Cell Adhesion

Question 1

What do cell-cell interactions promote?

Answer 1

• wound healing
• inflammation responses
• immune responses (recognition of self vs. non-self)
• tumor metastasis
• blood clotting
• growth and development

Question 2

Cell adherence is very _____ and ______

Answer 2

specific and reveresible

Question 3

Homotypic Adhesion

Answer 3

adherence of a cell to a similar cell

ex - epithelieal cells in an epithelial sheet

Question 4

Heterotypic Adhesion

Answer 4

adherence of a cell to a dissimilar cell

ex - Neuron and Schwann Cell; Neutrophil and Endothelial Cell

Question 5

Cadherins

Answer 5

• Found in Plasma Membrane in Most Animal Cells
• Discovered via Antibody Approach
• Require Calcium to function
• Have carbohydrate side chains that affect strength and specificity
• Homotypic Cell Adhesion
• Bind Through Adherens Junctions

Question 6

Integrins

Answer 6

• Linker Proteins that link ECM components and cells
• binding is weak
• low affinity prevents “gluing” of cell to ECM

Question 7

Types of Cell Junctions

Answer 7

• Adhesive (Anchoring) = includes desmosomes, hemidesmosomes, and adherens junctions
• tight junctions
• gap junctions

Question 8

Adhesive (Anchoring) Junctions

Answer 8

• Link cells in tissues
• connects cytoskeleton to cytoskeleton
• allows cells to function as a unit
• transfers stress between and within cells
• prominent in cells subject to high stress such as skin, bladder, heart, stomach

Question 9

The 3 types of Adhesive Junctions all contain….

Answer 9

• 2 distinct types of proteins
  
  • intracellular attachment proteins
  • transmembrane linker proteins

Question 10

Intracellular Attachment Proteins

Answer 10

• found in Adhesive Junctions
• adhesive junction to cytoskeleton filaments inside a plasma membrane
• form thick plaque on cytoplasmic side of PM

Question 11

Transmembrane Linker Proteins

Answer 11

• found in Adhesive Junctions
• outside plasma membrane
• bind cells to ECM

Question 12

Desmosomes

Answer 12

• Type of Adhesive junction
• between cells
• provides structural integrity to resist stress
• found in epithelial cells (simple and stratified squamous) and muscle cells
• abundant in heart, skin, and the neck of the uterus

Question 13

Hemidesmosomes

Answer 13

• connect epithelial cells to basal membrane

- plaque is only in one cell

Question 14

Adhesive Junctions

Answer 14

• 2 Types = adhesion belt and focal contact
• Adhesion belt encompasses entire cell and is common in layers of tissue that line body cavities. also connects to cytoskeleton and adjacent cells via actin
• Focal Contact attaches cells to ECM, is not continuous, and uses integrins

Question 15

Gap Junction

Answer 15

• channel formed by connexons that consist of six connexins

- mediate reciprocal exchange of ions and smal molecules

Question 16

Tight Junctions

Answer 16

• barrier to passage of both ions and molecules through paracellular pathway
• Leaves NO space between PM of adjacent cells
  
  • seals cell
  • prevents movement of fluids and ions between cells of 2 different body compartments
• degree of sealing can vary based on location in body
• can be regulated
• major types of proteins in tight junctions are claudins and occuludins

Question 17

Connexons

Answer 17

• hollow cylinders
• special type of protein grouped into an assembly of 6 subunits
• subunits are called connexins
• Takes 2 connexons from opposing cells normally sticking together to form complete gap junction

Question 18

Locations of Gap Junctions and why

Answer 18

• Muscle and Nerve = Rapid Communication
• Heart = facilitate flow of electrical current
• Brain = cerebellum for rapid muscle movement

Question 19

Pemphigus

Answer 19

• rare,severe autoimmune disease against cadherins in the body
• varying size blisters break out on skin, lining of mouth, genitals, and other mucous membranes
• other symptoms include loss of hair and skin falls/peels off
• occurs both in humans (middle-age or older) and animals (dogs, cats, horses, goats)
• Mainstay of treatmetn is high doses of corticosteroids

Question 20

Pemphigus vulgaris targets….

Answer 20

Dsg3

Question 21

IgA pemphigus targets…

Answer 21

Dsc1

Question 22

Pemphigus foliaceus targets…

Answer 22

Dsg1

Question 23

Pemphigus foliaceus

Answer 23

• least severe of 3 varieties of pemphigus
• Desmoglein 1, protien that is destroyed by autoantibody, is only found in top dry layer of skin
• symptoms = crusty sores that often being on skin of face, ears, and feet. Eventually on entire skin
• middle-aged to older dogs more prone to this disease
• more commonly seen in Akitas, Doberman pinschers, Chows, Dachschunds, Newfoundlands, Bearded Collies, and Schipperkes

Question 24

Natalizumab

Answer 24

• humanized monoclonal antibody against cellular adhesion molecule alpha4-integrin
• used in treatment of multiple sclerosis and Crohn’s disease
• could increase risk of infection