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Structural requirements for interactions between leucine-sorting signals and clathrin-associated adaptor protein
Dmitrii G Rodionov1, Stefan Höning, Aleksandra Silye
1Division of Molecular Cell Biology, Department of Biology, University of Oslo, Norway.
The Journal of Biological Chemistry
|October 9, 2002
Summary
Protein sorting signals in the cell are determined by residues upstream of leucine pairs, dictating interactions with adapter proteins (APs). This specificity directs proteins like LIMPII and the invariant chain to their correct cellular destinations.
Area of Science:
- Cell biology
- Molecular biology
- Protein trafficking
Background:
- Cytoplasmic tails of LIMPII and the invariant chain share leucine-based sorting signals.
- The invariant chain interacts with AP1 and AP2, while LIMPII binds strongly to AP3.
Purpose of the Study:
- Investigate how residues upstream of leucine pairs influence adapter protein binding.
- Determine the role of these upstream residues in protein sorting specificity.
Main Methods:
- In vitro binding assays to assess interactions between protein constructs and adapter proteins (AP1, AP2, AP3).
- In vivo studies using mutant LIMPII constructs to track protein localization and trafficking.
Main Results:
- Residues upstream of leucine signals dictate adapter protein specificity.
- Stronger AP3 interaction correlated with weaker AP1 interaction, and vice versa.
- Mutating LIMPII's upstream residues to mimic the invariant chain reduced AP3 binding and altered its trafficking pathway.
Conclusions:
- Upstream residues are critical determinants of leucine-based sorting signal specificity.
- Differential interactions with AP complexes (AP1, AP2, AP3) guide proteins from the trans-Golgi network to distinct cellular destinations like endosomes/lysosomes.
- AP2 may recognize a broader range of leucine signals, potentially involved in retrieving missorted proteins.