lecture 6- growth factors and receptors

Question 1

1) What is PDGF and name 2 functions of growth factors

Answer 1

Platelet Derived Growth Factor

- proliferations and migration of cells

Question 2

2) What type of protein is Src? What is Src’s main function? State the residue Src phosphorelates.

Answer 2

• Src is a protein kinase (removes phosphate group from Atp and transfers it to suitable protein substrate) and phosphoprotein (it carries phosphate groups).
• Phophorelates tyrosine residues

Question 3

3) Protein Kinases may phosphorelate many proteins, name 4 protein kinases and state what end result occurs within the cell.

Answer 3

• Gsk-3beta proliferation
• Hif-1alphaangiogenesis
• Badapoptosis
• TSC2protein synthesis

Question 4

4) What is the main function of the EGF-R and what does it stand for? What class of receptor does EGF-R fall under?

Answer 4

• functions similarly to Src, is it a tyrosine kinase
• has a region on homology with src
• Epidermal growth factor receptor
• tyrosine kinase receptor

Question 5

5) There are many ways that receptors may become deregulated and have oncogenic characteristics. Name 3. Also, describe what paracrine signaling is and whether it is normal for cells to do it or not.

Answer 5

• truncated extracellular structure, no ligand, always firing signal
• overexpression of receptors
• autocrine signaling
• paracrine signaling means the ligand and receptor are from different cell origins and it is found in normal cells.

Question 6

6) Name 3 ways to get over expression of protein.

Answer 6

• too many gene copies
• poly-a tail on mRNA is too long
• protein destruction becomes inhibited

Question 7

7) Name 3 distinct characteristics of Tyrosine Kinase receptors.
How may these receptors dimerize independently of ligand?

Answer 7

• dimerize
• transphosphorelate
• receptors move freely along the membrane
• Since they move freely they may collide and cause transphosphorelation, and the signal cascade for proliferation

Question 8

8) How are cytokine receptors similar to Tyrosine Kinase receptors? How are Transforming Growth Factor beta (TGF-beta) different from tyrosine kinase receptors? What is TGF-betas main function?

Answer 8

• cytosine kinases transphosphorelate
• TGF-beta= don’t transphosphorelate and have serine and threonine kinase domains, not tyrosine
• main function in normal cells is to slow proliferation and increases invasiveness in transformed cells.

Question 9

9) What type of transformation are notch receptors most common in and in what type of cancers are they mostly found?

Answer 9

• Contributes to the Ras mediated cell transformation

- found in leukemias

Question 10

10) How does the patched-smoothened signaling work?

Answer 10

• The Hedgehog ligand binds to patched, moves it away from smoothened receptor, then smoothened sends signal to the cytoplasmic complex to release the transcription factor that translocates to the nucleus, causing transcription of the target genes.

Question 11

11) Describe way the Wnt signaling system work, include the terms APC, GSK-3beta and Beta catenin.

Answer 11

• Wnt=ligand
• when no wnt= APC and GSK-3beta are active. GSK-3beta phosphorelates beta catenin and targets it for destruction by enzymes.
• When wnt binds to the frizzled receptor disheveled becomes active and GSK-3B is inactive, leaving B catenin intact allowing to do its function (increases proliferation).

Question 12

12) Describe what non-canonical Wnt signaling is and how the pathway works.

Answer 12

• uses G proteins

- Wnt binds to frizzled receptor and activates the G-proteins.

Question 13

13) How does lipid based molecule signaling work?

Answer 13

• they may travel through the membrane

- act as transcription factors or coactivators of transcription.