Quizzes 6-7

Question 1

Is the maturation of late endosomes into lysosomes accompanied by an increase in the number of v-SNAREs?

Answer 1

No

SNAREs would be sent back out via a recycling compartment before lysosomal maturation

Question 2

Is the maturation of late endosomes into lysosomes accompanied by an increase in pH?

Answer 2

No, a decrease in pH

Question 3

Is the maturation of late endosomes into lysosomes accompanied by an increase in the number of lysosomal enzymes?

Answer 3

Yes, duh

Question 4

Is the maturation of late endosomes into lysosomes accompanied by a decrease in the number of mannose-6-phosphate receptors?

Answer 4

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.

Question 5

Is the maturation of late endosomes into lysosomes accompanied by an increase in the number of V-type pumps?

Answer 5

Yes

V-type pumps burn ATP to create a proton gradient, acidifying lumens

Question 6

At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast Sec23 mutants?

Answer 6

Greatly expanded “boated” ER

Question 7

At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast Sec12 mutants?

Answer 7

Greatly expanded “bloated ER”

Remember that Sec12 is Sar1’s GEF

Question 8

At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast GlcNAc phosphotransferase mutants?

Answer 8

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

Question 9

At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast synaptic vesicle v-SNARE mutants?

Answer 9

Accumulation of uncoated synaptic vesicles

Vesicles would shed their coats and prepare for docking, but never actually fuse

Question 10

At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast KDEL receptor mutants?

Answer 10

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

Question 11

At the non-permissive temperature, what phenotype would you see in temperature sensitive yeast NSF (N-ethylmaleimide sensitive fusion protein) mutants?

Answer 11

Accumulation of entwined SNAREs in target membranes

NSF uses ATP hydrolysis to unwind v and t SNAREs

Question 12

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.

Answer 12

True

Key word: likely.

Question 13

Is the binding interaction between LDL receptors and LDL particles released by a change in pH?

Answer 13

Yes

Binding: pH ~7
Release: pH ~5

Question 14

Is the binding interaction between the intertwined v and t SNAREs released by a change in pH?

Answer 14

No

Requires NSF’s ATP hydrolysis to be released

Question 15

Is the binding interaction between mannose-6-phosphate receptors and lysosomal enzymes released by a change in pH?

Answer 15

Yes

Question 16

Is the binding interaction between KDEL receptors and ER resident proteins released by a change in pH?

Answer 16

Yes

Question 17

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.

Answer 17

Yes

Cisternal maturation: cargo cohort stays in the compartment, enzymes move retrograde to new cohort

Question 18

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

Answer 18

Yes

Cisternal maturation: cargo cohort stays in the compartment, enzymes move retrograde to new cohort

Question 19

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

Answer 19

No

Cisternal maturation: cargo cohort stays in the compartment, enzymes move retrograde to new cohort

Question 20

Would non-hydrolyzable ATP lead to an accumulation of COPII vesicles?

Answer 20

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)

Question 21

Would non-hydrolyzable ATP lead to an accumulation of COPI vesicles?

Answer 21

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)

Question 22

Would non-hydrolyzable ATP lead to an accumulation of clathrin-coated vesicles?

Answer 22

Yes

ATP is involved in the uncoating of clathrin-coated vesicles (Hsp70, an ATPase, allows for the clathrin coat to shed)

Question 23

True or false: during the process of vesicular fusion, energy from ATP hydrolysis is required for the tight wrapping/braiding of the SNARE pairs.

Answer 23

False

SNARE wrapping is energetically favorable, happens stochastically/spontaneously

Question 24

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

Answer 24

False

Internal vesicle membrane proteins are destined to be degraded

Question 25

Does targeting of plasma membrane proteins involve vesicular transport?

Answer 25

Yes

Question 26

Does targeting of histones involve vesicular transport?

Answer 26

No

Question 27

Does targeting of lysosomal enzymes involve vesicular transport?

Answer 27

Yes

Question 28

Does targeting of glycosylation enzymes within the golgi involve vesicular transport?

Answer 28

Yes

Question 29

Does targeting of protein hormones (like insulin) involve vesicular transport?

Answer 29

Yes Hormone, synthesized in the smooth ER. Requires a vesicle to get from the ER to wherever else it needs to go

Question 30

Is ApoA part of LDL particles?

Answer 30

No. (it's part of HDL particles)

Question 31

What is the role of the Rab GTPase?

Answer 31

"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

Question 32

What's the role of the dynamin GTPase?

Answer 32

Scission of clathrin coated vesicles from the donor membrane

Question 33

What's the role of the Sar1 GTPase?

Answer 33

"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

Question 34

What's the role of ARF GTPases?

Answer 34

"Key for moving glycosylation enzymes in a retrograde fashion within the golgi" It's the associate GTPase for COPI and clathrin coated vesicles.

Question 35

What vesicle type would you expect to be associated with mannose-6-phosphate receptors?

Answer 35

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

Question 36

What vesicle type would you expect to be associated with a clump of seemingly aggregated protein?

Answer 36

Formation of a regulatory secretory vesicle

Question 37

What vesicle type would you expect to be associated with medial-golgi enzymes?

Answer 37

COPI vesicles

Question 38

What vesicle type would you expect to be associated with antiporters that typically reside in the apical cell membrane?

Answer 38

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

Question 39

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.

Answer 39

True

Question 40

Can clathrin self-assemble into spheres?

Answer 40

Yes

Question 41

Can adaptor proteins AP1 and AP2 self-assemble into spheres?

Answer 41

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

Question 42

Can Sec13 and Sec31 self-assemble into spheres?

Answer 42

Yes

Question 43

Can Sar1 self-assemble into spheres?

Answer 43

No

Question 44

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.

Answer 44

True

Question 45

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).

Answer 45

True

Question 46

True or false: to measure receptor binding in the absence of internalization, Goldstein and Brown kept their cells at 37oC.

Answer 46

False

Question 47

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.

Answer 47

False

Question 48

Are heart attacks at a young age (related to the blocked coronary arteries) the most critical health issue of patients with familial hypercholesterolemia?

Answer 48

YES

Question 49

Were enzymes that inhibit protein translation the most essential piece of the Rothman lab's biochemical studies?

Answer 49

Yes

Question 50

What is the effect of using scaffold proteins on either the specificity or amplification of the cell signaling process?

Answer 50

Specificity and speed increased, but amplification is decreased.

Question 51

Pills that function as antagonists for beta 1 epinephrine receptors are helpful for...

Answer 51

Individuals who need to avoid elevated heart rates

Question 52

Does inactivation of G(alpha)i reduce/block cAMP signaling?

Answer 52

No

Question 53

Does inactivation of G(alpha)i increase intracellular calcium levels?

Answer 53

No

Question 54

Does inactivation of G(alpha)i cause cAMP to accumulate?

Answer 54

Yes

Question 55

Does inactivation of G(alpha)i block calcium signaling?

Answer 55

No

Question 56

If cholera toxin was instead introduced into a person's lungs, would it cause lung symptoms like the genetic disorder cystic fibrosis?

Answer 56

No, because cholera toxin ultimately hyperactives the cystic fibrosis transporter (CFTR) Cystic fibrosis is caused by CFTR being downregulated/nonfunctional

Question 57

True or false: If you are looking for a potent inhibitor against enzyme X, look for the one with the lowest IC50 value.

Answer 57

True

Question 58

True or false: If you are looking for a potent inhibitor against enzyme X, look for the one with the highest IC50 value.

Answer 58

False

Question 59

Could a GPCR be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?

Answer 59

Yes

Question 60

Could IP3 be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?

Answer 60

Yes

Question 61

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?

Answer 61

Yes

Question 62

Could G(alpha)q be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?

Answer 62

Yes

Question 63

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?

Answer 63

Yes

Question 64

Could Notch be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?

Answer 64

No

Question 65

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?

Answer 65

Yes

Question 66

Could an RTK be involved in either the cell signaling pathway or cell response associated with a rise in intracellular calcium levels?

Answer 66

Yes

Question 67

Is endocytosis of the receptor (and its bound ligand) for destruction in the lysosome a mechanism used by cells to turn signals off?

Answer 67

Yes

Question 68

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?

Answer 68

Yes

Question 69

Is reassociation of inhibitory subunits a mechanism used by cells to turn signals off?

Answer 69

Yes

Question 70

Is a phosphodiesterase that converts cAMP to AMP or cGMP to GMP a mechanism used by cells to turn signals off?

Answer 70

Yes

Question 71

Are cytosolic phosphatases that remove the phosphates that had previously been added by activated kinases a mechanism used by cells to turn signals off?

Answer 71

Yes

Question 72

Is a receptor being cleaved for the cytosolic fragment to enter the nucleus a mechanism used by cells to turn signals off?

Answer 72

No

Question 73

What's the cellular outcome of activation of PLC by either G(alpha)q-GTP or an RTK?

Answer 73

Elevation of intracellular Ca2+ levels and activation of PKC

Question 74

What's the cellular outcome of NO binding to its receptor within smooth muscle cells of the blood vessels?

Answer 74

Elevation of intracellular cGMP levels, leading to the activation of PKG

Question 75

What's the cellular outcome of adenylyl cyclase being activated by G(alpha)s-GTP?

Answer 75

Elevation of intracellular cAMP levels, leading to the activation of PKA

Question 76

What's the cellular outcome of G-protein Ras activation?

Answer 76

Activation of a MAPK

Question 77

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.

Answer 77

True

Question 78

What protein domain binds to phosphorylated tyrosines and surrounding amino acids?

Answer 78

SH2

Question 79

What protein domain is involved in many protein-protein binding interactions?

Answer 79

SH3

Question 80

What protein (or protein domain) acts as a NO receptor?

Answer 80

Guanylyl cyclase

Question 81

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?

Answer 81

Gbeta

Question 82

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?

Answer 82

MEK (MAPKK)

Question 83

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?

Answer 83

14-3-3

Question 84

What protein functions as a cell contact-dependent signaling molecule?

Answer 84

Delta/Serrate

Question 85

What molecule can freely diffuse across membranes, but due to its short half-life affects only nearby cells?

Answer 85

Nitric Oxide (NO)

Question 86

What molecule can freely diffuse across membranes, but due to its hydrophobicity is carried through the bloodstream in association with carrier proteins?

Answer 86

Estrogen and other steroid hormones

Question 87

The binding of which ligands often results in receptor dimerization?

Answer 87

Ligands for RTKs

Question 88

Activation of which plasma membrane anchored GTPase requires the signal mediated recruitment of its GEF to the membrane?

Answer 88

Ras

Question 89

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.

Answer 89

True

Question 90

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.

Answer 90

Yes

Question 91

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

Answer 91

Yes

Question 92

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

Answer 92

Yes

Question 93

List 3 ways two cells could respond differently to the same signaling molecule

Answer 93

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

Question 94

What is the structure of a generic G-protein coupled receptor?

Answer 94

7 alpha helix TMDs

Question 95

What is the structure of an RTK?

Answer 95

Single TMD with an enzymatic domain in its cytosolic tail

Question 96

What is the structure of a Notch receptor?

Answer 96

Single alpha helix TMD. Most forms include both a transcriptional activation domain and a nuclear localization sequence (NLS) in their cytosolic tail

Question 97

What is the structure of a nuclear hormone receptor?

Answer 97

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.

Question 98

What is the structure of a NO receptor?

Answer 98

Lacks transmembrane domains and is found in the cytosol or nucleus. In addition to having a ligand binding domain they are also guanylyl cyclases.

Question 99

What receptor's structure includes 7 alpha helix TMDs?

Answer 99

GPCR

Question 100

What receptor's structure has a single TMD with an enzymatic domain in its cytosolic tail?

Answer 100

RTK

Question 101

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?

Answer 101

Notch

Question 102

What receptor's structure lacks a TMD, is found in the cytosol or nucleus, has a ligand binding domain, and a DNA binding domain?

Answer 102

Nuclear hormone receptor

Question 103

What receptor's structure lacks TMDs, is found in the cytosol or nucleus, has a ligand binding domain, and guanylyl cyclases?

Answer 103

NO receptors