PHY6110 Lecture 9 PDF - Cell Adhesion

PHY6110 Lecture 9 CELL ADHESION A variety of cell adhesion mechanisms underlie the way that cells are organized in tissues. Stable cell interactions are needed to maintain the structural integrity of tissues Cell adhesion is crucial for normal embryonic development and adult maintenance of multi- c...

PHY6110 Lecture 9 CELL ADHESION A variety of cell adhesion mechanisms underlie the way that cells are organized in tissues. Stable cell interactions are needed to maintain the structural integrity of tissues Cell adhesion is crucial for normal embryonic development and adult maintenance of multi- cellular organisms by regulating cell migration, tissue organization, immune responses, and wound healing Cell adhesion is mediated by two broad classes of adhesion structures that promote cell adherence to their surrounding extracellular matrix (cell-matrix adhesions) or cells adhering to neighboring cells (cell-cell adhesions) In multicellular organisms of the animal kingdom, cells adhere to their neighbors either directly, or via a complex meshwork of fibers known as the ECM Purpose of cell adhesion Cell adhesion is involved in stimulating signals that regulate cell differentiation, cell cycle, cell migration, and cell survival Adhesion is not just for anchoring and placing cells to form tridimensional structures, but also for communication between each other Four types of adhesion molecules The CAMs are broadly classified into four families – integrins, cadherins, selectins, and immunoglobulin-like CAMs (IgCAMs). Integrins Integrins are the principal receptors used by animal cells to bind to the extracellular matrix Integrins also function as signal transducers, activating various intracellular signaling pathways when activated by matrix binding Integrins and conventional signaling receptors often cooperate to promote cell growth, cell survival, and cell proliferation Cadherins Cadherins are transmembrane proteins that mediate cell–cell adhesion in animals. By regulating contact formation and stability, cadherins play a crucial role in tissue morphogenesis and homeostasis Cadherins function in tissue morphogenesis by controlling both cell–cell adhesion and cell signaling. Cadherins have also been implicated in germ cell positioning and migration Cells also use cadherins to mediate signals that can control cell fate specification, cell polarity and cell proliferation Selectins Selectins are vascular cell adhesion molecules involved in adhesive interactions of platelets, leukocytes, and endothelial cells within the blood circulation This represents the first step in a cascade of molecular interactions that lead to leukocyte extravasation, enabling the processes of lymphocyte recirculation and leukocyte migration into inflamed tissue The selectins bind to carbohydrate structures on glycoproteins, glycolipids, and proteoglycans Immunoglobulin-like CAMS ICAM-1 is a member of the immunoglobulin superfamily, the superfamily of proteins including antibodies and T-cell receptors ICAM-1 is a cell surface glycoprotein expressed at a low basal level in immune, endothelial (EC) and epithelial cells, but is up-regulated in response to inflammatory stimulation ICAM-1 is a cell surface glycoprotein and an adhesion receptor that is best known for regulating leukocyte recruitment from circulation to sites of inflammation ICAM-1 has emerged as a master regulator of many essential tissue functions both at the onset and the resolution of pathologic conditions Immunoglobulins Immunoglobulins also serve two purposes: that of cell-surface receptors for antigen which permit cell signaling and cell activation and that of soluble effector molecules which can individually bind and neutralize antigens at a distance Immunoglobulin A IgA protects mucosal tissues in the respiratory, gastrointestinal, and genitourinary tracts from microbial invasion. It is the most abundant antibody in the body and is found in secretions like saliva and tears, as well as in breast milk Immunoglobulin D Immunoglobulin D (IgD) is an antibody that plays a role in the immune system, but its exact functions are not fully understood Immunoglobulin E Immunoglobulin E (IgE) are antibodies produced by the immune system If you have an allergy, your immune system overreacts to an allergen by producing antibodies called Immunoglobulin E (IgE) These antibodies travel to cells that release chemicals, causing an allergic reaction They are also geared towards binding to parasites such as worms and protozoa to destroy them Immunoglobulin G Immunoglobulin G (IgG) is the most common type of antibody in the blood, making up about 75% of serum antibodies IgG is a protein that helps prevent infections and attacks foreign substances in the body It can cross into the placenta and thus enter the developing fetus Immunoglobulin M IgM is the body's first line of defense against new infections, providing short-term protection IgM levels increase for several weeks after exposure, then decrease as the body produces other antibodies IgM is the largest antibody isotype in vertebrates