part 6

Question 1

what is the endomembrane system

Answer 1

ER, Golgi, transport vesicles, endosomes, lysosomes.

Question 2

what are the functions of the endomembrane system

Answer 2

transportation, storage, degradation, and production

Question 3

what are clathrin

Answer 3

a set of proteins that allow for the formation of the endosome as a pathogen is being taken in.
Found on the surface of the cell.

Question 4

what is cathepsin

Answer 4

Cysteine proteases
S, L, B, D
Need an acidic environment to be activated (acidification).

Question 5

what are the four types of cathepsin

Answer 5

S: almost all APCs express this enzyme
L: expressed in thymic cortisol cells (T cell training in thymus)
B and D: plays a role, but not much.

Question 6

what pathogens bind to MHC I

Answer 6

cytosolic

Question 7

what pathogens are are presented to CD8 cells

Answer 7

cytosolic
cell death

Question 8

what pathogens are presented on MHC II

Answer 8

intravesicular and extracellular

Question 9

what pathogens are presented to CD4 cells

Answer 9

intravesicular and extracellular

Question 10

how are intravesicular pathogens neutralized

Answer 10

activates killing; endocytic vesicles (low pH)

Question 11

how are extracellular pathogens neautralized

Answer 11

presenting cell activates B cells to secrete Ig; endocytic vesicles (low pH)

Question 12

what are TAPs

Answer 12

transports peptides from the cytosol into the endoplasmic reticulum, thereby selecting peptides matching in length and sequence to respective MHC class I molecules

Question 13

how many TAPs are there

Answer 13

1 and 2

Question 14

how long are the peptides TAP transports

Answer 14

8-16 AAs long

Question 15

what are the physical properties of TAP

Answer 15

TAP 1 and 2 transversing the membrane, with ATP binding cassesttes exposed on cytosol side

Question 16

what is the proteasome complex

Answer 16

Tube-like complex
Degradation complex
Takes chains of amino acids and chops them.
Main type of proteasome completely degrades proteins.

Question 17

what are the parts of the proteasome complex

Answer 17

The catalytic chamber (20S Core) is where digestion takes place.
Made up of 7 columns; 4 proteins per column.

Ubiquitin protein: highly-conserved, about 73 amino acids long
Targets proteins for degradation (tagging).

19S regulatory particle of proteasome binds to ubiquitin

Question 18

what is ubiquitin? why is it important

Answer 18

a protein found in most tissues (ubiquitous)
Proteins are marked for degradation by the attachment of ubiquitin to the amino group of the side chain of a lysine residue

Question 19

what is the immunoproteasome complex for

Answer 19

antigen presenting

Question 20

what does interferon secretion upregulate

Answer 20

upregulates the amount of MHC I presented on the surface, which allows for upregulation of TAP LMP2 and LMP7, (MECL-1) (core protein)
PA28 (regulatory proteins)

Question 21

what is the first step of MHC I expression

Answer 21

Partially folded MHC class I alpha chains bind to calnexin (chaperone protein) until B2-microglobulin binds.

Question 22

what is the second step of MHC I expression

Answer 22

MHC class I alpha:beta complex is released from calnexin, binds to chaperone complexes (calreticulin and ERp57) and binds to TAP via tapasin

Question 23

what does tapasin do

Answer 23

associates with TAP

Question 24

what is ERp57

Answer 24

thioreductase (breaking disulfide bonds)

Question 25

what are DRiPs

Answer 25

About 30% of all proteins are defective (DefectiveRibosomalProducts) DRiPs are chopped up by proteasome

Question 26

what is the third step of MHC I expression

Answer 26

Cytosolic proteins and DRiPs are degraded to fragments by proteasome. TAP delivers peptides to ER.

Question 27

what is TRiC

Answer 27

protects peptides from being degraded as they move to TAP.

Question 28

what is ERAAP

Answer 28

cuts and modify TriC from peptides

Question 29

what is the fourth step of MHC I expression

Answer 29

Peptide binds to MHC and the MHC finishes its folding. MHC is released from the TAP complex, is transported, and is expressed on cell membrane.

Question 30

how do viruses evade being destroyed by the immune system

Answer 30

by messing with the MHC, TAP, and MHC chaperone complex Herpes, adenovirus

Question 31

what happens in early endosomes when antigen is first taken in

Answer 31

pH is neutral and endosomal proteases are inactive. Chloroquine prevents acidification of endosomes.

Question 32

what is the first step of MHC II expression

Answer 32

Antigen is taken into the cytosol by vesicle

Question 33

what is the second step of MHC II expression

Answer 33

Acidification within the vesicle activates proteases to degrade antigen into peptide fragments.

Question 34

what is the third step of MHC II expression

Answer 34

Vesicles containing peptides fuse with vesicles containing MHC II molecules, where the MHC II is later expressed on the surface of the cell.

Question 35

what happens to the MHC II vesicle as it moves to the surface of the cell

Answer 35

it moves through different vesicles

Question 36

what maintains MHC II when not bound to pathogen proteins

Answer 36

bound to invariant protein

Question 37

what is the structure of an invariant protein

Answer 37

9 protein complex

Question 38

where is the invariant protein bound on MHC II

Answer 38

binds in the groove of MHC II

Question 39

what is the first step of invariant cleaving

Answer 39

Ii is cleaved initially to leave only a fragment bound to MHC II and membrane

Question 40

what is the second step of invariant cleaving

Answer 40

Ii is further cleaved into CLIP, which is only bound to the MHC II molecule

Question 41

what swaps the invariant with the antigen for MHC II

Answer 41

HLA-DM swaps invariant chains with the antigen (peptide editing)

Question 42

what does HLA-DM resemble

Answer 42

resembles MHC II with no binding site.

Question 43

where/when is the invariant switched with the antigen

Answer 43

MIIC (a compartment) is where HLA-DM swaps CLIP with antigen During second step

Question 44

what produces more HLA-DM

Answer 44

IFN a, b, and g

Question 45

what does HLA-DO do

Answer 45

it is an inhibitor to HLA-DM and competitor of HLA-DM

Question 46

when are self-peptides expressed

Answer 46

presented on MHC II in order for cell replacement in the periphery Tolerance

Question 47

what is special about dendritic cells

Answer 47

A dendritic cell (swallows cell) can take an antigen presented on MHC and present it on themselves.