Spatial control of calcineurin in response to heat shock in fission yeast

Abstract

In fission yeast, Ppb1, the Ca 2+ /calmodulin-dependent protein phosphatase calcineurin regulates multiple biological processes, such as cytokinesis, Ca 2+ -homeostasis, membrane trafficking and cell wall integrity. Calcineurin dephosphorylates the Prz1 transcription factor, leading to its nuclear translocation and gene expression under the control of CDRE (calcineurindependent response element). Although the calcineurin-mediated spatial control of downstream transcription factors has been intensively studied in many organisms, less is known about the spatial regulation of calcineurin on stresses. Here, we show that heat shock stimulates calcineurin-dependent nuclear translocation of Prz1 and CDRE-dependent gene expression. Notably, calcineurin exhibited a dramatic change in subcellular localization, translocating from diffuse cytoplasmic to dot-like structures on heat shock. The calcineurin dots colocalized with Dcp2 or Pabp, the constituent of P-bodies or stress granules, respectively, thus suggesting that calcineurin is a component of RNA granules under heat shock. Importantly, the calcineurin inhibitor FK506 markedly inhibited the accumulation of calcineurin granules, whereas the constitutively active calcineurin strongly accumulated in the granules on heat shock, suggesting that phosphatase activity is important for calcineurin localization. Notably, the depletion of calcineurin induced a rapid appearance of Nrd1-and Pabp-positive RNA granules. The possible roles of calcineurin in response to heat shock will be discussed.

The Orb6-Sts5 Axis Regulates Stress Granule Formation and Heat Stress Response in Fission Yeast

“…Since Orb6 kinase inhibition alone is not sufficient to drive stress granule formation, it is likely that additional factor(s) play a role in driving Sts5-mediated stress granule formation. For example, other factors such as the vigilin homologue Vgl1 (Wen et al ., 2010), signaling factors such as calcineurin (Higa et al ., 2015), and protein kinase C Pck2 (Kanda et al ., 2021) also associate with stress granules in response to thermal stress, and stress granule formation is also stimulated in response to heat stress by the RNA-binding protein Nrd1 (Satoh et al ., 2012). Additionally, the intrinsically disordered N-terminus of Sts5 is phosphorylated on multiple residues, suggesting it is the target of additional protein kinases (Magliozzi et al ., 2020).…”

Stress granules as a feedback mechanism of MAPK signaling by sequestering PKC/Pck2

“…The vic phenotype (growth in the presence of MgCl 2 plus the immunosuppressant FK506) is established as an indication of the downregulation of the Pmk1 MAPK signaling based on the counteractive interaction between calcineurin and Pmk1 MAPK. Thus, this phenotype has been used as a highly sensitive biological read-out for Pmk1 signaling activity in vivo (Ma et al, 2006;Doi et al, 2015;Sanchez-Mir et al, 2014). The Pck2 K712W mutant cells, similarly to Pmk1 deletion cells, exhibited the vic phenotype as indicated by the growth containing 0.12 M MgCl 2 and FK506 wherein the WT cells failed to grow (Ma et al, 2006) ( Figure 3E).…”

“…Representative components of SGs include poly(A)-binding protein (PABP), translation factors such as eIF3, eIF4E, and eIF4G, as well as specific RNA-binding proteins (RBPs), such as TIA-1 and TIAR (Panas et al, 2016). Notably, many signaling molecules, such as mTOR, RACK1, and calcineurin are recruited to SGs, thereby constituting signaling hubs that can rewire signal transduction (Thedieck et al, 2013;Wippich et al, 2013;Arimoto et al, 2008;Higa et al, 2015).…”

Yeast Hog1 proteins are sequestered in stress granules during high-temperature stress

“…For example, signaling through the target of rapamycin complex 1 (TORC1) pathway, which coordinates nutrient availability, was shown to be modulated by sequestration of TORC1 in SGs under conditions of high temperature in S. cerevisiae (Takahara and Maeda, 2012). In the fission yeast Schizosaccharomyces pombe, calcinurin, the Ca 2+ / calmodulin-dependent protein phosphatase, localized to SGs in response to heat shock and negatively regulated the assembly of SGs (Higa et al, 2015). As for regulation of the MAPK pathway, RACK1, the scaffold protein binding to MTK1 MAPKKK in mammalian cells, was sequestered in SGs under certain types of stress, such as hypoxia, heat shock and arsenite, to suppress MTK1mediated signaling pathways (Arimoto et al, 2008).…”