Different motifs regulate trafficking of SorCS1 isoforms
Morten S Nielsen1, Sady J Keat, Jida W Hamati
1MIND center, Department of Medical Biochemistry, University of Aarhus, Aarhus, Denmark.
Traffic (Copenhagen, Denmark)
|March 5, 2008
Summary
Researchers identified novel SorCS1 isoforms in mice, with SorCS1c mediating internalization via a tyrosine-based motif. Human SorCS1a and -c utilize the AP-2 complex for internalization, suggesting distinct endocytic pathways for SorCS1 variants.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- SorCS1 is a type I transmembrane protein in the Vps10p-domain receptor family.
- While Sortilin and SorLA functions are known, SorCS subgroup functions remain largely uncharacterized.
- SorCS1 binds platelet-derived growth factor-BB (PDGF-BB) and exhibits isoform diversity in cytoplasmic domains.
Purpose of the Study:
- To identify and characterize novel mouse SorCS1 isoforms.
- To investigate the internalization mechanisms of different SorCS1 variants.
- To elucidate the role of SorCS1 isoforms in protein trafficking and cellular sorting.
Main Methods:
- In situ hybridization to analyze expression patterns of SorCS1 variants in mouse tissues.
- Functional assays to determine internalization mediated by specific SorCS1 isoforms.
- Analysis of protein-protein interactions, including adaptor protein (AP)-2 complex binding.
Main Results:
- Two novel mouse SorCS1 isoforms, m-SorCS1c and m-SorCS1d, were identified with distinct expression patterns.
- Only mouse SorCS1c mediated internalization through a conserved tyrosine-based motif.
- Human SorCS1a and SorCS1c internalization depend on the AP-2 complex, interacting via a DXXLL motif in human SorCS1a.
Conclusions:
- SorCS1 exhibits isoform-specific internalization mechanisms, differing between mouse and human.
- The AP-2 complex plays a crucial role in the endocytosis of human SorCS1 isoforms.
- Endocytic SorCS1 isoforms primarily target cargo to lysosomes, with limited involvement in Golgi-endosomal transport.
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