Lecture 12: Signaling through immune receptors Flashcards
signal transduction is the process of _____ from outside source that activate ________ that are converted into ____ singals/responses
input signals; biochemical pathways; output
there are often _____ requirements since some outputs can be dangerous to a cell
threshold
the receptor/ligand is the ____
input
an example of an input threshold requirement is ________
receptor cross-linking or clustering; F(ab)2 BCR
Trimeric _____ released by NK and cytotoxic T cells binds to FAS and ______ it. Death domains cluster so Fas can recruit FADD. _______ recruit procaspase 8.
FasL; trimerizes; DED
Receptor signaling can be distributed to _____ or ______
cytoskeleton or nucleus
Signals to cytoskeleton impact ________, including ___, _____, and ____
cell morphology: cell shape, size, and mobility
Signals to the nucleus impact ______
gene expression: synthesis of new proteins, inducing cell division, proliferation, cell death
Protein kinases are enzymes that
catalyze attachment of phosphate
Protein phosphatases ______ phosphate group
remove
kinases add phosphate to 1 of 3 aa residues:
tyrosine, serine, threonine
______ catalyze attachment of a phosphate to a phospholipid
Phospholipid kinases
an example of phospholipid kinase
PI3K converts PIP2 -> PIP3
_____ carry kinase activity in the cytoplasmic tail of the surface receptor. They have an ____ activity. An example is FLT3 which is involved in hormone differentiation of CD34 cells to produce DC
Receptor tyrosine kinases; intrinsic
_____ noncovalently associate with intracellular tyrosine kinases on T and B cells
Nonreceptor kinases
propagation of intracellular signaling is mediated by ______
multiprotein signaling complexes
multiprotein signaling complexes can be common to several pathways and have distinct binding domains such as ___ and ___, which are generally found in _____ molecules
SH2/SH3; adaptor
SH is part of ____ homology (a nonreceptor tyrosine kinase)
Src
______ proteins (ex: LAT) are like power strip - many things can bind
scaffolding
______ proteins (ex: Grb2) link one protein to another (like a wall block)
Adaptor
_____ binds to SLP76. It makes a docking site complex for _____ during TCR signaling. It allows this molecule to be activated by phosphorylation by Itk
LAT; PLC-gamma
adaptor protein ____ recruits Sos via its ____ domain to an activated receptor that is tyrosine phosphorylated via its ___ domain
Grb2; SH3; SH2
Sos does activity on Ras as ____
GEF (guanine-nucleotide exchange factor)
SH2 binds in ___ format
pYXXZ (three aa away from phosphorylated tyrosine)
SH3 binds in ___ format
XPPXP (proline in 2nd and 5th position)
____ is a small G protein associated with pancreatic cancers
Ras
GTPases act as ______, triggered by GEF
on/off switch
Ras bound to ____ is inactive and is active when bound to _____.
GDP; GTP
___ helps to open up Ras bound to GDP so that it can be exchanged for GTP
GEF
_____ are recruited to the site of receptor activation
GEFs
The active receptor molecule is
GTP:Ras
activity of small G proteins will lead to shutdown/feedback conversion of ___ to ____. Alterations in this regulatory process lead to cancer.
GTP to GDP
_____ is the process of a kinase cascade
Amplification
_____ is example of kinase cascade (adding a kinase to a kinase). The higher the number = further upstream from the outcome
MAP (mitogen-activated protein)
Ras/MAP kinase
TCR signaling produces DAG, which recruits RasGRP where it activates Ras at the membrane. Ras binds to Sos - enhances Sos activity and amplifies Ras activation. Ras activates Raf (MAP3K), which phosphorylates Mek (MAP2K), which phosphorylates Erk (MAPK). Erk enters nucleus and activates TF like Elk-1
second messengers are small molecule biochemical _____ that diffuse through the cell
mediators
calcium ion influx from the ER to the cytosol is an example of ______. Ca2+ modifies _____ to act on effector protein that activates _______ which dephosphorylates and activates NFAT and transcription of IL2
second messenger; calmodulin; calcineurin
Regulation: kinase activity is often modulated by _____ activity
phosphatase
Signaling can be regulated by ______ and tagged for proteasomes
ubiquination
____ can turn on the proteasome that targets for MHC I
IFN-gamma
receptors and ligands can be directly ______ by antibodies, soluble receptors, and non-activating ligands
inhibited
what is signal 1?
antigen specific interaction between MHC and TCR (this is the antigen you need to interact with)
what is signal 2?
other info from APC regarding how serious the infection is, guiding the response
CD3 is made up of
delta, epsilon or gamma, epsilon
there are 2 _____ (homodimers) in cytoplasm underneath TCR
zeta chains
ITAMs (immunereceptor tyrosine based activation motifs) have 2 ___ domains and are present on cytoplasmic tail of ___
SH2; CD3 (4 total) and zeta (3 on each)
Phosphorylated ITAMs recruit _____ with tandem SH2 domains
ZAP70
______ is an example of ITIM on NK cell that stops NK cell from killing a self cell (recognizes MHC)
NKG2A
_____ is an example of ITIM that stops T cells from killing. Blocking the receptor would allow T cells to keep killing (cancer drug)
PD-1
ITIMs are _____ and recruit inhibitory phosphatases that ______ signaling pathways
phosphorylated; deactivate
____ helps TCR if its engaged to MHC II and enhances the signal to TCR
CD4
___ (on tail of CD4) adds phosphate to ITAMs (especially __ chains)
Lck; zeta
phosphorylation of TCR ITAMs by Lck, recruits _____ through tandem _____ domain
ZAP70; SH2
____ phosphorylates ZAP70
Lck
Lck on CD4/8 is _______ when phsophorylated on terminal tyrosine that binds the ___ domain and linker region binds ___ domain
inactive; SH2; SH3
_____ removes phosphate from Lck to activate it. TCR co-localize and polarize, pushing away ___. Physical contact between ____ and TCR removes phosphate group.
CD45
Lck is active when _____ is removed and _____ domain releases linker region
phosphate; SH3
Lck and ___ are both invovled in phosphorylated ITAMs and recruiting ZAP70
Fyn
ZAP70 is an early factor in 4 downstream signaling pathways. It begins by recruiting ____ and ____.
____ activation leads to metabolic activity
_____ activation leads to transcription of cytokines
___ activation leads to cytoskeletal (actin) reorganization
____ activation leads to adhesiveness clustering
LAT and SLP76;
Akt
Plc-gamma
Vav
ADAP
_______ phosphorylates and recruits scaffolding proteins LAT and SLP-76. Adaptor protein ______ holds LAT and SLP-76 together to create docking site.
ZAP70; Gads
____ costimulation (signal 2 from APC) recruits and activates PLC-gamma
CD28
DC have costimulatory molecules ____ and ___. Both signals binding to CD28 induce phosphorylation and activate _____ kinase to produce PIP3.
CD80 and CD86 (or B7.1 and B7.2);
PI3
PIP3 role
- recruits PLC-gamma
- Recruits Itk to membrane
____ is recruited by PIP3 and phosphorylates PLC-gamma
Itk
How do signal 1 and 2 work together?
signal 1: TCR leads to ZAP-70 activation, resulting in LAT/SLP76 complex, where PLC-gamma can dock
signal 2: CD28 costimulation activates PI3 kinase which converts PIP2 to PIP3. PIP3 recuits Itk and PLC-gamma, PLC-gamma can dock and be activated by Itk
PLC-gamma function
cleave PIP2
PIP2 is cleaved into
IP3 and DAG
IP3 function
- diffuses from membrane and allows for calcium influx from ER to cytoplasm and from outside cell
- Ca2+ leads to activation NFAT
DAG function
- PKC activator (activates NF-kappaB)
- recruits Ras-GRP (GEF) to activate RAS, MAP kinase cascade, and TF AP-1 (IL-2 cytokines)
in the lab, _____ is a DAG mimic and ______ is IP3 mimic
PMA;
ionomycin
