M1-C2-L19 --> Cell to Cell Communication
Terms
undefined, object
copy deck
- What are the three type of junctions found in cells?
-
1. Occluding junction
2. Anchoroing junctions
3. Communicating junctions - What are occluding junctions seen in vertebrates only?
- Tight junctions (Zonula Occludens)
- Another name for tight junctions is?
- Zonula occludens
- What are the two general function of zonula occludens?
-
1. To provide a barrier role in most epithelia.
2. To seal epithelial cells together. - Permeability of epithelial lining decreases with an increase in what?
- Number of sealing strands
- Give three examples of transmembrane tight junction proteins.
-
1. Occludin
2. Claudin
3. JAM (Junctional Adhesion Molecule) - What is unique about JAM as opposed to Occludin or Claudin?
-
JAM is a single pass transmembrane protein - Which part of the transmembrane tight junction protein is there an effector bind to molecules such as ZO-1?
- On the cytoplasmic tail end
- ZO proteins bind to what type of transmembrane proteins?
-
Occludins and/or Claudins and/or JAM - ZO's are almost always associated with what type of filaments?
-
Actin filaments - ZO's belong to what type of family?
-
MAGUK (Membrane Associated Guanine Kinase) family - Loss of ZO's will lead to increase in what?
- Permeability
- What is the purpose of anchoring junctions?
- Provide mechanical strength against mechanical stress
- What to anchoring junctions connect? X 2
-
1. Cytoskeleton to neighboring cells.
2. Cytoskeleton to matrix - What are the types of anchoring junctions and give their connections? X 4
-
1. Focal Adhesions (cell-ECM)
2. Adherens junctions (cell-cell)
3. Desmosomes (cell-cell)
4. Hemidesmosomes (cell-ECM) - What are the two main classes of proteins in anchoring junctions?
-
1. Intracellular anchor proteins
2. Transmembrane adhesion proteins -
What is 1 and 2? -
1. Intracellular anchor proteins
2. Transmembrane adhesion proteins - Adheren junctions connect what between cells?
- Bundles of actin filaments.
- Where do you expect to find anchoring junctions?
- Muscle, skin, heart
- What are Zonula Adherens?
-
Adhesion belts of adheren junctions - Catenin is an example of what?
- Intracellular anchoring protein
- Transmembrane adhesion proteins of anchoring junctions belong to what type of family?
- Cadherin family
- In order for tight junctions to form, cells must be attached by what?
- adheren junctions
- What is the character of the Cadherin family?
- Calcium dependent cell-cell adhesion.
- Where are two places where cadherins can be found?
- Adherens junctions and desmosomes.
- Under what condition do cadherin junctions occur?
- Calcium levels must be greater than 1 mM.
- Types of classical cadherins and where they are found X 4.
-
1. P-cadherins (placenta, epidermis, breast epithelium)
2. E-cadherins (epithelium)
3. N-cadherins (neurons, heart, skeletal muscle, lens, and fibroblasts)
4. VE-cadherins (endothelial) - The cytoplasmic tail of classical cadherins are linked to actin cytoskeleton by what?
-
Catenins (alpha and beta) and p120 protein - What is the purpose of p120?
-
To regulate cadherin function - What is the purpose of catenin beta?
-
Functions in intracellular signaling. -
How does adherens junctions involved in development? -
Tightening along selective adhesion belts will invaginate regions of cell sheet to produce epithelial tube. - What is the purpose of catenin alpha?
-
To associate with actin filaments - What is the purpose of focal adhesions?
-
To connect actin filaments to the basal lamina. - Transmembrane proteins of the focal adhesion junctions belong to what family?
- Integrin family
- Integrins can trigger what?
- Focal Adhesion Kinase (FAK)
- What is the function of focal adhesion junction assembly and activation?
- Assembly and activation serve as signaling events in modulating ENDOTHELIAL PERMEABILITY.
- What do desmosomes connect?
- Connects intermediate filaments (IF) between cells.
- What type of IF does desmosomes attach?
- Cell specific, but it is keratin in most epithelial cells.
- Transmembrane adhesion proteins of desmosomes belong to what family?
- Cadherin family
- Examples of transmembrane adhesion proteins of desmosomes. X 2
-
1. Desmoglein
2. Desmocollin - Examples of Intracellular anchoring proteins of desmosomes.
-
1. Plakoglobin (gamma catenin)
2. Desmoplakin - What does hemidesmosomes connect?
- Intermediate filaments to the basal lamina.
- Transmembrane proteins of hemidesmosomes belong to what family?
- Integrin
- Intracellular anchor protein of hemidesmosomes.
- Plectin
- Desmosomes and hemidesmosomes play an integral role in resisting mechanical stress (thus anchoring junctins), but due to their sensitivity to environment cues, they also play what other vital role? X 5.
-
1. Tissue remodeling
2. Differentiation
3. Wound healing
4. Invasion
5. Signal Cascades - Gap junction is what type of major junction?
- Communicating junction
- What are connexins?
- Membrane-spanning, channel-forming proteins of gap junctions (will assemble to become connexOn)
- What is the maximal pore size of connexons?
- 1.5 nm
- What do connexins allow for passing and what does it not allow?
- Allows small molecules, but NOT proteins.
- A connexon is made up of how many monomers?
- Six monomers
- Each connexin monomer is made up of how many membrane-spanning segments?
- Four membrane-spanning segments.
- What are the functions of gap junctions? X 3
-
1. Electrical synapse
2. Sharing of metabolites
3. Communication during development - Describe the benefits of electrical synapse function for gap junctions.
- Direct coupling allows propagation of an action potential from one cell to another without the need for a chemical intermidiate (much faster)
- Give an example of metabolite sharing seen in gap junctions.
- Hepatocytes not stimulated by a hormone, b/c many layers away from capillary/source of hormone, will detect signal by sharing a secondary messenger via gap junctions.
- Where do you see gap junctions during development?
- Between granulosa cells AND oocyte
- Mutation in connexin leads to what?
- Infertility and disruption in the development of both oocyte and granulosa cells.
- What regulates gap junction permeability?
-
1. pH
2. Cytosolic calcium
3. Extracellular signals (neurotransmitters) - Give an example of an extracellular signal that affects permeability of gap junctions.
- Dopamine
- Why regulate permeability?
- Cells need a way to close down connections to prevent widespread damage when one participant is damaged.
- Non-junctional cell-cell adhesion involves what families?
-
1. Immunoglobulin superfamily
2. Cadherin
3. Selectin
4. Integrin - Describe the three types of cell-cell adhesion mechanisms
-
1. Homophilic binding
2. Heterophilic binding
3. Binding through an extracellular linker molecule. - Why cell-cell adhesion?
- Before cells can form junctions, they need to adhere or stick ot each other.
- What generalized molecule is responsible for cell adhesion?
- Cell Adhesion Molecule (CAM)
- Cadherins mediate cell-cell adhesion by what mechanism?
-
Homophilic mechanism - Selectins mediate what and where?
- Mediates cell-cell adhesion in bloodstream.
- Selectins are found on what part of the cell?
- Cell surface
- Selectins bind what?
- Carbohydrates
- Selectins are dependent on what?
- Calcium
- What are the subtypes of selectin?
-
L-selectin
P-selectin
E-selectin - What type of cells are associated with L-selectin?
- White blood cells (Leukocytes)
- What type of cells are associated with P-selectin?
- Platelets and endothelial cells.
- What type of cells are associated with E-selectin?
- Activated Endothelial cells
- What type of WBC character is seen when on top of endothelial sheet with selectin dependent movement?
- Weak adhesion and ROLLING
- Give two examples of Calcium independent adhesion.
-
1. Neural Cell Adhesion Molecules (N-CAMs)
2. Intercellular Cell Adhesion Molecules (I-CAM) - N-CAMs belong to what family?
- Immunoglobulin superfamily
- Impaired desmosome functions can induce what disorders?
- Severe skin disorders
- Mutations in the genes of the desmosomal plaque proteins plakoglobin and desmoplakin have been linked to what disease?
- Cardiomyopathy