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ANAT3231 - Cell Biology
Lecture 12 and 13
School of Medical Sciences
The University of New South Wales
 
Dr Mark Hill
 
Cell Biology Laboratory
 
Room G20 Wallace Wurth Building
 
Email: m.hill@unsw.edu.au
 
  
UNSW Copyright Notice
 
ExtraCellular Matrix (ECM)
 
Cell-Cell, Cell-Matrix Adhesions
 
 
ECM References
 
Essential Cell Biology
 
Ch19 p594-604
 
Molecular Biology of  the Cell
 
p971-1009
 
Animal and Plant ECM
 
Material secreted and deposited by cells
 
 
ANAT3231 Lecture 8
 
Extracellular matrix
 
http://cellbiology.med.unsw.edu.au/units/science/lecture0812.htm
 
ECM Function
 
Support for cells
 
Pattern of ECM regulates
 
Polarity
 
cell division
 
adhesion
 
motility
 
Development
 
migration
 
differentiation
 
Growth factors
 
ECM Structure- Glycoproteins
 
Fibers
 
Collagen- main fibers
 
Elastin
 
Hydrated Matrix
 
Proteoglycans
 
high carbohydrate
 
Adhesive
 
Glycoprotein
 
Laminin
 
Fibronectin
 
Shapes and Sizes ECM molecules
 
Collagen
 
tensile strength and elasticity
 
Tendons
 
Cartilage
 
Bone
 
half total body proteins (by weight)
 
Collagen Components
 
Insoluble glycoprotein
 
protein + carbohydrate
 
Protein
 
high glycine and 2 modified amino acids
 
hydroxylysine
 
hydroxyproline
 
(gly-X-Y)n
 
Carbohydrate
 
glucose
 
galactose
 
Collagen Structure
 
Collagen Protein
 
3 polypeptide (a) chains
 
left hand helix, forms fibers
 
14 different (vertebrate) collagens by different combinations of  a-chains
 
numbered I - XIV
 
Type I, II, III
 
main fibers, flexible
 
Type I
 
bone, skin, tendons
 
90% of all collagen
 
Type II
 
cartilage
 
Collagen Fibers
 
Type I, II, III cross striated
 
showing overlapping packing of individual collagen molecules
 
Type IV fine unstriated
 
sheet-like supportive meshwork
 
mature basal laminae
 
tracks for embryonic migration
 
barriers for cell migration
 
Type V-XII
 
smaller diameter fibers than I-III
 
no striations
 
Collagen Fibers
 
Collagen Non-striated
 
Collagen Synthesis
 
Endoplasmic Reticulum
 
mRNA attached to ER
 
protein synthesized into ER lumen
 
3 proto-a-chains form soluble procollagen
 
moved to golgi apparatus
 
Golgi Apparatus
 
packed into secretion vesicles
 
fuse with membrane
 
Outside Cell
 
procollagen processed by enzymes outside cell
 
assemble into collagen fibers
 
Collagen Biosynthesis
 
Collagen Diseases - Excess
 
excess collagen
 
fibrosis
 
lung- pulmonary fibrosis
 
overproduction of collagen I
 
liver- over consumption of alcohol
 
arteries- atherosclerosis
 
Collagen Diseases - Insufficient
 
insufficient collagen
 
Ehlers-Danlos syndrome
 
rubber-man
 
skin and tendons easily stretched
 
contortionists often suffer from this disease
 
Osteogenesis imperfecta
 
brittle-bone syndrome
 
mutation in Type I procollagen
 
fail to assemble triple helix
 
degrade imperfect collagen
 
Leads to fragile bones
 
Collagen Diseases
 
scurvy
 
dietary Vitamin C deficiency
 
needed for hydroxylation
 
Proline  ->  Hydroxyproline
 
form too few hydrogen bonds in collagen
 
skin, bone, teeth weakness and malformation
 
blood vessels weakened, bleeding
 
Glycosaminoglycans (Gags)
 
10% by weight but fill most of space
 
unbranched polysaccharide chains
 
disaccharide subunits
 
amino sugar
 
4 groups
 
hyaluronan
 
chondroitin sulphate, dermatan sulphate
 
heparan sulphate, heparin
 
keratan sulphate
 
Glycosaminoglycans- Hyaluronan
 
Also called hyluronic acid or hyaluronate
 
Development
 
produce a “cell-free” space
 
for cell proliferation and migration into
 
heart, cornea
 
Adult
 
in areas of compression
 
tissues, joints
 
Hyaluronan Synthesis
 
synthesized at plasma membranes
 
nascent chains directly extruded into ECM
 
Proteoglycans
 
Proteoglycans- Function
 
trap water
 
resistant to compression
 
return to original shape
 
occupy space
 
link to collagen fibers
 
form network
 
in bone combined with calcium hydroxyapatite, calcium carbonate
 
Cell adhesion
 
embryonic migration
 
Proteoglycan- Disease
 
Cancer development
 
altered types and kinds of proteoglycans formed by cells
 
normal cells -> malignant
 
Arthritis
 
Cartilage breakdown
 
chondrocytes elicit a catabolic response which exceeds anabolism of new matrix molecules
 
Degrade proteoglycan (aggrecan)
 
Also a mouse model generates antibodies to proteogycan
 

Latest revision as of 20:14, 26 April 2009