88 research outputs found
Conformational states of annexin VI in solution induced by acidic pH
AbstractAcidic pH-induced folding of annexin (Anx)VI in solution was investigated in order to study the mechanism of formation of ion channels by the protein in membranes. Using 2-(p-toluidino)naphthalene-6-sulfonic acid as a hydrophobic probe, it was demonstrated that AnxVI exerts a large change in hydrophobicity at acidic pH. Moreover, circular dichroism spectra indicated that the native state of AnxVI changes at acidic pH towards a state characterized by a significant loss of α-helix content and appearance of new β-structures. These changes are reversible upon an increase of pH. It is postulated that the structural folding of AnxVI could explain how a soluble protein may undergo transition into a molecule able to penetrate the membrane hydrophobic region. The physiological significance of these observations is discussed
Do Media Extracellular Vesicles and Extracellular Vesicles Bound to the Extracellular Matrix Represent Distinct Types of Vesicles?
Mineralization-competent cells, including hypertrophic chondrocytes, mature osteoblasts, and osteogenic-differentiated smooth muscle cells secrete media extracellular vesicles (media vesicles) and extracellular vesicles bound to the extracellular matrix (matrix vesicles). Media vesicles are purified directly from the extracellular medium. On the other hand, matrix vesicles are purified after discarding the extracellular medium and subjecting the cells embedded in the extracellular matrix or bone or cartilage tissues to an enzymatic treatment. Several pieces of experimental evidence indicated that matrix vesicles and media vesicles isolated from the same types of mineralizing cells have distinct lipid and protein composition as well as functions. These findings support the view that matrix vesicles and media vesicles released by mineralizing cells have different functions in mineralized tissues due to their location, which is anchored to the extracellular matrix versus free-floating
Quantitative atomic force microscopy provides new insight into matrix vesicle mineralization
International audienc
A comparison of replicative senescence and doxorubicin-induced premature senescence of vascular smooth muscle cells isolated from human aorta
The network of calcium regulation in muscle.
In this review the molecular characteristics and reaction mechanisms of different Ca2+ transport systems associated with various membranes in muscle cells will be summarized. The following topics will be discussed in detail: a brief history of early observations concerning maintenance and regulation of cellular Ca2+ homeostasis, characterization of the Ca2+ pumps residing in plasma membranes and sarco(endo)plasmic reticulum, mitochondrial Ca2+ transport, Ca2+-binding proteins, coordinated expression of Ca2+ transport systems, a general background of muscle excitation-contraction coupling with emphasis to the calcium release channels of plasma membrane and sarcoplasmic reticulum, the structure and function of dihydropyridine and ryanodine receptors of skeletal and cardiac muscles, and finally their disposition in various types of muscles
The structure of the Ca2+-ATPase of sarcoplasmic reticulum.
In this article the morphology of sarcoplasmic reticulum, classification of Ca2+-ATPase (SERCA) isoenzymes presented in this membrane system, as well as their topology will be reviewed. The focus is on the structure and interactions of Ca2+-ATPase determined by electron and X-ray crystallography, lamellar X-ray and neutron diffraction analysis of the profile structure of Ca2+-ATPase in sarcoplasmic reticulum multilayers. In addition, targeting of the Ca2+-ATPase to the sarcoplasmic reticulum is discussed
Effects of Mutagenesis of W343 in Human Annexin A6 Isoform 1 on Its Interaction with GTP: Nucleotide-Induced Oligomer Formation and Ion Channel Activity †
Role of annexin A6 in matrix vesicles during the mineralization process
Les vésicules matricielles (MVs) sont des organites extracellulaires qui sont impliqués au cours de la première étape de la minéralisation. Les MVs ont été isolées à partir d'os d'embryons de poulets. Leurs compositions en protéines, en cholestétrol et en lipides ainsi que les activités des enzymes, ayant un effet sur l'AnxA6 ont été mesurés. AnxA6 a été détectée à la surface du feuillet externe et à la surface du feuillet interne de la membrane de la MV, suggérant que l'AnxA6 peut interagir avec les protéines de la matrice extra cellulaire ou participer à la nucléation du minéral. Les interactions entre l'AnxA6 et la partie hydrophobe de la membrane dépendent de la teneur en cholestérol. AnxA6 interagit avec le retinol et avec l'acide rétinoïque, favorisant la fixation calcium-dépendante de l'AnxA6 à la surface des membranes. L'analyse du protéome des MVs a révélé la présence d'AnxA1, AnxA2, AnxA5, AnxA6, AnxA11, protéines de la matrice extra cellulaire et des transporteurs des ionsLYON1-BU.Sciences (692662101) / SudocSudocFranceF
Origine, caractérisation et rôles des vésicules matricielles dans la minéralisation physiologique et pathologique
Matrix vesicles (MVs) are involved in the initiation of mineralization in tissues undergoing physiological and pathological calcification. Pyrophosphate (PPi) has a dual effect on mineralization: a source of phosphate (Pi) to sustain hydroxyapatite (HA) formation and an inhibitor of HA growth. We found that formation of HA was optimal when the Pi/PPi molar ratio was above 140, while calcium pyrophosphate dihydrate, identified in osteoarthritis was exclusively produced by MVs when the ratio was below 6. Proteomic analysis and lipid compositions on both MVs and microvilli from osteoblast-like Saos-2 cells, revealed that MVs have an endoplasmic reticular origin and characteristic lipids and proteins as in lipid rafts. Finally, we demonstrated that MV release from microvilli is caused by the concomitant actions of actin-depolymerizing and contractile motor proteins. Proteins involved in MV biogenesis could be new therapeutic targets to prevent pathological calcificationLes vésicules matricielles (VM) sont impliquées dans l'initiation des minéralisations physiologique ou pathologique. Le pyrophosphate (PPi) est une source de phosphate (Pi) pour maintenir la formation d'hydroxyapatite (HA) mais aussi un inhibiteur de la croissance de ces minéraux. Nous avons montré que la formation d HA était optimale lorsque le rapport molaire Pi/PPi était supérieur à 140, tandis que du calcium pyrophosphate dihydraté, marqueur de l arthrose, était exclusivement formé lorsque ce rapport était inférieur à 6. Des analyses protéomiques et en compositions lipidiques sur les VM et les microvillosités des cellules Saos-2 ont révélé que les VM étaient formées dans le réticulum endoplasmique et qu'elles possèdent des lipides et protéines caractéristiques de radeaux lipidiques. Finalement, nous avons montré que les VM sont libérées à partir des microvillosités grâce aux actions coordonnées de protéines dépolymérisant l'actine et de protéines contractiles. Les protéines impliquées dans la biogenèse des VM peuvent être des nouvelles cibles thérapeutiques pour prévenir des calcifications pathologiquesLYON1-BU.Sciences (692662101) / SudocSudocFranceF
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