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The human-specific invariant chain isoform Iip35 modulates Iip33 trafficking and function
Kine Marita Knudsen Sand1, Ole J B Landsverk1, Axel Berg-Larsen1
1Department of Biosciences and Centre for Immune Regulation, University of Oslo, Oslo, Norway.
Immunology and Cell Biology
|July 2, 2014
Summary
The human invariant chain (Ii) isoform Iip35 significantly alters Iip33's function. Iip35 delays Iip33 transport from the ER, prolongs its half-life, and reduces its impact on endosomal maturation.
Area of Science:
- Immunology
- Cell Biology
- Protein Isoforms
Background:
- The invariant chain (Ii) is crucial for MHC class II assembly and transport.
- Four Ii isoforms (Iip33, Iip35, Iip41, Iip43) arise from a single gene.
- Human-specific isoforms Iip35 and Iip43 possess an ER retention motif.
Purpose of the Study:
- To investigate how the Iip35 isoform influences the cellular properties of Iip33.
- To understand the impact of Iip35 on Iip33 trafficking and function in human cells.
Main Methods:
- Co-expression of Iip33 and Iip35 in human cells.
- Analysis of Ii isoform behavior with and without MHC II.
- Assessment of ER transport, half-life, and endosomal maturation.
Main Results:
- Iip35 significantly delays Iip33 transport out of the endoplasmic reticulum (ER).
- The half-life of Iip33 is dramatically prolonged in the presence of Iip35.
- Iip35 abrogates Iip33's ability to induce enlarged endosomes and delayed endosomal maturation.
Conclusions:
- The Iip35 isoform profoundly modifies the cellular behavior and function of Iip33.
- Understanding Ii isoform interactions is key to comprehending MHC II pathway regulation.
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