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What we’ll talk about…
- Types and properties of tissues
- Cell to cell adhesion
- Cell to ECM adhesion
- Communication
Cells to Tissues What well talk about Types and properties of - - PowerPoint PPT Presentation
Cells to Tissues What well talk about Types and properties of - - PowerPoint PPT Presentation
Cells to Tissues What well talk about Types and properties of tissues Cell to cell adhesion Cell to ECM adhesion Communication Organs are composed of four major tissue types. Epithelia Muscle Nervous
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Organs are composed of four major tissue types.
- Epithelia
- Muscle
- Nervous
- Connective
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From one cell to ensembles of cells.
Single cell Multiple cells
How do they stay together? How do they work together?
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Tissues have four essential properties.
- Adhesion
- Communication
- Identity
- Renewal
Extracellular Matrix
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Tissues have four essential properties.
- Adhesion
- Communication
- Identity
- Renewal
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Adhesion in Tissues
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Adhesion and communication are critical for the integrity and function of tissues.
Adhesion Adhesion Communication Communication
Extracellular
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Three complexes generate intercellular adhesion
Tight Junctions Adhering Junctions Desmosomes
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Cadherins in adjacent cells interact via their N- terminal domains.
Cadherin Cadherin Cell Membrane Cell Membrane
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Cadherins comprise a large family of proteins.
Cadherin Domain Intracellular Extracellular Classical Cadherins Desmoglein Desmocollin Protocadherins
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Cells can be sorted by the types of cadherins.
N-cadherin E-cadherin
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Cells can be sorted by the expression level of cadherins.
Low expression High expression
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Clustering of cadherins increases strength of interactions between cells. Weak Strong
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Links to cytoskeleton cluster cadherins in desmosomes and adhering junctions.
actin
intermediate filaments Intermediate filaments cluster cadherins in desmosomes Actin filaments cluster cadherins in adhering junctions
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Catenins link cadherins to actin filaments in adhering junctions.
Alpha-catenin Beta-catenin Actin Cadherin
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In desmosomes, cadherins are linked to intermediate filaments.
Desmoglein Intermediate Filaments Desmoplakin Desmocollin
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Interactions between neighboring cells and between cells and ECM hold tissues together.
Extracellular Matrix
Cell to ECM interaction Cell to cell interactions
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Extracellular matrix provides a common framework to support a group of cells.
Extracellular Matrix
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Collagens are a large family of proteins that form fibers or networks.
Fibrillar: type I, type II, type III Network: type IV
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Tension generates order in elastin networks that provides energy for recoil.
Tension Relaxation
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Proteoglycans are single polypeptide with several attached glycosaminoglycans.
Protein GAGs
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Fibronectin is a glycoprotein in the ECM that functions as molecular glue.
Binds Proteoglycans Binds Collagen Binds Integrins
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Attachment to the extracellular matrix
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Integrins are cell surface receptors that link fibers of the extracellular matrix to the cytoskeleton.
Alpha-integrin Beta-integrin ECM fiber
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Integrins in cells under mechanical stress link ECM to intermediate filaments.
Actin Intermediate Filament Integrins ECM
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Communication in Tissues
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Cell communication regulates cell division and coordinate activities between cells.
Diffusible signaling molecule Gap Junction Cell to cell signaling Cell to ECM signaling
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Gap junctions allow diffusion of small molecules between neighboring cells.
Gap Junction
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Connexins are transmembrane proteins that form ~1.5 nm pores between cells.
Connexin Cell Membrane 1 Cell Membrane 2
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Signaling molecules in the ECM regulate cell behavior and activity.
Cell growth and division Cell metabolism Signaling molecules
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Cadherins regulate cell division.
Cadherins Dividing cells Contact Inhibition No contact Inhibition Mutation/loss of cadherin
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Extracellular matrix regulates cell behavior.
ECM stiffness Morphology Gene expression
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Cells connect to extracellular matrix at sites called focal adhesions.
Actin Focal Adhesion
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Integrin attachment to ECM helps determine and maintain cell identity.
Actin filaments Cell membrane ECM Focal adhesion Integrins Signaling pathway Cell behavior
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Take home messages…
- Adhesion in tissues maintains tissue integrity and regulates cell behavior.
- Cadhernis mediate interactions between cells through adhering junctions and
desmosomes.
- Integrins mediate interaction between cells and the extracellular matrix
- Cells in tissues communicate through gap junctions, intercellular connections,