M1-C2-L19 --> Cell To Cell Communication

Front 1

What are the three type of junctions found in cells?

Back 1

1. Occluding junction
2. Anchoroing junctions
3. Communicating junctions

Front 2

What are occluding junctions seen in vertebrates only?

Back 2

Tight junctions (Zonula Occludens)

Front 3

Another name for tight junctions is?

Back 3

Zonula occludens

Front 4

What are the two general function of zonula occludens?

Back 4

1. To provide a barrier role in most epithelia.

2. To seal epithelial cells together.

Front 5

Permeability of epithelial lining decreases with an increase in what?

Back 5

Number of sealing strands

Front 6

Give three examples of transmembrane tight junction proteins.

Back 6

1. Occludin
2. Claudin
3. JAM (Junctional Adhesion Molecule)

Front 7

What is unique about JAM as opposed to Occludin or Claudin?

Back 7

JAM is a single pass transmembrane protein

Front 8

Which part of the transmembrane tight junction protein is there an effector bind to molecules such as ZO-1?

Back 8

On the cytoplasmic tail end

Front 9

ZO proteins bind to what type of transmembrane proteins?

Back 9

Occludins and/or Claudins and/or JAM

Front 10

ZO's are almost always associated with what type of filaments?

Back 10

Actin filaments

Front 11

ZO's belong to what type of family?

Back 11

MAGUK (Membrane Associated Guanine Kinase) family

Front 12

Loss of ZO's will lead to increase in what?

Back 12

Permeability

Front 13

What is the purpose of anchoring junctions?

Back 13

Provide mechanical strength against mechanical stress

Front 14

What to anchoring junctions connect? X 2

Back 14

1. Cytoskeleton to neighboring cells.
2. Cytoskeleton to matrix

Front 15

What are the types of anchoring junctions and give their connections? X 4

Back 15

1. Focal Adhesions (cell-ECM)
2. Adherens junctions (cell-cell)
3. Desmosomes (cell-cell)
4. Hemidesmosomes (cell-ECM)

Front 16

What are the two main classes of proteins in anchoring junctions?

Back 16

1. Intracellular anchor proteins
2. Transmembrane adhesion proteins

Front 17

What is 1 and 2?

Back 17

1. Intracellular anchor proteins
2. Transmembrane adhesion proteins

Front 18

Adheren junctions connect what between cells?

Back 18

Bundles of actin filaments.

Front 19

Where do you expect to find anchoring junctions?

Back 19

Muscle, skin, heart

Front 20

What are Zonula Adherens?

Back 20

Adhesion belts of adheren junctions

Front 21

Catenin is an example of what?

Back 21

Intracellular anchoring protein

Front 22

Transmembrane adhesion proteins of anchoring junctions belong to what type of family?

Back 22

Cadherin family

Front 23

In order for tight junctions to form, cells must be attached by what?

Back 23

adheren junctions

Front 24

What is the character of the Cadherin family?

Back 24

Calcium dependent cell-cell adhesion.

Front 25

Where are two places where cadherins can be found?

Back 25

Adherens junctions and desmosomes.

Front 26

Under what condition do cadherin junctions occur?

Back 26

Calcium levels must be greater than 1 mM.

Front 27

Types of classical cadherins and where they are found X 4.

Back 27

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)

Front 28

The cytoplasmic tail of classical cadherins are linked to actin cytoskeleton by what?

Back 28

Catenins (alpha and beta) and p120 protein

Front 29

What is the purpose of p120?

Back 29

To regulate cadherin function

Front 30

What is the purpose of catenin beta?

Back 30

Functions in intracellular signaling.

Front 31

How does adherens junctions involved in development?

Back 31

Tightening along selective adhesion belts will invaginate regions of cell sheet to produce epithelial tube.

Front 32

What is the purpose of catenin alpha?

Back 32

To associate with actin filaments

Front 33

What is the purpose of focal adhesions?

Back 33

To connect actin filaments to the basal lamina.

Front 34

Transmembrane proteins of the focal adhesion junctions belong to what family?

Back 34

Integrin family

Front 35

Integrins can trigger what?

Back 35

Focal Adhesion Kinase (FAK)

Front 36

What is the function of focal adhesion junction assembly and activation?

Back 36

Assembly and activation serve as signaling events in modulating ENDOTHELIAL PERMEABILITY.

Front 37

What do desmosomes connect?

Back 37

Connects intermediate filaments (IF) between cells.

Front 38

What type of IF does desmosomes attach?

Back 38

Cell specific, but it is keratin in most epithelial cells.

Front 39

Transmembrane adhesion proteins of desmosomes belong to what family?

Back 39

Cadherin family

Front 40

Examples of transmembrane adhesion proteins of desmosomes. X 2

Back 40

1. Desmoglein
2. Desmocollin

Front 41

Examples of Intracellular anchoring proteins of desmosomes.

Back 41

1. Plakoglobin (gamma catenin)
2. Desmoplakin

Front 42

What does hemidesmosomes connect?

Back 42

Intermediate filaments to the basal lamina.

Front 43

Transmembrane proteins of hemidesmosomes belong to what family?

Back 43

Integrin

Front 44

Intracellular anchor protein of hemidesmosomes.

Back 44

Plectin

Front 45

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.

Back 45

1. Tissue remodeling
2. Differentiation
3. Wound healing
4. Invasion
5. Signal Cascades

Front 46

Gap junction is what type of major junction?

Back 46

Communicating junction

Front 47

What are connexins?

Back 47

Membrane-spanning, channel-forming proteins of gap junctions (will assemble to become connexOn)

Front 48

What is the maximal pore size of connexons?

Back 48

1.5 nm

Front 49

What do connexins allow for passing and what does it not allow?

Back 49

Allows small molecules, but NOT proteins.

Front 50

A connexon is made up of how many monomers?

Back 50

Six monomers

Front 51

Each connexin monomer is made up of how many membrane-spanning segments?

Back 51

Four membrane-spanning segments.

Front 52

What are the functions of gap junctions? X 3

Back 52

1. Electrical synapse
2. Sharing of metabolites
3. Communication during development

Front 53

Describe the benefits of electrical synapse function for gap junctions.

Back 53

Direct coupling allows propagation of an action potential from one cell to another without the need for a chemical intermidiate (much faster)

Front 54

Give an example of metabolite sharing seen in gap junctions.

Back 54

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.

Front 55

Where do you see gap junctions during development?

Back 55

Between granulosa cells AND oocyte

Front 56

Mutation in connexin leads to what?

Back 56

Infertility and disruption in the development of both oocyte and granulosa cells.

Front 57

What regulates gap junction permeability?

Back 57

1. pH
2. Cytosolic calcium
3. Extracellular signals (neurotransmitters)

Front 58

Give an example of an extracellular signal that affects permeability of gap junctions.

Back 58

Dopamine

Front 59

Why regulate permeability?

Back 59

Cells need a way to close down connections to prevent widespread damage when one participant is damaged.

Front 60

Non-junctional cell-cell adhesion involves what families?

Back 60

1. Immunoglobulin superfamily
2. Cadherin
3. Selectin
4. Integrin

Front 61

Describe the three types of cell-cell adhesion mechanisms

Back 61

1. Homophilic binding
2. Heterophilic binding
3. Binding through an extracellular linker molecule.

Front 62

Why cell-cell adhesion?

Back 62

Before cells can form junctions, they need to adhere or stick ot each other.

Front 63

What generalized molecule is responsible for cell adhesion?

Back 63

Cell Adhesion Molecule (CAM)

Front 64

Cadherins mediate cell-cell adhesion by what mechanism?

Back 64

Homophilic mechanism

Front 65

Selectins mediate what and where?

Back 65

Mediates cell-cell adhesion in bloodstream.

Front 66

Selectins are found on what part of the cell?

Back 66

Cell surface

Front 67

Selectins bind what?

Back 67

Carbohydrates

Front 68

Selectins are dependent on what?

Back 68

Calcium

Front 69

What are the subtypes of selectin?

Back 69

L-selectin
P-selectin
E-selectin

Front 70

What type of cells are associated with L-selectin?

Back 70

White blood cells (Leukocytes)

Front 71

What type of cells are associated with P-selectin?

Back 71

Platelets and endothelial cells.

Front 72

What type of cells are associated with E-selectin?

Back 72

Activated Endothelial cells

Front 73

What type of WBC character is seen when on top of endothelial sheet with selectin dependent movement?

Back 73

Weak adhesion and ROLLING

Front 74

Give two examples of Calcium independent adhesion.

Back 74

1. Neural Cell Adhesion Molecules (N-CAMs)
2. Intercellular Cell Adhesion Molecules (I-CAM)

Front 75

N-CAMs belong to what family?

Back 75

Immunoglobulin superfamily

Front 76

Impaired desmosome functions can induce what disorders?

Back 76

Severe skin disorders

Front 77

Mutations in the genes of the desmosomal plaque proteins plakoglobin and desmoplakin have been linked to what disease?

Back 77

Cardiomyopathy