SFP: cell adhesion and the ECM Flashcards
name the three primary types of cell junctions
tight junctions, gap junctions, and anchoring junctions
describe tight junctions, including the proteins associated with them
found at the apicolateral surface; contribute to the barrier function of epithelial cell layers and separate fluids with different chemical compositions. Because of this, they can also set up gradients.
major proteins they’re associated with are claudins and occludins
describe gap junctions including the proteins they’re associated with
can be dispersed in various of the areas of the membrane and allow for communication between the cells. They allow the passing of small molecules. Super important in muscle cells
major protein they’re associated with is connexins that assemble to form connexons
describe how connexons work
they’re associated with gap junctions; Connexons from one cell bind to connexons on another cell, allow substances to pass between the two cells.
describe anchoring junctions including the major proteins they’re associated with
they have extracellular, membrane, and cytoplasmic domains. They use scaffolding proteins to connect to cytoskeletal elements. they include cell to cell connection as well as cell to ECM connections.
the major proteins they’re associated with are integrins and cadherins
name the 4 major types of anchoring junctions
adherens junctions, desmosomes, hemidesmosomes, focal adhesions
describe adherens junctions
cell to cell junctions that link actin bundles from one cell to those of another; they’re involved in structure and movement. they’re important for wound healing and morphogenic processes
they use cadherin proteins
describe desmosomes
cell to cell junctions that connect intermediate filaments of one cell to those of another; they are involved in stability.
they use cadherins
describe hemidesmosomes
cell to ECM junctions that connect intermediate filament of a cell to the basal lamina; they’re all about stability!
they use integrin proteins
describe focal adhesions
cell to ECM junctions that link actin in a cell to the ECM to anchor it; these can be used for cell stability and movement.
they utilize integrins
How does a cell junction differ from a cell attachment/cell adhesion?
Cell adhesion occurs before junctions; can use heterophilic or homophilic receptors. If they find they “agree” with each other, they’ll develop more complex structures like junctions.
describe integrins
receptors that bind externally to the ECM and internally to the actin cytoskeleton; they help with both movement and stability. they are inactivated and can be activated by intracellular signaling.
How does the cytoskeletal component of different types of anchoring junctions often dictate function
Linked to actin means the junction is likely involved in movement, while linking to an intermediate filament tends to indicate being involved in structure and stability only
define homophilic vs heterophilic receptor systems
Homophilic: same receptors linking
Heterophilic: different receptors linking
What role does tension play in initiation of cell adhesion events? Compare to the role of
tension in fibronectin ECM assembly
Tension created by cell attachment through receptors causes unfolding of cytoplasmic proteins bound to the receptors. This allows the exposed proteins to interact with other cytoplasmic proteins, such as actin-myosin cytoskeleton. This recruits additional adhesion that can form cell junctions. Without the tension there is no unfolding and this does not happen.
