Extracellular Matrix

Skin

Cell Adhesion

Collagen (type I) Fibres

Collagen triple helix

Introduction

This lecture introduces the materials lying outside the cell, known collectively as the extracellular matrix (ECM). There is no one matrix though, with different tissues having their own specific ECM, which may be dynamic or static in structure. In particular the ECM has significant roles in normal tissue development, function and disease. This matrix is manufactured by cells, secreted and modified outside the cell by several different enzymes.

This lecture introduces the ECM, describes the major fiber (fibre) and matrix components and will then cover the major ECM glycoproteins and experimental studies of ECM function.

Spelling - UK sulphate, US sulfate ; UK fibre, US fiber

Lecture Slides: 2017 Lecture PDF

2015 Group Projects

The projects Collagen and Elastic Fibres relate specifically to this lecture content.

Lab 7 Individual Assessment
The following peer assessment exercise should be completed before next lab (Lab 8 - 2 May) as your individual assessment for this week (lab missed due to public holiday). Your answer should be pasted in 2 places onto each project discussion page (Note you should add anonymously to the discussion page) your own individual student page for my assessment. Each individual will provide a brief assessment of the other groups projects. This should take the form of a brief critical (balanced) assessment identifying both the positive (good) and negative (bad) aspects of the project page as it currently exists online. You may if you choose, use the final project assessment criteria as a guide. Though you are also welcome to use your own criteria. Group Assessment Criteria The key points relating to the topic that your group allocated are clearly described. The choice of content, headings and sub-headings, diagrams, tables, graphs show a good understanding of the topic area. Content is correctly cited and referenced. The wiki has an element of teaching at a peer level using the student's own innovative diagrams, tables or figures and/or using interesting examples or explanations. Evidence of significant research relating to basic and applied sciences that goes beyond the formal teaching activities. Relates the topic and content of the Wiki entry to learning aims of cell biology. Clearly reflects on editing/feedback from group peers and articulates how the Wiki could be improved (or not) based on peer comments/feedback. Demonstrates an ability to review own work when criticised in an open edited wiki format. Reflects on what was learned from the process of editing a peer's wiki. Evaluates own performance and that of group peers to give a rounded summary of this wiki process in terms of group effort and achievement. The content of the wiki should demonstrate to the reader that your group has researched adequately on this topic and covered the key areas necessary to inform your peers in their learning. Develops and edits the wiki entries in accordance with the above guidelines.

Objectives

Understand the localisation and origin of extracellular matrix
Understand the 3 major components
- fibers, proteoglycans (matrix), adhesive glycoproteins
Broad understanding of structure and function
- collagen fibers
- elastin fibers
- proteoglycans

ECM Function

Support for cells
Pattern of ECM regulates
- polarity
- cell division
- adhesion
- motility
Development
- migration
- differentiation
- growth factors

Evolution of metazoan extracellular matrix

ECM Features

stable and able to be reorganised?
different for different tissues

| Figure 19-61. How the extracellular matrix could, in principle, propagate order from cell to cell within a tissue

Cell Walls/ECM?
Cell Wall - Cells of bacteria, fungi, algae, and higher plants are surrounded by rigid cell walls (form part of the cell). Gram-negative bacteria - peptidoglycan, linear polysaccharide chains crosslinked by short peptides Fungi, algae, and higher plants - polysaccharides (sugar polymer), algae and higher plants mainly cellulose. ExtraCellular Matrix (ECM) - animal cells of animal in tissues associated with extracellular matrix (ECM) composed of secreted proteins and polysaccharides (sugar polymer)

ECM Structure

Glycoproteins
Fibers
- Collagen- main fibers
- Elastin
Hydrated Matrix
- Proteoglycans
- high carbohydrate
Adhesive
- Laminin
- Fibronectin

Shapes and Sizes ECM molecules

|MBoC Figure 19-59. The comparative shapes and sizes of some of the major extracellular matrix macromolecules

Note the relative size and differential contribution of protein (green) and glycosaminoglycan (red)

Collagen

tensile strength and elasticity
- Tendons
- Cartilage
- Bone
half total body proteins (by weight)

Collagen Components

Insoluble glycoprotein
- protein + carbohydrate

Protein

high glycine
high proline
hydroxylysine
hydroxyproline
(gly-X-Y)n - any of 20 standard amino acids may occupy the X position and/or the Y position (Y position- hydroxylysine, hydroxyproline)
most frequently observed triplet is Gly-Pro-Hyp (10.5%) PMID 9724608

Carbohydrate

glucose
galactose

Collagen Structure

Collagen Fiber structure and size

Collagen Protein

3 polypeptide (a) chains
left hand helix, forms fibers
many different (vertebrate) collagens by different combinations of a-chains
Type I, II, III
- main fibers, flexible
Type I
- bone, skin, tendons
- 90% of all collagen
Type II
- cartilage

Collagen Fibers

Collagen Type I

Type I, II, III cross striated
- e.g. tendons - type I fibrils, have a 67-nm period striations and are oriented longitudinally (direction of the stress)
- showing overlapping packing of individual collagen molecules
- reticular fibres type III, support individual cells

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 Interactions

Collagen fibril types can interact with a variety of non-fibrous collagen types (microfiber)

fibrous collagens—types I, II, III, and V

- Cartilage - types II (fiber) and IX collagen microfibrils
- Tendons - type I fibrils bound and linked by type VI microfibrils.

MCB - Interactions of fibrous and nonfibrous collagens

MBoC Type IX collagen

Collagen Type Functions

Skin

Collagen Type I - skin, tendon, vascular, ligature, organs, bone (main component of bone)
Collagen Type II - cartilage (main component of cartilage)
Collagen Type III - reticular fibers with type I.
Collagen Type IV - forms bases of cell basement membrane
Collagen Type V - hair and nail

You do not need to know the protein table below in detail, just the major type/functions shown above.

Collagen Proteins

Collagen Types
Collagen type	Genes	Organization in tissue (where known)	References
I	COL1A1	Fibrils in tendon, bone, skin, cornea and blood vessel walls	Chu et al., 1982
	COL1A2		Myers et al., 1981
II	COL2A1	Fibrils in cartilage	Miller and Matukas, 1969
III	COL3A1	Forms heterotypic fibrils with type I collagen	Cameron et al., 2002
IV	COL4A1	Network in basement membrane	Timpl and Brown, 1996; Timpl et al., 1981
	COL4A2
	COL4A3
	COL4A4
	COL4A5
	COL4A6
V	COL5A1	Forms heterotypic fibrils with type I	Birk, 2001
	COL5A2
	COL5A3
VI	COL6A1	Fine microfibrils with ubiquitous distribution (distinct from fibrillin-	Kielty et al., 1992
	COL6A2	containing microfibrils
	COL6A3
VII	COL7A1	Forms anchoring fibrils in skin at the dermal/epidermal junction	Keene et al., 1987
		(basement membrane)
VIII	COL8A1	3D hexagonal lattice in Descemet's membrane in the eye	Kapoor et al., 1986; Kapoor et al., 1988;
	COL8A2		Stephan et al., 2004
IX	COL9A1	Associated with type II collagen fibrils	Olsen, 1997; Shimokomaki et al., 1990
	COL9A2
X	COL10A1	Mat-like structure/hexagonal lattice in the hypertrophic zone of the growth plate	Kwan et al., 1991

XI	COL11A1	Forms heterotypic fibrils with type II	Mendler et al., 1989
	COL11A2
	COL2A1
XII	COL12A1	Associated with type I fibrils	Keene et al., 1991; Nishiyama et al., 1994;
			Zhang et al., 2003
XIII	COL13A1	Transmembrane and possibly involved in cell adhesion	Latvanlehto et al., 2003
XIV	COL14A1	Associated with type I fibrils	Young et al., 2000b; Young et al., 2002
XV	COL15A1	Specialized basement membranes, cleaved to produce antiangiogenic	Myers et al., 1996; Ramchandran et al.,
		fragment (restin)	1999
XVI	COL16A1	Component of specialized fibrillin-rich microfibrils in skin and type II	Kassner et al., 2003
		collagen fibrils in cartilage
XVII	COL17A1	Transmembrane component of hemidesmosomes (cell-cell junctions), which	Hopkinson et al., 1998
		attach epidermis to basement membrane in skin
XVIII	COL18A1	Cleaved to produce antiangiogenic fragment (endostatin)	Sasaki et al., 1998
XIX	COL19A1	Radially distributed aggregates formed by association at one end in vitro	Myers et al., 2003
XX	COL20A1	May be associated with type I collagen fibrils	Koch et al., 2001
XXI	COL21A1	May be fibril associated, widespread expression pattern	Fitzgerald and Bateman, 2001
XXII	COL22A1	Located in specific tissue junctions and may be associated with microfbrils	Koch et al., 2004
XXIII	COL23A1	Transmembrane collagen identified in cell culture	Banyard et al., 2003
XXIV	COL24A1	Expressed in tissues containing type I collagen	Koch et al., 2003
XXV	COL25A1	Transmembrane collagen, cleaved form present in Alzheimer‚ amyloid plaques in neurons	Hashimoto et al., 2002
Table modified from Canty EG, Kadler KE. Procollagen trafficking, processing and fibrillogenesis. J Cell Sci. 2005 Apr 1;118(Pt 7):1341-53. Review. PMID: 15788652 \| JCS Link

Collagen Synthesis

Fibrillar collagen

Endoplasmic Reticulum
- mRNA attached to ER
- protein synthesized into ER lumen
- cotranslational and post-translational modifications
- endoplasmic reticulum (ER) requires Hsp47 (a molecular chaperone) transiently binds to procollagen in the ER, dissociates in the cis-Golgi or ER-Golgi intermediate compartment) PMID 27838364
- 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 (ADAMTS (N-proteinase) and tolloid (C-proteinase) family enzymes)
- assemble into collagen fibers
- collagen fibrils form lateral Interactions of triple helices

Link: MBoC - The intracellular and extracellular events in the formation of a collagen fibril | MCB - Collagen synthesis

Collagen Assembly
YouTube Link

Collagen in the ECM is modified/cleaved by matrix metalloproteinases (MMPs) - family of enzymes (calcium-dependent zinc-containing endopeptidases)

Collagen Diseases

Collagen Diseases - Excess

fibrosis
lung- pulmonary fibrosis
overproduction of collagen I
liver- over consumption of alcohol
arteries- atherosclerosis

Collagen Diseases - Insufficient

Ehlers-Danlos syndrome
- defect in the synthesis of Type I or III collagen
- 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

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

Elastin

Elastic Fibers Skin

MBoC - Collagen and elastin

Elastin in Aorta PMID 18248974

elastin and elastic fibres
- uncoils into an extended conformation when the fiber is stretched
- recoils spontaneously as soon as the stretching force is relaxed

Elastic fibers are composed of a core of cross-linked elastin embedded within a peripheral mantle of microfibrils.

Microfibrils

may regulate assembly and organization of elastic fibers by acting as a scaffold
guiding tropoelastin deposition
aggregates of threadlike filaments
periodically spaced globular domains (beads) connected by multiple linear arms
- beaded structure is parallel fibrillin monomers aligned head-to-tail
fibulin-5 induces elastic fiber assembly and maturation by organizing tropoelastin and cross-linking enzymes onto microfibrils PMID: 17371835

Links: MBoC - Collagen and elastin

Elastin Structure

elastic fiber synthesis

protein Mr 64 to 66 kDa
composed of the amino acids glycine, valine, alanine, and proline
cross-linked tropoelastin monomers
first secreted as soluble precursors (tropoelastin)
assembly and crosslinking of tropoelastin monomers
form insoluble elastin matrix into functional fibres
- lysine residues in the cross-linking domain of secreted tropoelastin rapidly cross-linked (both inter- and intra-molecularly by lysyl oxidase)
- hydrophobic segments - elastic properties
- α-helical segments (alanine- and lysine-rich) - form cross-links between adjacent molecules

elastic fiber assemby model

Links: Nature - Fibulin-5 is an elastin-binding protein

Elastin Function

structural integrity and function of tissues
requiring reversible extensibility or deformability
high levels in tissues that require elasticity
- lung, skin, major blood vessels

Elastin Disorders

Williams Syndrome

References

Recent Reviews

Textbooks

Essential Cell Biology

Essential Cell Biology Chapter 19 p594-604

Molecular Biology of the Cell

Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002

Molecular Biology of the Cell 4th ed. - V. Cells in Their Social Context Chapter 19. Cell Junctions, Cell Adhesion, and the Extracellular Matrix
The Extracellular Matrix of Animals

Molecular Cell Biology

Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James E. New York: W. H. Freeman & Co.; c1999

Molecular Cell Biology - Chapter 22. Integrating Cells into Tissues
Cell-Matrix Adhesion

The Cell- A Molecular Approach

Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000

The Cell- A Molecular Approach
The Cell - A Molecular Approach - III. Cell Structure and Function Chapter 12. The Cell Surface
The Extracellular Matrix

Essentials of Glycobiology, 2nd ed.

Varki, A.; Cummings, R.D.; Esko, J.D.; Freeze, H.H.; Stanley, P.; Bertozzi, C.R.; Hart, G.W.; Etzler, M.E., editors Plainview (NY): Cold Spring Harbor Laboratory Press; 2008

Search Online Textbooks

"extracellular matrix" Molecular Biology of the Cell | Molecular Cell Biology | The Cell- A molecular Approach | Bookshelf

"collagen" Molecular Biology of the Cell | Molecular Cell Biology | The Cell- A molecular Approach | Bookshelf

"elastin" Molecular Biology of the Cell | Molecular Cell Biology | The Cell- A molecular Approach | Bookshelf

"glycosaminoglycan" Molecular Biology of the Cell | Molecular Cell Biology | The Cell- A molecular Approach | Bookshelf

Books

PubMed

PubMed is a service of the U.S. National Library of Medicine that includes over 18 million citations from MEDLINE and other life science journals for biomedical articles back to 1948. PubMed includes links to full text articles and other related resources. PubMed

PubMed Central (PMC) is a free digital archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health (NIH) in the National Library of Medicine (NLM) allowing all users free access to the material in PubMed Central. PMC

Online Mendelian Inheritance in Man (OMIM) is a comprehensive compendium of human genes and genetic phenotypes. The full-text, referenced overviews in OMIM contain information on all known mendelian disorders and over 12,000 genes. OMIM

Entrez is the integrated, text-based search and retrieval system used at NCBI for the major databases, including PubMed, Nucleotide and Protein Sequences, Protein Structures, Complete Genomes, Taxonomy, and others Entrez

Search Pubmed

"extracellular matrix" Entrez all databases
"collagen" Entrez all databases
"elastin" Entrez all databases
"glycosaminoglycan" Entrez all databases
"proteoglycan" Entrez all databases
- note the spelling differences when carrying out other related ECM searches: UK sulphate, US sulfate ; UK fibre, US fiber

Reviews

Articles

Sandberg LB, Soskel NT, Leslie JG. Elastin structure, biosynthesis, and relation to disease states. N Engl J Med. 1981 Mar 5;304(10):566-79. Review.

PMID: 7005671

Links

Marfan syndrome is an autosomal dominant disorder that has been linked to the FBN1 gene on chromosome 15. FBN1 encodes a protein called fibrillin

Communication between the intra- and extracellular compartment

2017 Course Content

Moodle

2017 Laboratories: Introduction to Lab | Fixation and Staining |

2017 Projects: Group 1 - Delta | Group 2 - Duct | Group 3 - Beta | Group 4 - Alpha

Dr Mark Hill 2015, UNSW Cell Biology - UNSW CRICOS Provider Code No. 00098G

Extracellular Matrix 1

Contents