Deletion of HOG1 leads to Osmosensitivity in starvation-induced, but not rapamycin-dependent Atg8 degradation and proteolysis: further evidence for different regulatory mechanisms in yeast autophagy.

The mechanisms of regulation of autophagy are still obscure. In mammalian liver, starvation-induced autophagic proteolysis is regulated by the cellular hydration state in a microtubule- and p38(MAPK)-dependent way. Recent work shows that in yeast, loss of Hog1, the yeast orthologue of p38(MAPK), leads to osmosensitivity of starvation-induced autophagy (Prick et al., Biochem J 2006; 394:153-161), pointing to an evolutionarily conserved mechanism. In this addendum further experiments from hog1Delta yeast cells are shown, which support the hypothesis that starvation- and rapamycin-induced autophagy processes differ in their susceptibility to osmotic stress. The potential mechanisms are discussed.