adhesion and ecm Flashcards
what are the 6 connective tissue cells?
- fibroblasts
- myofibroblasts
- blood derived products
- osteoblasts
- chondroblasts
- adipocytes
what 2 things combine to make polysaccharides?
glycosaminoglycans and specific proteins
what is the ecm made from
fibrillar proteins - elastin, collagen, laminin, fibronectin.
GAGS
fibroblast function
synthesis and secrete collagen, elastin, proteoglycans
why is collagen secretion special?
- because collagen is packaged into specialised large vesicles in the RER.
- secretion occurs by exocytosis at specialised sites.
what is the membrane tube that collagen is produced in?
fibropositor
where are elastic fibres secreted from?
fibroblasts
smooth muscle cells
chondroblasts
how does elastin recoil?
it recoils because of its hydrophobic effect, it wants to recoil when it is stretched because its hydrophobic fibres are exposed to aqueous environment.
proteoglycan function?
- matrix support (cushioning/hydration)
- glue like function
what will intern attach to?
it is a transmembrane protein that will attach to fibronectin on the outside and an adaptor protein on the inside.
describe GAGs
- they are long chains of repeating disaccharide units.
- highly charged and highly hydrated.
what does hyaluronic acid do?
it links between the ecm and cytoskeleton. (across the plasma membrane)
what will collagen and proteoglycans link too?
fibronectin
what are the 2 functions of myofibroblasts?
fibroblast like- secretes collagen
smooth muscle like - synthesises collagen, myosin and desmin.
what is myofibroblasts involvement in tissue damage?
- proliferate
- secrete collagen for scaffold
- consolidate damage area (fibrous scar)
- contract (reducing the size of the damaged area)
how to myofibroblasts differentiate from fibroblasts?
they have different mechanical tension especially during wound healing.
granule content of mast cells?
heparin and histamine
plasma cells?
they produce antibodies through the secretory pathway
3 functions of adipocytes?
- insulation
- packing
- energy store
describe the shape of adipocytes?
they have a large lipid droplet with a peripheral cytoplasm and a squished nucleus.
what happens when adipocytes are paraffin embedded during staining?
the lipid will be lost during the processing
what can a mutant ob gene cause?
- excessive eating
- obesity
in mice with a mutant ob gene are injected with lectin, what happens?
they loose weight as their eating is curbed.
leptin
stop eating hormone
function of white fat
- energy store but it is extremely dynamic.
- produces adipokines (leptin)
function of adipokines?
they regulate nutritional balance and other systems.
why does leptin increase in fat people?
fat people have more leptin because they have a tissue defect, they have to produce more leptin to get the same response as another person. (resistance to leptin on obesity)
what does cell junctions and adhesion proteins do (over all)?
link cells to other cells and to the ecm
from top to bottoms, what are the main cell junction?
- tight junctions
- adhesion junctions
- desmosomes
- gap junctions
- hemidesmesomes
what are the 3 types of cell adhesions cells?
integrin
selectin
CAM
tight junctions
- define polarity as they fence off lipids and proteins
- control the passage of substances
- can link to actin
how does the permeability differ between cells?
because tight junctions are made of claudins (there are 24 different ones) so different Claudins= different permeability of the epithelium.
what does adherens junctions do?
they will anchor the actin filaments to the membrane
what 2 things will the adherens junction use intracellulary to bind to the actin filament? (anchor proteins)
catenin and vinculins
what will adherens junctions use extraceullarly to bind?
cadherin
are there different types of cadherin?
yes, each cadherin provides cell adhesion in different tissue.
E-cadherin
epithelia
N-cadherin
neurons and heart muscle
P-cadherin
placenta and epidermis
VE-cadherin
endothelial cells
desmosomes
they link between strong intermediate filaments in adjacent cells
in desmosomes what what do cadherin proteins bind to?
- adjacent cadherin
- cell membrane
- intracellular plaque glycoprotein
hemidesmesomes
- they link the outside of the cell through transmembrane proteins (integrins) to the cytoskeleton (intermediate filaments)
- they are more stable than focal adhesions
- link laminin to bm
symptoms of duchenne muscular dystrophy
muscle weakness
muscle wasting
damage to muscle fibres due to muscle tearing.
treatment for DMD?
PTC 124 (ataluren) though to override the premature stop codon to produce
what transition will carcinoma cells undergo?
they will undergo epithelial to mesenchymal transition
what happens in micro invasion
- reduced expression of cadherin due to the transition to mesenchymal cells (no longer epithelial)
- protrusion called invadopedia
- secretion of metalproteases
- bm breached
- tumour cells express integrin promoting interaction with non epithelial cells during movement.
what happens in metastasis?
where are gap junctions found
cardiac muscle
desmosomes bing to a glycoprotein plaque intracellularly, what is this plaque made of?
desmoplakin
plakoglobin
function of gap junctions
- communication
- make a hydrophilic Chanel
- allowing small molecules to pass
- coordination of function
what is cytoplasmically anchored to the plaque in desmosomes?
keratin filaments
what happens during metastasis
- the autocrine motility factors from the tumour increase the motility and decrease E-cadherin
- angiogenesis factors promote vasularisation allowing entry into bv and lymphatics
duchenne muscular dystrophy
lack of dystrophin adaptor protein due to a nonsense mutation causing the premature termination of translation
focal adhesions function
- they link the outside of the cell with the cytoskeleton (actin) via integrin transmembrane proteins.
- they can act as signalling platforms.
what are the cadherins made of in desmosomes
desmocollins
desmogleins
what are gap junctions made of
6 connexions (they all have a central hydrophilic pore)
