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Extracellular Matrix- cell biology


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Starlings law of capillaries
the volume of fluid and solutes reabsorbed is approximately the volume filtered
glycosaminoglycans (GAGs)
long, inflexible, unbranched polysaccharides w/ amino sugar which are negative and have a slippery texture
proteoglycan expressed in cartilage with keratan sulfate and chondroitin sulfate as the GAGs
proteoglycan found with all cells making basal lamina that is made with heparan sulfate
RGD sequence
simple 3-peptide sequence that is the integrin binding sites of many adhesive proteins
large glycoprotein dimer with binding sites for extracellular components and integrins. The main product of fibroblasts. Involved in adhesion of cells to ECM
large glycoprotein composed of 3 large polypeptide chains with binding sites for heparan sulfate, type IV collagen, entactin and PM. Located in the Basal Lamina
glycoprotein that binds to laminin and type IV collagen in the basal lamina
Type I Collagen
most common collagen; secreted by fibroblasts and provides tensile strenth in connective tissues
Type II Collagen
fill the extracellular matrix of cartilage
Type III Collagen
called reticular fibers; highly glycosylated collagen that forms thin fibers
Type IV Collagen
Sheets that surround organs and epithelia. Found in the basal lamina and external lamina for support and filtration
Type VII collagen
anchoring collagen found in epidermal-dermal junctions that links type IV collagen of the basal lamina to underlying connective tissue
procollagen peptidase
protein on E-surface of PM that cleaves registration peptides from procollagen to form tropocollagen
propeptides or registration peptides
guide the formation of triple helical structure and prevent intracellular formation of collagen fibers
lysyl oxidase
forms covalent crosslinks between tropocollagen molecules and tropoelastin molecules
glycoprotein distributed mainly as microfibrils on the elastic fiber surface
basal laminae
mats of specialized ECM (mostly type IV collagen) that underlie all epithelial cell cheets and tubes and surround individual muscle, fat and schwann cells
lamina rara
layer of basal lamina adjacent to basal PM and made of heparan sulfate (perlecan)
lamina densa
electron dense layer of basal lamina just beneath the lamina rara. Made mostly of type IV collagen
lamina reticularis
3rd layer of basal lamina that isn't always present. Connects the basal lamina to connective tissue below and composed of type III collagen
What is the principle ECM producing cell
3 kinds of extracellular macromolecules
glycosaminoglycans (GAG) and proteoglycans, fibrous protein (collagen and elastin) and adhesive glycoproteins (fibronectin and laminin)
Examples of highly specialized ECM structures
cartilage, tendons, bone, teeth and basal lamina
components of ECM
fibers (structural or adhesive) and ground substance
five sulfated GAGS
keratan sulfate, heparan sulfate, chondratin 4 and 6 sulfate, and dermatan sulfate
what are usually linked to proteins to form proteoglycans
sulfated GAGs
proteoglycan function
resist compression, retard rapid movement of microorganisms and metastatic cells, form molecular filters, binding sites for signaling molecules (and impede or enhance their function)
what mediates the cells ability to adhere to components of the ECM?
adhesive glycoproteins
3 major adhesive glycoproteins
fibronectin, laminin and enactin
where is laminin found?
basal lamina
fibrillar collagens
types I, II, and III
What are the four major amino acids in collagen
Pro, Gly, Hyp, Hyl
functions of Type III Collagen
1) support for capillaries, small nerves and muscle 2)component of basement membrane 3) main stromal fibers for myeloid and lympoid tissues and glands
three classes of collagen
fibrillar, sheet forming, and anchoring
what is the secretory product of fibroblasts?
Why does procollagen go straight to the Plasma membrane?
has no sorting signal
What type of secretion is responsible for transporting procollagen?
what gives tropoelastin its elasticity
lysyl oxidase crosslinks
what do dark bands correspond to in negatively stained collagen fibrils?
what do light bands correspond to in negatively stained collagen fibrils
zones of complete overlap
what is the spacing between zones of complete overlap in collagen fibrils?
67 or 64 nm
what four amino acids is elastin rich in?
pro, gly, desmosine, and isodesmosine
what are elastic fibers composed of
elastin and fibrillin
what is elastin secreted as?
tropoelastin and the fibrillin framework
Locations of elastin fibers
1) connective tissue 2) vocal cords 3)elastic ligaments 4) elastic cartilages 5) muscle layer of all blood vessels except capillaries
What synthesizes basal laminae
the cells that lie on it
what is the function of the basal laminae
1) cell polarity; 2) influence metabolism; 3)organize protein in the PM 4) induce differentiation 5) highways for cell migration
composition of basal lamina
type IV collagen + heparan sulfate proteoglycans + laminin + entactin
What don't cross the basal lamina in normal healthy cells?
blood vessels
what are the principle PM receptors for binding cytoskeleton to ECM proteins?
how is lamina densa tethered to underlying ct in some multilayered epithelial cells
anchoring fibrils of collagen VII
Non-sulfated GAG
hyaluronic acid

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