Transcript S1.Cell Signaling-Introduction to the MAPK pathway

Cell Signaling Pathways – A Case Study
Approach
By L. Emtage, L. Bradbury, N. Coleman, D. Davenport, A.
Dunning and J. Grew
Signaling: An overview
Signal
Receptor
Cell Membrane
Relay Molecules = signaling proteins
Output : effectors
Slide adapted from NESI 2012
Signal
The Receptor Tyrosine Kinase (RTK)
– MAP Kinase pathway
RTK
Plasma membrane
Grb2 Sos (Ras GEF)
(adapter)
Ras
GTP
MAPKKK
P
MAPKK
P
MAPK
Ras
GD
P
(G protein)
Optional Clicker Questions:
1. In the MAP kinase pathway, phosphorylation serves to:
A. Turn off the pathway
B. Inhibit the next component in the pathway
C. Activate the next component in the pathway
D. Prevent further phosphorylation of downstream components.
Optional Clicker Questions:
2. G proteins are described as molecular switches because:
A. G proteins can be turned on and off by Sos.
B. G proteins can activate or inhibit downstream components.
C. G proteins can activate different downstream components depending on
whether they are bound to GDP or GTP.
D. G proteins have inherent GTPase activity and will turn themselves off by
hydrolyzing GTP to GDP.
Optional Clicker Questions:
3. If a MAPKKK is lost due to homozygous mutation in the MAPKKK gene:
A. The pathway will function normally.
B. MAPK can still be activated if enough ligand is present.
C. MAPK cannot be activated regardless of the presence of ligand.
D. The pathway will be always active.
Signal
The Receptor Tyrosine Kinase (RTK)
– cell survival pathway
RTK
Plasma membrane
PI3 Kinase
PIP3 PDK1
P P P
PIP3
P P P
P
Akt
P
BAD
BAD
Apoptosis
Bcl2
Bcl2
Optional Clicker Questions:
4. Akt…..
A. prevents apoptosis (promotes cell survival) by inhibiting an inhibitor of Bcl2.
B. is a kinase that activates Bcl2 by phosphorylation.
C. promotes apoptosis but is inhibited by PDK1 phosphorylation.
D. is a phosphatase, and inhibits apoptosis by dephosphorylating PDK1 targets.
Optional Clicker Questions:
5. If all Akt activity is lost due to homozygous mutation in the AKT gene:
A. The pathway will function normally to inhibit apoptosis.
B. The pathway can still be activated if enough ligand is present.
C. The pathway can never be activated regardless of the presence of ligand, and
the cell will undergo apoptosis.
D. The pathway will be always active, and the cell will not undergo apoptosis even
under appropriate conditions (the absence of the ligand).
Example: SCF and Kit activate MITF in melanoblasts
SCF
Plasma membrane
Kit
Grb2 Sos (Ras GEF)
(adapter)
Ras
GTP
Ras
GD
P
RAF
(MAPKKK)
P
MEK
(MAPKK)
P
ERK
(MAPK)
P
P
(G protein)
Case Study: Tiger Syndrome
Instructions:
• Read the text carefully
• Think-Collaborate-Share (work in groups of approx. 4)
• Write or draw your group’s answer down (to be collected)
• You have 20 minutes to complete the activity
Signal
Case Study: Tiger Syndrome
RTK
Plasma membrane
Grb2 Sos (Ras GEF)
(adapter)
Ras
GTP
Ras
(G protein)
GD
P
Raf
(MAPKKK)
P
MEK
(MAPKK)
P
ERK
(MAPK)
Case Study: Tiger Syndrome
a) How do you think the T266K mutation in Sos might alter its activity?
b) How does this affect the upstream components of the MAP kinase pathway?
And the downstream components?
Signal
Case Study: Tiger Syndrome
RTK
Plasma membrane
Grb2 Sos (Ras GEF)
(adapter)
Ras
GTP
Ras
(G protein)
GD
P
Raf
(MAPKKK)
P
MEK
(MAPKK)
P
ERK
(MAPK)
Case Study: Tiger Syndrome
c) The other five individuals do not have mutations in RAF or Sos. Which
components of the pathway would you sequence next? Why?
Signal
Case Study: Tiger Syndrome
RTK
Plasma membrane
Grb2 Sos (Ras GEF)
(adapter)
Drug
Ras
GTP
✕
Ras
(G protein)
GD
P
Raf
(MAPKKK)
P
MEK
(MAPKK)
P
ERK
(MAPK)