Cell Adhesion and Cell Junction Flashcards
get along
why do we need to study cell adhesion
- need to dissociate cells in order to study them
- spontaneous cell sorting interested scientists
cell adhesion vs. cell junction
- cell adhesion are membrane proteins that bind and offer mechanical adhesion
- cell junction are aggregates of transmembrane, intracellular and have other functions like communication
major differences between cell adhesion and cell junction
complexity and size
transience and stability
functional classification of cell junction
- anchoring junctions
- occluding junctions
- channel forming junctions
- signal relaying junctions
what are the types of anchoring junctions based on attachment sites
actin = adherens (cell-cell) or actin-linked cell matrix adhesions
intermediate filament=
desmosomes (cell-cell)
hemidesmosomes (cell-matrix_
what are the adhesion molecule involved in adherens junctions
classical cadherins
what are the adhesion molecules associated with desomomes
desmosomal cadherins
what are adhesion molecules for focal adhesions
integrins
what are some experiments to measure cell adhesion
dual pipette assay
flipping assay
AFM assay
FRET
how can we visualize junctions
EM, freeze fracture and transmission
steps in preparing freeze fracture
- tissue fixation and cryoprotection
- freezing
- fracturing
- optional etching
- replication
- cleaning of replica to be viewed via EM
what are the two faces visualized in freeze fracture
E (ectoplasmic) face
P (protoplasmic face)
what do occluding junctions do
restrict passage of molecules between cells
ex: tight junctions
how do occluding junctions help maintain polarized localization of membrane proteins
they control the direction of molecules like glucose
what are the proteins involved in anchoring junctions
- transmembrane adhesion proteins
cadherions/integrins - intracellular adaptor proteins
actin and intermediate filaments
how does calcium affect cadherions
it binds in-between the cadherin repeats and aligns them in a tighter, straight line
explain mechanotransduction in adherens junctions
the tension of a near by cell pulls on the cadeherin creating tension nd recruiting actin intracellularly
what is the difference between hemidesmosomes and desmosomes
desmosomes connect cell to cell and hemi- connect cell to matrix, but both interact with intermediate filaments
what are focal contacts
link actin to ECM
important in wound healing
uses integrins and binds to various ECM proteins
what are selectins
adhesion molecules that aren’t involved in junctions
mediate weak adhesion
ligands are specific carbs
rapidly deployed
utilized in implantation of embryo and adhesion of leukocytes
what is the structure of selection and actin attachment
lectin domain binds EGF domain bind P-selectin in extracellular space. selection is transmembrane and binds anchor proteins and actin in the cytosol
what is extravasation
the weak adhesion and rolling of white blood cells (selection dependent) then slipping out into the tissue through strong adhesion and emigration (integrin dependent)
