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EXTRACELLULAR MATRIX PROTEINS AND
PROTEINASES
By,
Raghu Ambekar
Photonics Research of Bio/nano Environments
Department of Electrical & Computer Engineering
University of Illinois Urbana - Champaign
BioE 506
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Outline
Extracellular matrix proteins
Collagen
Classification
Fibril assembly and collagen diseases
Extracellular matrix proteinases
Role of MMP in metastasis
Modification of tumor collagen for therapeutics
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Extracellular matrix (ECM)
Surrounds cell
Provides mechanical support
Controls the flow of nutrients
and signals to the cells
Consists of
Fibrous: collagen,
elastin, fibronectin, laminin
Non-fibrous: Proteoglycansand polysaccharides
http://kentsimmons.uwinnipeg.ca/cm1504
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Collagen
Collagen : most abundant protein found in the human
body. About 1/3 rd of the total proteins.
Found abundantly in tendon, cartilage, bone and skin
Functions: cell migration
cell adhesion
molecular filtration tissue repair
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Structure of collagen
It has a triple-helix structure containing
three -polypeptide chains arranged in
right-handed supercoil
Glycine, proline, hydroxyproline
1.5 nm diameter
At least 28 different collagens found
The three -chains could be same
(collagen II) or different (collagen I)Collagen molecule
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Classification of collagen
No interruptions in triple helix
Regular arrangement results in characteristic ³D´ period of 67 nm
Diameter : 50-500 nm Example : Types I, II, III, V, XI
1. Fibril-forming collagens
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Classification of collagen
Forms network in basement (Collagen IV) and Descemet¶s
membrane (Collagen VIII)
Molecular filtration
Example : Types IV, VIII, X
2. Network-forming collagens
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Classification of collagen
Short collagens with interruptions
Linked to collagen II and carries a GAG chain
Found at the surface of fibril-forming collagens
Example : Types IX, XII, XIV
3. Fibril-associated collagens with interrupted triple helices (FACITs)
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Classification of collagen
Provides functional integrity by connecting epithelium to
stroma
Example : Type VII
4. Anchoring collagens
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Classification of collagen
Form structural links with cells
Example : Type VI
Collagen VI crosslink into tetramers that assemble into longmolecular chains (microfibrils) and have beaded repeat of 105 nm
5. Beaded-filament-forming collagens
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Type I Fibril assembly
Chain recognition sequence
Fibril assembly is determined by chain recognition sequence in C-propeptide
Fish scale
Bone osteon
Tendon
Skin
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seases assoc ate w t
collagen
Diseases caused by mutations
Subtypes of osteogenesis imperfecta (collagen I)
Ehlers-Danlos syndrome (collagen I and V)
Alport syndrome (collagen IV)
Certain arterial aneurysms (collagen III)
Ullrich muscular dystrophy (collagen VI)
Certain chondrodysplasias (collagen IX and XI)
Kniest dysplasia (collagen II)
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Role of MMP in metastasis
Metastasis
Metastasis
Spread of cancer from a primary tumor to distant sites of the body
A defining feature of cancer
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Role of MMP in metastasis
Understanding the molecular mechanisms of metastasis is crucial for the
design of therapeutics
Extracellular matrix metalloproteinases (MMP) associated with metastasis
MMPs are capable of digesting ECM and basement membrane under
physiologic conditions
Collagenases degrade fibrillar collagen
Stromelysins degrade proteoglycans and glycoproteins
Gelatinases degrade nonfibrillar and denatured collagens
At tumor sites, experiments have found
Increased number of MMPs
Increased levels of MMPs
Reduced levels of TIMPs (Tissue inhibitors of metalloproteinases)
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Role of MMP in metastasis
Major role of MMPs was to facilitate the breakdown of physical barriers,
thus promoting invasion, intravasation, extravasation and migration
MMPs targeted for antimetastasis therapies
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Role of MMP in metastasis
Clinical trials of inhibiting MMPs to cure cancer have failed
Metastasis is a complicated process
MMPs contribute to every stage in tumor progression at both
primary and metastatic sites
Specific MMPs play a role in each stage of metastasis
MMP 13, 14 ± invasion
MMP 9± angiogenesis
Understand the role of the MMPs in each cancer setting
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Modification of collagen for therapeutics
Structure and content of collagen governs the delivery of
therapeutic molecules in tumors
Penetration of therapeutic molecules improved by
developing agents that modify ECM and increase diffusion
Detect tumor collagen noninvasively to quantify collagen
content and estimate drug delivery characteristics
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Modification of collagen for therapeutics
Uses Second-harmonic generation (SHG) for imaging only collagen fibers
Conditions :
Non-centrosymmetric (collagen,
microtubules)
Lasers (high intensity)
Advantages :
No staining
3D imaging
No photobleaching
SAMPLE
Red
Wavelength=800 nm
SHG: Blue
Wavelength=400 nm
Collagen stained red and
imaged by fluorescence
microscopy
Collagen imaged by SHG
microscopy
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Modification of collagen for therapeutics
SHG intensity collected from live imaging of collagen fibers provides an good estimate of diffusion coefficient in tumors
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Modification of collagen for therapeutics
Chronic relaxin treatment degrades tumor matrix
and improve macromolecular diffusion in tumors
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