Site-1 protease cleavage site is important for the ER stress-induced activation of membrane-associated transcription factor bZIP28 in Arabidopsis

Sun, Li‐Zhong; Zhang, Shuang-Shuang; Lu, Sun-Jie

doi:10.1007/s11427-015-4807-6

Cited by 35 publications

(23 citation statements)

References 38 publications

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“…The recent study reported that the canonical S1P recognition site RRIL in bZIP28 is critical for the ER stressinduced activation of bZIP28 (Sun et al, 2015). This claim was based on their observation that the mutant version of bZIP28, in which the canonical S1P recognition site RRIL is changed to GGIL, was unable to restore the tunicamycinsensitive phenotype of bzip28 bzip60 double mutants and to activate the ER stress marker genes BiP3 and CNX1 (Sun et al, 2015). Because our experimental evidence in the present study shows that S1P is not involved in bZIP28 activation, the possibility for reconciliation is that RRIL ?…”

Section: Discussionmentioning

confidence: 99%

Activation of the Arabidopsis membrane‐bound transcription factor bZIP28 is mediated by site‐2 protease, but not site‐1 protease

et al. 2017

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The unfolded protein response (UPR) is a homeostatic cellular response conserved in eukaryotic cells to alleviate the accumulation of unfolded proteins in the endoplasmic reticulum (ER). Arabidopsis bZIP28 is a membrane-bound transcription factor activated by proteolytic cleavage in response to ER stress, thereby releasing its cytosolic portion containing the bZIP domain from the membrane to translocate into the nucleus where it induces the transcription of genes encoding ER-resident molecular chaperones and folding enzymes. It has been widely recognized that the proteolytic activation of bZIP28 is mediated by the sequential cleavage of site-1 protease (S1P) and site-2 protease (S2P). In the present study we provide evidence that bZIP28 protein is cleaved by S2P, but not by S1P. We demonstrated that wild-type and s1p mutant plants produce the active, nuclear form of bZIP28 in response to the ER stress inducer tunicamycin. In contrast, tunicamycin-treated s2p mutants do not accumulate the active, nuclear form of bZIP28. Consistent with these observations, s2p mutants, but not s1p mutants, exhibited a defective transcriptional response of ER stress-responsive genes and significantly higher sensitivity to tunicamycin. Interestingly, s2p mutants accumulate two membrane-bound bZIP28 fragments with a shorter ER lumen-facing C-terminal domain. Importantly, the predicted cleavage sites are located far from the canonical S1P recognition motif previously described. We propose that ER stress-induced proteolytic activation of bZIP28 is mediated by the sequential actions of as-yet-unidentified protease(s) and S2P, and does not require S1P.

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Section: Discussionmentioning

confidence: 99%

Activation of the Arabidopsis membrane‐bound transcription factor bZIP28 is mediated by site‐2 protease, but not site‐1 protease

et al. 2017

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“…However, NAC089 and NAC062 are essentially tail‐anchored proteins while bZIP28 has a long C‐terminal tail that faces the ER lumen and contains ER retention and export signals. Unlike NAC089 and NAC062 the C‐terminal tail on bZIP28 contains a conserved S1P cleavage site that allows for its further proteolytic processing by S2P (Sun et al ., ). Taken together, these findings indicate that NAC089 and NC062 must be activated by ER stress through unknown mechanisms.…”

Section: Membrane‐associated Transcription Factors and Endoplasmic Rementioning

confidence: 97%

Managing the protein folding demands in the endoplasmic reticulum of plants

2016

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Summary Endoplasmic reticulum (ER) stress occurs in plants during certain developmental stages or under adverse environmental conditions, as a result of the accumulation of unfolded or misfolded proteins in the ER. To minimize the accumulation of misfolded proteins in the ER, a protein quality control (PQC) system monitors protein folding and eliminates misfolded proteins through either ER‐associated protein degradation (ERAD) or autophagy. ER stress elicits the unfolded protein response (UPR), which enhances the operation in plant cells of the ER protein folding machinery and the PQC system. The UPR also reduces protein folding demands in the ER by degrading mRNAs encoding secretory proteins. In plants subjected to severe or chronic stress, UPR promotes programmed cell death (PCD). Progress in the field in recent years has provided insights into the regulatory networks and signaling mechanisms of the ER stress responses in plants. In addition, novel physiological functions of the ER stress responses in plants for coordinating plant growth and development with changing environment have been recently revealed.

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“…In the model plant Arabidopsis , UPR is mediated by several ER membrane‐associated basic leucine zipper (bZIP) transcription factors, for example AtbZIP28 and AtbZIP60 (Liu and Howell, ). When misfolded proteins are accumulated in ER, the transmembrane domain of AtbZIP28 is cleaved via intramembrane proteolysis by the Golgi‐resident protease site‐2 protease (S2P), and the activated AtbZIP28 relocates to the nucleus to up‐regulate downstream genes (Che et al , ; Gao et al , ; Liu et al , ; Liu et al , ; Sun et al , ; Tajima et al , ; Zhou et al , ). In contrast, activation of the ER membrane‐associated AtbZIP60 depends on unconventional mRNA splicing of At bZIP60 controlled by the ER‐localized Inositol‐requiring enzyme 1 (AtIRE1), and an open reading frame shift resulted from splicing leads to nuclear localization of AtbZIP60 (Deng et al , ; Moreno et al , ; Nagashima et al , ).…”

Section: Introductionmentioning

confidence: 99%

A membrane‐associated NAC transcription factor OsNTL3 is involved in thermotolerance in rice

Liu

Lyu

Yang

et al. 2019

Plant Biotechnology Journal

154

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Summary Heat stress induces misfolded protein accumulation in endoplasmic reticulum (ER), which initiates the unfolded protein response (UPR) in plants. Previous work has demonstrated the important role of a rice ER membrane‐associated transcription factor OsbZIP74 (also known as OsbZIP50) in UPR. However, how OsbZIP74 and other membrane‐associated transcription factors are involved in heat stress tolerance in rice is not reported. In the current study, we discovered that OsNTL3 is required for heat stress tolerance in rice. OsNTL3 is constitutively expressed and up‐regulated by heat and ER stresses. OsNTL3 encodes a NAC transcription factor with a predicted C‐terminal transmembrane domain. GFP‐OsNTL3 relocates from plasma membrane to nucleus in response to heat stress and ER stress inducers. Loss‐of‐function mutation of OsNTL3 confers heat sensitivity while inducible expression of the truncated form of OsNTL3 without the transmembrane domain increases heat tolerance in rice seedlings. RNA‐Seq analysis revealed that OsNTL3 regulates the expression of genes involved in ER protein folding and other processes. Interestingly, OsNTL3 directly binds to OsbZIP74 promoter and regulates its expression in response to heat stress. In turn, up‐regulation of OsNTL3 by heat stress is dependent on OsbZIP74. Thus, our work reveals the important role of OsNTL3 in thermotolerance, and a regulatory circuit mediated by OsbZIP74 and OsNTL3 in communications among ER, plasma membrane and nucleus under heat stress conditions.

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Site-1 protease cleavage site is important for the ER stress-induced activation of membrane-associated transcription factor bZIP28 in Arabidopsis

Cited by 35 publications

References 38 publications

Activation of the Arabidopsis membrane‐bound transcription factor bZIP28 is mediated by site‐2 protease, but not site‐1 protease

Activation of the Arabidopsis membrane‐bound transcription factor bZIP28 is mediated by site‐2 protease, but not site‐1 protease

Managing the protein folding demands in the endoplasmic reticulum of plants

A membrane‐associated NAC transcription factor OsNTL3 is involved in thermotolerance in rice

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