BSCI330 cell junctions Flashcards
how do squishy cells form structures in multicellular organisms
interactions with the extracellular matrix and their neighbors
how are animal cells bound together
connective tissues and epithelial tissues
what are the four classes of cell-cell junctions
anchoring, occluding, channel-forming, signal-relaying
what are anchorage junctions
cell-cell/cell-matrix adhesion
allow cells to be firmly attached to each other
cadherin or integrin proteins are required
what are occluding junctions
permeability barriers - prevent material from passing between two cells (“ziplock bag”)
claudin proteins are required for function
what are channel-forming junctions
allow cytosols of two cells to communicate
intercellular passages
connexin or innexin proteins
what are signal-relaying junctions
transmit signals
allow signal to be transmitted from one cell to another by secretion of cell-signal molecules in space between two cells
anchorage and signals proteins
what do anchorage junctions do
provide mechanical strength to tissues - transmembrane proteins link the cytoskeleton to extracellular structures
what are cadherins
adhesive proteins that require calcium to adhere
use homophilic binding - interactions between same types of proteins
how are cadherins organized
will sort out in vitro into clumps that are all composed of cells that express the same type or levels of cadherin
what do anchor proteins do
connect cadherins to cytoskeleton
what do desmoseomes do
helps the intermediate filaments in adjacent cells get connected together, this provides the cells with mechanical strength
what are selectins
adhesive protein - weaker adhesion than cadherins but more transient
bind to oligosaccharides on glycoproteins and glycolipids through its lectin domain (calcium dependent)
what are integrins
adhesive, heterophilic proteins
bind to adhesions with immunoglobulin-like domains
what are selectin-dependent adhesions
weak adhesion and rolling
what are integrin-dependent adhesions
strong adhesion and emigration
what do occluding junctions do
act as barriers to solute diffusion
their proteins seal the space between adjacent membranes
- act analogous to the seals in Ziploc bags and hold two lipid bilayers together
- the seal is mediated by transmembrane proteins in the bilayers of each cell
what proteins form the Ziploc seal in occluding junctions
claudin and occludin
what do channel-forming junctions do
are made of proteins such as connexins that connect the cytoplasm of two cells and form small channels
can have small or large gap junctions with few or a lot connexins
what do signal-relaying junctions do
help cells communicate quickly, allow cells to communicate with each other in an organized fashion
all the components of other junctions can be in these
what is the extracellular matrix called
basal lamina
what are the three ways to organize the extracellular matrix
surround cells (like in muscle)
underlie cells (like in epithelium)
between cells (like in kidney glomerulus)
what protein organizes the basal lamina
laminins
what do integrins do in extracellular matrix
connect it to actin cytoskeleton
