Last Class 1. ECM components: glycosaminoglycans (GAGs) and fibrous proteins a. GAGs: Hyaluronan; Chondroitin sulfate and dermatan sulfate; Heparan sulfate; Keratan sulfate b. Fibrous proteins: collagen, elastin, fibronectin, laminin 2. basal laminae, neuromuscular junction 3. Cell-ECM interaction, ECM degration 4. ECM receptor, integrins
Cell Junctions, Cell- Cell Adhesions
CrossSection View of Intestine Wall
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Tight Junctions Claudins, Occludins ZO Proteins
Tight Junctions as barriers to solute diffusion Electron-dense tracer is added in the apical (B) and basal sides of the cells (C).
Tight Junctions Structures Freeze-fracture EM
Models for Tight Junctions Claudin and occludin
Anchoring Junctions Connecting cytoskeletons
Two Classes of anchoring junctions
Anchoring junctions 1.Adherens junctions (cell-cell) 2.Desmosomes (cell-cell) 3.Focal adhesions and hemidesmosomes (cell-ECM)
Adherens Junctions
Folding of an epithelial sheet to form an epithelial tube
Desmosomes
Focal Adhesion
hemiDesmosomes and desmosomes
Gap Junctions Size of molecules allowed to pass
Gap Junctions
Gap Junctions in EM
Regulation of Gap Junctions Rabbit retina and dopamine treatment Switch between rod and cone photoreceptors Lucifer yellow injection
Gap Junctions Functions 1.Rapid communication between neighboring cells, e.g. cardiomyocytes need synchronized actions 2. Communication beyond nerve system, e.g. hepatocytes beyond sympathetic nerves need to be informed to produce glucose from glycogen 3. Embryogenesis, form specific tissue with coupled group of cells
Summary of cell junctions
Cell-Cell Adhesions
Cell to Tissue mechanism A Simple Model
Cell to Tissue mechanism A More Complex Model Cell adhesion molecules (CAM)
Cell-cell Adhesion cadherins
Cell-cell Adhesion Regulation of cadherins
The distribution of E-cadherin (ectoderm) and N-cadherin (neural tube) in Chick embryo
Three mechanisms of cell-cell adhesions
Cadherin-dependent Cell Sorting
Cadherins are linked to actin filaments
Adherens Junction Formation movie movie
Selectin-mediated cell-cell adhesion (blood cell rolling) E-selectin, L-selectin, P-selectin
White Blood Cell Rolling and Adhesion Movie Movie
Neural cell adhesion molecule (N-CAM), intercellular adhesion molecule (ICAM) Calcium-independent Immunoglobulin (Ig) superfamily
Summary Diagram non-junctional adhesion proceeds junctional adhesion
Summary 1. Junctions: Occluding Junctions, Anchoring Junctions, Communicating Junctions 2. Occluding Junctions: Tight Junction 3. Anchoring Junctions: adherens Junction 4. Communicating Junctions: Gap Junction 5. Cell-Cell Junction: adherens junction, cadherins
Overview of the Cell Membrane structure and components, membrane proteins, carrier proteins, channel proteins Signaling transduction, ligand-receptor interactions, ion-channels, GPCRs, RTKs, molecular switches (kinase, GTPases), molecular complex formation and signaling integration, signaling desensitization, GPCR, GPCR signaling: cAMP, Calcium (CaM Kinase as memory molecule) RTK, RTK signaling: Ras, PI3K (PLC, Akt, Rac) Protease mediated signaling: NF-kB Cytoskeleton: microtubules, actin, intermediate filament Regulation of microtubules and actin Molecular motors: myosin (Sliding Acto-Myosin filaments ), kinesin Cell migration and its relationship with actin filaments Extracellular matrix: GAG, fibrous proteins (collagen, elastin, fibronectin, laminin) Basal laminae, cell-ECM interaction, integrins, cell-cell adhesion (tight junction, adherens junction, gap junction), cadherins