Quizzes 6-7 Flashcards
Is the maturation of late endosomes into lysosomes accompanied by an increase in the number of v-SNAREs?
No
SNAREs would be sent back out via a recycling compartment before lysosomal maturation
Is the maturation of late endosomes into lysosomes accompanied by an increase in pH?
No, a decrease in pH
Is the maturation of late endosomes into lysosomes accompanied by an increase in the number of lysosomal enzymes?
Yes, duh
Is the maturation of late endosomes into lysosomes accompanied by a decrease in the number of mannose-6-phosphate receptors?
Yes
M6P receptors bind to newly synthesized lysosomal enzymes in the trans-golgi network and targets them to the lysosomes.
M6P receptors are not found in lysosomes. They cycle between the trans-golgi network and endosomes.
Is the maturation of late endosomes into lysosomes accompanied by an increase in the number of V-type pumps?
Yes
V-type pumps burn ATP to create a proton gradient, acidifying lumens
At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast Sec23 mutants?
Greatly expanded “boated” ER
At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast Sec12 mutants?
Greatly expanded “bloated ER”
Remember that Sec12 is Sar1’s GEF
At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast GlcNAc phosphotransferase mutants?
Swollen “constipated” lysosomes within cells and lysosomal enzymes in the extracellular media
GlcNAc phosphotransferase binds to the glycosylation of lysosomal enzymes (acid hydrolases). It transfers the M6P phosphate onto the hydrolase’s glycosylation. This M6P provides the tag for the hydrolase to be routed to the lysosome
At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast synaptic vesicle v-SNARE mutants?
Accumulation of uncoated synaptic vesicles
Vesicles would shed their coats and prepare for docking, but never actually fuse
At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast KDEL receptor mutants?
Some soluble ER resident proteins are present in the Golgi and extracellular media
KDEL sequence sends ER resident proteins back to the ER if they were to escape
At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast NSF (N-ethylmaleimide sensitive fusion protein) mutants?
Accumulation of entwined SNAREs in target membranes
NSF uses ATP hydrolysis to unwind v and t SNAREs
True or false: many of the receptors involved in receptor mediated endocytosis have single membrane domains. If they internalize only upon ligand binding, it is likely that ligand binding causes them to dimerize.
True
Key word: likely.
Is the binding interaction between LDL receptors and LDL particles released by a change in pH?
Yes
Binding: pH ~7
Release: pH ~5
Is the binding interaction between the intertwined v and t SNAREs released by a change in pH?
No
Requires NSF’s ATP hydrolysis to be released
Is the binding interaction between mannose-6-phosphate receptors and lysosomal enzymes released by a change in pH?
Yes
Is the binding interaction between KDEL receptors and ER resident proteins released by a change in pH?
Yes
Does the following evidence support the “cisternal maturation” model of transport through the golgi?
In live cells with GFP fusion proteins of cis-Golgi enzymes and RFP fusion proteins of medial Golgi enzymes, if you follow a single cisterna over time you can observe the compartment changing from green to red.
Yes
Cisternal maturation: cargo cohort stays in the compartment, enzymes move retrograde to new cohort
Does the following evidence support the “cisternal maturation” model of transport through the golgi?
Some cargo like algal scales are too big to fit within COPI vesicles and are consistently found within the Golgi cisternae
Yes
Cisternal maturation: cargo cohort stays in the compartment, enzymes move retrograde to new cohort
Does the following evidence support the “cisternal maturation” model of transport through the golgi?
Detection of abundant secretory proteins in the many vesicles that surround the Golgi
No
Cisternal maturation: cargo cohort stays in the compartment, enzymes move retrograde to new cohort
Would non-hydrolyzable ATP lead to an accumulation of COPII vesicles?
No
ATP isn’t involved in COPII vesicles (aside from NSF and SNARE unwinding, but that’s after the vesicle has fused so it doesn’t count here)
Would non-hydrolyzable ATP lead to an accumulation of COPI vesicles?
No
ATP isn’t involved in COPI vesicles (aside from NSF and SNARE unwinding, but that’s after the vesicle has fused so it doesn’t count here)
Would non-hydrolyzable ATP lead to an accumulation of clathrin-coated vesicles?
Yes
ATP is involved in the uncoating of clathrin-coated vesicles (Hsp70, an ATPase, allows for the clathrin coat to shed)
True or false: during the process of vesicular fusion, energy from ATP hydrolysis is required for the tight wrapping/braiding of the SNARE pairs.
False
SNARE wrapping is energetically favorable, happens stochastically/spontaneously
True or false: in multivesicular endosomes, the transmembrane proteins that are part of the internal vesicles are in the process of being recycled to the plasma membrane surface
False
Internal vesicle membrane proteins are destined to be degraded
Does targeting of plasma membrane proteins involve vesicular transport?
Yes
Does targeting of histones involve vesicular transport?
No
Does targeting of lysosomal enzymes involve vesicular transport?
Yes
Does targeting of glycosylation enzymes within the golgi involve vesicular transport?
Yes
Does targeting of protein hormones (like insulin) involve vesicular transport?
Yes
Hormone, synthesized in the smooth ER. Requires a vesicle to get from the ER to wherever else it needs to go
Is ApoA part of LDL particles?
No. (it’s part of HDL particles)
What is the role of the Rab GTPase?
“Provides specificity of vesicular fusion”
Rab-GTP is bound to incoming vesicles, binds to a Rab-effector (a tethering protein in the donor membrane) to confer specificity
What’s the role of the dynamin GTPase?
Scission of clathrin coated vesicles from the donor membrane
What’s the role of the Sar1 GTPase?
“Key for ER –> golgi transport”
It’s the associate GTPase for COPII vesicles. It binds to the budding vesicle membrane and provides a platform to recruit Sec23/24 dimers
What’s the role of ARF GTPases?
“Key for moving glycosylation enzymes in a retrograde fashion within the golgi”
It’s the associate GTPase for COPI and clathrin coated vesicles.
What vesicle type would you expect to be associated with mannose-6-phosphate receptors?
Clathrin coated vesicles
M6P receptors mainly cycle between the trans-golgi network and endosomes. This region of vesicular transport is the domain of clathrin coated vesicles
What vesicle type would you expect to be associated with a clump of seemingly aggregated protein?
Formation of a regulatory secretory vesicle
What vesicle type would you expect to be associated with medial-golgi enzymes?
COPI vesicles
What vesicle type would you expect to be associated with antiporters that typically reside in the apical cell membrane?
Formation of a vesicle with high concentrations of sphingomyelin and cholesterol
Proteins in the apical side of intestinal epithelial cells may need to be packaged in lipid rafts, which contain high amounts of sphingomyelin and cholesterol
True or false: the double-whammy of familial hypercholesterolemia is that because the patient’s cells are unable to endocytose LDL particles, their cells continue to synthesize high levels of cholesterol from acetyl-CoA.
True
Can clathrin self-assemble into spheres?
Yes
Can adaptor proteins AP1 and AP2 self-assemble into spheres?
No
Adaptor proteins bind to the cytosolic side of vesicle-membrane-bound cargo receptors. They provide a landing spot for clathrin coat proteins to bind to and form the coat
Can Sec13 and Sec31 self-assemble into spheres?
Yes
Can Sar1 self-assemble into spheres?
No
True or false: Goldstein and Brown found that if an LDL receptor can bind LDL particles but can not internalize them, the mutation is likely to be in the cytosolic C-terminal domain.
True
True or false: Goldstein and Brown found that when they measured “degradation”, they were assessing whether radioactively labelled tyrosine was part of the ApoB protein - or existed as free tryosine (an amino acid).
True
True or false: to measure receptor binding in the absence of internalization, Goldstein and Brown kept their cells at 37oC.
False
True or false: Goldstein and Brown found that if a patient’s cells failed to bind LDL-particles, the ONLY plausible explanation was that their receptors have a mutation in the LDL binding domain of the receptor.
False
Are heart attacks at a young age (related to the blocked coronary arteries) the most critical health issue of patients with familial hypercholesterolemia?
YES
Were enzymes that inhibit protein translation the most essential piece of the Rothman lab’s biochemical studies?
Yes
What is the effect of using scaffold proteins on either the specificity or amplification of the cell signaling process?
Specificity and speed increased, but amplification is decreased.
Pills that function as antagonists for beta 1 epinephrine receptors are helpful for…
Individuals who need to avoid elevated heart rates
Does inactivation of G(alpha)i reduce/block cAMP signaling?
No
Does inactivation of G(alpha)i increase intracellular calcium levels?
No
Does inactivation of G(alpha)i cause cAMP to accumulate?
Yes
Does inactivation of G(alpha)i block calcium signaling?
No
If cholera toxin was instead introduced into a person’s lungs, would it cause lung symptoms like the genetic disorder cystic fibrosis?
No, because cholera toxin ultimately hyperactives the cystic fibrosis transporter (CFTR)
Cystic fibrosis is caused by CFTR being downregulated/nonfunctional
True or false: If you are looking for a potent inhibitor against enzyme X, look for the one with the lowest IC50 value.
True
True or false: If you are looking for a potent inhibitor against enzyme X, look for the one with the highest IC50 value.
False
Could a GPCR be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Could IP3 be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Could secretory vesicles that fuse with the plasma membrane and release their contents be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Could G(alpha)q be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Could a ligand gated ion channel be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Could Notch be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
No
Could a change in cell shape be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Could an RTK be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?
Yes
Is endocytosis of the receptor (and its bound ligand) for destruction in the lysosome a mechanism used by cells to turn signals off?
Yes
Is a signaling molecule being a GTPase that hydrolyzes its bound GTP to GDP when it interacts with the effector a mechanism used by cells to turn signals off?
Yes
Is reassociation of inhibitory subunits a mechanism used by cells to turn signals off?
Yes
Is a phosphodiesterase that converts cAMP to AMP or cGMP to GMP a mechanism used by cells to turn signals off?
Yes
Are cytosolic phosphatases that remove the phosphates that had previously been added by activated kinases a mechanism used by cells to turn signals off?
Yes
Is a receptor being cleaved for the cytosolic fragment to enter the nucleus a mechanism used by cells to turn signals off?
No
What’s the cellular outcome of activation of PLC by either G(alpha)q-GTP or an RTK?
Elevation of intracellular Ca2+ levels and activation of PKC
What’s the cellular outcome of NO binding to its receptor within smooth muscle cells of the blood vessels?
Elevation of intracellular cGMP levels, leading to the activation of PKG
What’s the cellular outcome of adenylyl cyclase being activated by G(alpha)s-GTP?
Elevation of intracellular cAMP levels, leading to the activation of PKA
What’s the cellular outcome of G-protein Ras activation?
Activation of a MAPK
True or false: In the context of cell signaling, slower long-term responses generally involve changes in gene transcription whereas faster short-term responses involve modulating cytosolic enzymes involved in metabolism or the cell’s cytoskeleton.
True
What protein domain binds to phosphorylated tyrosines and surrounding amino acids?
SH2
What protein domain is involved in many protein-protein binding interactions?
SH3
What protein (or protein domain) acts as a NO receptor?
Guanylyl cyclase
What protein ( or protein domain) is part of the Gbeta/Ggamma dimer that forms a trimer with Galpha-GDP and sometimes activates effectors as a beta/gamma pair?
Gbeta
What protein (or protein domain) is the middle member of the MAPK kinase cascade and is a dual-specificity kinase that can phosphorylate ser/thr or tyr?
MEK (MAPKK)
What protein forms a dimer and binds to two phosphates of its substrates, has many roles, and in the context of cell signaling sequesters RAF (MAPKKK) in the cytosol?
14-3-3
What protein functions as a cell contact-dependent signaling molecule?
Delta/Serrate
What molecule can freely diffuse across membranes, but due to its short half-life affects only nearby cells?
Nitric Oxide (NO)
What molecule can freely diffuse across membranes, but due to its hydrophobicity is carried through the bloodstream in association with carrier proteins?
Estrogen and other steroid hormones
The binding of which ligands often results in receptor dimerization?
Ligands for RTKs
Activation of which plasma membrane anchored GTPase requires the signal mediated recruitment of its GEF to the membrane?
Ras
True or false: Gamma secretase is an enzyme that cleaves both Notch and the amyloid precursor protein (APP). One unusual feature of this enzyme is that it cleaves the transmembrane domain of its substrates.
True
Is the following a method by which two cells could respond differently to the same signaling molecule?
The two cells express the exact same receptor but they are different cell types and thus express different effectors and/or potential substrates.
Yes
Is the following a method by which two cells could respond differently to the same signaling molecule?
The two cells express different types of receptors that nevertheless bind to the same signaling molecule
Yes
Is the following a method by which two cells could respond differently to the same signaling molecule?
One cell expresses an appropriate receptor while the other does not
Yes
List 3 ways two cells could respond differently to the same signaling molecule
The two cells express the exact same receptor but they are different cell types and thus express different effectors and/or potential substrates.
One cell expresses an appropriate receptor while the other does not
The two cells express different types of receptors that nevertheless bind to the same signaling molecule
What is the structure of a generic G-protein coupled receptor?
7 alpha helix TMDs
What is the structure of an RTK?
Single TMD with an enzymatic domain in its cytosolic tail
What is the structure of a Notch receptor?
Single alpha helix TMD. Most forms include both a transcriptional activation domain and a nuclear localization sequence (NLS) in their cytosolic tail
What is the structure of a nuclear hormone receptor?
Lacks transmembrane domains and is found in the cytosol or nucleus. In addition to having a ligand binding domain, they also have a DNA binding domain.
What is the structure of a NO receptor?
Lacks transmembrane domains and is found in the cytosol or nucleus. In addition to having a ligand binding domain they are also guanylyl cyclases.
What receptor’s structure includes 7 alpha helix TMDs?
GPCR
What receptor’s structure has a single TMD with an enzymatic domain in its cytosolic tail?
RTK
What receptor’s structure has a single alpha helix TMD, and most forms include both a transcriptional activation domain and a nuclear localization sequence (NLS) in their cytosolic tail?
Notch
What receptor’s structure lacks a TMD, is found in the cytosol or nucleus, has a ligand binding domain, and a DNA binding domain?
Nuclear hormone receptor
What receptor’s structure lacks TMDs, is found in the cytosol or nucleus, has a ligand binding domain, and guanylyl cyclases?
NO receptors
