The structure of the PapD-PapGII pilin complex reveals an open and flexible P5 pocket

P pili are hairlike polymeric structures that mediate binding of uropathogenic Escherichia coli to the surface of the kidney via the PapG adhesin at their tips. PapG is composed of two domains: a lectin domain at the tip of the pilus followed by a pilin domain that comprises the initial polymerizing subunit of the 1,000-plus-subunit heteropolymeric pilus fiber. Prior to assembly, periplasmic pilin domains bind to a chaperone, PapD. PapD mediates donor strand complementation, in which a beta strand of PapD temporarily completes the pilin domain's fold, preventing premature, nonproductive interactions with other pilin subunits and facilitating subunit folding. Chaperone-subunit complexes are delivered to the outer membrane usher where donor strand exchange (DSE) replaces PapD's donated beta strand with an amino-terminal extension on the next incoming pilin subunit. This occurs via a zip-in-zip-out mechanism that initiates at a relatively accessible hydrophobic space termed the P5 pocket on the terminally incorporated pilus subunit. Here, we solve the structure of PapD in complex with the pilin domain of isoform II of PapG (PapGIIp). Our data revealed that PapGIIp adopts an immunoglobulin fold with a missing seventh strand, complemented in parallel by the G1 PapD strand, typical of pilin subunits. Comparisons with other chaperone-pilin complexes indicated that the interactive surfaces are highly conserved. Interestingly, the PapGIIp P5 pocket was in an open conformation, which, as molecular dynamics simulations revealed, switches between an open and a closed conformation due to the flexibility of the surrounding loops. Our study reveals the structural details of the DSE mechanism

Cell-scale degradation of peritumoural extracellular matrix fibre network and its role within tissue-scale cancer invasion

Local cancer invasion of tissue is a complex, multiscale process which plays an essential role in tumour progression. Occurring over many different temporal and spatial scales, the first stage of invasion is the secretion of matrix degrading enzymes (MDEs) by the cancer cells that consequently degrade the surrounding extracellular matrix (ECM). This process is vital for creating space in which the cancer cells can progress and it is driven by the activities of specific matrix metalloproteinases (MMPs). In this paper, we consider the key role of two MMPs by developing further the novel two-part multiscale model introduced in [33] to better relate at micro-scale the two micro-scale activities that were considered there, namely, the micro-dynamics concerning the continuous rearrangement of the naturally oriented ECM fibres within the bulk of the tumour and MDEs proteolytic micro-dynamics that take place in an appropriate cell-scale neighbourhood of the tumour boundary. Focussing primarily on the activities of the membrane-tethered MT1-MMP and the soluble MMP-2 with the fibrous ECM phase, in this work we investigate the MT1-MMP/MMP-2 cascade and its overall effect on tumour progression. To that end, we will propose a new multiscale modelling framework by considering the degradation of the ECM fibres not only to take place at macro-scale in the bulk of the tumour but also explicitly in the micro-scale neighbourhood of the tumour interface as a consequence of the interactions with molecular fluxes of MDEs that exercise their spatial dynamics at the invasive edge of the tumour

Radical SAM enzyme QueE defines a new minimal core fold and metal-dependent mechanism

7-carboxy-7-deazaguanine synthase (QueE) catalyzes a key S-adenosyl-L-methionine (AdoMet)- and Mg[superscript 2+]-dependent radical-mediated ring contraction step, which is common to the biosynthetic pathways of all deazapurine-containing compounds. QueE is a member of the AdoMet radical superfamily, which employs the 5′-deoxyadenosyl radical from reductive cleavage of AdoMet to initiate chemistry. To provide a mechanistic rationale for this elaborate transformation, we present the crystal structure of a QueE along with structures of pre- and post-turnover states. We find that substrate binds perpendicular to the [4Fe-4S]-bound AdoMet, exposing its C6 hydrogen atom for abstraction and generating the binding site for Mg[superscript 2+], which coordinates directly to the substrate. The Burkholderia multivorans structure reported here varies from all other previously characterized members of the AdoMet radical superfamily in that it contains a hypermodified ([β [subscript 6] over α [subscript 3]]) protein core and an expanded cluster-binding motif, CX[subscript 14]CX[subscript 2]C.United States. Dept. of Energy. Office of Biological and Environmental ResearchUnited States. Dept. of Energy. Office of Basic Energy SciencesNational Center for Research Resources (U.S.) (P41RR012408)National Institute of General Medical Sciences (U.S.) (P41GM103473)National Center for Research Resources (U.S.) (5P41RR015301-10)National Institute of General Medical Sciences (U.S.) (8 P41 GM 103403-10)United States. Dept. of Energy (Contract DE-AC02-06CH11357

Proinflammatory Phenotype and Increased Caveolin-1 in Alveolar Macrophages with Silenced CFTR mRNA

The inflammatory milieu in the respiratory tract in cystic fibrosis (CF) has been linked to the defective expression of the cystic transmembrane regulator (CFTR) in epithelial cells. Alveolar macrophages (AM), important contibutors to inflammatory responses in the lung, also express CFTR. The present study analyzes the phenotype of human AM with silenced CFTR. Expression of CFTR mRNA and the immature form of the CFTR protein decreased 100-fold and 5.2-fold, respectively, in AM transfected with a CFTR specific siRNA (CFTR-siRNA) compared to controls. Reduction of CFTR expression in AM resulted in increased secretion of IL-8, increased phosphorylation of NF-κB, a positive regulator of IL-8 expression, and decreased expression of IκB-α, the inhibitory protein of NF-κB activation. AM with silenced CFTR expression also showed increased apoptosis. We hypothesized that caveolin-1 (Cav1), a membrane protein that is co-localized with CFTR in lipid rafts and that is related to inflammation and apoptosis in macrophages, may be affected by decreased CFTR expression. Messenger RNA and protein levels of Cav1 were increased in AM with silenced CFTR. Expression and transcriptional activity of sterol regulatory element binding protein (SREBP), a negative transcriptional regulator of Cav1, was decreased in AM with silenced CFTR, but total and free cholesterol mass did not change. These findings indicate that silencing of CFTR in human AM results in an inflammatory phenotype and apoptosis, which is associated to SREBP-mediated regulation of Cav1

Dynamic light diffusion, Anderson localization and lasing in disordered inverted opals: 3D ab-initio Maxwell-Bloch computation

We report on 3D time-domain parallel simulations of Anderson localization of light in inverted disordered opals displaying a complete photonic band-gap. We investigate dynamic diffusion processes induced by femtosecond laser excitations, calculate the diffusion constant and the decay-time distribution versus the strength of the disorder. We report evidence of the transition from delocalized Bloch oscillations to strongly localized resonances in self-starting laser processes.Comment: 4 pages, 5 figure

Terminology for Achilles tendon related disorders

The terminology of Achilles tendon pathology has become inconsistent and confusing throughout the years. For proper research, assessment and treatment, a uniform and clear terminology is necessary. A new terminology is proposed; the definitions hereof encompass the anatomic location, symptoms, clinical findings and histopathology. It comprises the following definitions: Mid-portion Achilles tendinopathy: a clinical syndrome characterized by a combination of pain, swelling and impaired performance. It includes, but is not limited to, the histopathological diagnosis of tendinosis. Achilles paratendinopathy: an acute or chronic inflammation and/or degeneration of the thin membrane around the Achilles tendon. There are clear distinctions between acute paratendinopathy and chronic paratendinopathy, both in symptoms as in histopathology. Insertional Achilles tendinopathy: located at the insertion of the Achilles tendon onto the calcaneus, bone spurs and calcifications in the tendon proper at the insertion site may exist. Retrocalcaneal bursitis: an inflammation of the bursa in the recess between the anterior inferior side of the Achilles tendon and the posterosuperior aspect of the calcaneus (retrocalcaneal recess). Superficial calcaneal bursitis: inflammation of the bursa located between a calcaneal prominence or the Achilles tendon and the skin. Finally, it is suggested that previous terms as Haglund’s disease; Haglund’s syndrome; Haglund’s deformity; pump bump (calcaneus altus; high prow heels; knobbly heels; cucumber heel), are no longer used

Psychoactive Pharmaceuticals Induce Fish Gene Expression Profiles Associated with Human Idiopathic Autism

Idiopathic autism, caused by genetic susceptibility interacting with unknown environmental triggers, has increased dramatically in the past 25 years. Identifying environmental triggers has been difficult due to poorly understood pathophysiology and subjective definitions of autism. The use of antidepressants by pregnant women has been associated with autism. These and other unmetabolized psychoactive pharmaceuticals (UPPs) have also been found in drinking water from surface sources, providing another possible exposure route and raising questions about human health consequences. Here, we examined gene expression patterns of fathead minnows treated with a mixture of three psychoactive pharmaceuticals (fluoxetine, venlafaxine & carbamazepine) in dosages intended to be similar to the highest observed conservative estimates of environmental concentrations. We conducted microarray experiments examining brain tissue of fish exposed to individual pharmaceuticals and a mixture of all three. We used gene-class analysis to test for enrichment of gene sets involved with ten human neurological disorders. Only sets associated with idiopathic autism were unambiguously enriched. We found that UPPs induce autism-like gene expression patterns in fish. Our findings suggest a new potential trigger for idiopathic autism in genetically susceptible individuals involving an overlooked source of environmental contamination