Accumulation of unfolded proteins in the lumen of the endoplasmic reticulum (ER) causes ER stress. Snf1, the Saccharomyces cerevisiae ortholog of AMP–activated protein kinase (AMPK), plays a crucial role in the response to various environmental stresses. However, the role of Snf1 in ER stress response remains poorly understood. In this study, we characterize Snf1 as a negative regulator of Hog1 MAPK in ER stress response. The snf1 mutant cells showed the ER stress resistant phenotype. In contrast, Snf1-hyperactivated cells were sensitive to ER stress. Activated Hog1 levels were increased by snf1 mutation, although Snf1 hyperactivation interfered with Hog1 activation. Ssk1, a specific activator of MAPKKK functioning upstream of Hog1, was induced by ER stress, and its induction was inhibited in a manner dependent on Snf1 activity. Furthermore, we show that the SSK1 promoter is important not only for Snf1-modulated regulation of Ssk1 expression, but also for Ssk1 function in conferring ER stress tolerance. Our data suggest that Snf1 downregulates ER stress response signal mediated by Hog1 through negatively regulating expression of its specific activator Ssk1 at the transcriptional level. We also find that snf1 mutation upregulates the unfolded protein response (UPR) pathway, whereas Snf1 hyperactivation downregulates the UPR activity. Thus, Snf1 plays pleiotropic roles in ER stress response by negatively regulating the Hog1 MAPK pathway and the UPR pathway.

The beam deflection coefficients to the magnetic field fluctuation using a gold neutral beam probe was examined by numerical simulations. The beam deflection parallel to the magnetic field line was mainly caused by the azimuthal component of the magnetic field fluctuation in a case of the beam passing through the plasma center; on the other hand, the beam passing through the plasma edge was deflected by the radial component of the magnetic field fluctuation because the radial and azimuthal velocity components of the beam depend on the injection angle into the plasma. Then, the coefficients could be described as being the function of the injection angle which indicated the radial position of the ionization point and the measured point. As a result of numerical simulation, the coefficients were estimated to be 0.1 and 1.3 for the radial and the azimuthal components of the magnetic field fluctuation in the case of the beam passing through the plasma center. We also estimated the potential effects on the beam deflection parallel to the magnetic field line by the numerical simulation because the change of the beam energy caused the beam detected point to move. We found the potential effects to be smaller than the sensitivity of the magnetic field fluctuation.

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An improved gold neutral beam probe system has been developed in order to measure both the potential profile and the electron density profile simultaneously at the central cell of the tandem mirror GAMMA10. A gold film detector was also developed in order to measure the plasma density profile. The yield curves of secondary electrons were measured as a function of the incident angle and electron energy using both the gold neutral beam and ultraviolet ray injection. Time evolution of the plasma line density was measured by adjusting the incident angle and adding a beam chopping method. The result is in good agreement in comparison with the line density measured using a microwave interferometer. It was found that this film detector is very useful for simultaneous measurements of the electrostatic potential and plasma density.