Temporal system-level organization of the switch from glycolytic to gluconeogenic operation in yeast.

The diauxic shift in Saccharomyces cerevisiae is an ideal model to study how eukaryotic cells readjust their metabolism from glycolytic to gluconeogenic operation. In this work, we generated time-resolved physiological data, quantitative metabolome (69 intracellular metabolites) and proteome (72 enzymes) profiles. We found that the diauxic shift is accomplished by three key events that are temporally organized: (i) a reduction in the glycolytic flux and the production of storage compounds before glucose depletion, mediated by downregulation of phosphofructokinase and pyruvate kinase reactions; (ii) upon glucose exhaustion, the reversion of carbon flow through glycolysis and onset of the glyoxylate cycle operation triggered by an increased expression of the enzymes that catalyze the malate synthase and cytosolic citrate synthase reactions; and (iii) in the later stages of the adaptation, the shutting down of the pentose phosphate pathway with a change in NADPH regeneration.

Lack of stabilized microtubules as a result of the absence of major maps in CAD cells does not preclude neurite formation.

In many laboratories, the requirement of microtubule-associated proteins (MAPs) and the stabilization of microtubules for the elongation of neurites has been intensively investigated, with controversial results being obtained. We have observed that the neurite microtubules of Cath.a-differentiated (CAD) cells, a mouse brain derived cell, are highly dynamic structures, and so we analyzed several aspects of the cytoskeleton to investigate the molecular causes of this phenomenon.

Acetylated tubulin associates with the fifth cytoplasmic domain of Na(+)/K(+)-ATPase: possible anchorage site of microtubules to the plasma membrane.

We showed previously that NKA (Na(+)/K(+)-ATPase) interacts with acetylated tubulin resulting in inhibition of its catalytic activity. In the present work we determined that membrane-acetylated tubulin, in the presence of detergent, behaves as an entity of discrete molecular mass (320-400 kDa) during molecular exclusion chromatography. We also found that microtubules assembled in vitro are able to bind to NKA when incubated with a detergent-solubilized membrane preparation, and that isolated native microtubules have associated NKA.