ECM and Integrins

Question 1

what is the extracellular matric

Answer 1

meshwork of proteins that provides strength
secreted and assembled by local cells
found in ALL multi-cell organisms

Question 2

what are integrin receptors

Answer 2

transmembrane receptors that link the ECM and the inside of cells

Question 3

how are integrin receptors activated

Answer 3

inside out: GCPR and tyrosine kinase receptors activate talin which binds to integrins and activate them

outside in where a ligand binds to the heads of integrins and causes conformational change

Question 4

what are the components of the ECM

Answer 4

GAGs
proteoglycans
both are large and negatively charged which is important for keeping the ECM hydrated and able to withstand compressive forces

Question 5

what are the functions of the ECM

Answer 5

selective sive: poor size, charge density to regulate cell/molecular trafficking
regulate chemical signaling
regulate secreted proteins
co receptors

Question 6

what is the most abundant fibrous protein

Answer 6

collagen

Question 7

how is collagen formed

Answer 7

by local cells, pro collagen chain is formed, then hydroxylation and glycosylation then three chains form, then they form a triple helix and get secreted from the cell, then the pro peptide gets cleaved, they aggregate and assemble fibrils

Question 8

how do cells contribute to collagen formation

Answer 8

altering gene expression, protein turnover, secretion of collagen-interacting proteins that aid in organization

Question 9

what are examples of collagen-associated diseases

Answer 9

scurvy (vitamin C deficiency)

osteogenesis- brittle bones

Question 10

what do elastic fibers provide

Answer 10

provide tissues with resilience

rich in lysin and proline and able to stretch 1.5 times original size

Question 11

what is fibronectin

Answer 11

large glycoprotein important for ECM-cell interactions

has and RGD sequence important for integrin binding

Question 12

what is the basal lamina/basement membrane

Answer 12

thin, flexible sheet of ECM that underlies all epithelial cells
surrounds muscle and Schwann cells

Question 13

what is the basal lamina made up of

Answer 13

laminin, collagen perlecan,

Question 14

what is the function of the basal lamina

Answer 14

1. provides mechanical support
2. selective filter
3. compartmentalizes tissues to protect from harsh environments
4. scaffold during tissue regeneration

Question 15

what is the purpose of protein turnover

Answer 15

necessary for tissue repair, remodeling, adaption to stress, proliferation and migration

Question 16

what are the two classes of proteases for ECM degradation

Answer 16

matrix metalloprotease

serine proteases

Question 17

how are the protease activities regulated

Answer 17

local activation: secreted then cleaved when needed

receptor bind to confine activation

secretion of inhibitors

protease specificity

Question 18

explain focal adhesion assemble

Answer 18

integrins are activated by binding talin, adaptor proteins are recruited and bind to talin exposing the binding site for FAK. Fakir’s, a tyrosine kinase binds and clusters multiple FAKs which cross phosphorylate and expose docking sites for other signaling proteins