Research

In eukaryotic cells, segregation of DNA replication and RNA transcription in the nucleus and protein synthesis in the cytoplasm poses the requirement of transporting thousands of proteins between the two cellular compartments. Hexokinase 2 (Hxk2) from Saccharomyces cerevisiae was one of the first metabolic enzymes described as a multifunctional protein. Hxk2 has a double subcellular localization; it functions as an enzyme in the cytoplasm and as a regulator of gene transcription of several Mig1-regulated genes in the nucleus. In addition of Hxk2, the main mediators of glucose repression signaling in yeast (Mig1, Snf1, Snf4, Gal83 y Mig2) also have a double cellular localization. Their movement between nucleus and cytoplasm is regulated by glucose levels in the culture medium. In our laboratory, we investigate the machinery and strategies for regulating the nuclear influx and efflux of proteins involved in glucose signaling of two reference yeast, S. cerevisiae, a yeast model with a deep metabolic response to high glucose conditions and K. lactis, as a high interest industrial yeast with low sensibility to high-glucose conditions. Given that the nucleocytoplasmic traffic of these proteins is critical for proper localization of transcription factors involved in cell proliferation, we expect that the process is tightly regulated. We carry on a systematic study of the mechanisms regulating the transport of the major mediators of glucose repression signaling both at the transported macromolecules and the specific soluble receptors levels.

The major components of the mitochondrial fusion and fission machineries have been evolutionarily conserved from yeast to humans. Due to this conservation and the accumulated knowledge on the genetics and physiology of S. cerevisiae, this yeast emerged as one of the prime model organisms to study mitochondrial dynamics. Like other membrane-fusion events, mitochondria are first tethered together before their outer and inner membrane bilayers mix. Three conserved GTPases, Fzo1, Ugo1 and Mgm1, have central roles in mitochondrial fusion. Similar to mitochondrial fusion, mitochondrial fission requires a GTPase, called Dnm1. Since fusion and fission processes are regulated by several proteins and it seems likely that additional yet unknown factors are involved, one laboratory research group is interested in the study of novel mitochondrial proteins involved in maintaining the morphology of these organelles.

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