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M2MWeek6 > Cholera and Endocytosis/Protein Degradation > Flashcards

Cholera and Endocytosis/Protein Degradation Flashcards

1
Q

What are the two types of diarrhea?

A

Non-inflammatory (cholera) and inflammatory

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2
Q

How is non-inflammatory diarrhea characterized?

A

Watery. Small bowel

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3
Q

How is inflammatory diarrhea characterized?

A

^ Temp; fecal WBC; RBC. Colon

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4
Q

What is the name and type of bacteria that causes cholera?

A

Vibrio cholerae. Gram-negative motile rod (from brackish water). Infects only humans

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5
Q

What are clinical symptoms and signs?

A

Severe acute rapidly fatal watery diarrhea; vomiting; abd. pain; dehydration; renal failure low K+; Ca++; - ileus; muscle pain/spasm low HCO3- - metabolic/lactic acidosis; hypoglycemia; coma. OR you could be asymptomatic

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6
Q

What are 3 virulence factors of V. cholerae?

A

1: >200 serogroups (O-specific polysaccharide of LPS. EG 01 and 0139) 2: Pili (TCP: Toxin coregulated pilus) = colonization 3: Toxin (CT;AB5) = secretory diarrhea

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7
Q

What do 2 subunits of cholera toxin do?

A

A subunit is the active subunit that actually causes the secretion. B subunit is the binding subunit. 5 B subunits for each A subunit

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8
Q

What is the receptor for cholera toxin?

A

Ganglioside GM1 (on epithelial cells)

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9
Q

How does cholera toxin work?

A

Stimulates cAMP. Very similar to ETEC

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10
Q

What actually produces the CT?

A

A bacteriophage causes this change. Not the bacteria itself

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11
Q

How does increase of cAMP lead to diarrhea?

A

cAMP leads to more chloride secretion through CFTR (cysitc fibrosis transmembrane receptors?). Once you have chloride secretion sodium and water follow

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12
Q

How will histology of the bowel of a person with cholera look?

A

It will be completely normal

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13
Q

What are 5 factors that influence the pathogenesis of V. cholerae diarrhea?

A

Inoculum; pH (cholera is resistant); flagella; TCP (to cause adhesion/colonies); CT (cause diarrhea)

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14
Q

What are susceptibility factors to V.cholerae 01-related diarrhea?

A

Bug (colonizing strains); Host (children; hypochlorhydria; blood group O; Prior immunity; cystic fibrosis gene); Social (upheaval/war/migration)

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15
Q

How does cystic fibrosis transmembrane conductance regulate (CFTR) on chr. 7 affect cholera?

A

If you have cystic fibrosis your CFTR channel does not fold properly so you will be less susceptible to cholera. (This protective effect is seen in heterzygotes too)

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16
Q

Combined with IV fluids; what else really helps treat cholera?

A

Oral rehydration solution/treatment (ORT)

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17
Q

What is the mechanism of protection in cholera vaccine?

A

Antibodies to OPS of LPS are the primary mechanism of protection

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18
Q

What is present in the dukoral vaccine to cholera?

A

Killed V. cholerae 01 x2 + CtxB (WC-rBS). Killed bacteria plus B subunit of the toxin

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19
Q

What is present in the shanchol vaccine to cholera?

A

Killed V. cholerae 01 and 0139. Killed species of 2 different strains

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20
Q

Now onto endocytosis and protein degradation lecture

A

OK

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21
Q

What are the two mechanisms for vesicle formation?

A

Clathrin coat proteins (better understood) or caveolae

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22
Q

What does AP2 do with respect to LDL receptor-mediated endocytosis?

A

Lines the membrane pits and binds to clathrin and also to the LDL receptor

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23
Q

What is the order of vesicles after dynamin pinches it off from the plasma membrane?

A

Coated vesicle. Early endosome. Late endosome.

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24
Q

Where does the LDL particle become unbound from the LDL receptor? How does this happen? What is the fate of the LDLR and the LDL particle?

A

In the late endosome the pH is low (about 5.0). The LDLR gets recycled back to the plasma membrane and the LDL particle gets broken down into amino acids; fatty acids; and cholesterol in the lysosome.

25
Q

What are caveolae?

A

Small endocytic vesicles that form without coat proteins.

26
Q

What are caveolae especially important for?

A

Membrane domains known as lipid rafts (regions high in cholesterol and signaling molecules)

27
Q

What are some examples of bad things that enter specifically through caveolae?

A

Simian virus 40. Cholera toxin

28
Q

What structural protein is required for caveolae formation? What else is it important for?

A

Caveolin. Also important as a scaffolding protein for coordinating protein complexes

29
Q

How many caveolins are in each vesicle?

A

144

30
Q

Mutations in caveolin-3 gene leads to which diseases?

A

Limb Girdle disease and Rippling Muscle disease

31
Q

Which virus enters specifically through clathrin-mediated entry?

A

vesicular stomatitis virus (a problem for horses and cows)

32
Q

How does HIV enter the cells?

A

Fusion-entry

33
Q

How does vaccinia virus enter the cells?

A

Macropinocytosis-mediated entry

34
Q

How does herpes simplex virus enter the cells?

A

Phagocytosis-like-mediated entry

35
Q

How do bacteria enter the cells?

A

Phagocytosis-mediated entry

36
Q

What are three major protein degradation pathways in eukaryotic cells?

A

Ubiquitin-proteasome system (UPS - responsible for the rapid degradation of proteins when fast adaptation is needed). The lysosome (part of the endocytosis pathway). Autophagy (mainly involved in the degradation of long-lived proteins and entire organelles)

37
Q

What are the 2 best examples of chaperone (folding) proteins?

A

hsp70 and hsp60 (hsp=heat shock protein)

38
Q

How does hsp70 work?

A

helps fold a protein by binding to exposed hydrophobic patches in incompletely folded proteins and prevents aggregation

39
Q

How does hsp60 work?

A

Forms an elaborate barrel-shaped structure that acts as an isolation chamber. Misfolded proteins are fed into the chamber to prevent aggregation and to help it to refold

40
Q

How does the ER establish an environment conducive for protein folding?

A

Contains folding enzymes like ERp57 (allows formation of disulfide bonds). Contains molecular chaperones like BiP (similar to Hsp70 - uses ATP to help proteins fold). There are folding sensors that monitor unfolded proteins and hold them in the ER until they fold properly or are shuttled to a degradation pathway

41
Q

What two enzymes and two ER-resident proteins are involved in the protein refolding/degradation pathway?

A

Glucosyltransferase; glucosidase and calnexin; calreticulin

42
Q

What do calnexin and calreticulin do?

A

Bind the oligosaccharide chain if there is a glucose (they are lectins) and hold it until glucosidase removes the glucose. (Note: Calnexin is transmembrane and calreticulin is a soluble protein in the ER lumen)

43
Q

What does glucosyltransferase do?

A

Recognizes misfolded proteins and prevents them from leaving the ER. Puts a glucose back on the sugar chain so the protein will again be bound to calnexin/calreticulin. This process will continue until either the protein folds properly and exits the ER OR it “times out” and is retrotranslocated out of ER and destined for degradation

44
Q

What is the ubiquitin-proteasome degradation system?

A

Proteins destined for degradation are deglycosylated and have multiple ubiquitin molecules attached in order to target them to the proteosome. In the proteosome the misfolded protein is unwound and cut into short (7-9 AA) peptides.

45
Q

Where does proteolytic cleavage take place?

A

The central cylinder of the proteasome

46
Q

Which part of the proteasome recognizes polyubiquitin and uses ATP to unfold the protein?

A

The caps on each end of the cylinder

47
Q

What is required to attach ubiquitin to a protein?

A

3 ligase enzymes: E1; E2 and E3

48
Q

What is ubiquitin?

A

76 AA protein. Very conserved in all cells

49
Q

What does E1 do? How many genes code for it?

A

binds and activates ubiquitin and then pases it to E2. 1 gene codes for E1

50
Q

What does E3 do?

A

Has substrate specificity (roughly 500 E3 enzymes in mammals). Transfers ubiquitin from E2 to the protein by attaching the ubiquitin to a lysine in the protein. E3 then attaches a string of additional ubiquitins to the first one.

51
Q

How many ubiquitins are required by the proteasome as a tag for degradation?

A

A chain of at least four ubiquitins (polyubiquitins)

52
Q

How else are ubiquitins used?

A

mono or multiubiquitination can be use as regulatory signals (EX to regulate transcription)

53
Q

What is the primary role of lysososomes?

A

Degrade extracellular materials taken up by endocytosis (also degrade some intracellular components)

54
Q

How are plasma membrane proteins targeted for endocytosis/degradation?

A

They are monoubiquitinated. Then transferred via the late endosome/multivesicular body to the lysosome for degradation

55
Q

What is the multivesicular body?

A

A prelysosomal compartment; vesicles containing proteins slated for destruction bud into the lumen. When the multivesicular body fuses with the lysosome these vesicles are delivered into the lysosome for degradation

56
Q

Where do lysosomal membrane proteins like proton pumps and transporters come from?

A

They reach the lysosome by vesicles that bud from the Golgi and fuse with the lysosome. They are protected from degradation

57
Q

When is autophagy used?

A

A stress response to starvation or used to degrade organelles that are damaged or undergo normal turnover.

58
Q

Describe the general process of autophagy?

A

A double membrane forms around the organelle. The outer membrane fuses with the lysosome and the membrane enclosed organelle is delivered (like the vesicles in the multivesicular body) to the lysosome for degradation.

M2MWeek6 (8 decks)

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