Inositol-phospholipid signaling pathway

Question 1

Inositol-phospholipid signaling pathway

Answer 1

• Receptor R1 vings to a ligand which activates a G-protein-> Gq
• Gq then activates PLC
• PLC hydrolyzes PIP2 producing DAG and IPG
• IPG diffuses to the ER where it binds to Ca2+ channel which cause the channels to open and Ca2+ enters the cell
• Ca2+ activates Ca2+-dependent protein kinases
• PKC then binds to DAG which activates them
• PKCs phosphorylate target proteins-changing their activities

Question 2

Adenylyl Cyclase Signaling Pathway

Answer 2

• Stimulatory Hormone binds to the stimulatory receptor, which activates it
• Stimulatory receptor then activates a G-protein (Gas)-GTP
• Gas-GTP activates Adenylyl cyclase which synthesizes cAMP
• cAMP then binds to PKA which releases C subunit from R subunit and activates the PKA
• PKA then phosphorylates target proteins at Ser, Thr which activates them

Question 3

Adenylyl Cyclase Signaling Pathway Inhibtion

Answer 3

• An inhibiting hormone binds to a receptor (Ri) which activates Gia by stimulating exchange of GTP in place of GDP
• Gia-GTP inhibits adenylyl cyclase and subsequent steps are reversed

Question 4

Receptor Tyr Kinase Signaling

Answer 4

(insulin Receptor)

• work with growth factors and insulin
  1) tyrosine kinase domains of the receptor in the inactive state are separated, but once the ligand binds a conformational change brings them together and there is a autophosphorylation
• in the insulin pathway: the insulin receptor phosphorylates IRSs-these activate a number of kinases involved in nutrient utilization
• one of the IRSs activates PIP2
• PI phosphorylates PIP2 to PIP3
• PIP3 activates PIP3-dependent protein kinases