Lecture 7: Immune receptors and signal transduction Flashcards
(107 cards)
1
Q
What are the functions of cell surface receptors?
A
- induction of intracellular signaling
- adhesion of one cell to another
2
Q
Signaling from the cell surface activates a signal that contains two phases. What are these two phases?
A
- cytosolic phase, where transcription factors are modified in some way
- nuclear phase, where the modified factor enters the nucleus and induces the expression of the genes it signals for
3
Q
What are different ways of signal transduction at the cell surface?
A
- cross-linking: ligand induces clustering of receptor proteins
- ligand causes conformation to alteration to the receptor
4
Q
What is the primary mechanism that integrins signal by?
A
- non-receptor tyrosine kinases
5
Q
How do non-receptor tyrosine kinases work to be activated?
A
- intracellular kinase must bind and phosphorylate specific motifs on the receptor
6
Q
What are examples or receptor tyrosine kinases and how do they become active?
A
- activated by cross-linking
- c-Kit
- insulin
- epidermal growth factor
- platelet-driven growth factor
7
Q
What are nuclear receptors?
A
- receptors that are in or migrate to the nucleus to act as transcription factors
- controlled by lipid-soluble ligands
8
Q
What group of proteins can influence lymphopoeisis?
A
Wnt
9
Q
Which group of proteins cnotribute to cell fate during the lymphocyte development?
A
notch proteins
10
Q
What role does Src proteins play in Ag receptor activation?
A
Src proteins motif act as a binding site for SH2 domains in the Syk family. The binding of Sh2 domain to phosphotyrosine interaction is what causes activation of the Ag receptor
11
Q
What is the effect of having an active ITIM?
immunoreceptor tyrosine-based inhibitory motif
A
This will counteract the ITAM, by recruiting tyrosine or inositol lipid phosphatases; leading to deactivation
12
Q
How can BCR and TCR be used to direct a cell’s pathway?
A
The number (strength) of activated receptors can be interpreted differently by lymphocytes
13
Q
How is Ag receptor signaling fine-tuned and modulated?
A
- progressive ITAM use
- increased cellular activation by coreceptors
- modulation of signaling by inhibitory receptors
14
Q
How can progressive ITAM use contribute to modulating Ag receptor signaling?
A
- the Ag affinity influences how many ITAMs are phosphorylated, and can produce different types of cellular responses
15
Q
What are extracellular domains on lymphocytes able to recognize?
A
- soluble ligands or membrane structures of neighboring cells
16
Q
When a ligand binds what happens to the receptor?
A
- receptor undergoes a conformational alteration
17
Q
What is cross-linking?
A
- signaling of lingand-induced clustering of receptors
18
Q
Are nuclear receptors intracellular or extracellular?
A
- intracellular transcription factors that are activated by lipid-soluble ligands.
- these are able to cross the membrane
19
Q
What does ubiquitin molecule tag a protein for?
A
- protein degradation
- drive signal transduction
20
Q
Signaling molecules modified by covalent binding of lipids causes what at the PM?
A
- membrane localization of signaling molecules
21
Q
What are located in the tyrosine kinase families?
A
- Src families
- Syk families
- Tec families
22
Q
What are unique domains located on the tyrosine kinase families?
A
- SH2 domains bind phosphotyrosine
- Sh3 domain binds proline rich region (hydrophobic)
- PH domain recognize PIP3, phosphatidylinositol
23
Q
What do SH2 domains present in the Ag receptor complex?
A
Syk and ZAP-70
24
Q
What type of domain could a Btk tyrosine kinsae be categorized as?
A
PH domain, it does recognize a lipid moiety
25
What are adaptor proteins used for?
* link different enzymes that promote the assembly of complexes of LAT and BLNK
26
What doe adaptor proteins contain in terms of domains?
SH2 and SH3
27
In adaptor proteins what is required for them to bind to other proteins that contain SH3 domain?
proline-rich regions
28
In adaptor proteins what acts as a docking site for proteins with SH2 domain?
tyrosine residues
29
What is LAT?
integral membrane protein with functions of an adaptor
30
What cytosolic subunits are present areound LAT, in an unactivated T cell?
* GADS: SH3, SH3, SH2 domain
* SLP-76: SH2 domain
31
What happesn at the LAT adaptor protein when the T cell becomes activated?
1. LAT is phosphorylated by tyrosine
2. This causes PLC gamma and GADS to bind
3. Proline region on P-SLP-76 binds with SH3 on GADS
4. VAV binds to the (P) on SLP-76
32
When the LAT protein is activated it causes binding of PLCgamma and VAV. What are the effects of these binding?
VAV: induces actin cytoskeletal rearrangement
PLCgamma: Ca ion signaling
33
What is Fc(gamma)RIIB?
inhibitory receptor found on B cells and myeloid cells
34
When TCR and BCR signaling occurs clustering results, and what happens?
* conformational change to allow clustering occurs
* cytoplasmic tail of receptor exposes the ITAM motif
* Syk/Src tyrosine kinases phosphorylate tyrosine in the ITAM, by binding at the SH2 domain
* Active Syk kinase activates adaptor proteins to induce signaling downstream
35
How is the Ag affinity to the TCR best represented?
* the amount of ITAMs activated is directly related to length of Ag binding to the TCR
* longer binding= more ITAM phosphorylation
* short binding= less ITAM phosphorylation
36
How can a weak and strong signal be used in the body, specifically with TCR?
1. weak TCR signaling results in positive T cell selection in the thymus
2. Strong TCR signaling will result in negative T cell selection and apoptosis
37
What are the coreceptors for Th and Tc cells? What function do they possess?
1. CD4 and CD8
2. increase ITAM phosphorylation and activation of the Ag
38
What is the coreceptor for B cells?
* CR2/CD21
* increases the response when IgM binds with Ag
39
What are costimulation factors in T cell activation?
CD28-CD80/86
40
What is CTLA-4 and what effect will it produce?
* inhibitor or T cell receptor which will cause downregulation of immune system
41
What is CD22 responsible for?
* inhibitory receptor for B cells
* FC(gamma)RIIB is also inhibitory receptor for B cell
42
Why are CD3 and zeta proteins found in close association with the alpha/beta strands of TCR?
* TCR lack cytoplasmic tails that could induce signal-trandusction
* non-covalent binding with CD3 and zeta proteins allows the TCR to produce signal transduction
43
Describe the structure of CD4 coreceptor.
* four extracellular Ig-like domain (VHVH)
* hydrophobic transmembrane region
* 38 AA long cytoplasmic tail
44
Describe CD8 coreceptor structure.
* alpha/beta chains
* single Ig domain
* 25 AA cytoplasmic tail
45
What structures does a CD8 coreceptor interact with?
* Beta2-microglobulin and MHC I
46
What componenents combine in order to prevent T cell death via apoptosis?
1. TCR binds with Ag and CD28-CD80/86 activating PI3K
2. PI3K converts PIP2 to PIP3
3. PIP3 attracts PDK1 to PM and activates it by binding
4. PDK1 activates Akt
5. Akt inactivates pro-apoptotic proteins of Bcl-2 family
47
Describe the Ras-MAP kinase pathway when an Ag binds to receptor
1. Ag, activates Lck and ZAP-70
2. ZAP-70 activates LAT at the membrane
3. LAT binds to Grb2 adaptor
4. Grb2 allows binding of SOS factor
5. SOS converts Ras-GDP to Ras-GTP
6. Ras-GTP binds with Raf and activates MEK-1
7. MEK-1 activates ERK-1, 2
8. synthesizes and activate transcription factors
9. activating AP-1
48
What is the pathway activation to produce numerous cell responses that uses PLC(gamma)1?
1. LAT is activated and bind PLCgamma1
2. Ag binds, activating ZAP-70 which activates PLCgamma1
3. PLCgamma1 produces DAG and IP3 from PIP2 at the PM
4. IP3 causes Ca ion release from the ER
5. DAG converts to PKC which activates various proteins and causes cellular response specific to that protein
49
Activation of what two pathways, in T cells, will lead to IL-2 mRNA production?
* dephosphorylate cytoplasmic NFAT
* degradation of IkappaB (activates NF-kappaB)
50
Describe the activation of cytoplasmic NFAT in order to generate IL-2 mRNA.
1. Phosphorylated NFAT, combines with the calcineurin complex
2. Calcineurin complex is bound with calmodulin and Ca ion
3. NFAT is dephosphorylated by the calcineurin complex (Active NFAT)
4. NFAT enters nucleus and generates AP-1
51
Describe the activation of NF-kappa B to induce IL-2 mRNA production.
1. active PKC activates IkB kinase causing IkB and NF-kB to dissociate from one another
2. Active NF-kB enter the nucleus and is able to produce IL-2 mRNA production
52
What are the three types of MAP kinases?
* ERK (extracellular signal-regulated protein kinases)
* p38 MAP kinases
* JNK
* all activated by phosphorylation
53
The Fos protein combines with Jun-(P) to form active AP-1, what is the pathway to form the Fos protein?
1. Ras-GDP activates ERK
2. ERK phosphorylates ELK
3. ELK induces transcription of Fos gene
4. Fos gene waits to bind with AP-1 and start trascnription of IL-2 mRNA
54
Active AP-1 is formed by binding Fos protein with phosphorylated Jun. What is the pathway to activate Jun?
1. Rac-GTP activates JNK
2. JNK phosphorylates Jun
3. Jun-(P) combines with Fos protein and produces IL-2 mRNA
55
What receptors can a stimuli bind with to start the canonical NF-kB pathway?
* TCR/BCR
* TLR
* TNF-alpha
* RANK
* CD30
* CD40
56
How is teh Canonical NF-kB pathway activated?
1. stimulus binds to multiple receptors activating IKK alpha,beta,gamma complex
2. IKK beta is phosphorylated which causes ubiquitination of IKK beta
3. IKK beta is removed and sent to proteasome. p65/Rel and p50 are released to nucleus
4. p65/cRel and p50 complex bind and transcription occurs
57
TNFR, lymphotoxin beta or BAFF is able to activate the alternative NF-kB pathway. What is this pathway?
1. stimulus binds
2. NIK is activated, which activates/phosphorylates IKKalpha complex
3. IKKalpha phosphorylates RelB/p100 complex
4. p100 is ubiquitinated and sent to proteasome
5. RelB is dimerized with p52 in the nucleus to start transcription
58
What is clonal anergy and what is it produced by?
1. T cell unresponsiveness due to reduced ability to generate IL-2
2. problem with canonical pathway
59
What effects would counter anergy?
exogenous amounts of IL-2
60
What effects would produce Anergy?
* substimulatory levels in absence of costimulus from soluble cytokines
* absence of interaction between costimulatory receptors on T cell
* Absence of counterreceptor interaction on APC
61
What is the function of CD3?
signal transduction of TCR complex
62
What is the function of the zeta protein?
signal transduction by the TCR complex
63
What is the role of CD4?
* signal trandsuction when bound with MHC II ligand on APC
64
What is the role of CD8?
* signal transduction when bound with ligan MHC I from all nucleated cells
65
What is the role of CD28?
* costimulatory signal transduction when bound by B7-1/B7-2 on APC
66
What is the role of CTLA-4?
negative regulation signal transduction when bound with ligand B7-1/B7-2 on APC
67
What is the role of PD-1?
* negative regulation signal transduction when bound with ligan PD-L1/PD-L2 on APC, tissue or tumor cells
* Stimulates apoptosis
68
What is the role of LFA-1?
* adhesion with ICAM-1 from APC and endothelium
69
What is the function of B cell coreceptors CD19/CD21?
reduce the threshold required to activate the B cells
70
What is the role of coreceptor CD32 in B cells?
CD32 or FcgammaRIIB leads to suppression of the B cell activation
71
How is signal 1 produced?
Ag binds to the B cell via the receptor, not strong enough to lead to activation and could cause anergy do to inactivation
72
How is signal 2 produced?
Ag binds with receptor as well as with the costimulatory molecules
73
What immununoglobins are expressed on surface of naive B cells?
IgM and IgD
74
What do mature or memory B cells express on their surface?
IgG, IgA, IgE
75
Of the BCR complex what unit is able to generate intracellular signals?
- the IgAlpha, IgBeta subunits as they contain ITAMs, that are able to activate signaling functions
76
A BCR complex is activated by an Ag, what are the final factors that are produced?
1. NFAT
2. NF-kB
3. AP-1
77
With BCR activation, what is teh pathway to activate NFAT?
1. Src-Syk activation (phosphorylation) activates PLC gamma
2. PLC gamma increases Ca ions in cytosol
3. Activates Ca dependent enzymes
4. producing NFAT
78
With BCR activation, how is NF-kB formed?
1. Src-Syk is activated/phosphorylated
2. PLC gamma is then activated
3. DAG is activated
4. which activates PKC
5. which leads to activation of NF-kB
79
With BCR activation, how is AP-1 produced?
1. Src- Syk is activated
2. which activates SLP-65 and Grb2/SOS complex
3. This activates Ras-GTP and Rac-GTP
4. activates the ERK, and JNK
5. which combine to contribute to form AP-1
80
What three factors will lead to B cell development, negative selection, tolerance and regulatory function?
1. NFAT
2. NF-kB
3. ERK
4. all active in the nucleus
81
What cytosolic proteins are located in teh TCR that are not present in the BCR?
1. LAT
2. ZAP-90
3. SLP-76 is replaced with SLP-65
4. still able to perform the same final functions
82
GTP-Ras activates enzymatic cascade of MAP kinases. What is the final result of this process?
* phosphorylation of various transcription factors
* regulates changes in gene transcription
83
Describe the Calcium signaling pathway in B cells.
1. protein kinases(Lyn, BLNK, Syk) activate PLCgamma2 when Ag binds with the BCR
2. PLC2 hydrolyzes PIP2 into DAG and IP3
3. IP3 binds its receptor causing release of Ca ions
4. Calcium release activated Calcium channels now open to increase Ca release
5. DAG activates PKC and Ras-MAP kinase pathways which activate AP-1 and NF-kB
6. calmodulin-calcineurin pathway is activated to produce NFAT
84
What happens to the signal cascade if the BCR and CR2 is bound by and Ag?
signal cascade is greatly enhanced
85
What does CR2/CD21 on the BCR bind with on the Ag?
it binds with C3d which is a by-product of C3b
86
How does inhibitory signaling occur?
1. ligand binds to inhibitory receptor
2. Src family activates the ITIM
3. p-ITIM recruits SH2 domain tyrosine phosphatase that becomes activated
4. SH2 domains attenuate immune receptor signaling and de activate the substrates
87
What are key inhibitory receptors of B cells?
* FcgammaRIIB
* CD22
88
How do SHP and SHIP contribute to B cell inhibitory receptor activation?
* SH2 domains with SHP and SHIP are activated by the ITIMs
* these remove phosphates from PIP3 and inhibit PI3 kinase activity in lymphocytes
89
What sequence is required to target a protein for proteasome degradation?
* lysine-48 type ubiquitin chain
* lysine-63 type ubiquitin chain is not targeted for degradation
90
What stimulation activates the canonical pathway and what are the general results?
1. BCR and TCR activate
2. inflammation, survival, and proliferation of lymphocytes are the results
91
Whwat stimulation activates the non-canonical pathway and what are the overall results?
1. BAFFR, CD40, LTbetaR, RANK
2. results in chemokine, lymphoid stroma, and cell survival
92
What properties is unique to the canonical pathway?
1. rapid and short lasting
2. independent of protein synthesis
3. responds to numerous stiimuli
4. diverse function
5. translocates NF-kB heterodimer RelA/p50
93
What properties is unique to the non-canonical pathway?
1. slow and persistent
2. protein synthesis dependent
3. responds to TNFR signals
4. performs specific functions
5. produces mature NF-kB1/2 due to proteasome degradation of the p105, p100 factors
94
A naive T cell must interact with what cytokines to mature into Treg cell?
1. IL-2, TGFb
2. secretes IL-10 to suppress inflammatory response
95
A naive T cell must interact with what cytokines to mature into Th17 cell?
1. IL-6, TGFb
2. releases IL-17A, IL-17F, IL-22 which produce inflammation
96
A naive T cell must interact with what cytokines to mature into Th2 cell?
1. IL-4
2. releases: IL-4, IL-5, IL-13 to produce allergic and helminth response
97
A naive T cell must interact with what cytokines to mature into Tfh cell?
1. IL-6, IL-21
2. releases: IL-4, IL-21 which signals germinal center help
98
A naive T cell must interact with what cytokines to mature into Th1 cell?
1. IL-12, IFNgamma
2. releases: IFN gamma, TNF to produce macrophage activation and inflammation
99
If a B cell does no interact with a Th cell what immunoglobulin will it develop and what are the effects?
1. IgM
2. activates complement cascade
100
B cells that interact with Th cells and IFNgamma develop what Ig?
1. IgG1, IgG3
2. Fc receptor dependent phagocyte response, and complement activation
101
B cells that interact with Th cells and IL-4 develop what Ig?
1. IgE
2. provides immunity against helminths
3. causes mast cell degranulation
102
B cells that interact with Th cells and mucosal tissue cytokines develop what Ig?
1. IgA
2. cause transport of IgA through the epithelia
103
What are the five classes of cytokine receptor families?
1. Type I cytokine
2. Type II cytokine
3. TNF receptor
4. IL-1 receptor
5. Seven transmembrane GPCR which binds chemokines
104
What are the type I cytokine receptors and what [athway do they activate?
1. IL-2,-4,-15
2. activate the JAK-STAT pathway which binds to sequences in the promoter to produce transcription
105
What receptors are in the Type II (interferon receptor) family?
1. IFN-alpha/beta, IFN-gamma, IL-10,-20,-22
2. activate JAK-STAT or Tyk-STAT pathways
106
What is the structure of TNF receptors and what are the most important?
1. trimer, which ligand also forms trimer
2. TNFRI, TNFRII, CD40, Fas, TNF-beta, BAFF
3. these will activate apoptosis, NF-kB, AP-1 causing inclammation
107
Activation of a chemokine receptor activates a GPCR that signals production of what?
1. Akt
2. PKC
