Cell Adhesion & ECM - Student Notes PDF

Cell Adhesion and the Extracellular Matrix  Contact Karron J. James, Ph.D. Professor, Dept. Biochemistry, Cell Biology & Genetics Office: GB6, Block B Email: [email protected] Phone 484-8900 ext 1041 Office hours: Mon-Fri, by appointment Goal MCB.16: Understand the s...

Cell Adhesion and the Extracellular Matrix  Contact Karron J. James, Ph.D. Professor, Dept. Biochemistry, Cell Biology & Genetics Office: GB6, Block B Email: [email protected] Phone 484-8900 ext 1041 Office hours: Mon-Fri, by appointment Goal MCB.16: Understand the significance of cell adhesion and the extracellular matrix to maintain the integrity of tissues and organs Learning objectives Given a clinical or research vignette, scenario, table, graph, or diagram, students should be able to: MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. MCB.16.2. Recognize the molecular components of cell-cell and cell-matrix interactions. MCB.16.3. Describe the importance of matrix metalloproteinases in regulating cell adhesion. MCB.16.4. Differentiate the functions of extracellular matrix components, with emphasis on collagen, laminin, elastic fibers, fibrinogen, fibronectin, glycosaminoglycans, and proteoglycans.  Reading assignment Alberts, B. et al. (2002). Molecular Biology of the Cell. 4ed. New York: Garland Science. Chapter. 19: Cell Junctions Occluding Junctions Form a Selective Permeability Barrier Across Epithelial Cell Sheets Anchoring Junctions Connect the Cytoskeleton of a Cell Either to the Cytoskeleton of Its Neighbors or to the Extracellular Matrix Adherens Junctions Connect Bundles of Actin Filaments from Cell to Cell Desmosomes Connect Intermediate Filaments from Cell to Cell Anchoring Junctions Formed by Integrins Bind Cells to the Extracellular Matrix: Focal Adhesions and Hemidesmosomes Gap Junctions Allow Small Molecules to Pass Directly from Cell to Cell Gap Junctions Have Diverse Functions Cell-Cell Adhesion Cadherins Mediate Ca2+-dependent Cell-Cell Adhesion Selectins Mediate Transient Cell-Cell Adhesions in the Bloodstream Members of the Immunoglobulin Superfamily of Proteins Mediate Ca2+-independent Cell-Cell Adhesion (1st paragraph) Integrins (first 2 paragraphs and Summary) The Extracellular Matrix of Animals Glycosaminoglycan (GAG) Chains Occupy Large Amounts of Space and Form Hydrated Gels (first paragraph) Collagens Are the Major Proteins of the Extracellular Matrix (1st paragraph) Elastin Gives Tissues Their Elasticity (first 2 paragraphs) Fibronectin Exists in Both Soluble and Fibrillar Forms (1st paragraph) Basal Laminae Are Composed Mainly of Type IV Collagen, Laminin, Nidogen, and a Heparan Sulfate Proteoglycan (first 3 paragraphs) The Extracellular Matrix Can Influence Cell Shape, Cell Survival, and Cell Proliferation The Controlled Degradation of Matrix Components Helps Cells Migrate (first 2 paragraphs, section Summary) Goal MCB.16: Understand the significance of cell adhesion and the extracellular matrix to maintain the integrity of tissues and organs Learning objectives Given a clinical or research vignette, scenario, table, graph, or diagram, students should be able to: MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. MCB.16.2. Recognize the molecular components of cell-cell and cell-matrix interactions. MCB.16.3. Describe the importance of matrix metalloproteinases in regulating cell adhesion. MCB.16.4. Differentiate the functions of extracellular matrix components, with emphasis on collagen, laminin, elastic fibers, fibrinogen, fibronectin, glycosaminoglycans, and proteoglycans.  Cells to Tissues Epithelia line free surfaces of the body (eg. skin), body cavities (eg. small intestines), outer surface of internal organs (eg. heart) From Fig 19-8 in Lodish et al. 6ed. Functions: barrier, absorption, secretion,… Cells have apical, lateral, basal surfaces LATERAL Underlying: basal lamina (basement membrane) Connective tissue See Fig 19-13. Alberts.  Basic cell adhesion questions to answer Why do cells adhere? To what do cells adhere? Note: some cell types not adhesive at any time during their life span  Junctions mediate epithelial cell interactions Mediate cell-cell and cell-ECM adhesion Regulate cell polarity Involved in intercellular communication See Fig. 19-19. Alberts.  3 main classes of junctions mediate interactions between epithelial cells 1. Anchoring 2. Occluding 3. Communicating www.proprofs.com  1. Anchoring Junctions mediate cell- cell, cell-ECM adhesion Anchoring junctions attach cells to each other or to the extracellular matrix Types of anchoring junctions include: a) Adherens junction b) Desmosome c) Hemidesmosome d) Focal contact  1. Anchoring Junctions a) Adherens Junction (Zonula adherens) Found near apical surface in epithelial cell layer Function: cell-cell adhesion Adhesion molecules: – Cadherins primarily responsible for adhesion See Fig 19-9. Alberts. Adherens junction (Zonula adherens) https://www.mechanobio.info/development/ Cross-section of a blastocyst (no inner cell mass shown) Adherens junctions help maintain connection between adjacent cells. Adherens junction (Zonula adherens) Fig. 5 from Yeatman, T.J. Nature Reviews Cancer volume 4, pages 470–480 (2004)  Adherens junction (Zonula adherens) Associated with ________ (component of the cytoskeleton) Stabilised by desmosomes; interdependence in epithelia if both present – Helps resist mechanical stress, maintain tissue integrity See Fig. 19-19. Alberts. Pause for Retrieval Practice https://www.bookwidgets.c om/play/MHbYS4P7- iQAFq1lyygAAA/NENHTN9/a dherens- juncti?teacher_id=4837012 212285440 Pause for Retrieval Practice https://www.bookwidgets. com/play/Kh6_xA6w- iQAFYA42ygAAA/QEM3RQ N/sec-or-non- sec?teacher_id=48370122 12285440  1. Anchoring Junction b) Desmosome (Macula adherens) Located beneath adherens junction in epithelium Provides strong cell-cell adhesion Adhesion molecule: – Desmosomal cadherins, eg. desmoglein, desmocollin See Fig. 19-19. Alberts. Binds which component of the cytoskeleton?  Desmosome (Macula adherens) Strongly adhesive Most numerous in tissues subjected to significant mechanical stress, eg. epithelia of the skin and mucous membranes; myocardium – Found in simple epithelia, See Fig. 19-19. Alberts. non-epithelial cells Pemphigus vulgaris Robbins Basic Pathology ©2018. Fig. 24.10  Epidermolysis Bullosa simplex https://www.aad.org/public/diseases/a-z/epidermolysis-bullosa-overview https://www.nhs.uk/conditions/epidermolysis-bullosa/ https://www.nhs.uk/conditions/epidermolysis-bullosa/  Epithelial IFs form strong attachment sites at cell surface http://163.178.103.176/Fisiologia/general/celulas/Membrane%20Structure%20and%20Function.htm Keratins are IFs found in cytosol of epithelial cells Interconnect desmosomes in neighbouring cells to help stabilize epithelial sheets – Desmosome: adhesive junction that helps keep adjacent cells joined together Associated with strong adhesion between epithelial cells and underlying extracellular matrix Pause for Retrieval Practice https://www.bookw idgets.com/play/M p7D2a5o- iQAFqAf8ygAAA/LE M82LG/cytoskeletal -at  1. Anchoring Junction c) Hemidesmosome Common in epithelia subject to abrasion, mechanical forces, eg. skin, mucosa of oral cavity, cornea, rectum Function: strong adhesion between basal surface of cell and underlying ECM – Helps resist mechanical stress See Fig. 19-19. Alberts. Major adhesion molecules: integrins  Hemidesmosome Within hemidesmosome, integrins interact with laminin and collagen in basal lamina These filaments, in turn, interact with other collagen fibrils in underlying connective tissue Cytoplasmic attachment to ____________________ Contacts must be dynamic, eg. during cell migration See Fig 19-13. Alberts. Bullous pemphigoid Robbins Basic Pathology ©2018. Fig. 24.12  Epithelial IFs form strong attachment sites at cell surface http://163.178.103.176/Fisiologia/general/celulas/Membrane%20Structure%20and%20Function.htm Keratins are IFs found in cytosol of epithelial cells Interconnect desmosomes in neighbouring cells to help stabilize epithelial sheets – Desmosome: adhesive junction that helps keep adjacent cells joined together Associated with strong adhesion between epithelial cells and underlying extracellular matrix  1. Anchoring Junction d) Focal contacts Found between a cell’s basal surface and the ECM Function: adhesion of cell to substratum (ECM) Major adhesion molecules: _______________ Cytoplasmic attachment to actin  RECALL: Cells migrate along extracellular matrix via actin Necessary during embryogenesis, movement of axons in response to growth factors, movement of white blood cells toward site of infection, phagocytosis Leading edge temporarily attaches to extracellular matrix Fig 4.8 from Lippincott's Illustrated Reviews: Cell and Molecular Biology, 2e, 2019 Pause for Retrieval Practice https://www.bookw idgets.com/play/7w q3O-56- iQAFpe0jOgAAA/FE 94XFD/hemidesmos omes  Which of the following junctions mediate(s) adhesion between cells and which mediate(s) adhesion between cells and the extracellular matrix? Adherens junction Desmosome Focal contact Hemidesmosome  2. Occluding Junction Tight Junction (Zonula occludens) Forms seal, at PM of adjacent cells, that separates luminal surface (apical) from intercellular (lateral; paracellular) space and basal surface Main TM proteins = claudins and occludin Scaffold of ZO proteins link TM Fig 5.16. Ross & Pawlina. (2011) Histology: A Text and Atlas. 6ed. proteins to _______________ (component of the cytoskeleton)  Tight Junction (Zonula occludens) Component of junctional complex closest to apical surface – Eg. in blastocyst, epithelia of intestines and airways Functions in epithelial cells: – Forms seal between adjacent epithelial cells – Regulates selective diffusion of hydrophilic molecules through paracellular space – Restricts migration of membrane proteins See Fig. 19-19. Alberts. – Maintains cell polarity Tight Junction (Zonula occludens) https://www.mechanobio.info/development/ Cross-section of a blastocyst (no inner cell mass shown) Tight junctions seal the space between adjacent cells.  3. Communicating Junction Gap Junction Hydrophilic channel found on most cells – Allows direct exchange of small metabolites and signalling molecules between adjacent cells Channel formed by 2 connexons (hemi-channels) that bridge space between adjacent plasma membranes – Connexons are composed of individual connexin proteins Function: intercellular communication © 2012 Pearson Education Inc.  Gap Junction Cell-cell communication – Electrical coupling in cardiac muscle – Transfer of small metabolites between epithelial cells See Fig. 19-19. Alberts. Importance of Gap Junctions gfmer.ch Cell Adhesion Molecules mediate interactions within anchoring junctions Extracellular and cytoplasmic domains Homophilic and Fig 5.18, Ross & Pawlina. Histology, A Text and Atlas. 6ed. heterophilic adhesive molecules Goal MCB.16: Understand the significance of cell adhesion and the extracellular matrix to maintain the integrity of tissues and organs Learning objectives Given a clinical or research vignette, scenario, table, graph, or diagram, students should be able to: MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. MCB.16.2. Recognize the molecular components of cell-cell and cell-matrix interactions. MCB.16.3. Describe the importance of matrix metalloproteinases in regulating cell adhesion. MCB.16.4. Differentiate the functions of extracellular matrix components, with emphasis on collagen, laminin, elastic fibers, fibrinogen, fibronectin, glycosaminoglycans, and proteoglycans. 4 Major Families of Cellular Adhesion Molecules (CAMs) 1. Cadherin 2. Immunoglobulin 3. Integrin Fig 5.18, Ross & Pawlina. Histology, A Text and Atlas. 6ed. 4. Selectin  1. Cadherins—most common mediator of interactions in AJ’s Primary family of CAM in epithelial cells, usually homophilic Adhesion: cell-cell Bind catenins, which bind actin – Binding necessary for cadherin function Disruption of cadherin/β-catenin complex = normal part of cell turnover Ca2+-dependent See Fig 19-29. Alberts.  2. Immunoglobulin Super Family Homo-, heterophilic – Mainly cell-cell, incl. epithelial cells, leukocytes, endothelial cells – IgSF interact with self or integrins Adhesion molecules include ICAM and VCAM Cytoskeleton partners: actin, From Fig. 2, Ebnet, K. et al. J. Cell Sci, 2004 117: 19-29 actin-binding proteins  3. Integrins Adhesion: cell-cell, cell-ECM A single cell type (eg. platelets) can express multiple integrins Cytoskeleton partners: 1.actin 2.intermediate filaments Fig 19-56. Alberts. 6ed.  4. Selectins Heterophilic, cell-cell binding in the bloodstream Bind carbohydrates L, E, P-selectins – Function restricted to vascular system Cytoskeleton partner: actin Major role in initiating adhesion of leukocytes and platelets to endothelial cells during inflammation and hemostasis Pause for Retrieval Practice https://www.bookw idgets.com/play/AYl JG88Q- iQAFixxxOgAAA/TE9 XBTE/tj-gj-cams Goal MCB.16: Understand the significance of cell adhesion and the extracellular matrix to maintain the integrity of tissues and organs Learning objectives Given a clinical or research vignette, scenario, table, graph, or diagram, students should be able to: MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. MCB.16.2. Recognize the molecular components of cell-cell and cell-matrix interactions. MCB.16.3. Describe the importance of matrix metalloproteinases in regulating cell adhesion. MCB.16.4. Differentiate the functions of extracellular matrix components, with emphasis on collagen, laminin, elastic fibers, fibrinogen, fibronectin, glycosaminoglycans, and proteoglycans. Cell Adhesion Regulates Cell Proliferation Normal epithelial cells exhibit anchorage-dependence for proliferation Presence of bound integrins may inhibit activation of apoptosis genes Detached epithelial cells undergo programmed cell death Goodman, S.R. (2008). Medical Cell Biology. 3rd ed. Academic Press  MMPs degrade the ECM Matrix metalloproteinases (metalloproteases) – Collagenases, gelatinase, elastases, etc. Regulate cell differentiation, proliferation, wound healing, bone remodelling, etc. – Consequences of lack of regulation?  Cell Adhesion Functions—Summary Maintain epithelial barrier, cell polarity – Important that apical surfaces (eg. in intestines) be non-adhesive Regulation of cell proliferation Embryonic development Adhesion helps maintain cell barriers and polarity Academic Press Goodman, S.R. (2008). Medical Cell Biology. 3rd ed. Fig 6-20 http://www.siumed.edu/~dking2/intro/IN008b1.htm Summary—Major CAM Gene Families Molecules that mediate adhesion: CAMs -Cell adhesion molecules or Adhesion receptors Goodman, S.R. (2008). Medical Cell Biology. 3rd ed. Academic Press Goal MCB.16: Understand the significance of cell adhesion and the extracellular matrix to maintain the integrity of tissues and organs Learning objectives Given a clinical or research vignette, scenario, table, graph, or diagram, students should be able to: MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. MCB.16.2. Recognize the molecular components of cell-cell and cell-matrix interactions. MCB.16.3. Describe the importance of matrix metalloproteinases in regulating cell adhesion. MCB.16.4. Differentiate the functions of extracellular matrix components, with emphasis on collagen, laminin, elastic fibers, fibrinogen, fibronectin, glycosaminoglycans, and proteoglycans.  Extracellular Matrix Fibrous protein secreted by cells, especially fibroblasts Functions: structure— provides shape, strength, elasticity to tissues, acts as substratum for adhesion; signal transduction; reservoir for growth jpkc.scu.edu.cn factors Amount and character depends on tissue type Collagen family = very abundant component protein Robbins and Cotran Pathologic Basis of Disease. 8ed. Saunders. en.wikipedia.org https://lovetotherescue.org/no-small-wonder/  Collagen—Very Abundant ECM Protein Provides tensile strength and stability to connective tissue Helps impart structure to bone, cartilage, tendons, skin,… See Fig 19-44. Alberts.  sciencephoto.com Importance of Collagen Osteogenesis imperfecta http://www.oif.org/site/PageServer?pagena me=fastfacts Ehlers-Danlos syndrome (Cutis hyperelastica) http://sugarchurch.tumblr.com/post/7911575008/the-elastic- skin-man-james-morris-was-featured  Basement Membrane Highly cross-linked layer of ECM that anchors all epithelial cells to underlying connective tissue Compartmentalises tissues Physical barrier to macromolecules Influences cell shape and polarity Connected to overlying cells through interaction with integrins July 2013 – Type IV collagen, laminin  Laminin Major component of the basement membrane Interacts with other ECM components (type IV collagen, heparan sulphate, etc) and self Helps mediate See Fig 19-58. Alberts. hemidesmosomal attachment  Glycosaminoglycans GAGs = long carbohydrate chains (polysaccharides) Anionic groups (eg. COO-, SO42-) confer strong negative charge – Attract cations so have osmotic potential GAGs remain extended (not compact) and hold H2O – Able to resist compressive forces (eg. knee joint) Hyaluronic acid = non-sulphated GAG – Helps cartilage resist compression without inhibiting flexibility Include chondroitin sulfate, dermatan sulfate, keratan sulfate, heparan sulfate  Proteoglycans http://www.siumed.edu/~dking2/intro/IN008b1.htm Proteoglycans = polypeptide core covalently linked to GAG Osmotically active, attract H20, resist compression Most GAGs, except for hyaluronic acid, occur as proteoglycans Form a “ground substance” in which other matrix components are embedded intranet.tdmu.edu.ua  Elastic Fibres Allow recoil of stretched tissue; provide elasticity Form network with interwoven collagen marfan-association.org.uk Predominant in which tissue types? Elastin and fibrillin = major protein components of elastic fibres Boy with Marfan syndrome. Mutation in fibrillin gene. – Central core of elastin surrounded by fibrillin microfibrils  Fibronectin Adhesion glycoprotein that occurs as fibrils in connective tissue Attaches cells to other ECM components, commonly via integrins Has binding affinity for other ECM components (eg. collagen, fibrin), specific cell surface receptors, self  Fibrinogen Fibrinogen = a protein component of blood clots that binds cells and other ECM components ch.ic.ac.uk Cleavage of fibrinogen by thrombin (enzyme) → fibrin RBCs trapped by fibrin Binds integrins, fibronectin Goal MCB.16: Understand the significance of cell adhesion and the extracellular matrix to maintain the integrity of tissues and organs Learning objectives Given a clinical or research vignette, scenario, table, graph, or diagram, students should be able to: MCB.16.1. Determine the type of cell-cell and/or cell-matrix interaction important for the normal function of a tissue. MCB.16.2. Recognize the molecular components of cell-cell and cell-matrix interactions. MCB.16.3. Describe the importance of matrix metalloproteinases in regulating cell adhesion. MCB.16.4. Differentiate the functions of extracellular matrix components, with emphasis on collagen, laminin, elastic fibers, fibrinogen, fibronectin, glycosaminoglycans, and proteoglycans. Practice Questions Navigate to this link or the QR code to test your recall and understanding of concepts learned in Goal 16: https://forms.office.com/r/eG MuiGnGJD