Cell-Cell Interaction PDF

MDP10108 CELL BIOLOGY Cell-Cell interaction CELL CELL INTERACTION OBJECTIVES – Describe Cell Adhesion Molecule (CAM) and its classification – Describe cell junctions and its classification – Describe extracellular matrix  MAP of T/L activity Overview of CAM Cell Junctions Extr...

MDP10108 CELL BIOLOGY Cell-Cell interaction CELL CELL INTERACTION OBJECTIVES – Describe Cell Adhesion Molecule (CAM) and its classification – Describe cell junctions and its classification – Describe extracellular matrix  MAP of T/L activity Overview of CAM Cell Junctions Extracellular matrix  CELL ADHESION MOLECULES SELECTINS INTEGRINS IMMUNOGLOBULIN (Ig) SUPERFAMILY CADHERINS  CELL EXTERNAL STURUCTURE Cells are attached to build – Tissues – Organs – Systems – Body Organization into sheets are also important Cells express information and junction molecules  CELL Cells should be able to: – Receive from another cell – Transmit from itself – Interact with signals from its environment Cell membrane is a barrier Certain molecules can pass ? Ions and some other molecules cannot pass so how do they get through?  CELL BIOLOGY Membrane protein function? What we are interested today…… – Tight junctions – Cell cell recognition – Communication  CELL JUNCTIONS Cell junctions are especially abundant in epithelial tissues. They consist of protein complexes and provide contact: – between neighbouring cells – between a cell – the extracellular matrix – they built up the paracellular barrier of epithelia – control the paracellular transport.  CELL JUNCTIONS In vertebrates, there are four major types of cell junctions: – occluding junctions (e.g. tight junctions) – anchoring junctions (e.g. adherens junctions) – communicating junctions (e.g. gap junctions) – desmosomes – Moreover, mutations in the gap junction genes Cx43 and Cx56.6 cause white matter degeneration similar to that observed in Pelizaeus-Merzbacher disease and multiple sclerosis. – Reference: Orthmann-Murphy, Jennifer L.; Abrams, Charles K.; Scherer, Steven S. (May 2008). "Gap Junctions Couple Astrocytes and Oligodendrocytes". Journal of Molecular Neuroscience 35 (1): 101–116. doi:10.1007/s12031-007-9027-5. Retrieved 18 June 2012.  Medical perspective – Moreover, mutations in the gap junction genes Cx43 and Cx56.6 cause white matter degeneration similar to that observed in Pelizaeus-Merzbacher disease and multiple sclerosis. – Reference: Orthmann-Murphy, Jennifer L.; Abrams, Charles K.; Scherer, Steven S. (May 2008). "Gap Junctions Couple Astrocytes and Oligodendrocytes". Journal of Molecular Neuroscience 35 (1): 101– 116. doi:10.1007/s12031-007-9027-5. Retrieved 18 June 2012.  CELL JUNCTIONS Occluding - function to seal cells in an epithelial sheet Adhesive - mechanical attachement to one another Communicating - allow direct passage of chemical or electrical signals from cell to cell  CELL JUNCTIONS 1. TIGHT (Occluding) Seal adjacent epithelial in a narrow band APICAL SURFACE EPITHELIA Interface: masses of cells and cavity/lumen Block the flow of fluids between epithelial cells BASOLATERAL Epithelia sheets of cells provide the interface between masses of cells and a cavity or space (a lumen). apical surface The portion of the cell exposed to the lumen. basolateral surface The rest of the cell (i.e., its sides and base) Tight junctions seal adjacent epithelial cells in a narrow band just beneath their apical surface.  CELL JUNCTIONS 1. TIGHT (Occluding) 2 vital functions Prevent the passage of molecules and ions through the space between the cells Prevent the movement of integral membrane proteins between the apical and basolateral surface of cell Receptor mediated endocytosis AS Exocytosis at the BL  CELL JUNCTIONS 1. TIGHT (Occluding) Epithelial cells in the human lung – Growth stimulant (heregulin) AS – Receptor (erbB) BL Tight junction ensures there are no self stimulation If cells are injured ? Lung disorder (chronic bronchitis)- autocrine stimulation  CELL JUNCTIONS 2. ADHERENS (adhesive or anchoring) Mechanical attachments Functions as……. Cardiac muscles together as they expand and contract Epithelial cells together Contact inhibition Are built from – Cadherins -transmembrane protein – Catenins -connected to actin microfilaments  CELL JUNCTIONS 3. GAP Communicating Intracellular protein channels, 1.5-2 nm diameter Free passage of ions and small molecules 1000 daltons Permit changes in membrane potential Coordinated response to stimuli – During childbirth -coordinated movement of muscles  CELL JUNCTIONS 4. DESMOSOMES Adhesive Physically joints cells together at discrete spots Needed in tissues such as skin Provide connections between intermediate filaments of cell cytoskeleton Cancerous cells lack…….. So what?  CELL JUNCTIONS * PLASMODESMATA Communicating Connection between plant cells are easier Fine structure of cytoplasma Easy movement of – Ions – Small molecules ….sugar, amino acids – RNA Enable plants to transmit signal Sheated by plasma membrane  References Any cell biology, molecular biology or biochemistry textbook. Molecular Cell Biology. 2000. Lodish et. al. 4th edition.