08 Cell-cell Interactions.ppt 413u2a
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Cell-Cell Interactions
Chapter 11
Cell-Cell Interactions
Why do cells interact with one another?
How do cells interact with one another?
Importance of Cell-Cell Interactions Interactions between…
Adjacent cells Distant cells
Adjacent Cells: Connections & Communication Cells constantly interact with other cells
extracellular structures cell walls (plants) extracellular matrix (animals)
cell-cell attachments middle lamella (plants) tight junctions and desmosomes (animals)
cell-cell gaps plasmodesmata (plants) gap junctions (animals)
Strong Connections What are these bars for?
Fiber Composites: Plant Cell Walls
Extracellular Structures
Extracellular Matrix (animal cells) Functions Helps
to define cell shape May aid in adhesion to other cells May serve protective role Composition Fibrous
“rods” – collagen (protein) Ground substance/Matrix – gel-like polysaccharides
How do these materials get outside of the cell?
The Cell Surface: Cytoskeleton, Plasma Membrane and Extracellular Layers Gel-forming polysaccharides
Collagen
Extracellular Matrix (ECM)
Fibronectin Integrin
Plasma Membrane
Cytoskeleton Actin filament
Extracellular Matrix (ECM): Extracellular Layers in Animal Cells ECM quantity and composition vary by cell type
Epithelia
Cartilage
The structure of a cell’s ECM correlates with that cell’s function
Extracellular Matrix (ECM): Extracellular Layers in Animal Cells
The ECM is directly linked to cytoskeleton via integrins and fibronectins
Holds cells in place
Helps adjacent cells adhere to one another
Extracellular Matrix (ECM): Importance Conditions resulting from defective ECM:
Scurvy – insufficient hydroxyproline, a component of collagen (due to Vitamin C deficiency) Photoaging – loss of collagen from dermis
Cell-Cell Attachments
Cell-Cell Attachments – structures that hold cells together within multicellular organisms
Tight Junctions
Desmosomes
Tight Junctions: Cell-Cell Attachments in Animal Cells
specialized proteins in plasma membranes of adjacent cells that line up and bind to one another
form watertight seal between cells – important in epithelial tissues; prevent age of molecules/ions between cells
Plasma membranes of adjacent cells
Membrane proteins that form a tight junction
Where would you expect to find tight junctions?
Desmosomes: Cell-Cell Attachments in Animal Cells
cell-cell attachments that bind cytoskeletons of adjacent cells
composed of membrane proteins that link cells (cadherins) and anchoring proteins
Provide strength in smooth muscle and epithelial tissue
Where would you expect to find desmosomes? Plasma membranes of adjacent cells Anchoring proteins inside cell
Membrane proteins that link cells
(cadherins)
Intermediate filaments
Cell-Cell Attachments
Cells of the same tissue type aggregate. How do they ‘find’ and ‘stick to’ one another?
Cadherins and Selective Adhesion
Selective adhesion – tendency of cells of the same tissue type to adhere to one another
CADHERINS
Loss of N-cadherin in endothelial cells leads to embryonic lethality.
Luo Y , Radice G L J Cell Biol 2005;169:29-34
© 2005 Rockefeller University Press
Question 7
Colchicine is a drug that inhibits polymerization of the subunits that form microtubules. Would colchicine be effective in stopping bacterial flagella? _____ yes no
Test Question 9
Unicellular organisms live in a wide range of habitats, from the hot springs in Yellowstone National Park to the freezing temperatures of the Antarctic. Make a prediction about the saturation status of membrane phospholipids in organisms that live in extremely cold environments versus those that live in extremely hot environments. Organisms that live in extremely cold environments are likely to have the same number of saturated and unsaturated phospholipids. Organisms that live in extremely cold environments are likely to have highly unsaturated phospholipids versus those that live in extremely hot environments. Organisms that live in extremely cold environments are likely to have phospholipids with saturated tails versus those that live in extremely hot environments. The saturation status of membrane phospholipids does not depend on the environmental conditions.
Adjacent Cells: Connections & Communication Cells constantly interact with other cells
extracellular structures cell walls (plants) extracellular matrix (animals)
cell-cell attachments middle lamella (plants) tight junctions and desmosomes (animals)
cell-cell gaps plasmodesmata (plants) gap junctions (animals)
Cell-Cell Gaps
Cell-Cell Gaps – direct connections between the cytoplasm of adjacent cells Enables Enables
efficient communication between cells
cells within a tissue to act in concert (as an integrated whole)
Plasmodesmata: Cell-Cell Gaps in Plant Cells
Notice: cell membranes/cytoplasm are connected (continuous)
Gap Junctions: Cell-Cell Gaps in Animal Cells
Notice: cytoplasm is connected (continuous)
Group Question 1
What characteristics do tight junctions bestow on tissues that use these adhesions to connect adjacent cells? They
allow communication between adjacent
cells. They provide strong connections to resist pulling forces. They use the extracellular matrix to indirectly connect adjacent cells. They form a watertight barrier between the cells.
CELLS COMMUNICATE OVER LONG DISTANCES VIA HORMONES AND SIGNAL TRANSDUCTION PATHWAYS.
How do they communicate?
What do all of these have in common?
Relay a message (signal) from outside the cell into the cell.
= Signal Transduction: Way of transmitting information (signal) from outside a cell to the inside of a cell, resulting in a response.
Cell Signaling Pathway
Cell Signaling Pathways (General) Signal Sent – intercellular signal (hormone) released 1. 2.
3.
4.
5.
Signal Reception – hormone binds to signal receptor
Signal Transduction – transmission/conversion of a signal from outside the cell into the cell. Signal Amplification – signal magnified as it is “transported” through cell to its final destination. Signal Response – signal reaches intracellular target(s) and triggers a cellular response (activation/deactivation)
Signal Deactivation – intracellular signal is turned off
Stages of Signal Transduction
(5. Signal deactivation)
Signal Sent: Hormones
Hormones – chemical signals produced by one set of cells that affect a different set of cells Most are distributed by the bloodstream to target cells Only affect cells that have a receptor for that specific hormone (target cells)
Hormones
Steroid Hormones – hormones that are composed of four carbon rings (steroid structure)
Peptide (Non-Steroid) Hormones – hormones that are peptides, proteins, glycoproteins or modified amino acids
Hormones
There are others too!
Signal Reception
Peptide hormones bind to receptors on the cell surface.
Steroid hormones bind to receptors inside the cell.
Why?
Upon hormone binding, signal receptors change conformation (shape) resulting in a change in activity
Signal Reception
Signal receptors…
Are specific (bind specific hormones) Vary between cells (different cell types have different sets of signal receptors) Are dynamic (numbers may increase/decrease) Can be blocked (often used as drug target); Example: Tamoxifen
Signal Transduction Pathways Intercellular signal
Outside of cell
Receptor protein in membrane
Signal Reception
Signal Transduction • extraintracellular signal Inside of cell
Intracellular signal
Signal Amplification
Cell activity changes
Signal Response
Signal Transduction Pathways G Proteins
EnzymeLinked Receptors
Signal Amplification: Phosphorylation Cascade Signal Amplification: Second Messengers
Second Messengers Second Messengers – nonprotein intracellular signaling molecules
Signal Responses Intracellular Targets:
DNA – activate or deactivate gene expression (making a protein using DNA “instructions”)
Pre-existing proteins – activate or deactivate enzymes, membrane channels, etc.
Result… change in cell activities!
Signal Deactivation
Deactivation allows signal to be turned off quickly Hydrolysis of GTP by G proteins deactivates them Deactivation or sequestration of second messengers Dephosphorylation
Enables cells to respond rapidly to changing conditions
Group Question 2
What does it mean to say that a signal is transduced? The
signaling molecule enters the cell directly and binds to a receptor inside. The physical form of the signal changes between the outside of the cell and the inside. The signal is amplified, such that even a single molecule evokes a large response. The signal triggers a sequence of phosphorylation events inside the cell.
Steroid Hormone Signaling: Example
Estrogen – triggers production of proteins that promote cell proliferation (multiplication)
http://web.virginia.edu/Heidi/chapter34/Images/8883n34_42.jpg
Steroid Hormone Signaling: Example
Tamoxifen binds to the estrogen receptor (prevents estrogen binding)
http://web.virginia.edu/Heidi/chapter34/Images/8883n34_42.jpg
Steroid Hormone Signaling: Example
Tamoxifen binds to the estrogen receptor (prevents estrogen binding) Inhibits cell proliferation Inhibits tumor growth! http://web.virginia.edu/Heidi/chapter34/Images/8883n34_42.jpg
Chapter 11
Cell-Cell Interactions
Why do cells interact with one another?
How do cells interact with one another?
Importance of Cell-Cell Interactions Interactions between…
Adjacent cells Distant cells
Adjacent Cells: Connections & Communication Cells constantly interact with other cells
extracellular structures cell walls (plants) extracellular matrix (animals)
cell-cell attachments middle lamella (plants) tight junctions and desmosomes (animals)
cell-cell gaps plasmodesmata (plants) gap junctions (animals)
Strong Connections What are these bars for?
Fiber Composites: Plant Cell Walls
Extracellular Structures
Extracellular Matrix (animal cells) Functions Helps
to define cell shape May aid in adhesion to other cells May serve protective role Composition Fibrous
“rods” – collagen (protein) Ground substance/Matrix – gel-like polysaccharides
How do these materials get outside of the cell?
The Cell Surface: Cytoskeleton, Plasma Membrane and Extracellular Layers Gel-forming polysaccharides
Collagen
Extracellular Matrix (ECM)
Fibronectin Integrin
Plasma Membrane
Cytoskeleton Actin filament
Extracellular Matrix (ECM): Extracellular Layers in Animal Cells ECM quantity and composition vary by cell type
Epithelia
Cartilage
The structure of a cell’s ECM correlates with that cell’s function
Extracellular Matrix (ECM): Extracellular Layers in Animal Cells
The ECM is directly linked to cytoskeleton via integrins and fibronectins
Holds cells in place
Helps adjacent cells adhere to one another
Extracellular Matrix (ECM): Importance Conditions resulting from defective ECM:
Scurvy – insufficient hydroxyproline, a component of collagen (due to Vitamin C deficiency) Photoaging – loss of collagen from dermis
Cell-Cell Attachments
Cell-Cell Attachments – structures that hold cells together within multicellular organisms
Tight Junctions
Desmosomes
Tight Junctions: Cell-Cell Attachments in Animal Cells
specialized proteins in plasma membranes of adjacent cells that line up and bind to one another
form watertight seal between cells – important in epithelial tissues; prevent age of molecules/ions between cells
Plasma membranes of adjacent cells
Membrane proteins that form a tight junction
Where would you expect to find tight junctions?
Desmosomes: Cell-Cell Attachments in Animal Cells
cell-cell attachments that bind cytoskeletons of adjacent cells
composed of membrane proteins that link cells (cadherins) and anchoring proteins
Provide strength in smooth muscle and epithelial tissue
Where would you expect to find desmosomes? Plasma membranes of adjacent cells Anchoring proteins inside cell
Membrane proteins that link cells
(cadherins)
Intermediate filaments
Cell-Cell Attachments
Cells of the same tissue type aggregate. How do they ‘find’ and ‘stick to’ one another?
Cadherins and Selective Adhesion
Selective adhesion – tendency of cells of the same tissue type to adhere to one another
CADHERINS
Loss of N-cadherin in endothelial cells leads to embryonic lethality.
Luo Y , Radice G L J Cell Biol 2005;169:29-34
© 2005 Rockefeller University Press
Question 7
Colchicine is a drug that inhibits polymerization of the subunits that form microtubules. Would colchicine be effective in stopping bacterial flagella? _____ yes no
Test Question 9
Unicellular organisms live in a wide range of habitats, from the hot springs in Yellowstone National Park to the freezing temperatures of the Antarctic. Make a prediction about the saturation status of membrane phospholipids in organisms that live in extremely cold environments versus those that live in extremely hot environments. Organisms that live in extremely cold environments are likely to have the same number of saturated and unsaturated phospholipids. Organisms that live in extremely cold environments are likely to have highly unsaturated phospholipids versus those that live in extremely hot environments. Organisms that live in extremely cold environments are likely to have phospholipids with saturated tails versus those that live in extremely hot environments. The saturation status of membrane phospholipids does not depend on the environmental conditions.
Adjacent Cells: Connections & Communication Cells constantly interact with other cells
extracellular structures cell walls (plants) extracellular matrix (animals)
cell-cell attachments middle lamella (plants) tight junctions and desmosomes (animals)
cell-cell gaps plasmodesmata (plants) gap junctions (animals)
Cell-Cell Gaps
Cell-Cell Gaps – direct connections between the cytoplasm of adjacent cells Enables Enables
efficient communication between cells
cells within a tissue to act in concert (as an integrated whole)
Plasmodesmata: Cell-Cell Gaps in Plant Cells
Notice: cell membranes/cytoplasm are connected (continuous)
Gap Junctions: Cell-Cell Gaps in Animal Cells
Notice: cytoplasm is connected (continuous)
Group Question 1
What characteristics do tight junctions bestow on tissues that use these adhesions to connect adjacent cells? They
allow communication between adjacent
cells. They provide strong connections to resist pulling forces. They use the extracellular matrix to indirectly connect adjacent cells. They form a watertight barrier between the cells.
CELLS COMMUNICATE OVER LONG DISTANCES VIA HORMONES AND SIGNAL TRANSDUCTION PATHWAYS.
How do they communicate?
What do all of these have in common?
Relay a message (signal) from outside the cell into the cell.
= Signal Transduction: Way of transmitting information (signal) from outside a cell to the inside of a cell, resulting in a response.
Cell Signaling Pathway
Cell Signaling Pathways (General) Signal Sent – intercellular signal (hormone) released 1. 2.
3.
4.
5.
Signal Reception – hormone binds to signal receptor
Signal Transduction – transmission/conversion of a signal from outside the cell into the cell. Signal Amplification – signal magnified as it is “transported” through cell to its final destination. Signal Response – signal reaches intracellular target(s) and triggers a cellular response (activation/deactivation)
Signal Deactivation – intracellular signal is turned off
Stages of Signal Transduction
(5. Signal deactivation)
Signal Sent: Hormones
Hormones – chemical signals produced by one set of cells that affect a different set of cells Most are distributed by the bloodstream to target cells Only affect cells that have a receptor for that specific hormone (target cells)
Hormones
Steroid Hormones – hormones that are composed of four carbon rings (steroid structure)
Peptide (Non-Steroid) Hormones – hormones that are peptides, proteins, glycoproteins or modified amino acids
Hormones
There are others too!
Signal Reception
Peptide hormones bind to receptors on the cell surface.
Steroid hormones bind to receptors inside the cell.
Why?
Upon hormone binding, signal receptors change conformation (shape) resulting in a change in activity
Signal Reception
Signal receptors…
Are specific (bind specific hormones) Vary between cells (different cell types have different sets of signal receptors) Are dynamic (numbers may increase/decrease) Can be blocked (often used as drug target); Example: Tamoxifen
Signal Transduction Pathways Intercellular signal
Outside of cell
Receptor protein in membrane
Signal Reception
Signal Transduction • extraintracellular signal Inside of cell
Intracellular signal
Signal Amplification
Cell activity changes
Signal Response
Signal Transduction Pathways G Proteins
EnzymeLinked Receptors
Signal Amplification: Phosphorylation Cascade Signal Amplification: Second Messengers
Second Messengers Second Messengers – nonprotein intracellular signaling molecules
Signal Responses Intracellular Targets:
DNA – activate or deactivate gene expression (making a protein using DNA “instructions”)
Pre-existing proteins – activate or deactivate enzymes, membrane channels, etc.
Result… change in cell activities!
Signal Deactivation
Deactivation allows signal to be turned off quickly Hydrolysis of GTP by G proteins deactivates them Deactivation or sequestration of second messengers Dephosphorylation
Enables cells to respond rapidly to changing conditions
Group Question 2
What does it mean to say that a signal is transduced? The
signaling molecule enters the cell directly and binds to a receptor inside. The physical form of the signal changes between the outside of the cell and the inside. The signal is amplified, such that even a single molecule evokes a large response. The signal triggers a sequence of phosphorylation events inside the cell.
Steroid Hormone Signaling: Example
Estrogen – triggers production of proteins that promote cell proliferation (multiplication)
http://web.virginia.edu/Heidi/chapter34/Images/8883n34_42.jpg
Steroid Hormone Signaling: Example
Tamoxifen binds to the estrogen receptor (prevents estrogen binding)
http://web.virginia.edu/Heidi/chapter34/Images/8883n34_42.jpg
Steroid Hormone Signaling: Example
Tamoxifen binds to the estrogen receptor (prevents estrogen binding) Inhibits cell proliferation Inhibits tumor growth! http://web.virginia.edu/Heidi/chapter34/Images/8883n34_42.jpg
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