2010 Lecture 13

From CellBiology

Extracellular Matrix 1

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

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

Lecture Audio

The University has a system for automated recording of lectures called Lectopia. Lectopia requires login using your student number and unipass. I will be adding the link to each iLecture Audio following the Lecture. Due to the automated recording method, most lectures begin 4-5 minutes into MP3 recordings and occasionally stop before the end of the lecture.


Archive

MH - note that content listed below will not match exactly current lecture structure but has been selected as having similar content

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

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

ECM Structure

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

Shapes and Sizes ECM molecules

  • 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


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 Fibers Collagen Non-striated

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

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

Collagen Proteins

Collagen type
Genes
Organization in tissues (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

  • Endoplasmic Reticulum
    • mRNA attached to ER
    • protein synthesized into ER lumen
    • cotranslational and post-translational modifications
    • 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 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 synthesis


Collagen fibril assembly

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
    • 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
  • Atopic dermatitis (AD)
    • chronic inflammatory skin disorder and a major manifestation of allergic disease
    • mutation in collagen XXIX (COL29A1) gene

Elastin

Elastic Fibers Skin

MBoC - Collagen and elastin

  • 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

Fibrilin-microfibrils.jpg

  • 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

Proteoglycans

MBoC - Proteoglycans in the extracellular matrix of rat cartilage MBoC - Examples of a small (decorin) and a large (aggrecan) proteoglycan found in the extracellular matrix

  • consist of protein (~5%) and polysaccharide chain (~95%)
  • form a gel to embed the fibril network
  • Golgi apparatus - GAG disaccharides are added to protein cores to form proteoglycans
  • 10% by weight but fill most of space
  • unbranched polysaccharide chains
  • disaccharide subunits
  • amino sugar

Glycosaminoglycans (Gags)

Five types

  • Hyaluronan (or hyaluronic acid) main glycosaminoglycan in connective tissue
  • high molecular weight (~ MW 1,000,000 )
  • length of about 2.5 µm hyaluronan
  • "backbone" for the assembly of other glycosaminoglycans
    • Hyaluronan is also a major component of the synovial fluid, which fills joint cavities, and the vitreous body of the eye.
  • Other 4 major glycosaminoglycans
    • chondroitin sulphate, dermatan sulphate, keratan sulphate and heparan sulphate (UK sulphate, US sulfate)
    • attach through core and link proteins to hyaluronic acid backbone

Proteoglycan 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

Development

  • produce a “cell-free” space
  • for cell proliferation and migration into
  • heart, cornea

Adult

  • in areas of compression
  • tissues, joints

hyaluronan-binding proteins

Hyaluronan Synthesis

  • differs from other GAG synthesis
    • synthesized at plasma membranes
    • nascent chains directly extruded into ECM

Cell adhesion

embryonic migration

Proteoglycan- Disease

  • Mucopolysaccharidosis type I (MPS I) - Hurler disease
  • lysosomal storage disease, is associated with an altered elastic matrix
  • excess heparan sulphate and dermatan sulphate
  • Cancer development
    • altered types and kinds of proteoglycans formed by cells
    • normal cells -> malignant
  • Arthritis
    • Cartilage breakdown (cartilage erosion)
    • chondrocytes elicit a catabolic response which exceeds anabolism of new matrix molecules
    • Degrade proteoglycan (aggrecan)
    • Also a mouse model generates antibodies to proteogycan

History

Below are some example historical research finding related to cell junctions from the JCB Archive.

1978 Basal lamina instructs innervation Joshua Sanes and Jack McMahan show that regenerating nerve axons take their cues for new synapse formation from the extracellular matrix (ECM) of muscle cells and not from the muscle cells themselves.

References

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

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

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Books

PubMed

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  • 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

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Reviews

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

  • Hay ED. The extracellular matrix in development and regeneration. An interview with Elizabeth D. Hay. Int J Dev Biol. 2004;48(8-9):687-94. No abstract available. PMID: 15558460
  • Hay ED. Extracellular matrix. J Cell Biol. 1981 Dec;91(3 Pt 2):205s-223s. Review. No abstract available. PMID: 6172429
  • 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
  • Wagenseil JE, Mecham RP. New insights into elastic fiber assembly. Birth Defects Res C Embryo Today. 2007 Dec;81(4):229-40. Review. PMID: 18228265

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

2009 Course Content

Lectures

Cell Biology Introduction | Cells Eukaryotes and Prokaryotes | Cell Membranes and Compartments | Cell Nucleus | Cell Export - Exocytosis | Cell Import - Endocytosis | Cell Mitochondria | Cell Junctions | Cytoskeleton Introduction | Cytoskeleton 1 Intermediate Filaments | Cytoskeleton 2 Microtubules | Cytoskeleton 3 Microfilaments | Extracellular Matrix 1 | Extracellular Matrix 2 | Cell Cycle | Cell Division | Cell Death 1 | Cell Death 2 | Signal 1 | Signal 2 | Stem Cells | Stem Cells | Development | Revision

Laboratories

Introduction to Lab | Microscopy Methods | Preparation/Fixation | Immunochemistry | Cell Knockout Methods | Cytoskeleton Exercise | Confocal Microscopy | Tissue Culture 1 | Tissue Culture 2 | Microarray Lab visit

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