Cell Junctions and Surface Specializations Flashcards
What are cadherins?
Class of Proteins
Attach one cell to another by binding to other cadherins
Stabilized by the actin cytoskeleton of the cell.
What proteins link cadherins to the cells actin cytoskeleton?
Catenins
Function of cadherins and selectins is dependent on what molecule?
Ca+2
What do selectin proteins bind to?
Carbohydrates
Why are selectins integral to the inflammatory response?
They are important for controlling movement of leukocytes from blood into tissues.
Integrins?
Integral membrane proteins that will link to actin
Heterodimer - unique combination of alpha and beta chains
What do integrins bind to?
Inside cell - cytoskeletal actin
Outside cell - Tripeptide RGD (arg-gly-asp) on ligands (laminin, fibronectin, tenascin, vitronectin, collagen..)
CAM?
Cell adhesion molecule
Occluding (tight) junctions
Define cell polarity
prevent anything from slipping between cells
Zonula adherens (belt desmosome)
Associated with actin filiaments
beltlike distribution
Macula adherens (spot desmosome)
Associated with intermediate filaments
Stronger attachement than belt desmosome.
Like a “spot weld”
Hemidesmosome
Link the basal domain of an epithelial cell to the basal lamina
Intermediate filaments are associated with a plaque
Gap junctions
Allow cells to communicate with each other chemically and elctrostatically
What are gap junctions formed by?
Connexons - channel like structures that enable the passage of small molecules between cells.
Comprised of six integral membrane proteins called connexins
What is the usual order of the five anchoring junctions from top to bottom?
Occluding junction Zonula adherens (belt desmosomes) Macula adherens (spot desmosomes) Gap junctions Hemidesmosomes
What type of problems are usually associated with connexin mutations?
Nervous system problems
Microvilli purpose?
Increase cell surface area
Cilia purpose?
Motion/Movement
What is the terminal web?
A horizontal of actin filaments that links that actin cores of microvilli
What cytoskeleton filaments are cilia and flagella made of?
Microtubules
What provides the force for cilia movement?
Dyneins
Where do cilia develop from?
Basal bodies - derived from centrioles, rootlets anchor these structures to the cytoplasm
What are the 2 proteins involved in an occluding junction?
Occludin and claudin
Zonula Adherens (belt desmosomes) are constructed by what two proteins?
Cadherins and catenins
What is Leucocyte adhesion deficiency type 1 (LAD-1)?
Absence of mutations of beta 2 integrins
