The Arabidopsis Protein Disulfide Isomerase Subfamily M Isoform, PDI9, Localizes to the Endoplasmic Reticulum and Influences Pollen Viability and Proper Formation of the Pollen Exine During Heat Stress

Plants adapt to heat via thermotolerance pathways in which the activation of protein folding chaperones is essential. In eukaryotes, protein disulfide isomerases (PDIs) facilitate the folding of nascent and misfolded proteins in the secretory pathway by catalyzing the formation and isomerization of disulfide bonds and serving as molecular chaperones. In Arabidopsis, several members of the PDI family are upregulated in response to chemical inducers of the unfolded protein response (UPR), including both members of the non-classical PDI-M subfamily, PDI9 and PDI10. Unlike classical PDIs, which have two catalytic thioredoxin (TRX) domains separated by two non-catalytic TRX-fold domains, PDI-M isoforms are orthologs of mammalian P5/PDIA6 and possess two tandem catalytic domains. Here, PDI9 accumulation was found to be upregulated in pollen in response to heat stress. Histochemical staining of plants harboring the PDI9 and PDI10 promoters fused to the gusA gene indicated they were actively expressed in the anthers of flowers, specifically in the pollen and tapetum. Immunoelectron microscopy revealed that PDI9 localized to the endoplasmic reticulum in root and pollen cells. transfer DNA (T-DNA) insertional mutations in the PDI9 gene disrupted pollen viability and development in plants exposed to heat stress. In particular, the pollen grains of pdi9 mutants exhibited disruptions in the reticulated pattern of the exine and an increased adhesion of pollen grains. Pollen in the pdi10 single mutant did not display similar heat-associated defects, but pdi9 pdi10 double mutants (DMs) completely lost exine reticulation. Interestingly, overexpression of PDI9 partially led to heat-associated defects in the exine. We conclude that PDI9 plays an important role in pollen thermotolerance and exine biogenesis. Its role fits the mechanistic theory of proteostasis in which an ideal balance of PDI isoforms is required in the endoplasmic reticulum (ER) for normal exine formation in plants subjected to heat stress.

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The unfolded protein response coordinates the production of endoplasmic reticulum protein and endoplasmic reticulum membrane.

Molecular Biology of the Cell ◽

10.1091/mbc.8.9.1805 ◽

1997 ◽

Vol 8 (9) ◽

pp. 1805-1814 ◽

Cited By ~ 277

Author(s):

J S Cox ◽

R E Chapman ◽

P Walter

Keyword(s):

Endoplasmic Reticulum ◽

Unfolded Protein Response ◽

Secretory Pathway ◽

Lipid Synthesis ◽

Secretory Proteins ◽

Endoplasmic Reticulum Membrane ◽

Yeast Saccharomyces Cerevisiae ◽

Unfolded Protein ◽

The Unfolded Protein Response ◽

Protein Response

The endoplasmic reticulum (ER) is a multifunctional organelle responsible for production of both lumenal and membrane components of secretory pathway compartments. Secretory proteins are folded, processed, and sorted in the ER lumen and lipid synthesis occurs on the ER membrane itself. In the yeast Saccharomyces cerevisiae, synthesis of ER components is highly regulated: the ER-resident proteins by the unfolded protein response and membrane lipid synthesis by the inositol response. We demonstrate that these two responses are intimately linked, forming different branches of the same pathway. Furthermore, we present evidence indicating that this coordinate regulation plays a role in ER biogenesis.

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Pathogenic Effects of Impaired Retrieval between the Endoplasmic Reticulum and Golgi Complex

International Journal of Molecular Sciences ◽

10.3390/ijms20225614 ◽

2019 ◽

Vol 20 (22) ◽

pp. 5614 ◽

Cited By ~ 6

Author(s):

Hiroshi Kokubun ◽

Hisayo Jin ◽

Tomohiko Aoe

Keyword(s):

Endoplasmic Reticulum ◽

Golgi Complex ◽

Secretory Pathway ◽

Protein Transport ◽

Receptor Activation ◽

Toxic Substances ◽

Bidirectional Transport ◽

The Unfolded Protein Response ◽

Kdel Receptor ◽

Kdel Sequence

Cellular activities, such as growth and secretion, are dependent on correct protein folding and intracellular protein transport. Injury, like ischemia, malnutrition, and invasion of toxic substances, affect the folding environment in the endoplasmic reticulum (ER). The ER senses this information, following which cells adapt their response to varied situations through the unfolded protein response. Activation of the KDEL receptor, resulting from the secretion from the ER of chaperones containing the KDEL sequence, plays an important role in this adaptation. The KDEL receptor was initially shown to be necessary for the retention of KDEL sequence-containing proteins in the ER. However, it has become clear that the activated KDEL receptor also regulates bidirectional transport between the ER and the Golgi complex, as well as from the Golgi to the secretory pathway. In addition, it has been suggested that the signal for KDEL receptor activation may also affect several other cellular activities. In this review, we discuss KDEL receptor-mediated bidirectional transport and signaling and describe disease models and human diseases related to KDEL receptor dysfunction.

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Sequestration of Mutated α1-Antitrypsin into Inclusion Bodies Is a Cell-protective Mechanism to Maintain Endoplasmic Reticulum Function

Molecular Biology of the Cell ◽

10.1091/mbc.e07-06-0587 ◽

2008 ◽

Vol 19 (2) ◽

pp. 572-586 ◽

Cited By ~ 48

Author(s):

Susana Granell ◽

Giovanna Baldini ◽

Sameer Mohammad ◽

Vanessa Nicolin ◽

Paola Narducci ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Inclusion Bodies ◽

Secretory Pathway ◽

Hepatoma Cells ◽

Neuroendocrine Cells ◽

Protective Mechanism ◽

High Tendency ◽

A Cell ◽

Cell Type Specific ◽

Protein Disulfide

A variant α1-antitrypsin with E342K mutation has a high tendency to form intracellular polymers, and it is associated with liver disease. In the hepatocytes of individuals carrying the mutation, α1-antitrypsin localizes both to the endoplasmic reticulum (ER) and to membrane-surrounded inclusion bodies (IBs). It is unclear whether the IBs contribute to cell toxicity or whether they are protective to the cell. We found that in hepatoma cells, mutated α1-antitrypsin exited the ER and accumulated in IBs that were negative for autophagosomal and lysosomal markers, and contained several ER components, but not calnexin. Mutated α1-antitrypsin induced IBs also in neuroendocrine cells, showing that formation of these organelles is not cell type specific. In the presence of IBs, ER function was largely maintained. Increased levels of calnexin, but not of protein disulfide isomerase, inhibited formation of IBs and lead to retention of mutated α1-antitrypsin in the ER. In hepatoma cells, shift of mutated α1-antitrypsin localization to the ER by calnexin overexpression lead to cell shrinkage, ER stress, and impairment of the secretory pathway at the ER level. We conclude that segregation of mutated α1-antitrypsin from the ER to the IBs is a protective cell response to maintain a functional secretory pathway.

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Effect of high temperature on the reproductive development of chickpea genotypes under controlled environments

Functional Plant Biology ◽

10.1071/fp12033 ◽

2012 ◽

Vol 39 (12) ◽

pp. 1009 ◽

Cited By ~ 72

Author(s):

Viola Devasirvatham ◽

Pooran M. Gaur ◽

Nalini Mallikarjuna ◽

Raju N. Tokachichu ◽

Richard M. Trethowan ◽

...

Keyword(s):

Heat Stress ◽

High Temperature ◽

Pollen Germination ◽

Pollen Viability ◽

Pollen Grains ◽

High Temperature Stress ◽

Pollen Production ◽

Seed Number ◽

Controlled Environments

High temperature during the reproductive stage in chickpea (Cicer arietinum L.) is a major cause of yield loss. The objective of this research was to determine whether that variation can be explained by differences in anther and pollen development under heat stress: the effect of high temperature during the pre- and post-anthesis periods on pollen viability, pollen germination in a medium, pollen germination on the stigma, pollen tube growth and pod set in a heat-tolerant (ICCV 92944) and a heat-sensitive (ICC 5912) genotype was studied. The plants were evaluated under heat stress and non-heat stress conditions in controlled environments. High temperature stress (29/16°C to 40/25°C) was gradually applied at flowering to study pollen viability and stigma receptivity including flower production, pod set and seed number. This was compared with a non-stress treatment (27/16°C). The high temperatures reduced pod set by reducing pollen viability and pollen production per flower. The ICCV 92944 pollen was viable at 35/20°C (41% fertile) and at 40/25°C (13% fertile), whereas ICC 5912 pollen was completely sterile at 35/20°C with no in vitro germination and no germination on the stigma. However, the stigma of ICC 5912 remained receptive at 35/20°C and non-stressed pollen (27/16°C) germinated on it during reciprocal crossing. These data indicate that pollen grains were more sensitive to high temperature than the stigma in chickpea. High temperature also reduced pollen production per flower, % pollen germination, pod set and seed number.

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Protein disulfide isomerases contribute differentially to the endoplasmic reticulum–associated degradation of apolipoprotein B and other substrates

Molecular Biology of the Cell ◽

10.1091/mbc.e11-08-0704 ◽

2012 ◽

Vol 23 (4) ◽

pp. 520-532 ◽

Cited By ~ 41

Author(s):

Sarah Grubb ◽

Liang Guo ◽

Edward A. Fisher ◽

Jeffrey L. Brodsky

Keyword(s):

Apolipoprotein B ◽

Disulfide Bonds ◽

Secretory Pathway ◽

Expression System ◽

Chaperone Activity ◽

Redox Activity ◽

Carboxypeptidase Y ◽

Substrate Selection ◽

Yeast Expression System ◽

Protein Disulfide

ER-associated degradation (ERAD) rids the early secretory pathway of misfolded or misprocessed proteins. Some members of the protein disulfide isomerase (PDI) family appear to facilitate ERAD substrate selection and retrotranslocation, but a thorough characterization of PDIs during the degradation of diverse substrates has not been undertaken, in part because there are 20 PDI family members in mammals. PDIs can also exhibit disulfide redox, isomerization, and/or chaperone activity, but which of these activities is required for the ERAD of different substrate classes is unknown. We therefore examined the fates of unique substrates in yeast, which expresses five PDIs. Through the use of a yeast expression system for apolipoprotein B (ApoB), which is disulfide rich, we discovered that Pdi1 interacts with ApoB and facilitates degradation through its chaperone activity. In contrast, Pdi1's redox activity was required for the ERAD of CPY* (a misfolded version of carboxypeptidase Y that has five disulfide bonds). The ERAD of another substrate, the alpha subunit of the epithelial sodium channel, was Pdi1 independent. Distinct effects of mammalian PDI homologues on ApoB degradation were then observed in hepatic cells. These data indicate that PDIs contribute to the ERAD of proteins through different mechanisms and that PDI diversity is critical to recognize the spectrum of potential ERAD substrates.

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Ero1-α and PDIs constitute a hierarchical electron transfer network of endoplasmic reticulum oxidoreductases

The Journal of Cell Biology ◽

10.1083/jcb.201303027 ◽

2013 ◽

Vol 202 (6) ◽

pp. 861-874 ◽

Cited By ~ 75

Author(s):

Kazutaka Araki ◽

Shun-ichiro Iemura ◽

Yukiko Kamiya ◽

David Ron ◽

Koichi Kato ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Electron Transfer ◽

Disulfide Bonds ◽

Mammalian Cells ◽

Protein Disulfide Isomerase ◽

Equilibrium Analysis ◽

Intramolecular Electron Transfer ◽

Redox Equilibrium ◽

Kinetic Measurements ◽

Protein Disulfide

Ero1-α and endoplasmic reticulum (ER) oxidoreductases of the protein disulfide isomerase (PDI) family promote the efficient introduction of disulfide bonds into nascent polypeptides in the ER. However, the hierarchy of electron transfer among these oxidoreductases is poorly understood. In this paper, Ero1-α–associated oxidoreductases were identified by proteomic analysis and further confirmed by surface plasmon resonance. Ero1-α and PDI were found to constitute a regulatory hub, whereby PDI induced conformational flexibility in an Ero1-α shuttle cysteine (Cys99) facilitated intramolecular electron transfer to the active site. In isolation, Ero1-α also oxidized ERp46, ERp57, and P5; however, kinetic measurements and redox equilibrium analysis revealed that PDI preferentially oxidized other oxidoreductases. PDI accepted electrons from the other oxidoreductases via its a′ domain, bypassing the a domain, which serves as the electron acceptor from reduced glutathione. These observations provide an integrated picture of the hierarchy of cooperative redox interactions among ER oxidoreductases in mammalian cells.

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Endoplasmic reticulum stress regulates glutathione metabolism and activities of glutathione related enzymes in Arabidopsis

Functional Plant Biology ◽

10.1071/fp17151 ◽

2018 ◽

Vol 45 (2) ◽

pp. 284 ◽

Cited By ~ 7

Author(s):

Baris Uzilday ◽

Rengin Ozgur ◽

A. Hediye Sekmen ◽

Ismail Turkan

Keyword(s):

Endoplasmic Reticulum ◽

Protein Folding ◽

Er Stress ◽

Disulfide Bonds ◽

Degradation Pathway ◽

Glutathione Metabolism ◽

Unfolded Proteins ◽

Glutathione S Transferase ◽

Glutathione Biosynthesis ◽

Protein Disulfide

Stress conditions generate an extra load on protein folding machinery in the endoplasmic reticulum (ER) and if the ER cannot overcome this load, unfolded proteins accumulate in the ER lumen, causing ER stress. ER lumen localised protein disulfide isomerase (PDI) catalyses the generation of disulfide bonds in conjugation with ER oxidoreductase1 (ERO1) during protein folding. Mismatched disulfide bonds are reduced by the conversion of GSH to GSSG. Under prolonged ER stress, GSH pool is oxidised and H2O2 is produced via increased activity of PDI-ERO1. However, it is not known how glutathione metabolism is regulated under ER stress in plants. So, in this study, ER stress was induced with tunicamycin (0.15, 0.3, 0.45 μg mL–1 Tm) in Arabidopsis thaliana (L.) Heynh. Glutathione content was increased by ER stress, which was accompanied by induction of glutathione biosynthesis genes (GSH1, GSH2). Also, the apoplastic glutathione degradation pathway (GGT1) was induced. Further, the activities of glutathione reductase (GR), dehydroascorbate reductase (DHAR), glutathione peroxidase (GPX) and glutathione S-transferase (GST) were increased under ER stress. Results also showed that chloroplastic GPX genes were specifically downregulated with ER stress. This is the first report on regulation of glutathione metabolism and glutathione related enzymes in response to ER stress in plants.

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A Striking Quality Control Subcompartment in Saccharomyces cerevisiae: The Endoplasmic Reticulum-associated Compartment

Molecular Biology of the Cell ◽

10.1091/mbc.e03-07-0546 ◽

2004 ◽

Vol 15 (2) ◽

pp. 908-921 ◽

Cited By ~ 60

Author(s):

Gregory Huyer ◽

Gaby L. Longsworth ◽

Deborah L. Mason ◽

Monica P. Mallampalli ◽

J. Michael McCaffery ◽

...

Keyword(s):

Quality Control ◽

Endoplasmic Reticulum ◽

Membrane Proteins ◽

Secretory Pathway ◽

Secretory Protein ◽

Cellular Functions ◽

Er Quality Control ◽

Fluorescence And Electron Microscopy ◽

The Unfolded Protein Response ◽

Mutant Forms

The folding of nascent secretory and membrane proteins is monitored by the endoplasmic reticulum (ER) quality control system. Misfolded proteins are retained in the ER and can be removed by ER-associated degradation. As a model for the ER quality control of multispanning membrane proteins in yeast, we have been studying mutant forms of Ste6p. Here, we identify mislocalized mutant forms of Ste6p that induce the formation of, and localize to, prominent structures that are absent in normal cells. We have named these structures ER-associated compartments (ERACs), based on their juxtaposition to and connection with the ER, as observed by fluorescence and electron microscopy. ERACs comprise a network of tubulo-vesicular structures that seem to represent proliferated ER membranes. Resident ER lumenal and membrane proteins are present in ERACs in addition to their normal ER localization, suggesting there is no barrier for their entry into ERACs. However, the forms of Ste6p in ERACs are excluded from the ER and do not enter the secretory pathway; instead, they are ultimately targeted for ER-associated degradation. The presence of ERACs does not adversely affect secretory protein traffic through the ER and does not lead to induction of the unfolded protein response. We propose that ERACs may be holding sites to which misfolded membrane proteins are specifically diverted so as not to interfere with normal cellular functions. We discuss the likelihood that related ER membrane proliferations that form in response to certain other mutant or unassembled membrane proteins may be substantially similar to ERACs.

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Plant growth regulators interact with elevated temperature to alter heat stress signaling via the Unfolded Protein Response in maize

10.1101/532796 ◽

2019 ◽

Cited By ~ 2

Author(s):

Elena M. Neill ◽

Michael C. R. Byrd ◽

Thomas Billman ◽

Federica Brandizzi ◽

Ann E. Stapleton

Keyword(s):

Endoplasmic Reticulum ◽

Heat Stress ◽

Elevated Temperature ◽

Plant Growth ◽

Plant Growth Regulators ◽

Growth Regulators ◽

Plant Growth Regulator ◽

Unfolded Protein ◽

The Unfolded Protein Response ◽

Protein Response

ABSTRACTPlants are increasingly exposed to high temperatures, which can cause accumulation of unfolded protein in the endoplasmic reticulum (ER). This condition, known as ER stress, evokes the unfolded protein response (UPR), a cytoprotective signaling pathway. One important branch of the UPR is regulated by splicing of bZIP60 mRNA by the IRE1 stress sensor. There is increasing evidence that commercial plant growth regulators may protect against abiotic stressors including heat stress and drought, but there is very little mechanistic information about these effects or about the regulatory pathways involved. We evaluated evidence in the B73 Zea mays inbred for differences in the activity of the UPR between permissive and elevated temperature in conjunction with plant growth regulator application. Treatment with elevated temperature and plant growth regulators increased UPR activation, as assessed by an increase in splicing of the mRNA of the IRE1 target bZIP60 following paclobutrazol treatment. We propose that plant growth regulator treatment induces bZIP60 mRNA splicing which ‘primes’ plants for rapid adaptive response to subsequent endoplasmic reticulum-stress inducing conditions.

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