Shemanko lecture 3

Question 1

What is the glyocalyx?

Answer 1

Is the buffer before you see the extracellular matrix proteins around the cell, is a cell coat

Question 2

What are the features of glycoalyx? What is it’s roles?

Answer 2

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

Question 3

What is the ECM?

Answer 3

It extends past the immediate vicinity of the plasma membrane and consists of secreted proteins.

Question 4

Where do we find ECM in tissues?

Answer 4

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.

Question 5

How does the ECM in cartilage cells function?

Answer 5

It acts a barrier between the cartilage cells and red blood cells

Question 6

If cells need to move to get to a cartilage cell what does it do to the ecm?

Answer 6

Can digest it and then send signals back to the cartilage cell and change it’s behaviour

Question 7

Integrins come in which form?

Answer 7

as a pair with an alpha and beta

Question 8

When integrins are inactive what happens? What happens when they’re active? How do they activate

Answer 8

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

Question 9

What is inside out and outside in signalling of integrins?

Answer 9

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.

Question 10

How do integrins bind to extracellular matrix?

Answer 10

They have an RGD binding site, and binds to proteins that RDG peptides (Arg-Gly-Asp) are a part of.

Question 11

What does the basement membrane (ECM of epithelial cells) send critical signals for?

Answer 11

It sends critical signals for survival, orientation, and differentiation

Question 12

Why don’t breast cancer cells coagulate in ECM?

Answer 12

Because they don’t have junction molecules that interact with ECM to coagulate.

Question 13

What are the four different type of ECM proteins?

Answer 13

Collagen
Proteoglycans
Fibronectin
Laminins

Question 14

What is the structure of collagen?

Answer 14

Is a triple helix of 3 alpha helical chains, has a rope like structure

Question 15

Where is collagen found?

Answer 15

present in only extracellular matrixes

Question 16

What produces collagen?

Answer 16

Collagen is produced by fibroblasts which are found in connective tissues and are in the dermis below the basement membrane

Question 17

What does collagen bind too?

Answer 17

integrins

Question 18

What is collagen important for?

Answer 18

strength of tissues

Question 19

What are proteoglycans common in?

Answer 19

they’re common in cartilage, give cushioning effect

Question 20

What structural features of proteoglycans give it’s cushioning properties?

Answer 20

They bind a lot of cations which bind water mlcls to form a porous hydrated gel, have feather like structure

Question 21

How do collagen and proteoglycans work together to provide ECMs strength and resistance?

Answer 21

Collagen resists pulling forces and form a scaffold for proteoglycans, this then provides ECM strength and resistance.

Question 22

What is the structure of proteoglycans?

Answer 22

Has a core protein of hylauronic acid which is connected to multiple covalently attached GAGs

Question 23

What do proteoglycans bind too?

Answer 23

numerous ECM components, cell surface receptors (ex: integrins)

Question 24

What is the structure of fibronectin molecules?

Answer 24

it consists of two similar polypeptides joined by a pair of disulfide bonds, each peptide has distinct modules (binding domains)

Question 25

What does fibronectin bind too?

Answer 25

It binds to multiple ECM components (through it’s binding domains) and binds to cell surface receptors

Question 26

How does fibronectin bind to integrins?

Answer 26

Through the RGD loop in fibronectins that stick up and bind to integrins RGD binding domain

Question 27

What is the structure of laminin molecules?

Answer 27

these are glycoproteins made of 3 different proteins linked by disulfide bonds, have cross like shape

Question 28

What do laminin molecules bind to?

Answer 28

They bind to cell surface receptors, other laminins, to proteoglycans, and other basement membrane proteins and collagen

Question 29

What functions are laminins involved in?

Answer 29

migration, growth, and differentiation (specialization), strengthen basement membrane, develop neuronal outgrowth

Question 30

Do laminin and collagen form interconnected networks?

Answer 30

yes

Question 31

What role does laminin play in embryogenesis?

Answer 31

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