dendritic cells regulate exposure of mhc class ii at their plasma membrane by oligoubiquitination
Post on 01-Feb-2016
22 Views
Preview:
DESCRIPTION
TRANSCRIPT
Dendritic Cells Regulate Exposure of MHC Class II at Their Plasma Membrane by
Oligoubiquitination
Joost SnijderVera Verhage
Supervisor: Prof. W. Stoorvogel
Proteolytic processing of MHC-II
Research Aim
To establish what role ubiquitination has in sorting of MHC-II complexes in DC’s
MHCII-ß is oligo-ubiquitinated
Ubiquitination takes place in the MVB after peptide loading
Proteolytic processing of Ii is required for Ubiquitination, DC maturation interferes
Summary
• MHCII-ß is oligo-ubiquitinated
• Ubiquitination takes place in the MVB after peptide loading
• Proteolytic processing of Ii is required for ubiquitination
• LPS-induced maturation interferes with ubiquitination
Target residue 225
• Conserved Lysine residue 225• Ak-βK225A = mutant Lysine Alanine• 2 MHCII Haplotypes– Ab-α/β = Wild type– Ak-α/β = Transduced haplotype
Fig 4B
• Wild-type Ak-β was ubiquitinated – Not mutant Ak- βK225A
Fig 4A• Distribution of Ab-α in Ab-β-KO
+ Ak-β-(wt) BMDC equal to WT BMDC
• In Ab- β KO no MHCII expression
• Ak-b-K225 accumulates at PM– Does not get ubiquitinated
Fig 4C
• Exogenous mixes haplotypes are properly assembled in transduced WT– ubiquitination-deficient Ak-
βK225A located at plasma membrane
Fig 5
• Endogenous MHC II in MVB was associated 74% with LV (74%)
• In Ak-bK225A, 16% was found located in LV– Sorting is drastically changed
Sorting steps
• Where is ubiquitination involved or required?– Is it endocytosis or
recycling?
Fig 6A
• Transfer from EEA1 to DM positive structure– EEA1, early endosomal marker– DM class II compartment
• Delay in Mutant Ak-bK225A
• 20°C, endocytosis occurs,but no recycling and transport to lysosomes
• Less Ak-bK225A was detected intracellularly (vs Ab-b) (ratio 5.5 ± 1.4)
• Due to reduced uptake or accelerated recyling?
Conclusion
• Ubiquitination of MHC II-b – occurs at lysine 225 and is required for
intracellular retention of MHC II in immature DCs.– is required for sorting at MVB, failure result in
transfer by default to the plasma membrane– Is required for efficient endocytosis
top related