olds in the canton of St.Gallen. We compared mastectomy rates among cancer patients detected through the organised screening programme (MSP) vs. otherwise detected by stage. RESULTS: MSP-detected patients in St.Gallen presented with lower stages. 95% of MSP-detected had stages I-II vs 76% of Non-MSP-detected. Within all non-metastatic stage, tumour size and nodal status groups, MSP-detected patients had lower mastectomy rates, overall 10% vs 24% in 50-69-year-old non-participants. Their odds of receiving a mastectomy are about half of the Non-MSP-detected (OR = 0.48, p = 0.002). CONCLUSIONS: Our study showed that MSPs have a positive effect on lowering mastectomy rates. Screening participants are significantly less likely to receive a mastectomy compared to non-participants, which must be attributed to additional factors than just lower stages. Lower mastectomy rates lead to a higher quality of life for many patients.

Identifying classes of the pain, fatigue, and depression symptom cluster in long-term prostate cancer survivors-results from the multi-regional Prostate Cancer Survivorship Study in Switzerland (PROCAS).

PURPOSE: Aside from urological and sexual problems, long-term (≥5 years after initial diagnosis) prostate cancer (PC) survivors might suffer from pain, fatigue, and depression. These concurrent symptoms can form a cluster. In this study, we aimed to investigate classes of this symptom cluster in long-term PC survivors, to classify PC survivors accordingly, and to explore associations between classes of this cluster and health-related quality of life (HRQoL). METHODS: Six hundred fifty-three stage T1-T3N0M0 survivors were identified from the Prostate Cancer Survivorship in Switzerland (PROCAS) study. Fatigue was assessed with the EORTC QLQ-FA12, depressive symptoms with the MHI-5, and pain with the EORTC QLQ-C30 questionnaire. Latent class analysis was used to derive cluster classes. Factors associated with the derived classes were determined using multinomial logistic regression analysis. RESULTS: Three classes were identified: class 1 (61.4%) - "low pain, low physical and emotional fatigue, moderate depressive symptoms"; class 2 (15.1%) - "low physical fatigue and pain, moderate emotional fatigue, high depressive symptoms"; class 3 (23.5%) - high scores for all symptoms. Survivors in classes 2 and 3 were more likely to be physically inactive, report a history of depression or some other specific comorbidity, be treated with radiation therapy, and have worse HRQoL outcomes compared to class 1. CONCLUSION: Three distinct classes of the pain, fatigue, and depression cluster were identified, which are associated with treatment, comorbidities, lifestyle factors, and HRQoL outcomes. Improving classification of PC survivors according to severity of multiple symptoms could assist in developing interventions tailored to survivors' needs.

Phosphorylation orchestrates the structural ensemble of the intrinsically disordered protein HMGA1a and modulates its DNA binding to the NFκB promoter.

High Mobility Group Protein A1a (HMGA1a) is a highly abundant nuclear protein, which plays a crucial role during embryogenesis, cell differentiation, and neoplasia. Here, we present the first ever NMR-based structural ensemble of full length HMGA1a. Our results show that the protein is not completely random coil but adopts a compact structure consisting of transient long-range contacts, which is regulated by post-translational phosphorylation. The CK2-, cdc2- and cdc2/CK2-phosphorylated forms of HMGA1a each exhibit a different binding affinity towards the PRD2 element of the NFκB promoter. Our study identifies connected regions between phosphorylation sites in the wildtype ensemble that change considerably upon phosphorylation, indicating that these posttranslational modifications sites are part of an electrostatic contact network that alters the structural ensemble by shifting the conformational equilibrium. Moreover, ITC data reveal that the CK2-phosphorylated HMGA1a exhibits a different DNA promoter binding affinity for the PRD2 element. Furthermore, we present the first structural model for AT-hook 1 of HMGA1a that can adopt a transient α-helical structure, which might serve as an additional regulatory mechanism in HMAG1a. Our findings will help to develop new therapeutic strategies against HMGA1a-associated cancers by taking posttranslational modifications into consideration.

Associations between physical activity, basic motor competencies and automatic evaluations of exercise.

Dual process theories suggest that the decision to be physically active is influenced by reflective and automatic processes. However, associations of automatic (affective) evaluations of exercise with physical activity and underlying basic motor competencies have not yet been investigated in children and young adolescents. Ninety-one participants (52 male; age: 10-14 years) were recruited from academic high schools in Germany and Switzerland. Automatic evaluations of exercise were measured with the Single-Target Implicit Association Test (ST-IAT) and a D-score was calculated. Moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) per day were determined via wrist-worn actigraphy over the course of seven days. Basic motor competencies were measured using the MOBAK-5 test battery. Pearson correlations showed non-significant associations of automatic evaluations of exercise with MVPA, but significant associations with VPA. Basic motor competencies were associated with automatic evaluations of exercise, and the MOBAK subscale of object movement was associated with both MVPA and VPA. Our results underscore the relevance of affective processes for physical activity behaviour. This could potentially be relevant for interventions targeting physical activity promotion. Longitudinal investigations and intervention studies are necessary to verify causal relationships and potential underlying mechanisms.

De Novo Missense Mutations in TNNC1 and TNNI3 Causing Severe Infantile Cardiomyopathy Affect Myofilament Structure and Function and Are Modulated by Troponin Targeting Agents.

Rare pediatric non-compaction and restrictive cardiomyopathy are usually associated with a rapid and severe disease progression. While the non-compaction phenotype is characterized by structural defects and is correlated with systolic dysfunction, the restrictive phenotype exhibits diastolic dysfunction. The molecular mechanisms are poorly understood. Target genes encode among others, the cardiac troponin subunits forming the main regulatory protein complex of the thin filament for muscle contraction. Here, we compare the molecular effects of two infantile de novo point mutations in TNNC1 (p.cTnC-G34S) and TNNI3 (p.cTnI-D127Y) leading to severe non-compaction and restrictive phenotypes, respectively. We used skinned cardiomyocytes, skinned fibers, and reconstituted thin filaments to measure the impact of the mutations on contractile function. We investigated the interaction of these troponin variants with actin and their inter-subunit interactions, as well as the structural integrity of reconstituted thin filaments. Both mutations exhibited similar functional and structural impairments, though the patients developed different phenotypes. Furthermore, the protein quality control system was affected, as shown for TnC-G34S using patient's myocardial tissue samples. The two troponin targeting agents levosimendan and green tea extract (-)-epigallocatechin-3-gallate (EGCg) stabilized the structural integrity of reconstituted thin filaments and ameliorated contractile function in vitro in some, but not all, aspects to a similar degree for both mutations.

The relative risk of second primary cancers in Switzerland: a population-based retrospective cohort study.

BACKGROUND: More people than ever before are currently living with a diagnosis of cancer and the number of people concerned is likely to continue to rise. Cancer survivors are at risk of developing a second primary cancer (SPC). This study aims to investigate the risk of SPC in Switzerland. METHODS: The study cohort included all patients with a first primary cancer recorded in 9 Swiss population-based cancer registries 1981-2009 who had a minimum survival of 6 months, and a potential follow-up until the end of 2014. We calculated standardized incidence ratios (SIR) to estimate relative risks (RR) of SPC in cancer survivors compared with the cancer risk of the general population. SIR were stratified by type of first cancer, sex, age and period of first diagnosis, survival period and site of SPC. RESULTS: A total of 33,793 SPC were observed in 310,113 cancer patients. Both male (SIR 1.18, 95%CI 1.16-1.19) and female (SIR 1.20, 95%CI 1.18-1.22) cancer survivors had an elevated risk of developing a SPC. Risk estimates varied substantially according to type of first cancer and were highest in patients initially diagnosed with cancer of the oral cavity and pharynx, Hodgkin lymphoma, laryngeal, oesophageal, or lung cancer. Age-stratified analyses revealed a tendency towards higher RR in patients first diagnosed at younger ages. Stratified by survival period, risk estimates showed a rising trend with increasing time from the initial diagnosis. We observed strong associations between particular types of first and SPC, i.e. cancer types sharing common risk factors such as smoking or alcohol consumption (e.g. repeated cancer of the oral cavity and pharynx (SIRmales 20.12, 95%CI 17.91-22.33; SIRfemales 37.87, 95%CI 30.27-45.48). CONCLUSION: Swiss cancer survivors have an increased risk of developing a SPC compared to the general population, particularly patients first diagnosed before age 50 and those surviving more than 10 years. Cancer patients should remain under continued surveillance not only for recurrent cancers but also for new cancers. Some first and SPCs share lifestyle associated risk factors making it important to promote healthier lifestyles in both the general population and cancer survivors.

Correction to: The relative risk of second primary cancers in Switzerland: a population-based retrospective cohort study.

Following publication of the original article [1], an error was reported in the author group. The correct author group should read as follows.

The interaction strength of an intrinsically disordered protein domain with its binding partner is little affected by very different cosolutes.

A common feature of intrinsically disordered proteins (IDPs) is a disorder-to-order transition upon binding to other proteins, which has been tied to multiple benefits, including accelerated association rates or binding with low affinity, yet high specificity. Given the balanced equilibrium concentrations of folded and unfolded state of an IDP we asked the question if changes in the chemical environment, such as the presence of osmolytes or crowding agents, have a strong influence on the interaction of an IDP. Here, we demonstrate the impact of cosolutes on the interaction of the intrinsically disordered transcription factor c-Myb and its binding partner, the kinase-inducible interaction domain (KIX) of the CREB-binding protein. Temperature jump relaxation kinetics and microscale thermophoresis were employed in order to quantify the rate constants and the binding affinity of the c-Myb/KIX complex, respectively, in the presence of various cosolutes. We find the binding free energy of the c-Myb/KIX complex only marginally modulated by cosolutes, whereas the enthalpy and entropy of the interaction are very sensitive to the respective solvent conditions. For different cosolutes we observe substantial changes in enthalpy, both favorable and unfavorable, which are going with entropy changes largely compensating the enthalpy effects in each case. These characteristics might reflect a potential mechanism by which c-Myb offsets changes in the physico-chemical environment to maintain a roughly unaltered binding affinity.

The Role of Motor Competences in Predicting Working Memory Maintenance and Preparatory Processing.

The purpose of the study was the examination of the longitudinal association between motor competences and changes in preparatory processing during a task requiring working memory maintenance. At baseline, 52 Caucasian children aged 10-12 years completed the MOBAK-5 test battery and a Sternberg task, whereas the cue-P300 and the initial contingent negative variation (iCNV) were recorded via electroencephalography. After 9 months, the Sternberg task was administered again to assess changes in these neurophysiological indices and behavioral performance. Path analyses revealed that motor competences predicted the change in cue-P300 and iCNV from baseline to follow-up. The present findings indicate that the cognitive control strategy during a task demanding working memory maintenance changes as a function of children's baseline motor competences.

Does progress achieved in the treatment of patients with metastatic non-small-cell lung cancer reach the elderly population? A cohort study from a cancer centre from Eastern Switzerland.

OBJECTIVE: Treatment options for non-small-cell lung cancer (NSCLC) have been evolving. The goal of our study was to evaluate whether novel therapeutics are used in the elderly population and improve outcomes to a similar extent as in young patients. METHODS: We enrolled patients registered in the Cancer Registry of Eastern Switzerland and grouped them into four cohorts: Elderly patients aged ≥70 years diagnosed 2005-2007 and 2015-2016 (elderly cohorts 1,2) were compared to cohorts of patients < 70 years diagnosed during the same time periods (young cohorts 1,2). RESULTS: 499 individuals were analysed. Median cancer-specific survival in the elderly cohorts 1 and 2 was 3.9 months and 6.3 months, respectively, and 8.0 and 12.7 months in the young cohorts 1 and 2. 12-month survival significantly improved over ten years only in younger patients (35.6% and 54.9%), however not in the elderly cohorts (20% vs. 35%). Proportion of patients receiving any line of systemic treatment remained lower in the elderly cohorts (53% vs. 78%). CONCLUSION: Despite the increase in median cancer-specific survival in both cohorts, a significant and clinically meaningful improvement of 12-month cancer-specific survival was only seen in young patients. The adoption of novel treatment approaches is lagging behind in the elderly population.

Nucleotide-dependent farnesyl switch orchestrates polymerization and membrane binding of human guanylate-binding protein 1.

Dynamin-like proteins (DLPs) mediate various membrane fusion and fission processes within the cell, which often require the polymerization of DLPs. An IFN-inducible family of DLPs, the guanylate-binding proteins (GBPs), is involved in antimicrobial and antiviral responses within the cell. Human guanylate-binding protein 1 (hGBP1), the founding member of GBPs, is also engaged in the regulation of cell adhesion and migration. Here, we show how the GTPase cycle of farnesylated hGBP1 (hGBP1F) regulates its self-assembly and membrane interaction. Using vesicles of various sizes as a lipid bilayer model, we show GTP-dependent membrane binding of hGBP1F In addition, we demonstrate nucleotide-dependent tethering ability of hGBP1F Furthermore, we report nucleotide-dependent polymerization of hGBP1F, which competes with membrane binding of the protein. Our results show that hGBP1F acts as a nucleotide-controlled molecular switch by modulating the accessibility of its farnesyl moiety, which does not require any supportive proteins.

Motor tests for primary school aged children: A systematic review.

Motor testing in education has gained in relevance in light of recent developments in educational systems (Köller & Baumert, 2012). The purpose of this systematic review was to identify studies using motor tests in primary school children aged 4 to 12 years and to synthetize information about the quality and application of the test instruments used. A systematic review of 910 records identified by a search of nine databases yielded 144 papers reporting motor testing in primary school age children, including 25 articles reporting on the quality of 20 test instruments. In the selected articles, tests grounded on the constructs of "motor abilities" and/or "motor skills" are the most frequent and are mostly used for monitoring purposes or for impact research. Tests based on the construct "motor competencies" have become popular only recently, being relevant for educational motor testing due to their curricular validity. The test instruments have been investigated towards their validity and reliability to different extents. However, for several test instruments factorial validity has not been established and more validation studies are needed to improve their psychometric quality especially if used in educational contexts.

The Structure in Solution of Fibronectin Type III Domain 14 Reveals Its Synergistic Heparin Binding Site.

Fibronectin is a large multidomain protein of the extracellular matrix that harbors two heparin binding sites, Hep-I and Hep-II, which support the heparin-dependent adhesion of melanoma and neuroblastoma cells [Barkalow, F. J. B., and Schwarzbauer, J. E. (1991) J. Biol. Chem. 266, 7812-7818; McCarthy, J. B., et al. (1988) Biochemistry 27, 1380-1388; Drake, S. L., et al. (1993) J. Biol. Chem. 268, 15859-15867]. The stronger heparin/HS binding site on fibronectin, Hep-II, spans fibronectin type III domains 12-14. Previous site-directed mutagenesis, nuclear magnetic resonance (NMR) chemical shift perturbation, and crystallographic structural studies all agree that the main heparin binding site is located on the surface of fibronectin type III domain 13 [Ingham, K. C., et al. (1993) Biochemistry 32, 12548-12553; Sharma, A., et al. (1999) EMBO J. 18, 1468-1479; Sachchidanand, L. O., et al. (2002) J. Biol. Chem. 277, 50629-50635]. However, the "synergy site" for heparin binding located on fibronectin type III domain 14 remained elusive because the actual binding sites could not be identified. Using NMR spectroscopy and isothermal titration calorimetry, we show here that heparin is able to bind to a cationic 'cradle' of fibronectin type III domain 14 formed by the PRARI sequence, which is involved in the integrin α4ß1 interaction [Mould, A. P., and Humphries, M. J. (1991) EMBO J. 10, 4089-4095], and to the flexible loop comprising residues KNNQKSE between the last two ß-strands, D and E, of FN14. Our data reveal that the individual FN14 domain binds to the sulfated sugars Dp8 and Reviparin with affinities similar to those of the individual domain FN13 [Breddin, H. K. (2002) Expert Opin. Pharmacother. 3, 173-182]. It is noteworthy that by introduction of the last ß-strand of FN13 and the linker region between FN type III domains 13 and 14, the perturbation of NMR chemical shifts by heparin is significantly reduced, especially at the PRARI site. This indicates that the Hep-II binding site of fibronectin is mainly located on FN13 and the synergistic binding site on FN14 involves only the KNNQKSE sequence.

Heat Shock Proteins Revisited: Using a Mutasynthetically Generated Reblastatin Library to Compare the Inhibition of Human and Leishmania Hsp90s.

Thirteen new reblastatin derivatives, with alkynyl, amino and fluoro substituents on the aromatic ring, were prepared by a chemo-biosynthetic approach using an AHBA(-) mutant strain of Streptomyces hygroscopicus, the geldanamycin producer. The inhibitory potencies of these mutaproducts and of an extended library of natural products and derivatives were probed with purified heat shock proteins (Hsps), obtained from Leishmania braziliensis (LbHsp90) as well as from human sources (HsHsp90). We determined the activities of potential inhibitors by means of a displacement assay in which fluorescence-labelled ATP competes for the ATP binding sites of Hsps in the presence of the inhibitor in question. The results were compared with those of cell-based assays and, in selected cases, of isothermal titration calorimetry (ITC) measurements. In essence, reblastatin derivatives are also able to bind effectively to the ATP-binding site of LbHsp90, and for selected derivatives, moderate differences in binding to LbHsp90 and HsHsp90 were encountered. This work demonstrates that parasitic heat shock proteins can be developed as potential pharmaceutical targets.

A Multiperspective Approach to Solvent Regulation of Enzymatic Activity: HMG-CoA Reductase.

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase was investigated in different organic cosolvents by means of kinetic and calorimetric measurements, molecular dynamics simulations, and small-angle X-ray scattering. The combined experimental and theoretical techniques were essential to complement each other's limitations in the investigation of the complex interaction pattern between the enzyme, different solvent types, and concentrations. In this way, the underlying mechanisms for the loss of enzyme activity in different water-miscible solvents could be elucidated. These include direct inhibitory effects onto the active center and structural distortions.