EXTRACELLULAR MATRIX
PROTEINS AND
PROTEINASES
By,
Raghu Ambekar
Photonics Research of Bio/nano Environments
Department of Electrical & Computer Engineering
University of Illinois Urbana - Champaign
04/19/10
BioE 506
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: Proteoglycans
and polysaccharides
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http://kentsimmons.uwinnipeg.ca/cm1504
Collagen
 Collagen : most abundant protein found in the human
body. About 1/3rd 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 α-polypeptide chains arranged in
right-handed supercoil
 Glycine, proline, hydroxyproline
 1.5 nm diameter
 At least 28 different collagens found
 The three α-chains could be same
(collagen II) or different (collagen I)
Collagen molecule
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Classification of collagen
1. Fibril-forming collagens
 No interruptions in triple helix
 Regular arrangement results in characteristic “D” period of 67 nm
 Diameter : 50-500 nm
 Example : Types I, II, III, V, XI
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Classification of collagen
2. Network-forming collagens
 Forms network in basement (Collagen IV) and Descemet’s
membrane (Collagen VIII)
 Molecular filtration
 Example : Types IV, VIII, X
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Classification of collagen
3. Fibril-associated collagens with interrupted triple helices (FACITs)
 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
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Classification of collagen
4. Anchoring collagens
 Provides functional integrity by connecting epithelium to
stroma
 Example : Type VII
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Classification of collagen
5. Beaded-filament-forming collagens
 Form structural links with cells
 Example : Type VI
 Collagen VI crosslink into tetramers that assemble into long
molecular chains (microfibrils) and have beaded repeat of 105 nm
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Type I Fibril assembly
Fibril assembly is determined by chain recognition sequence in C-propeptide
Fish scale
Bone osteon
Tendon
Chain recognition sequence
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Skin
Diseases associated with 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 :
Red
Wavelength=800 nm
SHG: Blue
Wavelength=400 nm
Non-centrosymmetric (collagen,
microtubules)
Lasers (high intensity)
Advantages :
No staining
3D imaging
No photobleaching
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SAMPLE
Collagen stained red and
imaged by fluorescence
microscopy
Collagen imaged by SHG
microscopy
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
0th day
3rd day
6th day
9th day
12th day
 Chronic relaxin treatment degrades tumor matrix
and improve macromolecular diffusion in tumors
THANK YOU!
04/19/10