Shemanko lecture 3 Flashcards
What is the glyocalyx?
Is the buffer before you see the extracellular matrix proteins around the cell, is a cell coat
What are the features of glycoalyx? What is it’s roles?
Are carbohydrates extending from integral membrane proteins in the membrane
Roles of the glycoalyx: mediate cell-cell and cell-substratum interactions
provide mechanjcal protection to the cells
serve as a barrier
What is the ECM?
It extends past the immediate vicinity of the plasma membrane and consists of secreted proteins.
Where do we find ECM in tissues?
Are in epithelial tissues, ex skin and lining of intenstines etc, but are also found surrounding muscle and fat cells and lines the digestive and respiratory tracts and inner endothelial lining of blood vessels.
How does the ECM in cartilage cells function?
It acts a barrier between the cartilage cells and red blood cells
If cells need to move to get to a cartilage cell what does it do to the ecm?
Can digest it and then send signals back to the cartilage cell and change it’s behaviour
Integrins come in which form?
as a pair with an alpha and beta
When integrins are inactive what happens? What happens when they’re active? How do they activate
They are stuck, when active binding of talin to the beta subunit causes integrin subunits to sperate and extend, talin connects to actin cytoskeleton and transmits signals to help cytoskeleton move
What is inside out and outside in signalling of integrins?
inside-out activation of integrin proteins means that something is effecting integrin within the cell which causes it to activate
Outside in activation- the binding of the substrate by integrins that are outside of the cell send a signal to focal adhesion kinase which starts a signaling cascade to the nuceleus.
How do integrins bind to extracellular matrix?
They have an RGD binding site, and binds to proteins that RDG peptides (Arg-Gly-Asp) are a part of.
What does the basement membrane (ECM of epithelial cells) send critical signals for?
It sends critical signals for survival, orientation, and differentiation
Why don’t breast cancer cells coagulate in ECM?
Because they don’t have junction molecules that interact with ECM to coagulate.
What are the four different type of ECM proteins?
Collagen
Proteoglycans
Fibronectin
Laminins
What is the structure of collagen?
Is a triple helix of 3 alpha helical chains, has a rope like structure
Where is collagen found?
present in only extracellular matrixes
What produces collagen?
Collagen is produced by fibroblasts which are found in connective tissues and are in the dermis below the basement membrane
What does collagen bind too?
integrins
What is collagen important for?
strength of tissues
What are proteoglycans common in?
they’re common in cartilage, give cushioning effect
What structural features of proteoglycans give it’s cushioning properties?
They bind a lot of cations which bind water mlcls to form a porous hydrated gel, have feather like structure
How do collagen and proteoglycans work together to provide ECMs strength and resistance?
Collagen resists pulling forces and form a scaffold for proteoglycans, this then provides ECM strength and resistance.
What is the structure of proteoglycans?
Has a core protein of hylauronic acid which is connected to multiple covalently attached GAGs
What do proteoglycans bind too?
numerous ECM components, cell surface receptors (ex: integrins)
What is the structure of fibronectin molecules?
it consists of two similar polypeptides joined by a pair of disulfide bonds, each peptide has distinct modules (binding domains)
What does fibronectin bind too?
It binds to multiple ECM components (through it’s binding domains) and binds to cell surface receptors
How does fibronectin bind to integrins?
Through the RGD loop in fibronectins that stick up and bind to integrins RGD binding domain
What is the structure of laminin molecules?
these are glycoproteins made of 3 different proteins linked by disulfide bonds, have cross like shape
What do laminin molecules bind to?
They bind to cell surface receptors, other laminins, to proteoglycans, and other basement membrane proteins and collagen
What functions are laminins involved in?
migration, growth, and differentiation (specialization), strengthen basement membrane, develop neuronal outgrowth
Do laminin and collagen form interconnected networks?
yes
What role does laminin play in embryogenesis?
cells that will become germ cells travel from 1 side of the embryo to the other to get to the gonads, during this they use laminins to move
