The Interplay between Chemistry and Mechanics in the Transduction of a Mechanical Signal into a Biochemical Function

There are many processes in biology in which mechanical forces are generated. Force-bearing networks can transduce locally developed mechanical signals very extensively over different parts of the cell or tissues. In this article we conduct an overview of this kind of mechanical transduction, focusing in particular on the multiple layers of complexity displayed by the mechanisms that control and trigger the conversion of a mechanical signal into a biochemical function. Single molecule methodologies, through their capability to introduce the force in studies of biological processes in which mechanical stresses are developed, are unveiling subtle intertwining mechanisms between chemistry and mechanics and in particular are revealing how chemistry can control mechanics. The possibility that chemistry interplays with mechanics should be always considered in biochemical studies.Comment: 50 pages, 18 figure

Overexpression of HTRA1 Leads to Ultrastructural Changes in the Elastic Layer of Bruch's Membrane via Cleavage of Extracellular Matrix Components

Variants in the chromosomal region 10q26 are strongly associated with an increased risk for age-related macular degeneration (AMD). Two potential AMD genes are located in this region: ARMS2 and HTRA1 (high-temperature requirement A1). Previous studies have suggested that polymorphisms in the promotor region of HTRA1 result in overexpression of HTRA1 protein. This study investigated the role of HTRA1 overexpression in the pathogenesis of AMD. Transgenic Htra1 mice overexpressing the murine protein in the retinal pigment epithelium (RPE) layer of the retina were generated and characterized by transmission electron microscopy, immunofluorescence staining and Western Blot analysis. The elastic layer of Bruch's membrane (BM) in the Htra1 transgenic mice was fragmented and less continuous than in wild type (WT) controls. Recombinant HTRA1 lacking the N-terminal domain cleaved various extracellular matrix (ECM) proteins. Subsequent Western Blot analysis revealed an overexpression of fibronectin fragments and a reduction of fibulin 5 and tropoelastin in the RPE/choroid layer in transgenic mice compared to WT. Fibulin 5 is essential for elastogenesis by promoting elastic fiber assembly and maturation. Taken together, our data implicate that HTRA1 overexpression leads to an altered elastogenesis in BM through fibulin 5 cleavage. It highlights the importance of ECM related proteins in the development of AMD and links HTRA1 to other AMD risk genes such as fibulin 5, fibulin 6, ARMS2 and TIMP3

L'activite proteolytique potentielle de la fibronectine du plasma humain; systeme proteolytique issu de la partie N-terminale

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 80862 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Broad Coverage Identification of Multiple Proteolytic Cleavage Site Sequences in Complex High Molecular Weight Proteins Using Quantitative Proteomics as a Complement to Edman Sequencing*

Proteolytic processing modifies the pleiotropic functions of many large, complex, and modular proteins and can generate cleavage products with new biological activity. The identification of exact proteolytic cleavage sites in the extracellular matrix laminins, fibronectin, and other extracellular matrix proteins is not only important for understanding protein turnover but is needed for the identification of new bioactive cleavage products. Several such products have recently been recognized that are suggested to play important cellular regulatory roles in processes, including angiogenesis. However, identifying multiple cleavage sites in extracellular matrix proteins and other large proteins is challenging as N-terminal Edman sequencing of multiple and often closely spaced cleavage fragments on SDS-PAGE gels is difficult, thus limiting throughput and coverage. We developed a new liquid chromatography-mass spectrometry approach we call amino-terminal oriented mass spectrometry of substrates (ATOMS) for the N-terminal identification of protein cleavage fragments in solution. ATOMS utilizes efficient and low cost dimethylation isotopic labeling of original N-terminal and proteolytically generated N termini of protein cleavage fragments followed by quantitative tandem mass spectrometry analysis. Being a peptide-centric approach, ATOMS is not dependent on the SDS-PAGE resolution limits for protein fragments of similar mass. We demonstrate that ATOMS reliably identifies multiple proteolytic sites per reaction in complex proteins. Fifty-five neutrophil elastase cleavage sites were identified in laminin-1 and fibronectin-1 with 34 more identified by matrix metalloproteinase cleavage. Hence, our degradomics approach offers a complimentary alternative to Edman sequencing with broad applicability in identifying N termini such as cleavage sites in complex high molecular weight extracellular matrix proteins after in vitro cleavage assays. ATOMS can therefore be useful in identifying new cleavage products of extracellular matrix proteins cleaved by proteases in pathology for bioactivity screening

Perceived Discrimination and Markers of Cardiovascular Risk Among Low-Income African American Youth

Objectives: Our study examines the relationship between perceived discrimination and levels of C-reactive protein and blood pressure in low-income youth ages 10215 years old. Methods: Data were collected from 10 to 15 year old focal children and their mothers. Face-to-face interviews were implemented to collect data on stressors including experiences of everyday discrimination from youth. High sensitivity CRP in dried blood spot samples and diastolic and systolic blood pressure were also collected at the time of the interview. Results: Perceived discrimination among youth was significantly associated with higher levels of CRP, systolic, and diastolic blood pressure. CRP, systolic, and diastolic blood pressure remained significant after controlling for ageadjusted BMI, waist circumference, and other factors. Conclusions: Discrimination is a salient risk factor for inflammation and cardiovascular health. Early life course inflammation and cardiovascular reactivity are important candidate pathways through which the repeated exposure to discrimination for minority group members contributes to racial and economic health inequities in adulthood