Open AccessSpatial and temporal regulation of the endoproteolytic activity of the SPS-sensor–controlled Ssy5 signaling protease
Author(s) -
Antônio Roberto Martins,
Andreas Ring,
Deike J. Omnus,
Stijn Heessen,
Thorsten Pfirrmann,
Per O. Ljungdahl
Publication year - 2019
Publication title -
molecular biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.463
H-Index - 225
eISSN - 1939-4586
pISSN - 1059-1524
DOI - 10.1091/mbc.e19-02-0096
Subject(s) - biology , endoplasmic reticulum , microbiology and biotechnology , protease , amino acid , saccharomyces cerevisiae , ubiquitin , extracellular , biochemistry , cleavage (geology) , proteolysis , ubiquitin ligase , intracellular , biophysics , enzyme , yeast , gene , paleontology , fracture (geology)
The Saccharomyces cerevisiae Ssy5 signaling protease is a core component of the plasma membrane (PM)–localized SPS (Ssy1-Ptr3-Ssy5) sensor . In response to extracellular amino acids, the SPS-sensor orchestrates the proteasomal degradation of the inhibitory Ssy5 prodomain. The unfettered catalytic (Cat)-domain cleaves latent transcription factors Stp1 and Stp2, freeing them from negative N-terminal regulatory domains. By studying the spatial and temporal constraints affecting the unfettered Cat-domain, we found that it can cleave substrates not associated with the PM; the Cat-domain efficiently cleaves Stp1 even when fused to the carboxy terminus of the endoplasmic reticulum (ER) membrane protein Shr3. The amino acid–induced cleavage of this synthetic membrane–anchored substrate occurs in a Δtether strain lacking ER–PM junctions. We report that the bulk of the Cat-domain is soluble, exhibits a disperse intracellular distribution, and is subject to ubiquitylation. Cat-domain ubiquitylation is dependent on Ptr3 and the integral PM casein kinase I (Yck1/2). Time-course experiments reveal that the non- and ubiquitylated forms of the Cat-domain are stable in cells grown in the absence of inducing amino acids. By contrast, amino acid induction significantly accelerates Cat-domain degradation. These findings provide novel insights into the SPS-sensing pathway and suggest that Cat-domain degradation is a requisite for resetting SPS-sensor signaling.