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Sna3 is an Rsp5 adaptor protein that relies on ubiquitination for its MVB sorting

Chris MacDonald1, Daniel K Stringer, Robert C Piper

  • 1Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52246, USA.

Traffic (Copenhagen, Denmark)
|January 4, 2012
PubMed

Insights

Ubiquitin-independent protein sorting is less understood. This study reveals that yeast protein Sna3, previously thought to be sorted independently, actually requires ubiquitin conjugation for its trafficking and degradation.

Area of Science:

  • Cell biology
  • Molecular and cell biology
  • Protein trafficking

Background:

  • Ubiquitin conjugation is essential for integral membrane protein trafficking into multivesicular bodies (MVBs) and subsequent lysosomal degradation.
  • Ubiquitin-independent pathways for MVB sorting remain poorly understood.

Purpose of the Study:

  • To investigate the sorting mechanism of the yeast membrane protein Sna3, a putative ubiquitin-independent cargo.
  • To elucidate the role of Rsp5 ligase and ubiquitination in Sna3 trafficking.

Main Methods:

  • Characterization of Sna3 trafficking in yeast.
  • Analysis of Sna3 ubiquitination status.
  • Functional studies involving Sna3 as an adaptor protein.

Main Results:

  • Sna3 trafficking to the vacuole is dependent on Rsp5 ligase activity and ubiquitination.
  • Sna3 sorting into MVBs occurs in a ubiquitin-dependent manner, either through self-ubiquitination or association with other ubiquitinated proteins.
  • Sna3 functions as an adaptor protein, recruiting Rsp5 to cargo like Mup1 for efficient vacuolar delivery.

Conclusions:

  • Contrary to previous assumptions, Sna3 sorting is ubiquitin-dependent.
  • Sna3 plays a crucial role in recruiting the E3 ligase Rsp5 for the ubiquitination and trafficking of specific cargo proteins, such as Mup1.

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