FIGURE 1.

Spatial protein quality control sites in Saccharomyces cerevisiae. When induced to misfold, proteins aggregate in the cytosol and on the ER membrane (Escusa-Toret et al., 2013). These initial cytosolic aggregates are called CytoQ (Miller et al., 2015), stress foci (Spokoini et al., 2012), peripheral aggregates (Specht et al., 2011), cytosolic puncta (Kaganovich et al., 2008) or Q-bodies (Escusa-Toret et al., 2013). These coalesce into larger structures, usually referred to as inclusions. Smaller inclusions have been observed tethered to actin cables (Liu et al., 2010; Song et al., 2014) or are captured by mitochondria (Zhou et al., 2014; Böckler et al., 2017). Yeast cells have several distinct larger inclusions including, but not limited to, the intranuclear quality control site (INQ), the juxtanuclear quality control site (JUNQ), and the perivacuolar IPOD site (Kaganovich et al., 2008; Miller et al., 2015). Other IPOD-like peripheral inclusions likely exist as some aggregates of model substrates do not co-localize with the IPOD, e.g., the non-amyloidogenic disease protein OPTN (Kryndushkin et al., 2012). An additional site, the age-associated protein deposit site (APOD, not depicted here) has been identified in aged cells (Saarikangas and Barral, 2015).