Intercellular Architecture- Lecture 38-39 Flashcards
Name the different types of cell adhesion molecules.
cadherins, the Ig superfamily, integrins, and selectins
What are the characteristics of cadherins?
homophelic
Ca2+ binding
bind actins and IF
What are the characteristics of integrins?
connect cells to extracellular matrix (heterophilic binding)
bind actins
What are the characteristics of selectins?
mostly on immune cells help cells find their way out of blood stream
What types of proteins are contained in the Extracellular Matrix?
collagen
proteoglycans
multi-adhesive proteins
What is the function of the ER?
hold tissues together, provide cushoning (cartilage) and strength (tendons), act as reservoirs for growth factors
Polarized cellular organization of epithelial cells allows for ______.
different functions such as absorbtion of nutrients on one membrane and their secretion from another
How do the apical, lateral, and basal membranes differ?
apical usually has large surface area (due to presence of vili)
lateral and basal usually separated from apical via specialized cell junctions
What is inside out signaling?
intracellular events promote interactions between the cell and the ECM
What is outside-in signaling?
extracellular events such as ligand binding that cause interactions between the cell and the ECM
Name the types of cell junctions found in epithelial cells.
tight (seal epithelial cells together in sheets– prevent passage of small molecules between cells)
anchoring (join cells to each other and to ECM via two different types: adherens junctions/ desmosomes and focal adhesions/ hemidesmosomes)
What are cadherins?
large glycoproteins that link by a homophilic mechanism to actin cytoskeleton (via catenins alpha or beta)
What are integrins?
cell matrix receptors on cells that bind ligand with low affinity
composed of alpha and beta subunits held together non-covalently
most are connected to bundled actin filaments (except alpha6beta4 which interacts with IF at hemidesmosomes) mediated by anchor proteins
Provide examples of a conditions caused by mutations in connexons in gap junctions.
Charcot-Marie-Tooth X (neurodegenerative demyelinating disease)
sensorineural hearing loss (mutation in GBJ2)
What are communicating (gap) junctions?
found in virtually every cell
composed of heximeric complexes called connexons in membranes forming channel
used for amplifying a response across a tissue from a local source such as a neuromuscular junction
allow for movement of molecules less than 1200 daltons across gap junctions
Name the components of the ECM.
collagens, proteogycans, and multi-adhesive connectors (fibronectin and laminin)
What is the structure and function of the basal lamina?
flexible mats of specialized matrix that underlies epithelial cell sheets and tubes, separating cells from surrounding connective tissue
serve as a highly selective filter
What are the main components of the basil lamina for epithelium?
laminins
type IV collagen
perlecan
nidogen
Provide an example of a collagen linked disease.
Scurvy- hydroxyproline requires vitamin C, and in its absence, the ECM becomes instable leading to teeth falling out
Describe the structure and function of collagen.
trimeric triple helix in structure with regions containing Gly-X-X (X most often is proline or hydroxyl-proline) formed in the ER
withstands tensile forces (stretching)
Describe the structure and function of proteoglycans.
formations of carbohydrates and proteins (mostly GAG chains) that bind water and provide hydration
resist compressive forces
______ serve as bridges to reinforce the network and connect ECM to cells and other small molecules.
Multi-domain glycoproteins (eg. laminin or fibronectin)
Describe the structure and function of elastin.
gllycine, rpoline, hydroxyproline righ fibers sheathed by microfibrils containing fibrillin
allow for recoil after transient stretch
Describe Marfan’s Syndrome.
mutation in fibrillin leading to defects in tissues rich in elastic fibers (eg. the aorta)
also associated with increased TGFbeta
