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Characterization of multiple multivesicular body sorting determinants within Sna3: a role for the ubiquitin ligase

Andrea J Oestreich1, Mariam Aboian, Jacqueline Lee

  • 1Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.

Molecular Biology of the Cell
|December 22, 2006
PubMed

Insights

This study reveals how the protein Sna3 is sorted into multivesicular bodies (MVBs), identifying key regions and the ubiquitin ligase Rsp5. These findings uncover new mechanisms for MVB targeting beyond ubiquitination.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Protein Trafficking

Background:

  • Multivesicular bodies (MVBs) are crucial for cellular processes like receptor downregulation and antigen presentation.
  • Protein sorting into MVBs is a regulated process, often modulated by ubiquitination.
  • The protein Sna3 is a known MVB cargo, with sorting not strictly dependent on ubiquitination.

Purpose of the Study:

  • To identify novel sorting signals for MVB targeting.
  • To investigate the role of ubiquitination and other factors in Sna3 MVB sorting.
  • To elucidate the function of the ubiquitin ligase Rsp5 in MVB protein trafficking.

Main Methods:

  • Analysis of Sna3 mutants lacking lysine residues to identify sorting determinants.
  • Investigating the interaction between Sna3 motifs and the ubiquitin ligase Rsp5.
  • Assessing the impact of mutations in Rsp5 domains on Sna3 MVB targeting.

Main Results:

  • Two critical regions for Sna3 MVB sorting were identified: an N-terminal tyrosine-containing region and a C-terminal PPAY motif.
  • The PPAY motif interacts with the WW domains of Rsp5.
  • Mutations in Rsp5, including its HECT domain, impaired MVB targeting of Sna3, suggesting a role beyond ubiquitination.

Conclusions:

  • Sna3 MVB sorting is influenced by specific motifs and the ubiquitin ligase Rsp5.
  • Rsp5 plays a role in MVB targeting of Sna3 independent of its ubiquitination function.
  • These findings expand the understanding of MVB biogenesis and protein sorting mechanisms.

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