LONP1 and mtHSP70 cooperate to promote mitochondrial protein folding.

Most mitochondrial precursor polypeptides are imported from the cytosol into the mitochondrion, where they must efficiently undergo folding. Mitochondrial precursors are imported as unfolded polypeptides. For proteins of the mitochondrial matrix and inner membrane, two separate chaperone systems, HSP60 and mitochondrial HSP70 (mtHSP70), facilitate protein folding.

The glutamate/cystine xCT antiporter antagonizes glutamine metabolism and reduces nutrient flexibility.

As noted by Warburg, many cancer cells depend on the consumption of glucose. We performed a genetic screen to identify factors responsible for glucose addiction and recovered the two subunits of the xCT antiporter (system x), which plays an antioxidant role by exporting glutamate for cystine. Disruption of the xCT antiporter greatly improves cell viability after glucose withdrawal, because conservation of glutamate enables cells to maintain mitochondrial respiration.

Bidirectional regulation between TORC1 and autophagy in Saccharomyces cerevisiae.

It has been reported in various model organisms that autophagy and the target of rapamycin complex 1 (TORC1) signaling are strongly involved in eukaryotic cell aging and decreasing TORC1 activity extends longevity by an autophagy-dependent mechanism. Thus, to expand our knowledge of the regulation of eukaryotic cell aging, it is important to understand the relationship between TORC1 signaling and autophagy. Many researchers have shown that TORC1 represses autophagy under normal growth conditions, and TORC1 inactivation contributes to the upregulation of autophagy.

Regulation of yeast Yak1 kinase by PKA and autophosphorylation-dependent 14-3-3 binding.

Yak1 is a member of an evolutionarily conserved family of Ser/Thr protein kinases known as dual-specificity Tyr phosphorylation-regulated kinases (DYRKs). Yak1 was originally identified as a growth antagonist, which functions downstream of Ras/PKA signalling pathway. It has been known that Yak1 is phosphorylated by PKA in vitro and is translocated to the nucleus upon nutrient deprivation.

TORC1 controls degradation of the transcription factor Stp1, a key effector of the SPS amino-acid-sensing pathway in Saccharomyces cerevisiae.

The target of rapamycin (TOR) signaling pathway plays crucial roles in the regulation of eukaryotic cell growth. In Saccharomyces cerevisiae, nitrogen sources in the extracellular environment activate the TOR signaling pathway. However, the precise mechanisms underlying the regulation of TOR activity in response to extracellular nitrogen sources are poorly understood.