CBG Lecture 38: Extracellular Matrix Flashcards
define ECM - extracellular matrix
complex network of polysacchs and proteins secreted by cells for strengthening tissues
what is a cell junction
directly links cells together in flexible tissues
what are the two types of animal tissue
connective
epithelial
what are the two main types of extracellular molecules that make up the matrix
GAGs - gycosaminoglycans
Fibrous proteins - collagen,lamins,elastin,fibronectin
what are GAGs
glycosaminoglycans
extracellular molecules that make up the matrix - usually found covalently linked to protein in the form of proteogylcans
what are proteoglans
GAGs - glycosaminoglycan polysaccharide chains usually found covalently linked to protein
name some fibrous proteins
collagen
laminin
elastin
fibronectin
what are epithelial sheets
sheet of cells covering surface of tissue which creates a barrier for multicellular orgs
what are the four main structures of cell
- epithelial tissue
- basal lamina
- connective tissue
- collagen fibres
what are the different epithelial tissues
simple stratified columnar cuboidal squamous
how are epithelial sheets polarised
have two faces: apical (exposed) and basal (rests on connective tissue)
what is basal end of epithelial sheet supported by
basal lamina - thin sheet of ECM
what is basal lamina composed of
type 4 collagen and laminin
what is laminin
links integrin - in the plasma membrane of epithelial cells - to CT (like fibronectin)
what links integrin to connective tissue
laminin
what is a cell-cell junction
connection between 2 cells or between cell and ECM
separates apical/basal surface and helps in cell-cell communication
give the names of cell-cell junctions
tight junction adherens junction desmosome gap junction hemidesmosome
what is the function of a tight junction
seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them
what is an adherens junction
joins an actin bundle in one cell to a similar bundle in a neightbouring cells
what junction seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them
tight junction
what junction connects actin bundle in one cell to a similar bundle in neighbouring cells
adherens junction
what is a desmosome
joins the intermediate filaments in one cell to those in a neighbour
what joins the intermediate filaments in one cell to the intermediate filaments of a neighbour
desmosome
what is a gap junction
forms channels that allow small water soluble molecules including ions to pass from cell to cells
what junction provides channels that allows small water soluble molecules including ions to pass from one cell to another
gap junction
what is a hemidesmosome
anchors intermediate filaments in a cell to the basal lamina
what anchors intermediate filaments in a cell to the basal lamina
hemidesomosome
what are CAMs
cell adhesion molecules
how to cells adhere to other cells
via transmembrane cadherin molecules that are connected to the cytoskeleton via linker proteins
what are the major families of cell adhesion molecules
- cadherins
- Ig-superfamily
- integrins
- selectins
name some cadherins
E-cadherins - has calcium binding sites
what do integrins contain
fibronectin
what do selectins contain
sugars
lectins
glycoproteins
what do spatial and temporal expression of CAMs regulate
adhesion
what are the roles of CAMs
proliferation
migration
differentiation
fighting infection - movement of WBCs
why is it so important to have CAMs
disruptions in cell-cell interactions have devastating effects on embryo development
cancer metastasis
what are the models for generating cell-cell adhesion
homotypic (cis)
homophilic
heterophilic (trans)
outline cell-cell adhesion via homophilic binding
molecules on one cell bind to other molecules of the same kind on adj molecules
outline cell-cell adhesion via heterophilic binding
molecules on one cell bind to molecules of a different kind on adj cells
outline cell cell adhesion by binding through an extracellular linker
cell surface receptors on adj cells are linked to one another by secreted multivalent linker molecules
how do cadherins link cells
via the homophilic mechanism - calcium dependent
the longer CAM = stronger the chain
what conformations do integrins exist in
low affinity - inactive
high affinity - active
what do integrins do
mediate cell-adhesion to the ECM by bridging between ECM and cytoskeleton
what is the level of adhesion of a cell affected by
the expression level on integrin cell surface
what is the basal lamina
thin mesh of ECM molecules - important in tissue repair and development
what does the basal lamina contain
multiadhesive matrix proteins
laminin (interact with integrins @ hemidesmosomes)
type 4 collagen
perlecan - proteoglycan - bind diverse partners, crosslink components
what are main components of basal lamina
type 4 collagen
laminin
entactin
perlecan
name some connective tissue
tendon -tough and flexible
bone -hard and dense
cartilage - shockabsorbing
soft - jelly in eye
what do various types of CT depend on
collagen
what are collagen fibrils organised into
bundles
discuss structure/flowchart of a collagen fibril
single collagen peptide chain -> triple stranded collagen molecule -> collagen fibril -> triple stranded structure
what is collagen rich in
proline and glycine
what is CT release by skin called
fibroblasts
what is CT released by bone called
osteoblasts
how is collagen released by fibroblast
exocytosis
what does fibronectin and integrin do
helps attach CSK to ECM
what are preoteoglycans - what do they do
help resist compression and function as space fillers in ECM
what are GAGs made of
Extra cellular proteins linked to negatively charged polysacchs - glycosaminoglycans -GAGs
