Lecture 25 - Cell Communication 2

Question 1

What variation of the GPCR pathway is associated with Gαq or Gαo binding to GPCR?

(L25 S7)

Answer 1

• phospholipidase C is the target effector
• phospholipidase C cleaves membrane protein PIP2 to form IP3 (soluble) and DAG (membrane bound) second messengers
• IP3 binds IP3 gated calcium channel on ER
• calcium binds DAG allowing it to activate PKC

Question 2

What is a receptor tyrosine kinase and what does it do?

Answer 2

• enzyme linked receptor that responds to GROWTH FACTORS
• binding of ligand causes DIMERIZATION and AUTOPHOSPHORYLATION
• binding of Grb2-SOS-Ras-Raf
• activation of MAP KINASE CASCADE which causes cell PROLIFERATION

Question 3

What is a JAK-STAT receptor and what does it do?

Answer 3

• ligand binds receptor and causes dimerization
• receptors bind JAKs which phosphorylate one another
• JAKs phosphorylate receptor causing STAT to bind
• STAT is phosphorylated and dimerize becoming active
• STAT bind DNA and caused gene translation causing erythropoietin

Question 4

What is hereditary hemochromatosis and what causes it?

Answer 4

• autosomal recessive disease caused by mutation of HFE gene
• mutation of HFE gene prevents Hfe binding to TfR2 (transferrin receptor)
• prevents hepcidin expression which acts to inhibit ferroportin (imports iron into blood)
• results in iron overloading