Anti-SMN autoantibodies in mixed connective tissue disease are associated with a severe systemic sclerosis phenotype.

OBJECTIVES: The survival of motor neuron (SMN) complex has an essential role in the assembly of small nuclear ribonucleoproteins (RNP). Recent reports have described autoantibodies (aAbs) to the SMN complex as novel biomarkers in anti-U1RNP+ myositis patients. The aim of this study was to compare phenotypic features of anti-U1RNP+ mixed connective tissue disease (MCTD) patients with and without anti-SMN aAbs. METHODS: A retrospective MCTD cohort was studied. Addressable laser bead immunoassay was used to detect specific anti-SMN aAbs with <300 mean fluorescence intensity (MFI) as normal reference range, 300-999 MFI as low-titre and ≥1000 MFI as high-titre positivity. Comparison of clinical features between anti-SMN+ and anti-SMN- subgroups used two-tailed Fisher's exact test, and logistic regression analyses. RESULTS: Sixty-six patients were included. Median age at MCTD diagnosis was 40.6 years, and duration of follow-up was 12 years. Based on the highest available titre, 39 (59%) were anti-SMN+: 10 (26%) had low titre and 29 (74%) had high titre. Anti-SMN+ patients had a higher frequency of fingertip pitting scars (anti-SMN+ 23% vs anti-SMN- 4%, p=0.04), lower gastrointestinal (GI) involvement (26% vs 4%, p=0.04), and myocarditis (16% vs 0%, p=0.04). The combined outcome of pitting scars and/or lower GI involvement and/or myositis and/or myocarditis was highest among high-titre anti-SMN+ patients: adjusted OR 7.79 (2.33 to 30.45, p=0.002). CONCLUSIONS: Anti-SMN aAbs were present in 59% of our MCTD cohort. Their presence, especially at high-titres, was associated with a severe systemic sclerosis (scleroderma) phenotype including myositis, myocarditis and lower GI involvement.

Concomitant symptomatic cardiac sarcoidosis and systemic sclerosis with cardiac involvement: a case report.

Sarcoidosis and systemic sclerosis are two inflammatory multisystemic disorders of unknown etiology that may be life-threatening especially when there is cardiac involvement. Both diseases may coexist, however, there are very few case reports of patients with both cardiac sarcoidosis and systemic sclerosis in the literature. We report the case of a 72-year-old female who was initially referred for dyspnea. A chest computed tomography scan showed multiple hilar and mediastinal adenopathy with a non-specific opacity in the middle pulmonary lobe. FDG-PET-scan showed increased FDG uptake in the adenopathy, the middle lobe and the right ventricular free wall. Sarcoidosis was confirmed with a lung biopsy. Both electrocardiogram and echocardiogram were normal. Four months later, the patient developed a high-grade atrioventricular block deemed secondary to her cardiac sarcoidosis. Two years later, the patient was referred to a rheumatologist for severe Raynaud's symptoms, sclerodactyly and acrocyanosis. After thorough investigations, a diagnosis of limited cutaneous systemic sclerosis with systemic and cardiac sarcoidosis was made. This case demonstrates that both cardiac sarcoidosis and systemic sclerosis may coexist. In the literature, either disease may come first. In cases where cardiac symptoms appear after the diagnosis of concomitant sarcoidosis and systemic sclerosis, it might be difficult for clinicians to confirm which disease is responsible for the heart involvement. This is important since early cardiac sarcoidosis treatment should be done to prevent major complications and may well differ from systemic sclerosis treatment. In this review, we discuss the main clinical manifestations and imaging findings seen with cardiac disease secondary to sarcoidosis and systemic sclerosis.

Meta-evaluation of a whole systems programme, ActEarly: A study protocol.

INTRODUCTION: Living in an area with high levels of child poverty predisposes children to poorer mental and physical health. ActEarly is a 5-year research programme that comprises a large number of interventions (>20) with citizen science and co-production embedded. It aims to improve the health and well-being of children and families living in two areas of the UK with high levels of deprivation; Bradford in West Yorkshire, and the London Borough of Tower Hamlets. This protocol outlines the meta-evaluation (an evaluation of evaluations) of the ActEarly programme from a systems perspective, where individual interventions are viewed as events in the wider policy system across the two geographical areas. It includes investigating the programme's impact on early life health and well-being outcomes, interdisciplinary prevention research collaboration and capacity building, and local and national decision making. METHODS: The ActEarly meta-evaluation will follow and adapt the five iterative stages of the 'Evaluation of Programmes in Complex Adaptive Systems' (ENCOMPASS) framework for evaluation of public health programmes in complex adaptive systems. Theory-based and mixed-methods approaches will be used to investigate the fidelity of the ActEarly research programme, and whether, why and how ActEarly contributes to changes in the policy system, and whether alternative explanations can be ruled out. Ripple effects and systems mapping will be used to explore the relationships between interventions and their outcomes, and the degree to which the ActEarly programme encouraged interdisciplinary and prevention research collaboration as intended. A computer simulation model ("LifeSim") will also be used to evaluate the scale of the potential long-term benefits of cross-sectoral action to tackle the financial, educational and health disadvantages faced by children in Bradford and Tower Hamlets. Together, these approaches will be used to evaluate ActEarly's dynamic programme outputs at different system levels and measure the programme's system changes on early life health and well-being. DISCUSSION: This meta-evaluation protocol presents our plans for using and adapting the ENCOMPASS framework to evaluate the system-wide impact of the early life health and well-being programme, ActEarly. Due to the collaborative and non-linear nature of the work, we reserve the option to change and query some of our evaluation choices based on the feedback we receive from stakeholders to ensure that our evaluation remains relevant and fit for purpose.

Nothing about us without us: A co-production strategy for communities, researchers and stakeholders to identify ways of improving health and reducing inequalities.

INTRODUCTION: Co-production with communities is increasingly seen as best practice that can improve the quality, relevance and effectiveness of research and service delivery. Despite this promising position, there remains uncertainty around definitions of co-production and how to operationalize it. The current paper describes the development of a co-production strategy to guide the work of the ActEarly multistakeholder preventative research programme to improve children's health in Bradford and Tower Hamlets, UK. METHODS: The strategy used Appreciative Inquiry (AI), an approach following a five-step iterative process: to define (Step 1) scope and guide progress; to discover (Step 2) key issues through seven focus groups (N = 36) and eight in-depth interviews with key stakeholders representing community groups, and the voluntary and statutory sectors; to dream (Step 3) best practice through two workshops with AI participants to review findings; to design (Step 4) a co-production strategy building on AI findings and to deliver (Step 5) the practical guidance in the strategy. RESULTS: Nine principles for how to do co-production well were identified: power should be shared; embrace a wide range of perspectives and skills; respect and value the lived experience; benefits should be for all involved parties; go to communities and do not expect them to come to you; work flexibly; avoid jargon and ensure availability of the right information; relationships should be built for the long-term; co-production activities should be adequately resourced. These principles were based on three underlying values of equality, reciprocity and agency. CONCLUSION: The empirical insights of the paper highlight the crucial importance of adequate resources and infrastructure to deliver effective co-production. This documentation of one approach to operationalizing co-production serves to avert any misappropriations of the term 'co-production' by listening to service users, stakeholders and other relevant groups, to develop trust and long-term relationships, and build on the learning that already exists amongst such groups. PATIENT OR PUBLIC CONTRIBUTION: The work was overseen by a steering group (N = 17) of individuals, both professional and members of the public with experience in undertaking co-production, and/or with some knowledge of the context of the two ActEarly field sites, who provided regular oversight and feedback on the AI process.

Brain metastatic outgrowth and osimertinib resistance are potentiated by RhoA in EGFR-mutant lung cancer.

The brain is a major sanctuary site for metastatic cancer cells that evade systemic therapies. Through pre-clinical pharmacological, biological, and molecular studies, we characterize the functional link between drug resistance and central nervous system (CNS) relapse in Epidermal Growth Factor Receptor- (EGFR-) mutant non-small cell lung cancer, which can progress in the brain when treated with the CNS-penetrant EGFR inhibitor osimertinib. Despite widespread osimertinib distribution in vivo, the brain microvascular tumor microenvironment (TME) is associated with the persistence of malignant cell sub-populations, which are poised to proliferate in the brain as osimertinib-resistant lesions over time. Cellular and molecular features of this poised state are regulated through a Ras homolog family member A (RhoA) and Serum Responsive Factor (SRF) gene expression program. RhoA potentiates the outgrowth of disseminated tumor cells on osimertinib treatment, preferentially in response to extracellular laminin and in the brain. Thus, we identify pre-existing and adaptive features of metastatic and drug-resistant cancer cells, which are enhanced by RhoA/SRF signaling and the brain TME during the evolution of osimertinib-resistant disease.

Exploring the Interactions between Housing and Neighbourhood Environments for Enhanced Child Wellbeing: The Lived Experience of Parents Living in Areas of High Child Poverty in England, UK.

Children's health can be affected by the interrelated characteristics of the physical and social environment where they live, including housing quality, neighbourhood characteristics and the local community. Following a systems-based approach, this exploratory project sought to understand how the needs and aspirations associated with the home environment can work in synergy with, or be exacerbated by, other aspects of the local area. The study recruited parents of children aged 2-12 years old from two local authorities in England with high levels of child poverty: Tower Hamlets in East London, and Bradford District in West Yorkshire. Thematic analysis of participant interviews highlighted ten themes and opportunities for improvements. The evidence presented in this research emphasises how environmental quality issues within and outside the home, compounded further by delays in repairs and reduction in service standards, as well as affordability issues, are likely to deeply affect the wellbeing of an entire generation of disadvantaged children whose parents can feel disempowered, neglected and often isolated when attempting to tackle various dimensions of inequalities. Interventions which can improve the quality of housing, and access to space and services, are urgently needed, including initiatives to support and empower families and local communities, especially those prioritising opportunities for action.

Cortical Organoids to Model Microcephaly.

How the brain develops and achieves its final size is a fascinating issue that questions cortical evolution across species and man's place in the animal kingdom. Although animal models have so far been highly valuable in understanding the key steps of cortical development, many human specificities call for appropriate models. In particular, microcephaly, a neurodevelopmental disorder that is characterized by a smaller head circumference has been challenging to model in mice, which often do not fully recapitulate the human phenotype. The relatively recent development of brain organoid technology from induced pluripotent stem cells (iPSCs) now makes it possible to model human microcephaly, both due to genetic and environmental origins, and to generate developing cortical tissue from the patients themselves. These 3D tissues rely on iPSCs differentiation into cortical progenitors that self-organize into neuroepithelial rosettes mimicking the earliest stages of human neurogenesis in vitro. Over the last ten years, numerous protocols have been developed to control the identity of the induced brain areas, the reproducibility of the experiments and the longevity of the cultures, allowing analysis of the later stages. In this review, we describe the different approaches that instruct human iPSCs to form cortical organoids, summarize the different microcephalic conditions that have so far been modeled by organoids, and discuss the relevance of this model to decipher the cellular and molecular mechanisms of primary and secondary microcephalies.

Development of Public Health Core Outcome Sets for Systems-Wide Promotion of Early Life Health and Wellbeing.

We aimed to develop a core outcome set (COS) for systems-wide public health interventions seeking to promote early life health and wellbeing. Research was embedded within the existing systems-based intervention research programme 'ActEarly', located in two different areas with high rates of child poverty, Bradford (West Yorkshire) and the Borough of Tower Hamlets (London). 168 potential outcomes were derived from five local government outcome frameworks, a community-led survey and an ActEarly consortium workshop. Two rounds of a Delphi study (Round 1: 37 participants; Round 2: 56 participants) reduced the number of outcomes to 64. 199 members of the community then took part in consultations across ActEarly sites, resulting in a final COS for systems-based public health interventions of 40 outcomes. These were grouped into the domains of: Development & education (N = 6); Physical health & health behaviors (N = 6); Mental health (N = 5); Social environment (N = 4); Physical environment (N = 7); and Poverty & inequality (N = 7). This process has led to a COS with outcomes prioritized from the perspectives of local communities. It provides the means to increase standardization and guide the selection of outcome measures for systems-based evaluation of public health programmes and supports evaluation of individual interventions within system change approaches.

Measuring the Built Environment in Studies of Child Health-A Meta-Narrative Review of Associations.

Although the built environment (BE) is important for children's health, there is little consensus about which features are most important due to differences in measurement and outcomes across disciplines. This meta-narrative review was undertaken by a multi-disciplinary team of researchers to summarise ways in which the BE is measured, and how this links to children's health. A structured search of four databases across the relevant disciplines retrieved 108 relevant references. The most commonly addressed health-related outcomes were active travel, physical activity and play, and obesity. Many studies used objective (GIS and street audits) or standardised subjective (perceived) measurements of the BE. However, there was a wide variety, and sometimes inconsistency, in their definition and use. There were clear associations between the BE and children's health. Objective physical activity and self-reported active travel, or obesity, were positively associated with higher street connectivity or walkability measures, while self-reported physical activity and play had the strongest association with reduced street connectivity, indicated by quieter, one-way streets. Despite the high heterogeneity found in BE measures and health outcomes, the meta-narrative approach enabled us to identify ten BE categories that are likely to support children's health and be protective against some non-communicable disease risk factors. Future research should implement consistent BE measures to ensure key features are explored. A systems approach will be particularly relevant for addressing place-based health inequalities, given potential unintended health consequences of making changes to the BE.

Tumor progression and chromatin landscape of lung cancer are regulated by the lineage factor GATA6.

Lineage selective transcription factors (TFs) are important regulators of tumorigenesis, but their biological functions are often context dependent with undefined epigenetic mechanisms of action. In this study, we uncover a conditional role for the endodermal and pulmonary specifying TF GATA6 in lung adenocarcinoma (LUAD) progression. Impairing Gata6 in genetically engineered mouse models reduces the proliferation and increases the differentiation of Kras mutant LUAD tumors. These effects are influenced by the epithelial cell type that is targeted for transformation and genetic context of Kras-mediated tumor initiation. In LUAD cells derived from surfactant protein C expressing progenitors, we identify multiple genomic loci that are bound by GATA6. Moreover, suppression of Gata6 in these cells significantly alters chromatin accessibility, particularly at distal enhancer elements. Analogous to its paradoxical activity in lung development, GATA6 expression fluctuates during different stages of LUAD progression and can epigenetically control diverse transcriptional programs associated with bone morphogenetic protein signaling, alveolar specification, and tumor suppression. These findings reveal how GATA6 can modulate the chromatin landscape of lung cancer cells to control their proliferation and divergent lineage dependencies during tumor progression.

Adaptive Protein Translation by the Integrated Stress Response Maintains the Proliferative and Migratory Capacity of Lung Adenocarcinoma Cells.

The integrated stress response (ISR) is a conserved pathway that is activated by cells that are exposed to stress. In lung adenocarcinoma, activation of the ATF4 branch of the ISR by certain oncogenic mutations has been linked to the regulation of amino acid metabolism. In the present study, we provide evidence for ATF4 activation across multiple stages and molecular subtypes of human lung adenocarcinoma. In response to extracellular amino acid limitation, lung adenocarcinoma cells with diverse genotypes commonly induce ATF4 in an eIF2α-dependent manner, which can be blocked pharmacologically using an ISR inhibitor. Although suppressing eIF2α or ATF4 can trigger different biological consequences, adaptive cell-cycle progression and cell migration are particularly sensitive to inhibition of the ISR. These phenotypes require the ATF4 target gene asparagine synthetase (ASNS), which maintains protein translation independently of the mTOR/PI3K pathway. Moreover, NRF2 protein levels and oxidative stress can be modulated by the ISR downstream of ASNS. Finally, we demonstrate that ASNS controls the biosynthesis of select proteins, including the cell-cycle regulator cyclin B1, which are associated with poor lung adenocarcinoma patient outcome. Our findings uncover new regulatory layers of the ISR pathway and its control of proteostasis in lung cancer cells. IMPLICATIONS: We reveal novel regulatory mechanisms by which the ISR controls selective protein translation and is required for cell-cycle progression and migration of lung cancer cells.

Atorvastatin-induced necrotizing autoimmune myositis: An emerging dominant entity in patients with autoimmune myositis presenting with a pure polymyositis phenotype.

The general aim of this study was to evaluate the disease spectrum in patients presenting with a pure polymyositis (pPM) phenotype. Specific objectives were to characterize clinical features, autoantibodies (aAbs), and membrane attack complex (MAC) in muscle biopsies of patients with treatment-responsive, statin-exposed necrotizing autoimmune myositis (NAM). Patients from the Centre hospitalier de l'Université de Montréal autoimmune myositis (AIM) Cohort with a pPM phenotype, response to immunosuppression, and follow-up ≥3 years were included. Of 17 consecutive patients with pPM, 14 patients had a NAM, of whom 12 were previously exposed to atorvastatin (mean 38.8 months). These 12 patients were therefore suspected of atorvastatin-induced AIM (atorAIM) and selected for study. All had aAbs to 3-hydroxy-3-methylglutaryl coenzyme A reductase, and none had overlap aAbs, aAbs to signal recognition particle, or cancer. Three stages of myopathy were recognized: stage 1 (isolated serum creatine kinase [CK] elevation), stage 2 (CK elevation, normal strength, and abnormal electromyogram [EMG]), and stage 3 (CK elevation, proximal weakness, and abnormal EMG). At diagnosis, 10/12 (83%) patients had stage 3 myopathy (mean CK elevation: 7247 U/L). The presenting mode was stage 1 in 6 patients (50%) (mean CK elevation: 1540 U/L), all of whom progressed to stage 3 (mean delay: 37 months) despite atorvastatin discontinuation. MAC deposition was observed in all muscle biopsies (isolated sarcolemmal deposition on non-necrotic fibers, isolated granular deposition on endomysial capillaries, or mixed pattern). Oral corticosteroids alone failed to normalize CKs and induce remission. Ten patients (83%) received intravenous immune globulin (IVIG) as part of an induction regimen. Of 10 patients with ≥1 year remission on stable maintenance therapy, IVIG was needed in 50%, either with methotrexate (MTX) monotherapy or combination immunosuppression. In the remaining patients, MTX monotherapy or combination therapy maintained remission without IVIG. AtorAIM emerged as the dominant entity in patients with a pPM phenotype and treatment-responsive myopathy. Isolated CK elevation was the mode of presentation of atorAIM. The new onset of isolated CK elevation on atorvastatin and persistent CK elevation on statin discontinuation should raise early suspicion for atorAIM. Statin-induced AIM should be included in the differential diagnosis of asymptomatic hyperCKemia. Three patterns of MAC deposition, while nonpathognomonic, were pathological clues to atorAIM. AtorAIM was uniformly corticosteroid resistant but responsive to IVIG as induction and maintenance therapy.

Clinical correlates of faecal incontinence in systemic sclerosis: identifying therapeutic avenues.

Objectives: The aim was to establish the prevalence and severity of faecal incontinence (FI) in SSc, its association with other intestinal manifestations and potential predictors of FI, and its impact on quality of life. Methods: A multicentre, cross-sectional study of 298 SSc subjects followed in the Canadian Scleroderma Research Group cohort was performed using validated questionnaires: Jorge-Wexner score (an FI severity scale), Bristol stool scale (a visual scale of stool consistency) and FI Quality-of-Life scale. Constipation was defined by the Rome III criteria. Associations between the Jorge-Wexner score and other clinical variables were determined using multivariate regression analyses. Results: Eighty-one (27.2%) subjects had FI, which was mild in 37 (12.4%) and moderate to severe in 44 (14.8%). Most patients had well-formed stools, 111 (38.8%) reported constipation and 38 (13.4%) had been previously treated for small intestinal bacterial overgrowth (SIBO). Variables independently associated with FI were: loose vs well-formed stools [odds ratio (OR) = 7.01, 95% CI: 2.09, 23.51)], constipation (OR = 3.64, 95% CI: 1.61, 8.27, P = 0.002), history of SIBO (OR = 2.97, 95% CI: 1.06, 8.27) and urinary incontinence (OR = 2.45, 95% CI: 1.14, 5.27). Quality of life measured with the FI Quality-of-Life scale was inversely correlated with FI severity (correlation coefficients between -0.602 and -0.702, P < 0.001). Conclusion: FI was common and often severe in SSc. Loose stools, SIBO, constipation and urinary incontinence were strongly associated with FI. Other than targeting anorectal dysfunction, concomitant treatment of clinical correlates could lead to improvement in FI and quality of life in SSc.

Human C6orf211 encodes Armt1, a protein carboxyl methyltransferase that targets PCNA and is linked to the DNA damage response.

Recent evidence supports the presence of an L-glutamyl methyltransferase(s) in eukaryotic cells, but this enzyme class has been defined only in certain prokaryotic species. Here, we characterize the human C6orf211 gene product as "acidic residue methyltransferase-1" (Armt1), an enzyme that specifically targets proliferating cell nuclear antigen (PCNA) in breast cancer cells, predominately methylating glutamate side chains. Armt1 homologs share structural similarities with the SAM-dependent methyltransferases, and negative regulation of activity by automethylation indicates a means for cellular control. Notably, shRNA-based knockdown of Armt1 expression in two breast cancer cell lines altered survival in response to genotoxic stress. Increased sensitivity to UV, adriamycin, and MMS was observed in SK-Br-3 cells, while in contrast, increased resistance to these agents was observed in MCF7 cells. Together, these results lay the foundation for defining the mechanism by which this post-translational modification operates in the DNA damage response (DDR).

The exposure of autoantigens by microparticles underlies the formation of potent inflammatory components: the microparticle-associated immune complexes.

Immunoglobulins, antigens and complement can assemble to form immune complexes (IC). ICs can be detrimental as they propagate inflammation in autoimmune diseases. Like ICs, submicron extracellular vesicles termed microparticles (MP) are present in the synovial fluid from patients affected with autoimmune arthritis. We examined MPs in rheumatoid arthritis (RA) using high sensitivity flow cytometry and electron microscopy. We find that the MPs in RA synovial fluid are highly heterogeneous in size. The observed larger MPs were in fact MP-containing ICs (mpICs) and account for the majority of the detectable ICs. These mpICs frequently express the integrin CD41, consistent with platelet origin. Despite expression of the Fc receptor FcγRIIa by platelet-derived MPs, we find that the mpICs form independently of this receptor. Rather, mpICs display autoantigens vimentin and fibrinogen, and recognition of these targets by anti-citrullinated peptide antibodies contributes to the production of mpICs. Functionally, platelet mpICs are highly pro-inflammatory, eliciting leukotriene production by neutrophils. Taken together, our data suggest a unique role for platelet MPs as autoantigen-expressing elements capable of perpetuating formation of inflammatory ICs.

The multifunctional nuclear protein p54nrb is multiphosphorylated in mitosis and interacts with the mitotic regulator Pin1.

The human protein p54nrb and its mouse homolog NonO have been implicated in a variety of nuclear processes including transcription, pre-mRNA processing, nuclear retention of edited RNA and DNA relaxation. We have identified p54nrb as an antigen of the phosphodependent monoclonal antibodies CC-3 and MPM-2 and shown that this protein is phosphorylated on multiple sites during mitosis. The use of the cyclin-dependent protein kinase inhibitor roscovitine and immunodepletion studies with an anti-cyclin B1 antibody established that Cdk1 was responsible for the phosphorylation of the carboxy-terminal extremity of p54nrb whereas a different kinase appeared to be involved in the generation of CC-3 epitope(s) in the amino-terminal moiety of the protein. Like many CC-3 and MPM-2 antigens, we show that p54nrb is a target of the peptidylprolyl isomerase Pin1, suggesting that it may be regulated by phosphorylation-dependent conformational changes as many other nuclear proteins upon entry into mitosis. In addition, site-directed mutagenesis indicated that the interaction of Pin1 with p54nrb was mediated by three threonine residues located in the proline-rich carboxy-terminal extremity of the protein. Our results also showed that Pin1 binding was favored when at least two of the three threonine residues were phosphorylated, suggesting a regulation mechanism based on multisite phosphorylation.

Multisite phosphorylation of Pin1-associated mitotic phosphoproteins revealed by monoclonal antibodies MPM-2 and CC-3.

BACKGROUND: The peptidyl-prolyl isomerase Pin1 recently revealed itself as a new player in the regulation of protein function by phosphorylation. Pin1 isomerizes the peptide bond of specific phosphorylated serine or threonine residues preceding proline in several proteins involved in various cellular events including mitosis, transcription, differentiation and DNA damage response. Many Pin1 substrates are antigens of the phosphodependent monoclonal antibody MPM-2, which reacts with a subset of proteins phosphorylated at the G2/M transition. RESULTS: As MPM-2 is not a general marker of mitotic phosphoproteins, and as most mitotic substrates are phosphorylated more than once, we used a different phosphodependent antibody, mAb CC-3, to identify additional mitotic phosphoproteins and eventual Pin1 substrates by combining affinity purification, MALDI-TOF mass spectrometry and immunoblotting. Most CC-3-reactive phosphoproteins appeared to be known or novel MPM-2 antigens and included the RNA-binding protein p54nrb/nmt55, the spliceosomal protein SAP155, the Ki-67 antigen, MAP-1B, DNA topoisomerases II alpha and beta, the elongation factor hSpt5 and the largest subunit of RNA polymerase II. The CC-3 mitotic antigens were also shown to be Pin1 targets. The fine CC-3- and MPM-2-epitope mapping of the RNA polymerase II carboxy-terminal domain confirmed that the epitopes were different and could be generated in vitro by distinct kinases. Finally, the post-mitotic dephosphorylation of both CC-3 and MPM-2 antigens was prevented when cellular Pin1 activity was blocked by the selective inhibitor juglone. CONCLUSION: These observations indicate that the mitotic phosphoproteins associated with Pin1 are phosphorylated on multiple sites, suggesting combinatorial regulation of substrate recognition and isomerization.

[Unexpected roles of the peptidyl-prolyl cis/trans isomerase Pin1]. / Pin1: une peptidyl-prolyl cis/trans isomérase aux rôles insoupçonnés.

Peptidyl-prolyl isomerases (PPIases) are chaperone enzymes which alter the peptide bond between a given amino acid and a proline, changing it from the cis to the trans conformation and vice versa. This modification can cause dramatic structural modifications which can affect the properties of targeted proteins. The ubiquitous PPIase Pin1, conserved from yeast to human, has been shown to be necessary for entry into mitosis. The yeast homologue, Ess1, is essential for cell survival. Pin1 possesses a WW domain which specifically recognizes pSer-Pro and pThr-Pro motifs in which the first amino acid is phosphorylated. Pin1 binds to many proteins implicated in cell cycle regulation (e.g. p53, Myt1, Wee1, and Cdc25C). Pin1 also targets tau, a protein forming part of hte neuronal cytoskeleton which is hyper-phosphorylated in patients suffering from Alzheimer's disease (AD). Pin1 could, therefore, be involved in the pathogenesis of Ad. Furthermore, Pin1 also binds two proteins involved in transcription: Rpb1, the largest subunit of RNA polymerase II and Spt5, a regulator of the elongation of transcription. Both theses proteins possess domains rich in S/T-P motifs which can be targeted by Pin1 when phosphorylated. Recent studies show that Pin1 modulates the dephosphorylation of some proteins by allowing trans-specific phosphatases to recognize their target after isomerization. This unexpected role might allow protein regulation via peptidyl-prolyl isomerase activity.