Lecture 5- Ag presentation

Lecture 5- Ag presentation - A cell can be divided into an...

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A cell can be divided into an extracellular (including the vesicular system) and intracellular compartment During an infection, different organisms can gain access or are actively recruited to each compartment
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Cytoplasmic proteins (native, viral, bacterial) can be degraded into peptides by the uniquitin/proteosome system This is generally a response to misfolded proteins, but many folded proteins are also substrates at a lower efficiency
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Once degraded into peptides, protein antigens can be imported into the ER and loaded onto MHC I molecules for display to CD8+ T cells The immunoproteasome contains 3 distinct subunits that substitute for the cellular proteasome components. Genes are IFN- g inducible.
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TAP ( t ransporters associated with a ntigen p rocessing) were found though a mutation that caused a defect in antigen presentation, yet there was no defect in production of MHC I molecules Antigen presentation could be restored if peptides were added to the outside of the cell TAP was localized to the ER membrane, and shown to form a pore
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Once peptides are generated in the cytosol and transported into the ER by TAP, they may be trimmed at their amino-termini by ERAAP ( e ndoplasmic r eticulum a minopeptidase associated with a ntigen p rocessing)
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Once peptides are generated in the cytosol and transported into the ER by TAP, they may be trimmed at their amino-termini by ERAAP ( e ndoplasmic r eticulum a minopeptidase associated with a ntigen p rocessing) Retrograde transport of misfolded proteins from the ER (upon co- translational translocation) to the cytosol are also substrates for the immunoproteosome. Peptides are then imported back into the ER by TAP for presentation by MHC class I
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