Cell Adhesion Flashcards
Functions of cell-to-cell interactions
- Wound healing
- Inflammation response
- Immune response (self vs. non-self recognition)
- Tumor metastasis
- Blood clotting
- Growth and development
Cell adherence is?
Specific and reversible
2 types of cell adherence
- Homotypic adhesion
2. Heterotypic adhesion
Cell-cell interactions are dependent on?
- Cell-cell recognition
2. Cell-cell adhesion → allows for communication
Cadherins need ____ to function, which is to:
Require calcium
Allow interaction with neighboring cell via cadherins of same time
Cadherin adhesion
Homotypic adhesion → bind through adherens junctions (actin cytoskeleton, desmosomes)
Integrins are?
Linker proteins (link ECM components and cell)
Types of cell junctions
- Adhesive (anchoring)
- Tight
- Gap
Adhesive (anchoring) junctions
Links cells in tissues by connecting cytoskeletons → allows cells to function as unit and share stress
Adhesive junctions are prominent in?
Cells subjected to high stress;
- Skin
- Bladder
- Heart
- Stomach
Adhesive junction types
- Desmosomes
- Hemidesmosomes
- Adherens junction
All adhesive junctions contain 2 distinct types of proteins. What are they?
- Intracellular attachment proteins (inside plasma membrane)
- Transmembrane linker proteins (outside plasma membrane → bind cells to ECM)
Desmosome adhesion
Between cells (linker proteins)
Provides structural integrity (resists stress)
Desmosomes are in what kind of cells?
Squamous epithelial and muscle cells
Desmosomes are abundant in what types of tissues?
- Heart
- Skin
- Neck of uterus
Hemidesmosomes connect
Epithelial cell to basal membrane (plaque only in 1 cell)
2 types of adhesive junctions
- Adhesion belt
2. Focal contact
Adhesion belts
Are:
Common in:
Connection:
Encompass entire cell
Common in layer of tissue that line body cavities
Connect to cytoskeleton and adjacent cell via actin
Focal contact
Attach cells to ECM
Not continuous
Use integrins
What are connexons?
Hollow cylinders → special type of protein composed of assembly of 6 connexin subunits
Gap junctions are abundant in tissue with what requirements?
Rapid communication (muscle and nerve)
What do gap junctions facilitate in the heart?
Flow of electrical current
Where are gap junctions in the brain?
Cerebellum → facilitates rapid muscle movements
Tight junctions
Leave NO space between plasma membranes of adjacent cells → prevents movement of fluids and ions between cells (or of 2 different body compartments)
Tight junction with the least amount of sealing are found where?
Bladder
Tightest tight junctions in the body
Epithelial cells of inner ear
Function of blood-brain barrier derives largely from?
Tight junctions
How is the efficiency of a tight junction regulated?
Number of independent sealing strands
Major proteins in sealing strands of tight junctions
Claudins and occuludin
What are sealing strands in tight junctions formed from?
Row of transmembrane proteins embedded in both plasma membranes
Extracellular domains join one another directly
Tight junctions joint together the ______ of adjacent cells
Cytoskeleton
Pemphigus
Autoimmune disorder which produces antibodies against cadherins
Skin gets attached by immue system and looks fucked up (lots of blisters and such)
Natalizumab
Anti-integrin antibodies (attached alpha 4-integrin)
Used to treat MS (multiple sclerosis) and IBD (inflammatory bowel disease)
Cadherins do what type of cell adhesion?
Homotypic (especially epithelia)
Cadherins bind through
Adherens junction: actin cytoskeleton + desmosomes
Desmogelins
Type of cadherin, targeted by pemphigus
Most common immune mediated skin disease in dog and cat
Pemphigus foliaceus
alpha 4-integrins
Important for recruitment of lymphocytes ad monocytes to inflammation sites
Homotypic adhesion
Adherence of cell to similar cell
Ex: epithelial cells in epithelial sheet
Heterotypic adhesion
Adherence of cell to dissimilar cell
Ex: neuron + Schwann cell, neutrophil + endothelial cell
Cadherin location
Plasma membrane of most cells
Cadherin side chains
Carbohydrate side chains (affect strength and specificity)
Intracellular attachment proteins
Attach adhesive junction to cytoskeleton filaments (inside plasma membrane)
How do intracellular attachment proteins attach adhesive junction to cytoskeleton filaments?
Form thick plaque on cytoplasmic side of plasma membrane
How do connexins form gap junctions?
2 hemichannels/connexins from opposing cells stick together to form intercellular gap junction channel
Why are integrins “linker” and no “adhesive” proteins?
Weak binding → low affinity allows for exploration of environment → prevents “gluing” of cell to ECM
