final cell junctions, adhesions, and extracellular matrix Flashcards
how can squishy cells can form structures in multicellular organisms
- by secreting complex and sturdy substances that form part of the extracellular matrix and then attaching to the matrix
- by reinforcing their cytoskeleton through interactions with the extracellular matrix and their neighbors
how can cells move from one place to another
some cells can dynamically control their attachments with their environment or other cells
how can sets of cells function together
through their inter-cellular interactions or through channels that connect the cytoplasm of one cell with that of another
what are cell-to-cell contacts and the extracellular matrix crucial for
the control of cell division and the prevention of cancer
how are animal cells bound together
with connective tissues and epithelial tissues
what stress is shared between cells
mechanical stress
where are cells embedded in connective tissues
extracellular matrix - it bears mechanical stresses of tension and compression
what do fibroblasts do in the connective tissue
make and secrete the extracellular matrix material
what do anchoring junctions do and what is required for their function
they’re for cell-cell or cell-matrix adhesion
cadherin or integrin proteins are required for the two functions
what do occluding junctions do and what is required for their function
make permeability barrier for solute diffusion
claudin proteins are required for function
what do channel-forming junctions do and what is required for their function
provide intercellular passages
connexin or innexin proteins are required for function
what are signal-relaying junctions and what is required for their function
they transmit signals
anchorage and signaling proteins are required for function
what links the cytoskeleton to extracellular structures
transmembrane proteins
what interactions do anchoring junctions involve
cell-cell interactions where cells are held together for structural strength
what do connections between the cytoskeleton filaments and integrins/cadherins occur via
intracellular anchor proteins
what do cell-to-matrix communication use
intgerins
what do cell-to-cell communication use
cadherins and integrins
what are cadherins
transmembrane protein: adhering protein
requires calcium ions to adhere
what type of binding do cadherins use
homophilic binding (interact with molecules of the same type)
how do cadherins sort themselves
different types sort out into clumps composed of cells that express the same type of cadherin, which will sort into zones composed of same expression level
what do anchoring proteins do
couple cadherins to cytoskeleton filaments
what do desmosomes do
provides cell with mechanical strength to withstand compressive and tensile disturbances
what is the difference between cadherins and selectins
cadherins are involved in long term interactions, selectins are involved in transient adhesion
what do selectins do
mediate transient interactions by heterophilic binding (interact with other molecules) to carbohydrates - calcium dependent
what can the immunoglobulin superfamily proteins do
enable interactions between cells in the absence of calcium
how do Ig family proteins bind
homotopically to neurons
heterotypically to integrins on white blood cells
what is a similarity between cadherins and selectins
both are calcium dependent
what is the two stage fashion of adhesion molecules
selectin-dependent use weak adhesion and rolling adhesion
integrin-dependent use strong adhesion and emigration
using one weak and one strong adhesion molecule allows cells to migrate and exit through the blood vessels so they can enter infected tissue
how do selectin-dependent molecules allow cells to find location to leave bloodstream and stop
selectin-carbohydrate interaction is weak, so white blood cells starts to interact with blood vessel, but protein-carb interactions aren’t strong enough to stop white blood cell for moving all together, so they act as brakes to slow white blood cell down
how do integrin-dependent molecules allow cells to find location to leave bloodstream and stop
integrins on white blood cells interact strongly with iCAM or vCAM or other CAMS on endothelial cells - causes cells to stop completely. cells can then crawl along surface until they find junction on two cells - they can then exit blood cell and enter the infected tissue
what do occulding junctions do (more detail)
allows cells to regulate concentration of solutes on each side of a cell layer so that in order for a solute to get from one side to another it has to pass through the cell - allows for directional movement of glucose
how are occluding junctions like a ziplock bag
they seal the space between adjacent membranes - they hold two lipid bilayers together - claudin seals the space between membranes
what is planar cell polarity of epithelial cells
the ordered arrangement of molecules in a plane, which can be disrupted by the disruption of cadherins
what are channel-forming junctions (more detail)
aka gap junctions
form pores that allow small molecules and ions to pass from one cell to another so their intercellular environments can be electrically connected
connexins form channel from one cell to the next (forms gap)
what is the basal lamina
extracellular matrix that allows cells to have additional strength bc they’re anchored to fixed point
what are the three ways the basal lamina can be arranged
- in epithelial cells they’re resting on basal lamina
- in muscle cells the basal lamina surrounds it
- in kidney glomerulus: basal membrane is interspersed between two cells: endothelial cell of blood cell and epithelial cell of kidney
what is the purpose of laminins
they’re able to self assemble and interact with many components of the extracellular matrix and with integrins, so this class of proteins is a key organizer
what do integrins do
connect extracellular matrix to actin cytoskeleton
what are GAGs
sugar polymers that oxxupy large volumes of space and form hydrated gels to provide cushioning against compressive forces
what is collagen
helical protein that makes permanent modifications and allows for intermolecular crosslinks to happen, providing meshwork of tensile strength to extracellular matrix
