Peroxide-Induced Damage to Plasminogen Molecules

Doklady Biochemistry and Biophysics - Plasminogen is a zymogenic form of plasmin, an enzyme that plays a fundamental role in the dissolution of fibrin clots as well as in many other physiological...     

Isolation and distribution of iridescent Cellulophaga and other iridescent marine bacteria from the Charente-Maritime coast,French Atlantic

An intense colored marine bacterium, identified as Cellulophaga lytica, was isolated previously from a sea anemone surface on the Charente-Maritime rocky shore (Atlantic Coast, France), and iridescence of its colonies under direct light was recently described. In addition, iridescence intensities were found to differ strongly between C. lytica strains from different culture collections. However, importantly, the occurrence and distribution of iridescent bacteria in the marine environment were still unknown. Therefore, in this study, a search was undertaken for marine iridescent bacterial strains in different biotopes of the Charente-Maritime coast. Various marine samples (water, sediment, macroalgae, other macroorganisms and detritus) were collected from seven biotopes using a direct plate inoculation method. As a result, 34 iridescent strains related to the genus Cellulophaga, as well as 63 iridescent strains affiliated to the genera Tenacibaculum and Aquimarina, were isolated. Iridescent colors were different according to the genera but iridescent marine bacteria were widely distributed. However, a majority of strains were isolated from rocky shores and, in particular, red seaweed surfaces and mollusks. The data from the study suggested that isolates with iridescent properties were well conserved in stressful environments such as the coastal shoreline. This origin may provide an insight into the ecological and biological functions of iridescence.     

Determinants of Maximal Force Transmission in a Motor-Clutch Model of Cell Traction in a Compliant Microenvironment

The mechanical stiffness of a cell’s environment exerts a strong, but variable, influence on cell behavior and fate. For example, different cell types cultured on compliant substrates have opposite trends of cell migration and traction as a function of substrate stiffness. Here, we describe how a motor-clutch model of cell traction, which exhibits a maximum in traction force with respect to substrate stiffness, may provide a mechanistic basis for understanding how cells are tuned to sense the stiffness of specific microenvironments. We find that the optimal stiffness is generally more sensitive to clutch parameters than to motor parameters, but that single parameter changes are generally only effective over a small range of values. By contrast, dual parameter changes, such as coordinately increasing the numbers of both motors and clutches offer a larger dynamic range for tuning the optimum. The model exhibits distinct regimes: at high substrate stiffness, clutches quickly build force and fail (so-called frictional slippage), whereas at low substrate stiffness, clutches fail spontaneously before the motors can load the substrate appreciably (a second regime of frictional slippage). Between the two extremes, we find the maximum traction force, which occurs when the substrate load-and-fail cycle time equals the expected time for all clutches to bind. At this stiffness, clutches are used to their fullest extent, and motors are therefore resisted to their fullest extent. The analysis suggests that coordinate parameter shifts, such as increasing the numbers of motors and clutches, could underlie tumor progression and collective cell migration.     

Exome Sequencing Identifies Mutations in CCDC114 as a Cause of Primary Ciliary Dyskinesia

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous, autosomal-recessive disorder, characterized by oto-sino-pulmonary disease and situs abnormalities. PCD-causing mutations have been identified in 14 genes, but they collectively account for only ∼60% of all PCD. To identify mutations that cause PCD, we performed exome sequencing on six unrelated probands with ciliary outer dynein arm (ODA) defects. Mutations in CCDC114, an ortholog of the Chlamydomonas reinhardtii motility gene DCC2, were identified in a family with two affected siblings. Sanger sequencing of 67 additional individuals with PCD with ODA defects from 58 families revealed CCDC114 mutations in 4 individuals in 3 families. All 6 individuals with CCDC114 mutations had characteristic oto-sino-pulmonary disease, but none had situs abnormalities. In the remaining 5 individuals with PCD who underwent exome sequencing, we identified mutations in two genes (DNAI2, DNAH5) known to cause PCD, including an Ashkenazi Jewish founder mutation in DNAI2. These results revealed that mutations in CCDC114 are a cause of ciliary dysmotility and PCD and further demonstrate the utility of exome sequencing to identify genetic causes in heterogeneous recessive disorders.     

The strengthening role of <Emphasis Type="Italic">D</Emphasis>:<Emphasis Type="Italic">D</Emphasis> interactions in fibrin self-assembly under oxidation

The effect on ozone-induced oxidation on the self-assembly of fibrin in the presence of fibrin-stabilizing factor FXIIIa of soluble cross-linked fibrin oligomers was studied in a medium containing moderate urea concentrations. It is established that fibrin oligomers were formed by the protofibrils cross-linked through γ-γ dimers and the fibrils additionally cross-linked by through α-polymers. The oxidation promoted both the accumulation of greater amounts of γ-γ dimers and the formation of protofibrils, fibrils, and their dissociation products emerging with increasing urea concentrations, which have a high molecular weight. It is concluded that the oxidation enhances the axial interactions between D-regions of fibrin molecules.     

Cloning and characterization of ADAMTS11, an aggrecanase from the ADAMTS family.

Aggrecan is responsible for the mechanical properties of cartilage. One of the earliest changes observed in arthritis is the depletion of cartilage aggrecan due to increased proteolytic cleavage within the interglobular domain. Two major sites of cleavage have been identified in this region at Asn(341)-Phe(342) and Glu(373)-Ala(374). While several matrix metalloproteinases have been shown to cleave at Asn(341)-Phe(342), an as yet unidentified protein termed "aggrecanase" is responsible for cleavage at Glu(373)-Ala(374) and is hypothesized to play a pivotal role in cartilage damage. We have identified and cloned a novel disintegrin metalloproteinase with thrombospondin motifs that possesses aggrecanase activity, ADAMTS11 (aggrecanase-2), which has extensive homology to ADAMTS4 (aggrecanase-1) and the inflammation-associated gene ADAMTS1. ADAMTS11 possesses a number of conserved domains that have been shown to play a role in integrin binding, cell-cell interactions, and extracellular matrix binding. We have expressed recombinant human ADAMTS11 in insect cells and shown that it cleaves aggrecan at the Glu(373)-Ala(374) site, with the cleavage pattern and inhibitor profile being indistinguishable from that observed with native aggrecanase. A comparison of the structure and expression patterns of ADAMTS11, ADAMTS4, and ADAMTS1 is also described. Our findings will facilitate the study of the mechanisms of cartilage degradation and provide targets to search for effective inhibitors of cartilage depletion in arthritic disease.