Cell and Molecular Biology Ninth Edition Chapter 7 PDF

Cell and Molecular Biology Ninth Edition Gerald Karp, Janet Iwasa, Wallace Marshall Chapter 7 Interactions Between Cells and Their Environment 7.1 | Overview of Extracellular Interactions (1 of 2) ▪ Materials present outside the plasma membrane pla...

Cell and Molecular Biology Ninth Edition Gerald Karp, Janet Iwasa, Wallace Marshall Chapter 7 Interactions Between Cells and Their Environment 7.1 | Overview of Extracellular Interactions (1 of 2) ▪ Materials present outside the plasma membrane play an important role in the life of a cell. ▪ Most cells in a multicellular plant or animal are organized into clearly defined tissues. ▪ There are many diverse activities that are regulated by this. Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Overview of Extracellular Interactions (2 of 2) ▪ Cells interact with their extracellular environment ▪ The epidermis has closely packed cells of epithelial tissue ▪ The dermis is a type of connective tissue ▪ Fibroblasts of the dermis have receptors that mediate interactions and transmit message. Copyright ©2020 John Wiley & Sons, Inc. An overview of how cells are organized into tissues and how they interact with one another and with their extracellular environment. Copyright ©2020 John Wiley & Sons, Inc. 7.1 | The Extracellular Matrix (1 of 3) ▪ Carbohydrate projections form part of the glycocalyx on the outer surface of the plasma membrane. ▪ Roles of the glycocalyx Mediator of cell–cell and cell–substratum interactions Mechanical protection Barrier to molecular movement Regulatory factor binding site Basal surface of EM: endothelial glycocalyx Molecular model of the ectodermal cell, early chick in a coronary capillary glycocalyx embryo Copyright ©2020 John Wiley & Sons, Inc. 7.1 | The Extracellular Matrix (2 of 3) ▪ One of the best defined extracellular matrices (ECM) is the basement membrane that surrounds muscles that nerves and fat cells. ▪ Underlies the epidermis of the skin, the digestive and respiratory tract and the lining of blood vessels. Scanning electron micrographs of human skin Copyright ©2020 John Wiley & Sons, Inc. 7.1 | The Extracellular Matrix (3 of 3) ▪ The ECM may take diverse forms in different tissues and organisms ▪ Most proteins inside cells are globular, those of the extracellular space are typically extended, fibrous ▪ These proteins are secreted into the extracellular space. Organized network of extracellular materials outside plasma membrane, provides support and determines shape and activity of cell. Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (1 of 7) Collagen ▪ Collagen molecule: triple helix of three helical alpha chains ▪ Collagens comprise a family of fibrous glycoproteins present only in the ECM. ▪ Collagen is the single most abundant protein in the human body. ▪ Collagen is produced by fibroblasts, smooth muscle and epithelial cells. Collagen I molecules become aligned in staggered rows ▪ 28 fiber types, often mixed in ECM Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (2 of 7) Collagen ▪ Collagen provides the insoluble framework that determines many of the mechanical properties of the matrix. ▪ Tissue properties can often be correlated with the 3D organization of its collagen (e.g., tendons, cornea). Corneal stroma: layers of collagen fibrils of uniform diameter and spacing arranged at right angles Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (3 of 7) Proteoglycans ▪ Proteoglycans – protein- polysaccharide complex, with a core protein attached to glycosaminoglycans (GAGs). ▪ Have a repeating disaccharide structure, -A-B-A-B-, where A and B represent two different sugars. ▪ Common in basement membranes, attract water, Schematic representations of a single forming gel proteoglycan, repeating disaccharide structure of GAGs, and linkage to hyaluronic acid to form a giant complex Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (4 of 7) Fibronectin ▪ Fibronectin consists of a linear array of 30 Fn domains to give a modular construction ▪ Fn-type domains are found in blood clotting factors and receptors. ▪ Bind to numerous ECM components ▪ Bind to cell surface receptors Human fibronectin molecule consists of two similar polypeptides joined by disulfide bonds. Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (5 of 7) Fibronectin ▪ Fibronectin and other extracellular proteins have important roles during embryonic development. ▪ Development is characterized by waves of cell migration. A summary of some of the cellular traffic occurring during mammalian development Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (6 of 7) Fibronectin ▪ Several organs (e.g., salivary gland, kidney, and lung) are formed by a process of branching/cleft formation. ▪ Cell adhesion and shape determination also fibronectin- dependent Fibronectin in embryonic salivary gland cleft formation Endothelial cell spread over a square‐shaped patch of fibronectin Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Components of the Extracellular Matrix (7 of 7) Laminin ▪ Family of at least 15 extracellular glycoproteins. ▪ Laminin has three polypeptide chains linked by disulfide bonds ▪ They can greatly influence a cell’s potential for migration, growth, and differentiation. ▪ Role in development of neuronal outgrowth ▪ Strengthen basement membrane Primordial germ cells (green) migrating along a tract of laminin (red) from the dorsal mesentery to the developing gonad. Copyright ©2020 John Wiley & Sons, Inc. 7.1 | Dynamic Properties of the Extracellular Matrix ▪ ECM can exhibit dynamic properties both in space and time ▪ Spatially, ECM fibrils can stretch several times their normal length ▪ Matrix metalloproteinases degrade ECM materials ▪ The physiological roles of MMPs are thought to be involved in tissue remodeling, embryonic cell migration, wound healing, and the formation of blood vessels ▪ Abnormal expression of MMPs linked to a variety of diseases Copyright ©2020 John Wiley & Sons, Inc. 7.2| Engineering Linkage: Organoids ▪ Several different methods support the growth of 3D cell cultures. ▪ The engineering of organoids has made advances over the years. Intestine Pancreas Stomach Optic cup Brain ▪ Applications: Disease research Pharmaceutical research Copyright ©2020 John Wiley & Sons, Inc. 7.3 | Interactions of Cells with Extracellular Materials (1 of 4) Integrins ▪ Family of membrane proteins unique to animals. ▪ Composed of two membrane- spanning polypeptide chains, an α chain and a β chain. ▪ The bent conformation of integrin corresponds to its inactive state, Integrins with a bound ligand are found in an upright conformation. ▪ The transmembrane domains of EMs and ribbon drawings of the extracellular the two subunits are in close domains of an integrin (avb3) in the “bent”/inactive proximity. and “upright”/active conformation. Changes driven by divalent metal ions. Copyright ©2020 John Wiley & Sons, Inc. 7.3 | Interactions of Cells with Extracellular Materials (2 of 4) Integrins ▪ Integrins have two major activities: adhesion of cells to their substratum (or to other cells) and transmission of signals between the external environment and the cell interior. ▪ Outside-in signals can induce a conformational change in talin. ▪ Cytoplasmic protein kinases (e.g. FAK and Src) can be activated to phosphorylate other proteins. Outside-in signals transmitted by integrins can influence differentiation, motility, growth, and cell survival. ▪ Most malignant cells are capable of growing in liquid suspension. ▪ Normal cells can only grow and divide if they are cultured on a solid substratum. Copyright ©2020 John Wiley & Sons, Inc. 7.3 | Interactions of Cells with Extracellular Materials (3 of 4) Focal Adhesions ▪ Cultured cells are Cultured cell: actin anchored to the surface filaments (gray-green), of the dish only at integrins (red); sites of focal adhesions scattered, discrete sites, called focal adhesions. ▪ Focal adhesions play a key role in cell locomotion. ▪ Focal adhesions are dynamic structures. Amphibian cell processed for quick-freeze, deep-etch analysis Copyright ©2020 John Wiley & Sons, Inc. 7.3 | Interactions of Cells with Extracellular Materials (4 of 4) Hemidesmosomes ▪ Cell-matrix attachment in vivo is seen at the basal surface of epithelial cells, anchored to the underlying basement membrane. ▪ Hemidesmosomes contain a dense cytoplasmic plaque with keratin filaments. ▪ Keratin filaments are linked to the ECM by integrins. Hemidesmosomes: EM and schematic diagram. Copyright ©2020 John Wiley & Sons, Inc. 7.4| Interactions of Cells with Other Cells (1 of 2) ▪ Organs have a complex architecture involving a variety of different cell types. ▪ Dependent on selective interactions between cells of the same type, as well as between cells of different types. ▪ Experiments demonstrated that separated cells would redistribute themselves so that each cell adhered only to cells of the same type Ectoderm and mesoderm from an early amphibian embryo re-associate after initial random dissociation Copyright ©2020 John Wiley & Sons, Inc. 7.4| Interactions of Cells with Other Cells (2 of 2) Selectins ▪ Selectins are a family of membrane glycoproteins that bind to specific oligosaccharides. ▪ “Lectin,” is a term for a compound that binds to specific carbohydrate groups. ▪ Selectins have a small cytoplasmic segment, a single membrane- spanning domain, and a large extracellular portion. Schematic of the three selectins and their CHO ligand Copyright ©2020 John Wiley & Sons, Inc. 7.4 | The Human Perspective (1 of 3) The Role of Cell Adhesion in Inflammation and Metastasis ▪ Inflammation is one of the primary responses to infection, but can produce adverse side effects like fever, swelling, redness, and pain. ▪ Following a puncture wound to the skin, white blood cells (leukocytes) from the bloodstream are stimulated to traverse the endothelial layer that lines the smallest veins (venules) and enter the tissue. ▪ Leukocytes recruitment has focused on three types of cell adhesion molecules: selectins, integrins, and IgSF proteins. Copyright ©2020 John Wiley & Sons, Inc. 7.4 | The Human Perspective (2 of 3) The Role of Cell Adhesion in Inflammation and Metastasis ▪ Endothelial cells that line venules become more adhesive to circulating neutrophils through display of P‐ and E‐selectins. ▪ Platelet activating factor (PAF) on endothelial cells stimulates an increase in the integrin binding activity on neutrophils. ▪ Bound neutrophils then change their shape and squeeze between adjacent endothelial cells into the damaged tissue. Movement of neutrophils during inflammation Copyright ©2020 John Wiley & Sons, Inc. 7.4 | The Human Perspective (3 of 3) The Role of Cell Adhesion in Inflammation and Metastasis ▪ Cancer cells escape the normal growth control mechanisms and proliferate in an unregulated manner. ▪ Most malignant tumors are not readily contained. ▪ Metastatic cells are thought to have special cell‐surface properties that are not shared by most other cells in the Steps leading to metastatic spread tumor. Copyright ©2020 John Wiley & Sons, Inc. 7.4 | Interactions of Cells with Other Cells (1 of 4) The Immunoglobulin Superfamily ▪ The human genome encodes 765 distinct Ig domains. ▪ These are members of the immunoglobulin superfamily. ▪ Immune functions for most ▪ Original function likely cell- adhesion mediators (Ca2+ independent) ▪ Developmental roles in neuronal growth and circuitry Cell–cell adhesion from homotypic interactions of two L1 molecules through Ig domains at the N-termini. Copyright ©2020 John Wiley & Sons, Inc. 7.4 | Interactions of Cells with Other Cells (2 of 4) Cadherins ▪ Glycoprotein family ▪ Cadherins typically join cells of similar type to one another (Ca2+ dependent). ▪ Possibly the single most important factor in molding cells into cohesive tissues in the embryo and holding them together in the adult. ▪ Cadherin loss associated with malignancy Schematic of two adhering cells due to interactions between cadherins projecting from the plasma membrane of each cell Copyright ©2020 John Wiley & Sons, Inc. 7.4 | Interactions of Cells with Other Cells (3 of 4) Cadherins ▪ Over 100 cadherins have been identified in humans. ▪ Usher syndrome is characterized by deafness and gradual loss of vision and can result from mutations in non-classical cadherins. Cadherins form tip links of stereocilia Copyright ©2020 John Wiley & Sons, Inc. 7.4 | Interactions of Cells with Other Cells (4 of 4) Adherens Junctions and Desmosomes ▪ Cadherins are also found in specialized intercellular junctions. ▪ These are calcium- dependent linkages. ▪ The network of intermediate filaments provides structural continuity and tensile strength. Diagram and EM showing the junctional complexes on the lateral surfaces of a simple columnar epithelial cell Copyright ©2020 John Wiley & Sons, Inc. 7.5 | Tight Junctions: Sealing the Extracellular Space ▪ Tight junctions occur EM: apical region of between neighboring adjoining epithelial cells. epithelial cells ▪ Prevent solute distribution where different solute concentrations are in adjacent compartments ▪ The points of cell–cell Tight junction model contact are sites where showing intermittent integral proteins of two contact points adjacent membranes meet between proteins within the extracellular from two apposing space. membranes Copyright ©2020 John Wiley & Sons, Inc. 7.6 | Intercellular Communication (1 of 4) Gap Junctions ▪ Plasma membranes of a gap junction contain channels that connect the cytoplasm of one cell with the cytoplasm of the adjoining cell. ▪ Gap junctions are sites between Electron micrograph of a section through a gap junction perpendicular to the plane of animal cells that are specialized the two adjacent membranes for intercellular communication. ▪ Plasma membranes come very close to one another but do not make direct contact at gap junction Copyright ©2020 John Wiley & Sons, Inc. 7.6 | Intercellular Communication (2 of 4) Gap Junctions ▪ Gap junctions are molecular “pipelines” that pass through the adjoining plasma membranes and open into the cytoplasm of the adjoining cells. ▪ They are composed of an integral membrane protein connexin, and organized into multisubunit complexes, connexons, that span the membrane. Schematic model of a gap junction showing the arrangement of six connexin subunits to form a connexon Copyright ©2020 John Wiley & Sons, Inc. 7.6 | Experimental Pathways The Role of Gap Junctions in Intercellular Communication ▪ A small, subthreshold depolarization induced in the presynaptic nerve cell produced a very rapid depolarization in the postsynaptic cell, not possible through a chemical synapse or neurotransmitter release. ▪ It was predicted that nerve cells were connected by an electrotonic synapse, in which ionic currents in the presynaptic cell could flow directly into the post-synaptic cell on the other side of the synapse. Copyright ©2020 John Wiley & Sons, Inc. 7.6 | Intercellular Communication (3 of 4) Plasmodesmata ▪ Plant cells are separated from one another by a cell wall, and lack the specialized junctions found Plasmodesma of a in animal tissues. fern gametophyte ▪ For cell-cell communication, most plant cells are connected by plasmodesmata, cytoplasmic channels that pass through the cell walls Schematic drawing of adjacent cells. of a plasmodesma Copyright ©2020 John Wiley & Sons, Inc. 7.6 | Intercellular Communication (4 of 4) Plasmodesmata ▪ Plasmodesmata allow larger molecules (to pass since the pore is capable of dilation. ▪ Plant cells produce their own movement through proteins that regulate the flow of proteins and RNAs from cell to cell. Protein movement from one cell to another within a plant root Copyright ©2020 John Wiley & Sons, Inc. 7.7 | Cell Walls (1 of 3) ▪ The cells of nearly all organisms other than animals are enclosed EM: onion cell in a protective outer envelope. wall showing ▪ Plants: cellulose Individual cell support microfibrils and hemicellulose Plant skeleton cross-links ▪ Plant cell walls contain a fibrous element embedded in a nonfibrous, gel-like matrix. ▪ Cellulose provides the fibrous component of the cell wall, and Schematic proteins and pectin provide the diagram of a matrix. model of a generalized ▪ Cellulose molecules are plant cell wall organized into rod-like microfibrils. Copyright ©2020 John Wiley & Sons, Inc. 7.7 | Cell Walls (2 of 3) The matrix of the cell wall is composed of three types of macromolecules: 1. Hemicelluloses: branched polysaccharides whose backbone consists of one sugar (e.g., glucose, and side chains of other sugar (e.g., xylose). 2. Pectins: negatively charged polysaccharides containing galacturonic acid. 3. Proteins: mediate dynamic EM: Golgi complex stained with antibodies activities. against a component of pectin Copyright ©2020 John Wiley & Sons, Inc. 7.7 | Cell Walls (3 of 3) ▪ Cell walls arise as a thin cell plate that forms between the plasma membranes of newly formed daughter cells following cell division. ▪ The cell wall of a young, undifferentiated plant cell must be able to grow in conjunction with the growth of the cell it surrounds. ▪ The lignin in the walls of water- conducting cells of the xylem provides the support required to Electron micrograph of a plant cell move water through the plant. Copyright ©2020 John Wiley & Sons, Inc. 7.8 | Green Cells: Cell Walls and Plant Terrestrialization ▪ A population of green algae started to moved onto land. ▪ This is what is thought to give rise to the vast diversity of land plants seen today. ▪ Certain cell wall innovations may have helped the first land- dwelling plants resist environmental stressors. Copyright ©2020 John Wiley & Sons, Inc. Copyright Copyright 2020 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. 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