Mig1 localization exhibits biphasic behavior which is controlled by both metabolic and regulatory roles of the sugar kinases

Gregor W Schmidt,Niek Welkenhuysen,Marija Cvijovic,Tian Ye,Stefan Hohmann

doi:10.1007/s00438-020-01715-4

Gregor W Schmidt, Niek Welkenhuysen + Show 3 more

Open Access

https://doi.org/10.1007/s00438-020-01715-4

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Abstract

Glucose, fructose and mannose are the preferred carbon/energy sources for the yeast Saccharomyces cerevisiae. Absence of preferred energy sources activates glucose derepression, which is regulated by the kinase Snf1. Snf1 phosphorylates the transcriptional repressor Mig1, which results in its exit from the nucleus and subsequent derepression of genes. In contrast, Snf1 is inactive when preferred carbon sources are available, which leads to dephosphorylation of Mig1 and its translocation to the nucleus where Mig1 acts as a transcription repressor. Here we revisit the role of the three hexose kinases, Hxk1, Hxk2 and Glk1, in glucose de/repression. We demonstrate that all three sugar kinases initially affect Mig1 nuclear localization upon addition of glucose, fructose and mannose. This initial import of Mig1 into the nucleus was temporary; for continuous nucleocytoplasmic shuttling of Mig1, Hxk2 is required in the presence of glucose and mannose and in the presence of fructose Hxk2 or Hxk1 is required. Our data suggest that Mig1 import following exposure to preferred energy sources is controlled via two different pathways, where (1) the initial import is regulated by signals derived from metabolism and (2) continuous shuttling is regulated by the Hxk2 and Hxk1 proteins. Mig1 nucleocytoplasmic shuttling appears to be important for the maintenance of the repressed state in which Hxk1/2 seems to play an essential role.

Highlights

The ability to sense and appropriately respond to the availability of nutrients is a central feature of all living organisms
When wild type cells preincubated with ethanol as a sole energy source were exposed to any of the three hexoses, Mig1 localized to the nucleus and reached its maximum nuclear localization signal within ~ 30 min (Fig. 2a)
We demonstrate that the Mig1 localization dynamics exhibit a short- and a long-term response after addition of hexoses to ethanol-grown cells

Summary

Introduction

The ability to sense and appropriately respond to the availability of nutrients is a central feature of all living organisms. The yeast Saccharomyces cerevisiae has evolved a complex signal transduction network for the sensing of carbon/energy sources and maintenance of energy homeostasis. Availability of the preferred energy source glucose (or fructose, mannose) mediates, among others, catabolite repression of genes whose products are required for utilization of alternative energy sources via the transcriptional repressor Mig (Gancedo 1992; Thevelein 1994). When the preferred energy sources become limiting the Snf kinase is phosphorylated and activated (Schmidt and McCartney 2000; Mayer et al 2011; Xiao et al 2011; Chandrashekarappa et al 2013). Activated Snf phosphorylates Mig which is exported from the nucleus to the cytosol (Treitel et al 1998; DeVit and Johnston 1999), leading to derepression of genes for utilization of alternative energy sources (Fig. 1a). When preferred energy sources become available, Snf and Mig are dephosphorylated (Ludin et al 1998; Ruiz et al 2011, 2013) and Mig re-enters the nucleus and

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