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MATRICE EXTRACELLULAIRE
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BASAL LAMINAExtensive interaction between ECM molecules
ECM: Extra-cellular Matrix
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Controlled degradation of the ECM by locally secreted proteolytic enzymes
b) serine proteases u-PA = urokinase type plasminogen activator
specifically cleaves plasminogen into plasmin: Plasmin cleaves fibrin, fibronectin, laminin.
u-PA receptors (uPAR) is present onnerve growth cones,
leading edges of migrating white blood cellson cancer cells
required for metastasis, the invasive capacity of cellsa negative prognostic marker in many cancers
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A)Human prostate cancer cells secrete the serine protease, u-PA (red).u-PA binds to u-PA receptor (uPAR) proteins on prostate cancer cell surface (green).B)Human prostate cancer cells were transfected and secrete an inactive serine protease(yellow).The inactive serine protease occupies / blocks most of the receptors.
Both A) and B) cells are grow and produce tumours when injected into animalsBUT only A is metastatic
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Complexes de jonction Celule-cellule
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CELL - CELL
CELL - Matrix
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epithelial cells of the small intestine
anchoringjunctions
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CAMCAM
1) Extra Cellular Matrix Molecules (ECM) proteins and polysacharides secreted locally and assembled into a meshwork
2) Transmembrane linker proteins or Cell Adhesion Molecules (CAMs ) cytoplasmic domain
transmembrane domainextracellular domain
3) Intracellular attachment proteins a plaque, connecting the junction to (micro- or intermediate) filaments
E CM
ANCHORING JUNCTIONS:
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JUNCTIONAL ADHESION MECHANISMS Non-JUNCTIONAL CONTACTS
CELL -MATRIXADHESION
CELL -CELLADHESION
basal lamina
actin
NO attachment
plague
CADHERINS
IG-LIKE CAMS
INTEGRINSSELECTINS
adhesion belt(CADHERINS)
desmosomes(CADHERINS)
Gap junctions(connexins)
tightjunctions
focal contacts(integrins)
hemidesm.(integrins) integrins
non-epithelial cellsepithelial cells
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Cellule - Celluleliaison transmembranaire
ouCAMs (cell adhesion molecules)
1) CAMs Ca2+-dependantes :cadherins, selectins, integrins
2) CAMs Ca2+-independantes
Cellules se lient à CAMs d’autres cellules et transmettent la signalisation
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Cadherines and Catenines
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Les Cadherines effectuent la transductioncellulaire entre ECM et cytoplasm
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Structure des desmosomes
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Les Cadherines jouent un rôle dans:• Development embryonaire
• Souris knockout of E-, P- and N-cadherine meurent dans les stadesembryonaires
• Development neuronal• neurite outgrowth
• Architecture tissulaire:• adherens junctions-associatées à des filaments d’actin• La polarité produite par-E-cadherin induit une polarité
apicale/basolaterale• cell sorting: des cellules exprimant une même cadherine se differencient
ensembles lorsqu’elles sont mélangées• Cancer
• prevention d’invasion et de metastasis• differentiation• organization du cytosquelette/polarité
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•Ca2+-dependent:•requière Ca2+ pour se lier (cellules se dissocient si Ca2+ bas)•Protection contre trypsinisation en presence de Ca2+
•Ca2+ lie ensemble 5 EC domaines et confére une forme en tube
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Structure des Domainesextracellulaires des Cadherines
• domaines extracelllulaire (EC) de 110 AA:• ca 30% identité entre differentes cadherines• en général 5 domaines mais seul 4 domaines sont homologues• chaque domaine a 2 motifs liant Ca2+
• domaine EC 1 contient le site de liaison• domaine HAV requis pour liaison homophile• autres AA necessaires pour la liaison
• Sequences très conservées• LDRE• DXNDNXP-site liant le Ca2+
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Liaison Homophile(liaison forte)
• La plupart des cadherines interagissent par liaisonhomophile dans la plupart des conditions
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Liaison Heterophile(liaison plus faible)
• T lymphocytes: lient les cellules de la muqueuse epithelials(integrine α3β7 lie E-cadherine)
• FGFR: possède une séquence HAV qui peut interagir avec N-Cadherine
• Superoxide dismutase: contient HAV qui affecte l’aggrégationde N-cadherines
• virus Influenza souche A hemagglutinines: contient la séquenceHAV
• Shigella flexneri (bacterie entérique): utilise cadherines pourpénétrer dans les cellules
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Groupe 1: cadherines classiques• E-, N-, and P-cadherines
• ont le site HAV
• T cadherines• liées via phosphatidylinositol (pas de domaine
cytoplasmique)
Group 2: cadherines prototypes• 5 ou plus domaines EC• Pas de séquence HAV• Domaines cytoplasmiques complétement
differents• faible adhesion entre molecules
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Groupe 3: cadherines desmosomales:
• desmogleines et desmocollines• 4 domaines EC• domaine cytoplasmique seulement 30% identique• (90% dans les cadherines classiques)
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Groupe 4: autres cadherines• quelques variations du segment
extracellulaire• differents domaines cytoplasmiques
– transporter de peptides (intestin)– recepteur bacterien de B. thuringiensis– “Fat tumor suppressor” from Drosophila– Ret receptor tyrosine kinase
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Modèle d’architecture moleculaire d’un desmosome
• membres de la familledes Cadherines : Desmogleines Desmocollines
• Desmoplakines: lient lesfilaments intermédiaires
Rôle important pour prevention d’invasion et de metastases.
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PROTEINES contenant des sites HAV
• FGFR• INFLUENZA STRAIN A HEMAGGLUTININ• SUPEROXIDE DISMUTASE• PTPκ & PCP-2/PTPλ
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Cadherin Associated Proteins:α- & β-Catenines
• domaines intracellular conservés (sites deliaison):
• Domaines liant ß catenine/plakoglobine– Domaines mutuellement exclusifs
• Domaine liant p120
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α catenines• lient directement ß catenines and
plakoglobines• lient actine• lient α-actinine et vinculine• lient ZO-1
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β catenines• 60% identiques à plakoglobine• 70% identiques à armadillo• lient Cadherines (&APC and Tcf/LEF-1) via unités
repetitives (“arm repeats”)• lient alpha-Catenines via N-terminus
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1) CA-DEPENDENT CAMs (CELL ADHESION MOLECULES):
a) classic CADHERINS: involved in both junctional and non junctional adhesions
E-, N- and P- cadherins (Epithelial, Nerve, Placenta)
single-pass transmembrane glycoproteins (~700-750 AA s), 5 cadherin repeatsselective adhesion, homophilicdifferential expression during development + morphogenesis
the extracellular side: 5 cadherin repeats of 100 AA, (3 are Ca2+ -binding)in the absence of Ca >>> rapid proteolysis
the cytoplasmic side:the intracellular attachment proteins: catenins α,β,γ (bind actin) (required for cell-cell adhesion)
B) INTEGRINS: (both junctional and non-junctional adhesions)
C) SELECTINS (non-junctional, endothelium and blood cells only)
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2) CA-INDEPENDENT CAMs (Ig-like CAMs) members of the immunoglobulin superfamily involved cell-cell non-junctional adhesions
single-pass transmembrane glycoproteins many isoforms, weaker interactions,changes of N-CAM expression in development
N-CAMs: mostly homophilic (Neural CAM)I-CAMs: heterophilic (Intercellular CAMs (on activated endothelial cells)
the extracellular side: 5 Ig-like repeats and 1-2 fibronectin (type III) repeatsvarious extent of glycosylation
the cytoplasmic side:variable, involved in cell signalling, binds to the cytoskel., to GPI or secreted
no adhesion plaques (?)
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CadherinesCa 2+ -dep. homophilic adhesion functional unit = dimer
Superfamile Immunoglobines (CAMs)homophiles or heterophiles
SelectinesheterophilesP selectine + contre-recepteur PSGL-1, glycosylé
Integrinesheterodimères, heterophileslient ECM, Ig-CAMs, cadherinesadhesion, polarité, migration
Cadh. repeats
Ig and Fn III repeats
lectin repeats
I-CAM
CELL ADHESION MOLECULESCELL-CELL adhesion
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Gap Junctions
Rôles physiological:1. communication intercellulaire2. restreindre la proliferation cellulaire3. role dans la differentiation4. synchronise la communication electrique et
metabolique (Ca2+) entre cellules
Structure presente danspratiquement toute cellule encontact avec les cellules d’autrestissus
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Composants du complexe dejunction
Tight junction (zonula occludens)
Desmosome (macula adherens)
Adherens junction (zonula adherens)
Gap Junctions/Nexus Junctions: (GJIC)
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Gap junctions : structures dynamiques• Connexons peuvent s’ouvrir et se fermer.• Ca2+
in élevé & faible pHin = stimulus pour fermeturerapide de connexons.
• Limite supérieure pour passage à travers gap junctions : 1000 Da.
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Proteines de gap junctions• Connexines• Connexine-43 et Connexine-45 interagissent avec
ZO-1
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Connexons