Vocabulary and Objectives Week 7

Question 1

PA28

Answer 1

binds to either end of inducible proteosome; Opens up the ends and increases rate at which peptides are released; induced by IFN-g

Question 2

Proteosome

Answer 2

large protease complex that degrades cytosolic proteins

Question 3

Constitutive Proteosome

Answer 3

Always on; has alpha and beta subunits

Question 4

Immunoproteasome

Answer 4

Induced by IFN-g; LMP2, MECL-1, LMP7

Question 5

TAP

Answer 5

binds peptides from cytosol and transports them to the ER lumen to bind to Class I MHC

Question 6

ERAAP

Answer 6

Endoplasmic reticulum aminopeptidase associated with antigen processing; responsible for further processing of peptides so they can better fit into MHC I

Question 7

Rule 1

Answer 7

endogenous antigens are processed and presented in the class I pathway to CD8 T cells, endogenous antigens are found inside the cell

Question 8

Exception to Rule 1

Answer 8

cross presentation allows specialized DC to endocytose virally infected cells and present via class I to naïve CD8 cells; DC can take up pieces of virally infected cells in the endosome that then gets shuttled to the cytosolic compartment to be chopped up via the proteosome

Question 9

How do proteins from phagosome get into cytosol?

Answer 9

Phagosome to cytosol; Retro-translocation through Sec61-Endosome to ER; Fusion of ER and phagosome

Question 10

Calnexin

Answer 10

Binds to MHC I until B2m can bind

Question 11

What three proteins bind to MHCI and stabilize it in the ER?

Answer 11

Calreticulin, Erp57 and calnexin

Question 12

Tapasin

Answer 12

Binds to TAP and aids in TAP presenting peptides to MHC I

Question 13

Antigen processing

Answer 13

refers to the generation of peptides from an intact antigen that involves modification of native protein

Question 14

Antigen presentation

Answer 14

refers to the display of the peptide at the cell surface by MHC molecules to T cells

Question 15

CLIP

Answer 15

Class II Invariant Chain Peptide; sits in the peptide binding cleft of MHC II; stabilizes MHC II and keeps peptides from binding

Question 16

HLA-DM

Answer 16

acts as a peptide exchanger, facilitating the removal of CLIP and the addition of other peptides to class II MHC molecules

Question 17

Autophagy

Answer 17

enzymatic digestion of cytoplasmic contents

Question 18

Invariant Chain

Answer 18

Blocks premature binding of Class II MHC; promotes folding and assembly of class II MHC molecules and directs newly formed class II MHC molecules to the late endosomes and lysosomes; degraded by cathepsins

Question 19

Cathepsins

Answer 19

proteases in endosomal compartments, for class II,

Question 20

Evasins

Answer 20

can degrade class I or
bind to TAP and inhibit peptide loading

Question 21

MIIC endosomal Compartment

Answer 21

contains the enzymes that degrade protein antigens, class II MHC molecules, and two molecules involved in peptide loading of class II MHC molecules, the invariant chain and HLA-DM

Question 22

Where is the Class II MHC molecule generated?

Answer 22

Class II MHC molecules are synthesized in the ER and transported to endosomes with an associated protein, the invariant chain, which occupies the peptide-binding clefts of the newly synthesized class II MHC molecules