PT  - JOURNAL ARTICLE
AU  - Nicholas R. Weir
AU  - Roarke A. Kamber
AU  - James S. Martenson
AU  - Vladimir Denic
TI  - A New Quantitative Cell Microscopy Approach Reveals Mechanistic Insights into Clearance of Membrane Substrates by the AAA Protein Msp1
AID  - 10.1101/136572
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 136572
4099  - http://biorxiv.org/content/early/2017/05/10/136572.short
4100  - http://biorxiv.org/content/early/2017/05/10/136572.full
AB  - Msp1 is a conserved AAA ATPase in budding yeast localized to the surface of mitochondria where it prevents accumulation of mistargeted tail-anchored (TA) proteins, including the peroxisomal TA protein Pex15. Msp1 also resides on peroxisomes but it remains unknown how TA proteins native to mitochondria and peroxisomes evade Msp1 surveillance. Using new quantitative cell microscopy tools for studying Msp1 function, we observed that a fraction of peroxisomal Pex15, exaggerated by overexpression, is turned over by Msp1. Kinetic analysis and theoretical modeling revealed that mitochondrial Pex15 molecules are all equally susceptible to Msp1. By contrast, peroxisomal Pex15 molecules are converted from an initial Msp1-sensitive to an Msp1-resistant state. Lastly, we show that Pex15 interacts with the peroxisomal membrane protein Pex3, which shields Pex15 from Msp1-dependent turnover. In sum, our work argues that Msp1 selects its substrates on the basis of their solitary membrane existence.