Lecture 8

Question 1

What do proteasomes, Autophagy, and ERAD (ER-associated Degradation) all have in common?

Answer 1

they are all methods/tools of the cellular quality control system

Question 2

State the 5 problems that can arise due to improper protein folding

Answer 2

1. Improper degradation
2. Improper localization
3. Dominant negative mutations
4. Gain-of-toxic function
5. Amyloid accumulation

Question 3

generally explain 2 methods that can lead to “Improper degradation” caused by protein misfolding

Answer 3

Overactive ERAD and autophagy can lead to improper degradation due to misfolded proteins

Question 4

generally explain 2 examples of “improper localization”

caused by protein misfolding

Answer 4

Loss-of-function and Gain-of-function toxicity caused by misfolding are both examples of improper localization

Question 5

generally explain 2 examples of “Dominant negative mutations” caused by protein misfolding

Answer 5

A mutant protein antagonizes the function of the wild-type protein and causes one of the following:

Loss of protein activity

mutant protein presence interferes with the function of the WT protein at cellular and structural levels

Question 6

generally explain 3 examples of “Gain-of-toxic function” caused by protein misfolding

Answer 6

protein misfoldings can cause dominant phenotypes that cause the following:

APOE4 disrupts mito function, which impairs neurite outgrowth

(Cu-Zn) Superoxide dismutase (SOD1)

Src kinases in cancer

Question 7

Give 2 characteristics of Amyloidogenic proteins (sequence and function).

Answer 7

Characteristics:
Have a VQIVY sequence

Can cause amyloid-related diseases

Question 8

Define Amyloid fibers.

Answer 8

Amyloid fibers: insoluble protein aggregates

Question 9

Explain how an amyloid deposit could be a protective mechanism

Answer 9

an amyloid deposit may be created in an attempt to “isolate” a defective/misfolded protein to battle it’s negative functions

Question 10

what order of oligomers can cause a toxic effect? given an example of a toxic effect that an amyloidogenic protein can conduct on the cell membrane.

Answer 10

low order oligomers can cause a toxic effect.

Several amyloidogenic proteins form a “pore-like” structure that disrupts the integrity of the cell membrane

Question 11

state the 2 demographics that misfolded proteins are most commonly observed in.

Answer 11

elderly people (due to the aging process)

individuals with mutation in their proteins that occurred early in life

Question 12

True or False:

Amyloid fibrils cannot be “rescued” once they have been formed. explain.

Answer 12

true

their conformation is so low in energy that we have not yet found a treatment that can unfold the proteins from this conformationally stable state. (you can’t surgically remove it either bc its too invasive on the brain)

Question 13

Describe the stepwise process by which amyloid plaques are formed.(3 steps)

Answer 13

1. seeding occurs (nucleation)
2. Fibril formation occurs
3. amyloid fibers are deposited

Question 14

what enhances the formation of amyloid fibers?

Answer 14

covalent modifications enhance the formation of amyloid fibers

Question 15

Explain how small molecules and site-specific antibodies can block the formation of misfolded protein aggreagates

Answer 15

small molecules can act as a stabilizer

Site-specific antibodies can recognize conformational changes that occur AND sequence specific issues (like VQIVY)

Question 16

Intrinsic induction of stress defense programs can result in _____ and can increase ____ ____.

Answer 16

adaptation

life expectancy

Question 17

State the 3 keystones for environmental stressors

Answer 17

to detect

to respond

to adopt

(DRA mnemonic)

Question 18

Give an example of hormetic stress and then give an example of it that can lead to a longer lifespan

Answer 18

Hormetic Stress: moderate level of stress that can trigger beneficial/adaptive stress defense pathways, which may lead to loner life (what doesn’t kill you makes you stronger)

caloric restriction

Question 19

Define proteostasis. Then state the 3 activities (of both cellular and organismal functionality) it requires

Answer 19

Proteostasis: the maintenance of protein homeostasis, which is usually carried out via UPR’s (unfolded protein responses)

Requires:
Protein production

Folding

Degradation

Question 20

Describe the origin/setting of the following pathways that function to maintain proteostasis:

HSR:

UPR^ER:

UPR^mt:

Answer 20

HSR: (heat shock response) manages denatured proteins in the cytosol using HSF1

UPR^ER: ER stress initiated signal pathway

UPR^mt: Mitochondria initiated signal pathway

Question 21

Cellular proteins are folded by what?

Answer 21

chaperons

Question 22

Explain the synthesis/maturation of membrane and secreted protiens

Answer 22

membrane and secreted proteins fold and mature in the ER

Question 23

What is the last line of defense when it comes to managing misfolded proteins?

Answer 23

apoptosis (via an apoptotic pathway)

Question 24

State the 3 effects that occur when the UPR (unfolded protein response) signal pathway is activated

(UPR^ER and UPR^mt are examples of UPR)

Answer 24

1. Increase in protein chaperones
2. Increased rate of ERAD
3. Decreased protein production

Question 25

What are the 2 main players in the mitochondrial chaperon system?

Answer 25

mtHSP70 Multimeric HSP60-HSP10 machinery in the matrix (of the mito)

Question 26

Describe PQC proteases

Answer 26

PQC (protein quality control) proteases recognize and degrade the proteins that don't fold or are improperly assembled

Question 27

True or False: | There are specific PQC proteases for each mitochondrial compartment. explain.

Answer 27

True

Question 28

Explain how UPR^mt is initiated and what it does after it is initiated

Answer 28

UPR^mt senses the overload of the QC system capacity and activates the transcription of nuclear encoded protective genes in order to re-establish mitochondrial homeostasis