Thiol-based direct threat sensing by the stress-activated protein kinase Hog1

Abstract

The yeast stress-activated protein kinase Hog1 is best known for its role in mediating the response to osmotic stress, but it is also activated by various mechanistically distinct environmental stressors, including heat shock, endoplasmic reticulum stress, and arsenic. In the osmotic stress response, the signal is sensed upstream and relayed to Hog1 through a kinase cascade. Here, we identified a mode of Hog1 function whereby Hog1 senses arsenic through a direct physical interaction that requires three conserved cysteine residues located adjacent to the catalytic loop. These residues were essential for Hog1-mediated protection against arsenic, were dispensable for the response to osmotic stress, and promoted the nuclear localization of Hog1 upon exposure of cells to arsenic. Hog1 promoted arsenic detoxification by stimulating phosphorylation of the transcription factor Yap8, promoting Yap8 nuclear localization, and stimulating the transcription of the only known Yap8 targets, ARR2 and ARR3, both of which encode proteins that promote arsenic efflux. The related human kinases ERK1 and ERK2 also bound to arsenic in vitro, suggesting that this may be a conserved feature of some members of the mitogen-activated protein kinase (MAPK) family. These data provide a mechanistic basis for understanding how stress-activated kinases can sense distinct threats and perform highly specific adaptive responses.

Differential metabolism of arsenicals regulates Fps1-mediated arsenite transport

“…Because we have found that some cysteine residues in proteins are specifically targeted by MAs(III) (Lee and Levin, 2018;2019), we examined whether Hog1 is modified by As(III), or by MAs(III). Pre-treatment of wild-type cells with either As(III) or As(V) diminished As-biotin binding to Hog1 (Figure 2G).…”

“…However, some As-biotin binding to Hog1 remained even in the Hog1-3C/S mutant form. Guerra-Moreno et al (2019) reported recently that Hog1 becomes modified on three cysteine residues --Cys156, Cys161, and Cys205 in response to As(III) treatment. Because we had not included Cys161 in our initial analysis, we added the Cys161Ser mutation to the hog1-3C/S allele, yielding hog1-4C/S.…”

“…It is thought that conversion of As(III) to MAs(III) and DMA(III) in humans assists in its excretion in the urine (Vahter and Concha, 2001;Dong et al, 2015;Jansen et al, 2016). However, our recent work in yeast reveals that production of MAs(III) from As(III) is also a metabolic activation step required to mobilize a coherent cellular response to As(III) (Lee and Levin, 2018;2019;.…”

Pathways for Sensing and Responding to Hydrogen Peroxide at the Endoplasmic Reticulum

“…Yet, if and/or what alternative signaling is activated in yeast upon IRE1 modification remains to be elucidated. Hog1, the homologous yeast p38 MAP kinase, is activated by arsenite exposure [ 117 , 118 ]; yet, activation does not require the IRE1 cysteine [ 117 ]. The ultimate transcriptional output is also bound to be different.…”

Etp1 confers arsenite resistance by affecting ACR3 expression

“…Additionally, Yap8 is phosphorylated by the Hog1 kinase during As(III) stress and this phosphorylation contributes to efficient induction of ACR2 and ACR3 expression by an unknown mechanism (Guerra-Moreno et al . 2019 ). Full induction of ACR2 and ACR3 expression also involves coactivator complexes and chromatin remodeling factors (Menezes et al .…”