Lecture 8 Flashcards
What are the 2 types of plasma membrane receptors? Give 2 examples of each
GPCRs
Ex. Chemokines and prostaglandins
RTKs (or Src kinases)
Ex. Insulin (RTK)
Ex. Integrin (Src)
Describe nuclear receptors and give an example.
Inside cell (usually in the nucleus) Can only bind lipid soluble ligands
Ex. Glucocorticoids/Vitamin D
During signal transduction, describe Tyrosine, Serine, Threonine receptors.
They are phosphorylated by Tyrosine, Serine, and Threonine kinases.
What are 3 other modifications for signal transduction?
Ubiquitination
Addition of lipids
Acetylation/methylation
Describe Tyrosine Kinase family receptors. What are the 3 domains they contain?
All are made of SH3, SH2, and PH domains or some combo of them
- SH2 phosphorylation
- SH3: Proline rich peptides
- PH:PI3 or phosphatidylinositol (aka lipids)
What are the 3 types of Tyrosine Kinase receptors?
Src
Syk
Tec
Describe Src tyrosine receptor in terms of their domains. Give 2 examples.
Src (ex. Lyn and Lck)
SH3 domain
SH2 domain
Describe Syk tyrosine receptor in terms of their 2 domains. Give 2 examples.
Syk (Syk and ZAP-70)
SH2 x 2 domains
Describe Tec tyrosine receptor in terms of their 3 domains. Give 2 examples.
Tec (Btk and Itk)
SH2 domain
SH3 domain
PH domain
What activates the Src family and specifically where on the Tyrosine residue?
(There is one spot that can inactivated)
Activated by both phosphorylation and dephosphorylation
Phosphorylated at Tyr416= active
Phosphorylated at Tyr527=inactive
Dephosphorylation at Tyr527
Do adaptor proteins have any catalytic activity?
NO!
What is the main function of adaptor proteins and give an example?
Main Job: Link enzymes and promote assembly of LAT and BLNK
LAT and BLNK needed for proper activation and signaling of B and T cells
What 4 structures do adaptor proteins contain?
Can contain:
SH2 and SH3
Tyrosine residues (will bind SH2 on other cells)
Proline-rich peptides (will bind SH3 on other cells)
What are the 3 adaptor proteins in T-cell activation?
LAT
SLP-76
VAV (recruited by Tyrosine phosphorylation)
Describe the adaptor protein LAT. Where is it and what does it recruit?
Only one in membrane
Recruits PLC gamma and GADS (Similar to GRB2)
Describe the adaptor protein SLP-76. What is it rich in and what does it bind? What does this binding lead to?
Proline rich
Binds with SH3 domain on GADS –> phosphorylation of Tyrosine residue
Describe the adaptor protein VAV. What is it an example of?
Is an example of GEF
GEF will replace GDP with GTP activation of enzymes/TF.
- Actin/cytoskeletal rearrangement
- Transcription changes
What are the 4 components of the TCR?
Alpha Beta TCR
CD3 (x2)- Signal Transducer
Zeta chain- Signal Transducer
CD8 or CD4 coreceptor
Describe CD4 and CD8 coreceptors in TCR complex. What are each composed of and what does CD8 bind to?
CD8 has alpha and beta chains
- Each with 1 Ig domain
- Binds with MHC class I an interacts with Beta 2 microglobulin
CD4 has 4 Ig like domain (variant and heavy chains)
Describe ITAMS. Where is it found. Describe positive and negative selection in terms of ITAMs and TCR signals.
Activating
Found on CD3 and Zeta chains
Number of ITAMs is indicative the affinity of the Ag to the TCR
- Weak TCR signal for self Ag= positive selection - Strong TCR signal for self Ag= negative selection
The longer an Ag is bound to TCR= increased number of active ITAMs
Describe ITIMS. Where are they commonly found?
Inhibit
Commonly found on FcyRIIB (on B cells and myeloid cells)
Describe the process of T-cell activation.
Ag binds TCR and coreceptor (Activates Lck)
Lck phosphorylates ITAMs –> activates ZAP70
Zap70 (type of syk) autophosphorylates after interaction with active zeta chain
Zap70 –> activate adaptor proteins (ex. LAT)
-Activates PLCy 1 or RAS/MAPK
What are the 3 results of PLC pathway activation?
PIP2 binds to PLC and splits it into PI3 and DAG
PKC
- Phosphorylates ikB, which causes dissociation from NFkB
- NFkB –> nucleus
- TF for IL-2 gene production
Increased Ca2+
What does PI3 do after PIP2 binds to PLC and splits it into PI3 and DAG?
PI3 is phosphorylated to cause an increase in Ca2+
What does DAG do after PIP2 binds to PLC and splits it into PI3 and DAG?
DAG is phosphorylated to PKC
What does an increase in calcium cause?
Binds calmodulin
+NFAT–> nucleus (TF for IL-2 gene production)
What 3 ways can you activate the NFKB pathway?
TCR/BCR
TLRs
CD40
What happens after activation of TCR/ BCR, TLRs, or CD40 in terms of NFkB?
Activates IKK, which phosphorylates IKB
Phosphorylation of IkB causes Ubiquitination
IkB normally binds NFkB, but if it is ubiquitinated NFkB is now free
Free NFkB to nucleus –> GENE TRANSCRIPTION
Describe the RAS-MAPK pathway.
Lck –> ZAP70 –> LAT –> GRB2 –> SOS –> Ras-GDP and Ras-GTP
Ras-GTP from the previous step –> MAPK –> AP-1
How do you regulate TCR/BCR signaling? What does this cause and give 3 examples?
Coreceptors
This causes ITAM phosphorylation
CD4 (T cell)
CD8 (T cell)
CR2/CD21 (B cell)
Describe 2 forms of Costimulation that leads to activation of T cells.
CD28 (on T cells)- CD80/86 (aka B7 on APCs)
CD40L (on T cells)- CD40 (on APCs)
Describe 2 forms of costimulation that leads to T-cell inhibition.
CTLA-4- CD80/86
PD-1- PDL1
Describe costimulation that leads to B-cell inhibition.
FcyRIIB (on B cells): CD22
What 2 signals are required for costimulation? And what happens if only one of those signals is found? What does this cause?
TCR= signal 1 CD28= signal 2
Signal 1 only= only NFAT –> decreased ability for IL-2 gene transcription
- NFAT alone stimulation anergy- inducing genes
- These genes inhibit T cell function and induce T-cell unresponsiveness
What is the immunologic synapse?
Space where MHC and TCR contact each other with all other accessory molecules
What are the 4 accessory molecules of the immunologic synapse and what is their function?
Accessory molecules stabilize the interaction:
CD4+ binds TCR-MHC –> CD4:TCR:MHC
LFA1: ICAM1 move away from TCR:MHC complex
CD2:LFA-3 and costimulation CD28:CD80/86 moves towards TCR:MHC complex (Allows for close interaction leading to signal #2)
