T&H8 Cellular Signaling Pathways Flashcards
Name three growth factor receptors with split kinase domains, in which autophosphorylation sites are present on a kinase insert with in the catalytic subunit.
PDGFR
VEGFR
KIT (SCFR)
Name 2 growth factors that are monomeric polypeptides.
EGF and FGF
Name a growth factor that is a dimeric polypeptide.
PDGF
When EGF binds to EGFR, a conformational change of the extracellular domain occurs. This leads to dimerization of _______ and intracellular autophosphorylation of ______ residues, which opens up the catalytic site and creates docking sites for cytoplasmic adaptor proteins, such as ______ and ______, that contain ______ or ______ domains.
- RTKs
- tyrosine
- GRB2 and p85
- SH2 or PTB
Following binding of GRB2 to the activated RTK (via its SH2 domain), it associates with _____, which is an GEF, via its _____ domain. _____ catalyzes exchange of GDP to GTP on Ras for activation. Ras binds _____, which activates a kinase cascade including ____ and _____.
- SOS
- SH3
- SOS
- RAF
- MEK and ERK
Mutations in juxtamembrane regulatory regions of ____ and ____ are implicated in human GISTs.
c-kit
FLT3
Binding of specific domains to their target sometimes requires phosphorylation of ________ within the sequence-specific binding motif.
amino acids
Proteins that contain either ____ or ____ domain, which recognize phosphorylated sequence motifs, are central for the formulation of signaling complexes following activation of GF RTKs.
SH2 or PTB
______ is an SH2 and SH3 domain-containing adaptor protein that plays a critical role in activation of small GTPase protein, Ras.
GRB2
Termination of RAS activity occurs via _____ of GTP, converting to GDP by ______.
- hydrolysis
- GAPs
RAS is activated by effects of ____, which release RAS-bound GDP and allows GTP binding to RAS.
GEFs
Besides RAF, RAS also interacts with _____ and ______.
PI3 kinases and RALGDS
What are the three distinct MAPK pathways?
- ERK1/2
- JNK/SAPK
- p38
MAPK pathway is activated by phosphorylation of _______ and ______ residues.
threonine and tyrosine
RAS leads to activation of ______ (MAP3K), which then activates _______ (MAPKK) via phosphorylation of ______ residues. MAPKK activates ______ (MAPK) via phosphorylation of ______ and ______ residues. MAPK activation induces phosphorylation of cytoplasmic and nuclear proteins that regulate ________, ________, and ________. MAPK also phosphorylates ______ proteins and _____ family of protein kinases, which regulate translation. transcription, and survival signaling. MAPK translocates to nucleus to activate ____.
- RAF
- MEK 1/2
- serine
- ERK
- threonine and tyrosine
- cell migration, proliferation, and differentiation
- cytoskeletal proteins and RSK
- TFs
PI3 kinase is comprised of a catalytic subunit ______ and regulatory subunit ______.
- p110
- p85
p85, the regulatory subunit of PI3K, contains two _____ domains
SH2
Binding of p110/p85 complex to activated growth factor receptors via _____ SH2 domain activates catalytic activity of _____, which then phosphorylates ____, converting it to PIP3. PIP3 recruits _____- domain containing proteins, such as _____ and _____. ____ contributes to activation of ______.
- p85
- p110
- PIP2
- PH-domain
- AKT and PDK1
- PDK1
- AKT
AKT leads to activation of _____, which regulates cell growth. It also phosphorylates and causes nuclear exclusion of _____ transcription factors, which prevents expression of genes that induce cell death.
- TORC1
- FOXO
mTOR is a serine threonine kinase that forms 2 distinct complexes, _____ and _____. Name the main function of each complex.
- TORC1: controls/promotes cell proliferation
- TORC2: promotes cell growth by activating AKT
Rapamycin is an _____ inhibitor and is used as an ________.
- mTOR
- immunosuppressant
The rapamycin analogs, ________ and _______, can be used to treat what cancer in people?
- temsirolimus and everolimus
- RCC
______ functions are a major negative regulator of PI3K signaling.
PTEN
Substrates for AKT fall into 2 main classes as regulators of ______ or regulators of _____.
- cell survival
- cell proliferation
Transcription of genes is catalyzed by _______ and regulated by supporting molecules termed ______.
- RNA polymerase II
- transcription factors
Activity of transcription factors can be modified by phosphorylation through activity of signaling pathways, such as _____ and ____, which can act in the nucleus to directly modify TF activity.
- MAPK and PI3K
Name the 4 groups of transcription factors and give an example of each.
- Homeodomain (a.k.a. helix-turn-helic)
- Ex) oct 1 - Zinc finger
- Ex) glucocorticoid receptor - Leucine zipper
- Ex) c-jun - Helix-loop-helix
- Ex) myc
Enzymes that regulate ________________________ are key components of transcriptional activator and repressor complexes.
histone acetylation and phosphorylation
Histone _____ near the promoter regions of genes facilitates interaction of DNA with TFs.
acetylation
The ________ pathway is an important mechanism for signal termination.
ubiquitination
In the ubiquitination pathway, free ubiquitin attaches to _________ and is transferred to ______. In partner with __________, ubiquitin is transferred to a substrate. Polyubiquinated substrates are degraded by ________. Monoubiquinated substrates serve as signal for receptor _______. which is then transferred to a _______ for degradation.
- ubiquitin-activating enzyme (E1)
- ubiquitin-conjugating enzyme (E2)
- ubiquitin ligase (E3)
- 26S proteosome
- endocytosis
- lysosome
Receptors in cytokine signaling do not contain intrinsic TK activity, but instead transmit intracellular signaling through _______ family of kinases.
JAK
_____ domain functions to both regulate JAK kinase activity and mediate association with receptors.
FERM
Cytokine binding leads to ______ phosphorylation of the GBP130 receptor subunit via specific ______ residues. This recruits _____, which binds via its _____ domain and becomes phosphorylated via ____ residues and is transported to _____ to regulate gene expression. GBP130 phosphorylation also results in recruitment of tyrosine phosphatase, ___, which is turn leads to ____ activation.
- JAK
- Tyrosine
- STAT
- SH2
- Tyrosine
- nucleus
- SHP2
- Ras
In addition to JAK, STAT can be phosphorylated by ______ and ___.
mTOR and ERK
_______ is a JAK 2 inhibitor that reduces tumor burden and improves QOL, but does not cause remission.
Ruxolitinib
Gene translocations and activating point mutations in JAK2 have been identified in _______ and ____.
myeloproliferative disorders and leukemia
Are integrins upregulated or downregulated in tumor progression? Or both?
both up and down regulation
Loss of integrin _____ is observed in some tumors.
a2B1
Upregulation of integrins ____, ______, and ____ are seen in epithelial tumors.
avB3, avB6, and a5B1
Name developmental signaling pathways. Hint: there’s 6.
- WNT
- HH
- TGF-B
- NOTCH
- JAK/STAT
- nuclear hormone pathways
The ______ family of transmembrane receptors are seen in Wnt signaling pathway.
Frizzled (FZ)
Name the 3 Wnt pathways.
- Canonical (major) WNT pathway
- WNT/Planar cell polarity pathway
- WNT/Ca2+ pathway
What is the key mediator of the canonical WNT pathway?
B-catenin
WNT activation leads to inactivation of the destruction complex, which leads to _____ accumulation and entry into the nucleus where it interacts with _____ and ____ family of TFs to regulate transcription of target genes.
- B-catenin
- LEF and TCF
What are the target genes of the WNT pathway?
c-myc, MMP-7, cyclin D1
What syndrome is associated with upregulated WNT signaling? Mutations in the _____ tumor suppressor gene leads to ineffective B-catenin degradation and constitutive activation of B-catenin/TCF targent genes.
- Familial adenomatous polyposis (FAP)
- APC
What are the ligands and receptors of the NOTCH pathway?
- Ligands: DELTA-LIKE 1, 3, 4, and JAGGED 1-2
- receptors: NOTCH 1-4
In NOTCH signaling, the ligand binds to its receptor, which causes a release of the extracellular domain mediated by ______. This triggers cleavage by ________ complex, releasing ________. This enters the nucleus and converts ____ repressor to an activator of transcription.
- ADAM family of MMPs
- gamma-secretase
- NOTCH intracellular domain (NIC)
- CSL
NOTCH1 activation, resulting from a chromosomal translocation, is strongly linked to humans cancers, such as ______.
T-ALL
What are potential therapy targets for NOTCH signaling?
inhibition of gamma-secretase (GSI) or ADAM
Hedgehog gene products encode ligands that signal through membrane receptor complexes, ______ and ____.
Patched (PTC) and Smoothened (SMO)
In HH signaling, ____ inhibits ____ in absence of ligand.
PTC inhibits SMO
When HH ligand binds to its receptor _____, there is a release and activation of ______, which allows expression of zinc-finger transcription factors and transcription of HH target genes.
- PTC
- SMO
HH pathway can lead to cancer through several mechanisms including loss of function of TSG ______ or gain of function through oncogene ______.
PTC1
SMO
Inhibition of _____ signaling in stroma can improve delivery of cytotoxic chemotherapy.
HH
In ________ cancer, HH signaling is upregulated and accompanied by elevated expression of ______, which is a protein involved in EMT and metastasis.
- primary colon cancer
- SNAIL
What is TGF-B’s role in cancer?
functions as a antiproliferative factor and tumor promoter
TGF-B is activated following dimerization and binds to type I and type II receptors, which leads to _________ phosphorylation and activation of kinase domain of type I and type II receptors. Activated type I signals to ____ family of mediators, which carry the signal from cell surface directly to _______.
- unidirectional
- SMAD
- Nucleus
Inhibitory SMADs counteract receptor-regulated SMADs (R-SMADs) and antagonize ______ signaling.
TGF-B
______ and ____ are E3 ubiquitin-protein ligases that regulate SMAD levels and orchestrate ubiquitin transfer to the _____ SMADs leading to degradation.
- SMURF 1 and SMURF 2
- R-SMADs
What is the growth factor receptor for SCF (stem cell factor)?
c-kit
What are the growth factor receptors for HGF (hepatocyte growth factor)?
MET, RON
What is the ligand for HER2?
HER2 does not have a known ligand
What are the growth factor receptors (a.k.a targets) for Palladia?
- VEGFR2
- PDGFRB
- KIT
- CSF1R
- FLT3
What are the growth factor receptors (a.k.a targets) for Masitinib?
- KIT
- PDGFRa/B
- Lyn
- Fyn
- FGFR3
Phosphoinositidines are phospholipids from _______. They are dynamically regulated in response to growth factor signaling. They contribute to signal propragation via two main mechanisms. The first is by serving as precursors of the second messengers _______ and ________. The second is by binding to signaling proteins that have PI binding molecules.
- cell membrane
- diacylglycerol (DAG) and inositol triphosphate and Ca2+
Which cyclin is primary responsible for regulating Rb protein?
D-type cyclins
Most cytokine receptors have unique extracellular ligand binding region, a single transmembrane domain, and a cytoplasmic domain. Do most of the receptors exist as single chain OR multi-subunit chains?
With exception of the receptors for G-CSF and erythropoietin, most cytokine receptors are multisubunit complexes
______ mediate cellular interaction between the ECM and actin skeleton, which enables direct communication across plasma membrane.
Integrins
B-catenin is abnormally expressed in canine _____ and ______ but doesn’t correlate with outcome nor does targeting the WNT pathway seem relevant.
OSA and melanoma
HES1, a target of NOTCH signaling, is elevated in canine ______ but reduced in most aggressive tumors.
OSA
HH signaling is activated in canine _____ and contributes to cell proliferation and survival. Inhibition with ________ and _____ led to significantly decreased cell proliferation but had smaller effect on apoptosis.
- TCC
- Cyclopamine and GANT61
Canine ____ cell lines possess TGF-B1 signaling machinery, potentially allowing for establishment of autocrine and paracrine pro-tumorigenic signaling loop. TGFB1 inhibitors might impede localized progression in dogs.
OSA
______ is an enzyme that removes a high energy phosphate group from ATP and transfers it to a protein substrate.
Kinase
What are two types of TGF-B family serine threonine receptors and how do they differ?
- Type I: normally inactive
- Type II: constitutively active but do not normally phosphorylate substrates
- ligand mediated dimerization causes type II to phosphorylate type I, which converts it to an active kinase
What event markedly reduces activity of most kinases?
dephosphorylation of T loop (transactivation loop)
JAKs contain a _____ domain, which stands for _____________, an SH2 domain, a functional kinase domain, and a ______ domain that can exert auto-inhibitory activity on the kinase domain. The function of the _____ domain is unclear because it does not appear to bind to tyrosine phosphorylated proteins.
- FERM
- F (4.1 protein), E (ezrin), R (radixin) and M (moesin)
- kinase-like domain
- SH2
Activated JAK receptor generates docking sites for SH2 domain containing proteins, such as _____, ______, and ______.
- STAT
- PI3 kinase
- GRB2
STATs contain a conserved _________ domain that is specific to the STAT family, a conserved _____ domain, and a carboxyterminal _____ residue that mediates dimerization.
- aminoterminal DNA binding
- SH2 domain
- tyrosine
Point mutations, such as ______, are found frequently in myeloproliferative diseases and thought to disrupt the auto-inhibitory activity interaction between pseudokinase and catalytic kinase domain of JAK.
V617F
STAT upregulates what target genes and downregulates ___.
- upregulation: Mcl-1, survivin, BCL-2, and VEGF
- Inhibits p53
TORC1 controls protein synthesis through phosphorylation of ____ and ______ that in turn promote cap-dependent protein translation.
- eukaryotic translation initiation factor binding protein (4R-BP1)
- S6 kinase 1 (S6K1)
TORC1 regulates ATP production and metabolism by promoting the expression of ________ that regulates expression of glycolytic genes controlling glucose metabolism.
HIF-1a
TORC1 inhibits autophagy by phosphorylation and inhibition of the activity of ______, which forms part of a kinase complex required to initiate autophagy.
autophagy-related gene 13 (ATG13)
TORC2 promotes cell growth through activation of protein kinases _____, ______, and ____.
AKT, SGK1, PKCa
Anabolic state is programmed by growth factor signaling pathways and transcription factors, particularly the ________ network and _____.
PI3K/mTOR
c-myc
______ kinase acts as a central regulator of cellular metabolism by integrating upstream signaling pathways that monitor growth factors, energy and nutrients, and coupling them to regulation of protein synthesis and ribosomal biogenesis, autophagy, and metabolism.
mTOR
_______ inhibits mTOR signaling through multiple pathways, both upstream and downstream of the kinase, particularly in concert with other stresses.
hypoxia
Inhibition of ______ stimulates autophagy.
mTOR
“Cap-independent translation” affects several important genes, including _____ and _____, which facilitates tumor growth in locally advanced breast cancers.
HIF-1a and VEGF
_____ inhibition promotes tolerance to hypoxia, which can increase the proportion of viable hypoxic cells and reduce effectiveness of other therapies.
mTOR
If a substrate is recognized by ______, they may hydrolyze the covalent bond with ubiquitin from the substrate, preempting substrate degradation
deubiquinating enzymes
