Regulated nucleo/cytoplasmic exchange of HOG1 MAPK requires the importin beta homologs NMD5 and XPO1

EMBO J. 1998 Oct 1;17(19):5606-14. doi: 10.1093/emboj/17.19.5606.

Abstract

MAP kinase signaling modules serve to transduce extracellular signals to the nucleus of eukaryotic cells, but little is known about how signals cross the nuclear envelope. Exposure of yeast cells to increases in extracellular osmolarity activates the HOG1 MAP kinase cascade, which is composed of three tiers of protein kinases, namely the SSK2, SSK22 and STE11 MAPKKKs, the PBS2 MAPKK, and the HOG1 MAPK. Using green fluorescent protein (GFP) fusions of these kinases, we found that HOG1, PBS2 and STE11 localize to the cytoplasm of unstressed cells. Following osmotic stress, HOG1, but neither PBS2 nor STE11, translocates into the nucleus. HOG1 translocation occurs very rapidly, is transient, and correlates with the phosphorylation and activation of the MAP kinase by its MAPKK. HOG1 phosphorylation is necessary and sufficient for nuclear translocation, because a catalytically inactive kinase when phosphorylated is translocated to the nucleus as efficiently as the wild-type. Nuclear import of the MAPK under stress conditions requires the activity of the small GTP binding protein Ran-GSP1, but not the NLS-binding importin alpha/beta heterodimer. Rather, HOG1 import requires the activity of a gene, NMD5, that encodes a novel importin beta homolog. Similarly, export of dephosphorylated HOG1 from the nucleus requires the activity of the NES receptor XPO1/CRM1. Our findings define the requirements for the regulated nuclear transport of a stress-activated MAP kinase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biological Transport
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Carrier Proteins / metabolism*
  • Cell Compartmentation
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • Exportin 1 Protein
  • Fungal Proteins / metabolism
  • GTP-Binding Proteins / metabolism
  • Karyopherins
  • Mitogen-Activated Protein Kinase Kinases*
  • Mitogen-Activated Protein Kinases*
  • Monomeric GTP-Binding Proteins*
  • Nuclear Proteins / metabolism*
  • Osmotic Pressure
  • Phosphorylation
  • Protein Kinases / metabolism
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Saccharomyces
  • Saccharomyces cerevisiae Proteins*
  • Schizosaccharomyces pombe Proteins*
  • Signal Transduction
  • Transcription Factors / metabolism

Substances

  • Carrier Proteins
  • Fungal Proteins
  • GSP1 protein, S cerevisiae
  • Karyopherins
  • Nuclear Proteins
  • Receptors, Cytoplasmic and Nuclear
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • Transcription Factors
  • ste11 protein, S pombe
  • Protein Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • HOG1 protein, S cerevisiae
  • Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinase Kinases
  • PBS2 protein, S cerevisiae
  • GTP-Binding Proteins
  • Monomeric GTP-Binding Proteins