Growth Factors

Question 1

How does the processing of PDGF A and B vs C and D differ?

Answer 1

A and B - pp chain synthesis and assembly inactive disulphide linked diners in ER AND proteolytic cleavage in Golgi.

C and D - secreted via exocytosis as inactive diners and proteolytically cleaved extracellularly.

Question 2

What growth factor is sis linked to?

Answer 2

Derived fromB chain of PDGF
cells transformed with sis secrete functional PDGF (BB)

Only transforms cells with PDGF receptors (inappropriate expression - cells with receptors now make ligand)

Question 3

How is EGF discovered?

Answer 3

1960s Stanley cohen
Mouse submandibular gland extracts painted onto early foetal eyelids and incisors
Both opened / erupted early.

Question 4

How is TGF-B synthesised?

Answer 4

Covalently linked to LAP
SS removed in Golgi 
Disulphides bond homodimer forms 
Secreted into ECM
RGD sequences on LAPs can bind integrins
Further sequestered by additional latent TGFB binding protein - large latency complex.

Question 5

What is a member of the TGF-a family and what comprises the TGF-b family?

Answer 5

EGF

activins, BMPs, inhibins.

Question 6

How is TGF-B involved in cell adhesion and tissue repair?

Answer 6

Upregulates adhesion in CT, epithelial, blood cells by increasing integrins receptor expression, ECM protein expression and inhibiting ECM degradation.

Stored in platelets, a chemoattractant for WBCs and induces new vessel formation.

Question 7

Describe the synthesis of HGF.

Answer 7

Synthesised as inactive 728 as peptide.
Pro-HGF localised to cell
Surface or in ECM.
Cleaves into mature ab heterodimer by serum components. 
Heterodimer linked by disulphides bond 
Circular Kringle domains mediate ppis.

Question 8

What is IFN-y?

Answer 8

Released by virally infected cells

Directly activates macrophages and NK to interfere with viral replication.

Question 9

What are interleukins?

Answer 9

Promote immune function.
Majority synthesised by helper T lymphocytes
Act on haematopoietic cells.