Lecture 20: Cell Junctions Flashcards
cell junctions (def.)
Specialized contact sites linking cells with each other and to extracellular matrix
cell junctions are important for what type of cells?
epithelial and endothelial cells
Changes in physiological conditions can affect _____ of cell junctions
the assembly and stability
mechanical stresses are transmitted from cell to cell by ______
cytoskeletal filaments anchored to cell-matrix and cell-cell adhesion sites
extracellular matrix directly bears _____
mechanical stresses of tension and compression
cell junctions are modified extensively during ___
oncogenesis (process of cell becoming cancerous)
Cancer cells with modified cell junctions become _____ and are able to ____
motile
invade other tissues
cell junctions are important for ______
anchoring
cell-cell communication
maintaining cellular barriers and polarity
tight junction seals ___
gap between epithelial cells
adherens junction connects ___
actin filament bundle in one cell with that in the next cell
desmosome connects ______
intermediate filaments in one cell with that in the next cell
gap junction allows the ____
passage of small water-soluble molecules from cell to cell
actin-linked cell-matrix junction anchors _____
actin filaments in cell to extracellular matrix
hemidesmosome anchors ____
intermediate filaments in cell to extracellular matrix
Two types of proteins associated with cell junctions
-intracellular adaptor proteins (which connect to cytoskeletal filaments) a.k.a peripheral membrane proteins
-transmembrane adhesion proteins
other cofactors of proteins associated with cell junctions
calcium
calcium in cell junction is associated with _____
the ectodomain of the transmembrane protein
ectodomain (def.)
domain of a membrane protein that extends into the extracellular space
removing Ca+ with a chelating agent will have this effect on cell junctions?
disrupts the interactions between cells
gap junction are ____ to allow ____
small direct channels between two cells
ions to pass for cell communication
gap junctions are not a _____; what can’t pass?
tunnel
proteins
Tight junctions regulate ____ transport
paracellular transport (fence function)
Tight junctions provide _______ on either side of _____
selective barrier for extracellular fluids
epithelia (gut) or endothelia (blood vessel)
Tight junctions form this in the brain?
blood-brain barrier
Tight junctions regulates _____permeability
paracellular
paracellular permeability (def.)
movement of molecules across epithelium between cells
the effectiveness of barrier varies depending on ____
type of epithelium
Tight junctions restricts ____ between _____which is essential for _____
diffusion of proteins/lipids
apical and basolateral membranes
polarity
Tight junctions are important for ______ in gut
selective nutrient uptake
transport of this nutrient requires tight seal between epithelial cells?
glucose
Tight junctions are _____ and can allow _____ through blood vessels
dynamic
immune cells to move
TJs appear as a network of ____ that completely encircles _____
fibrils
apical end of cell
Fibrils creates a ____
labyrinth that ensures low permeability
The purification of fibrils requires ____
monoclonal antibodies
antibodies production in the lab method
1) antigen injected into mouse
2) animal will start generating antibodies for antigen in serum
3)serum will have mixture of different antibodies to same antigen (may react with different regions of antigen)
antibodies production for tight junction in the lab method
1)”purify” tight junctions
2) same technique
3) different antibodies produced for different proteins that make up tight junctions
polyclonal antibodies can recognize _____
multiple epitopes (different regions)on one or more a ntigens
polyclonal antibodies is made from ____
multiple antibody-producing cells
polyclonal antibodies = ___ regions
different
If antigen contains multiple proteins, resulting
polyclonal antibodies recognize ______
multiple antigens
sometimes polyclonal antibodies are made to
_______on a single particle (viruses)
multiple proteins
monoclonal antibodies can recognize _____
single epitope on a single antigen
monoclonal antibodies is made from ____
a single-antibody producing cell
Monoclonal antibodies = ___ regions
single region (within a protein)
monoclonal antibodies are only able to recognize _____
one thing
monoclonal antibodies offer us _____
specificity
production of monoclonal antibodies method? benefit?
1) Produce and select hybrid of myeloma (cancer)and B cell that produces desired antibody»_space;hybridoma
2) Screen for hybridomas that produce
antibody of interest (ex. binds organelle, structure or protein of interest)
3) Each hybridoma produces one unique
antibody
Benefit: Do not need highly purified antigen to produce monoclonal antibodies
monoclonal antibodies uses
1) infectious disease
2) diagnostic tool
3) bioengineering
ZO1 protein at TJ is a ___
large peripheral membrane protein
ZO1 protein & co-immunoprecipitation & Western Blot helps us to ____
identify other proteins associated with TJs
Western blot tells you that ____
those two proteins interact but not where they interact
Transmembrane proteins that are associated with TJs are ____
occludin or claudin
Trans-epithelial resistance (TER)
the measurement of electrical resistance across a cellular monolayer
TER is used to confirm the ____
the integrity and permeability of the monolayer
Trans-epithelial flux is a measure of _____
transit across an epithelium
↑ TER = ____ trans-epithelial flux
↓
scrambled protein helps us to determine if protein action is ___
sequence -specific
↑ trans-epithelial flux = ___ TER
↓
Loss of resistance to ion current correlates with_____
increase in flux of small molecules
Junction integrity can be affected by ____
pathogenic microbes
______(e.g. ____) serve as entry factors for some viruses but they may not affect ____
Claudins
CLDN1
function of TJ
WNV (West Nile virus) infection targets a subset of ___, reducing ____ and increasing ___
Tight Junction proteins for degradation (claudins)
TER
trans-epithelial flux
WNV-induced degradation of tight junction proteins involves ___ and requires ___
endocytosis
dynamin
