L8. ECM Flashcards
What is the function of the ECM?
provide structural support for cells to organize into tissues
all tissues need ECM to assemble
What is the ECM
- composed of proteins and polysaccharides
2. substance secreted by cells into their outside environment
What does the ECM do?
- gives structural support
- regulates growth and development of cell
- regulates migration of the cell
- signals that regulate cell survival
- forms adhesive contacts with the cell
- modifies cell shape and function
- directs proliferative activity
What are the 2 types of ECM?
- Basement Membrane
2. Connective tissue
What is the connective tissue composed of?
- fibers
2. ground substance
What is the function of ground substance in connective tissue?
- resist compression
2. permits diffusion of nutrients and waste between cells
What is the function of fibers in connective tissue?
provide structural support
What are the 2 proteins that make fibers
collagen +elastin
what is ground substance
kelly like
made up of water,electrolyte , polysaccharide and proteins
How many collagen genes are there in humans
29
Describe collagen
- flexible,strong resistant to stretching
- main protein in the ECM
- major body protein
- made of 3 intertwining fibers: tropocollagen ( alpha helical)
Name 2 GAGs
- heparin
2. hyaluronic acid
What is hyaluronic acid?
- huge and abundant GAG
- only GAG that indirectly binds to proteins
- good lubricant found in joints
- involved in wound repair, cell migration, inflammation
What causes MPS (mucopolysaccharidoses)
inability to break down GAGs
What is fibronectin?
a GP; needed for blood clottting
what is aggracan
PG ; found in cartilage
draw how hyaluronic acid binds to collagen
associates with link proteins ( L8, pg 11b)
what do fibroblasts secrete
they secrete precursors for BOTH collagen and the ECM.
What is the basement membrane
interface between the epithelial cells and the connective tissue
What are the 2 distinct parts of the basement membrane
- basal lamina ( made by epithelial cells)
2. reticular lamina (made by CT)
What are the 2 layers of the basal lamina ?
- lamina lucida
2. lamina densa
What is the lamina lucida, what does it contain
(part of the basal lamina of the basement membrane)
GP laminin and GP integrins
What is integrin
A Glycoprotein
Name some PG
aggracan, perlecan
Paul Gifted A Pelican
Name some GP
fibronectin,laminin, integrins
God Paul Licked Fido’s Intestines
What is the lamina densa, consists of?
(part of the basal lamina of the basement membrane)
collagen 4
PG perlecan
GAG heparan
What is the functin of laminins
A GP that binds collagen and integrins - bridge between both layers
What does the reticular lamina contain?
collagen 1 and 3
anchoring fibrils
GP fibrillin
Draw the relation between the BM, epithelial cells and CT ( add the basal lamina ( lamina lucida and lamina reticular) and the reticular lamina)
pg 14a
What are the functions of the BM?
- provide structural support
- anchor the epithelium ( firm +flexible)
- molecular filter for the epithelium
What is alport syndrome?
lost of collagen 4
How is the ECM attached to cells
junctional anchoring transmembrane protein
link to cytsokeleton via cytoskeletal linkers with adhesion complex
What are the 2 types of integrin, how many of each
the 2 PG : alpha (18) and beta (8)
What composes a functional integrin
an alpha and beta integrin
What determines the function of the integrin heterodimer
the individual alpha beta subunits that compose the dimer
Draw the integrin adhesion complex
(pg 17a)
describe focal contacts, which cytoskeleton do they link to
link to actin filaments
made up of integrins
composed of a variety of integrin heterodimers
Describe hemidesmosomes, which cytoskeleton do they link to
feature of epithelial cells
binds to lamina lucidia
link to intermediate filament
made up of a6b4 integrin
What are the 2 modes of integrin activation?
- intracellular: integrin bind proteins inside the cell and convert it to high affinity
- extracellular: integrin bind to ECM proteins converts it from low affinity to high affinity
What are the 4 functions of integrin?
- cell migration
- would healing
- neuron path finding
- immune function - cell signalling
- cytoskeletal organization (because of link to junctional proteins)
- stable adhesion
- muscle tendon attachemnt
- attachment to diff skin layers
What causes junctional epidermolysis bullosa?
loss of integrin
What is collagen 4 in the BM used for
- part of the lamina densa ( and part of reticular lamina)
What collagen makes anchoring fibrils
collagen 7