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44 Cards in this Set
- Front
- Back
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Intergrin |
Facilitates the interaction between cell+ECM |
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2 types of adhesion molecules Intergrin forms |
1) Focal adhesions 2) Hemidesmosomes |
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Where are tight junctions found |
Near the apical surface of epithelium- therefore are important in cell polarity |
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How do tight junctions maintain polarity |
They are at the apical surface and bind to the actin cytoskeleton |
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Structure of tight junctions |
Tight junctions form via homodimerisation.
Therefore claudin+claudin occludin +occludin etc are the basis of tight junctions
Adaptor proteins enable components of tight junctions to anchor to actin and provides structural integrity |
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Main components of TJ |
- Claudin - Occludin - JAMs |
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Location of Adherens Junctions |
Sit underneath the TJ |
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Function of AJ |
To maintain cell-cell adhesion |
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Cadherins in AJ |
The predominant type of receptors in AJ + desmosomes
Adhesion is homotypic (homodimerisation)
In AJ the type of cadherins used is E-cadherin
Are also ca2+ dependent |
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Structure of AJ |
Cadherins in AJ link to actin via anchor proteins
Adaptor proteins are catinins, actinin, vinculin
Adaptor proteins are important in connecting receptor to F-actin and also proved structural integrity |
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Desomosome |
Are important in maintaining cell to cell adhesion |
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Cadherins in desmosomes |
Main component is desmosomal cadherins - desmoglein and desmocollin
Cadherins are bound to plakophillin and plakoglobin adaptor proteins.
Adaptor proteins anchor desmosome to the intermediary filaments of cytoskeleton |
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Focal Adhesions |
Anchor cells to ECM.
Main receptor family are intergrins that act as connection between ECM and cytoskeleton |
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Structure of Focal adhesions |
Hetrodimeric transmembrane receptors with alpha and beta subunits
There are many types of subunits and different interaction between different subunits mean that there are 24 different intergrins |
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Basement Membrane |
Is a thin ECM tissue which separates the epithelium and the endothelium from the underlying connective tissue. Consists of two sublayers: Basal Laminae - nearest to the epithelial cells (laminin + collagen IV) Reticular laminae - nearest to connective tissue |
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Molecular structure of Laminins |
Cross shaped, trimeric glycoprotein of polypeptides alpha, beta and gamma Different combinations of alpha, beta and gamma chain = 15 types of chains |
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Size of Laminins |
900 kDa |
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Laminin |
A fibrous protein present in the basal lamina of the epithelium and is essential for structural integrity. |
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Laminin contains binding domains for... |
Collagen IV, Nidogen, Heparin, Heparin sulphate, Perlecan, cell binding |
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Structural arrangement of laminins |
'short' arms of cross structure bind other laminins to create sheet |
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Collagen |
Ubiquitous structure protein which provides tensile strength and elasticity in: tendons, cartilage, bone |
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Molecular structure of collagen |
3 polypeptide alpha chains of a left-handed helix form right handed fibres Different forms of collage is created by different combinations of alpha chains |
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Type I collagen |
Found in bone, skin, tendons (90% of all collagen) |
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Type II collagen |
Found in cartilage |
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Type IV collagen |
found in the basement membrane |
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collagen synthesis |
Synthesised on mRNA @ER protein into ER lumen and post-translation modification Soluble procollagen moved to golgi apparatus @golgi packaged into secretory vesicles Procollagen processed outside the cell and is assembled into fibrils |
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Fibrosis |
@lungs, liver, skin Excessive deposition of Collagen I or III by fibroblasts Results in loss of tissue function: lungs loss of oxygen exchange |
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Scurvy |
Lack of vitamin C = formation of unstable procollagen |
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Brittle bone disease |
Mutations in genes encoding type I collagen and results in poorly formed collagen helices |
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Fibronectin |
Is a glycoprotein of the ECM and is most abundant in heart lungs and liver. Can be soluble/ insoluble |
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Soluble Fibronectin |
a major component of blood plasma Required for wound healing. Plasma FN @ wound cluster platelets and recruit fibroblasts to the site |
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Insoluble fibronectin |
assembles into a fibrillar ECM at the cell membrane. Can bind to collagens, fibrin and proteoglycans. |
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Function of fibroblasts |
Essential for mammalian development and embryogenesis and cell migration. Also for wound healing |
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Tropoelastin |
Precursor of elastin: - soluble monomer - assembles into microfibrils - cross links to form insoluble matrix fibres |
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Elastin |
Provides structural integrity and flexibility to tissues with collagen Highly expressed in lungs, skin, major blood vessels |
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Proteoglycans |
Heavily glycosylated protein core and from a gel which acts to link fibrillar ECM network, resist pressure and act as signalling molecules |
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Hyaluronan |
The main GAG in connective tissue. Form the back bone for assembly of other GAGs Major component of synovial fluid and vitreous humour |
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Matrix metalloproteinases |
Degrade matrix components + depend on ca2+ and zn2+ Inhibited by tissue inhibitors of metalloproteinases |
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Serine proteases |
Degrade matrix components via highly reactive serine residues Acts via cleavage of peptide bonds in proteins Have a highly reactive seriene @ active site Inhibited by serine protease inhibitors |
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Focal adhesions in migrating cells |
When a cell is migrating new adhesions assemble at the front and old disassemble at the rear |
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Hemi-desmosomes |
Integrin containing adhesion linking ECM to intermediate filaments Intracellular domains of integrin linked to keratin via anchor proteins plectins Hemi-desmosome and focal adhesions occupy distinct areas of the cell membrane |
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GAP junctions |
Channel forming junctions main component are connexins Allow passage of small ions and 2nd messenger molecules between cells |
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Connexins |
Are the main component of the GAP junctions. They are transmembrane proteins that connect to form channels and can open and close |
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Pemphigus Vulgaris |
Antibodies against desmogleins in desmosomes. Leads to separation of keratinocytes and from basal layer if the epidermis Causes skin blistering |
