Fibroblasts: the missing link between fibrotic lung diseases of different etiologies?

CommentaryInternational audienc

Oriented Scanning Is the Leading Mechanism Underlying 5′ Splice Site Selection in Mammals

Splice site selection is a key element of pre-mRNA splicing. Although it is known to involve specific recognition of short consensus sequences by the splicing machinery, the mechanisms by which 5′ splice sites are accurately identified remain controversial and incompletely resolved. The human F7 gene contains in its seventh intron (IVS7) a 37-bp VNTR minisatellite whose first element spans the exon7–IVS7 boundary. As a consequence, the IVS7 authentic donor splice site is followed by several cryptic splice sites identical in sequence, referred to as 5′ pseudo-sites, which normally remain silent. This region, therefore, provides a remarkable model to decipher the mechanism underlying 5′ splice site selection in mammals. We previously suggested a model for splice site selection that, in the presence of consecutive splice consensus sequences, would stimulate exclusively the selection of the most upstream 5′ splice site, rather than repressing the 3′ following pseudo-sites. In the present study, we provide experimental support to this hypothesis by using a mutational approach involving a panel of 50 mutant and wild-type F7 constructs expressed in various cell types. We demonstrate that the F7 IVS7 5′ pseudo-sites are functional, but do not compete with the authentic donor splice site. Moreover, we show that the selection of the 5′ splice site follows a scanning-type mechanism, precluding competition with other functional 5′ pseudo-sites available on immediate sequence context downstream of the activated one. In addition, 5′ pseudo-sites with an increased complementarity to U1snRNA up to 91% do not compete with the identified scanning mechanism. Altogether, these findings, which unveil a cell type–independent 5′−3′-oriented scanning process for accurate recognition of the authentic 5′ splice site, reconciliate apparently contradictory observations by establishing a hierarchy of competitiveness among the determinants involved in 5′ splice site selection

Protean proteases: At the cutting edge of lung diseases

Proteases were traditionally viewed as mere protein-degrading enzymes with a very restricted spectrum of substrates. A major expansion in protease research has uncovered a variety of novel substrates, and it is now evident that proteases are critical pleiotropic actors orchestrating pathophysiological processes. Recent findings evidenced that the net proteolytic activity also relies upon interconnections between different protease and protease inhibitor families in the protease web.In this review, we provide an overview of these novel concepts with a particular focus on pulmonary pathophysiology. We describe the emerging roles of several protease families including cysteine and serine proteases.The complexity of the protease web is exemplified in the light of multidimensional regulation of serine protease activity by matrix metalloproteases through cognate serine protease inhibitor processing. Finally, we will highlight how deregulated protease activity during pulmonary pathogenesis may be exploited for diagnosis/prognosis purposes, and utilised as a therapeutic tool using nanotechnologies.Considering proteases as part of an integrative biology perspective may pave the way for the development of new therapeutic targets to treat pulmonary diseases related to intrinsic protease deregulation

Pharmacological targeting of protease-activated receptor 2 affords protection from bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis is the most devastating diffuse fibrosing lung disease that remains refractory to therapy. Despite increasing evidence that protease-activated receptor 2 (PAR-2) contributes to fibrosis, its importance in pulmonary fibrosis is under debate. We addressed whether PAR-2 deficiency persistently reduces bleomycin-induced pulmonary fibrosis or merely delays disease progression and whether pharmacological PAR-2 inhibition limits experimental pulmonary fibrosis. Bleomycin was instilled intranasally into wild-type or PAR-2-deficient mice in the presence/absence of a specific PAR-2 antagonist (P2pal-18S). Pulmonary fibrosis was consistently reduced in PAR-2-deficient mice throughout the fibrotic phase, as evident from reduced Ashcroft scores (29%) and hydroxyproline levels (26%) at d 28. Moreover, P2pal-18S inhibited PAR-2-induced profibrotic responses in both murine and primary human pulmonary fibroblasts (p < 0.05). Once daily treatment with P2pal-18S reduced the severity and extent of fibrotic lesions in lungs of bleomycin-treated wild-type mice but did not further reduce fibrosis in PAR-2-deficient mice. Importantly, P2pal-18S treatment starting even 7 d after the onset of fibrosis limits pulmonary fibrosis as effectively as when treatment was started together with bleomycin instillation. Overall, PAR-2 contributes to the progression of pulmonary fibrosis, and targeting PAR-2 may be a promising therapeutic strategy for treating pulmonary fibrosis

Action and Function of coagulation FXa on cellular signaling

In the late 1970s, during a program set to identify potential mitogenic components of serum, thrombin was shown to be a powerful mitogen for fibroblasts and to induce fibroblast migration in wound scratch assays via a direct mechanism requiring thrombin’s catalytic activity and involving receptor activation. The quandary as to how coagulation factors influenced cellular responses, which was suspected since the observation of Trousseau and the eponym syndrome, was elucidated by the identification of the thrombin receptor PAR-1 in 1991. PAR-1 represented the first member of a fundamentally unique subclass within the seven transmembrane domain protein superfamily, as receptors in this subclass are activated by proteolytic cleavage. At the approximately the same time the structural homology of tissue factor (TF) with the class 2 cytokine receptor superfamily led to the hypothesis that binding of FVIIa to TF would induce intracellular signaling as well. Indeed, FVIIa binding to TF triggers signaling pathways. The interaction of FVIIa with TF is essential for signaling as the binding induces a major structural change in the serine protease domain allowing its full activity. Interestingly, TF/FVIIa signaling appears to be mediated via PAR-2 activation, reuniting the different components of the coagulation signaling-associated plasma membrane-localized components. Over the last decade, a plethora of studies established the pleiotropic role of FVIIa and thrombin in health and disease (e.g. inflammation, cancer, angiogenesis, but also wound healing and bone development for thrombin. However, as an intermediate in the coagulation cascade, FXa has long been considered a passive bystander only, and consequently its role in cell biology remained relatively unexplored. It is now clear that FXa plays a crucial non-haemostatic role. Thus, it has become clear that vitamin K-dependent coagulation factors in general and factor X in particular are principal players in pathophysiology. Hence understanding its biology better as well as its role in pathophysiology my provide exiting insights in both the understanding of human and animal physiology in general and provide clues to improved therapy in particular. In thesis I explore the biology of factor X and its associated signaling components, in particular factor VII. To this end, following a literature study on the molecular genetics and pathophysiology of coagulation FVII and FX inherited deficiencies (chapter 2), I start in the nucleus with a study on the regulation of splice site selection in the FVII gene as its intron 7 provides an excellent for such a study, with repetition of the intron 7 splice donor site (chapter 3). Next, I investigate the effects of coagulation FVIIa and FXa on signaling and their functional consequences on cell biology. Subsequently it turned out that factor VII is a relatively minor player in pathophysiology (chapter 4) and its downstream target, factor X (which acts as the point of convergence of the intrinsic and extrinsic pathways of coagulation; chapter 5) should actually be the focus point of relevant research. Hence, I decided to mainly explore factor X biology, firstly addressing of this signalling to cell survival (of obvious relevance for cancer cell biology; chapter 6) and migration (chapter 7) and this notion was confirmed in detailed comparisons of the biochemical changes induced by the three major vitamin K-dependent coagulation factors (chapter 8). It appeared, however, that the effects in the clinically highly relevant –but underexplored- phenomenon of fibrosis were a more rewarding of research and the research of these efforts are described in the remaining chapters. Finally I conclude that factor X is essential mediator of tissue repair, whose inappropriate activation may lead to fibrotic responses. In this sense, factor X as a passive mediator of coagulation has been hijacked by the body to mediate repair.

Blood coagulation factor Xa as an emerging drug target

Introduction: Factor (F) Xa is well-known as an important player in the coagulation cascade responsible for thrombin generation. More recently, FXa emerged as an essential player in cell biology via activation of proteaseactivated receptors (PAR)-1 and -2. This pleiotropic role of FXa forms the basis for its potential contribution to the pathogenesis of several diseases. Areas covered: The role of FXa in pathophysiology is reviewed with special emphasis on its signal transduction properties. To this end, we first discuss the important role of FXa in the coagulation cascade, we continue with recent data on FXa induced signaling in pathophysiology with special emphasis on tissue remodeling and fibrosis and discuss the potential of FXa as an emerging drug target. Expert opinion: FXa is more than a passive intermediate in the coagulation cascade and FXa may in fact orchestrate fundamental processes during pathophysiology. Targeting FXa may be an exciting new therapeutic strategy in the treatment of (fibro)proliferative diseases for which current treatment options are limite

Genetic causes and clinical management of pediatric interstitial lung diseases

Purpose of review: Interstitial lung disease (ILD) in children (chILD) is an umbrella term for a heterogeneous group of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. The pathogenesis of the various chILD is complex and implicates genetic contributors. The purpose of this review is to provide updated information on the molecular defects associated with the development of chILD.Recent findings: Currently, the main mutations are identified in the surfactant genes SFTPA1, SFTPA2, SFTPB, SFTPC, ABCA3, and NKX2-1. In addition, pulmonary alveolar proteinosis is associated with mutations in CSF2RA, CSF2RB, and MARS, and specific auto-inflammatory forms of chILD implicate STING and COPA disorders. The relationships between the genetic defects and the disease expression remain poorly understood, with no genotype-phenotype correlations identified so far. Although targeted therapies are emerging, the management strategies are still largely empirical, relying mostly on corticosteroids.Summary: Genetic factors play an important role in chILD, and the ongoing development of novel technologies will rapidly broaden the genetic landscape of chILD. Therefore, in the coming years, it is expected that newly identified molecular defects and markers will help predicting disease courses and tailoring individual therapies

Facteur VII de la coagulation (génétique et physiopathologie des déficits constitutionnels. Approche moléculaire)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF