Tonoplast CBL–CIPK calcium signaling network regulates magnesium homeostasis in Arabidopsis

Although Mg2+ is essential for a myriad of cellular processes, high levels of Mg2+ in the environment, such as those found in serpentine soils, become toxic to plants. In this study, we identified two calcineurin B-like (CBL) proteins, CBL2 and CBL3, as key regulators for plant growth under high-Mg conditions. The Arabidopsis mutant lacking both CBL2 and CBL3 displayed severe growth retardation in the presence of excess Mg2+, implying elevated Mg2+ toxicity in these plants. Unexpectedly, the cbl2 cbl3 mutant plants retained lower Mg content than wild-type plants under either normal or high-Mg conditions, suggesting that CBL2 and CBL3 may be required for vacuolar Mg2+ sequestration. Indeed, patch-clamp analysis showed that the cbl2 cbl3 mutant exhibited reduced Mg2+ influx into the vacuole. We further identified four CBL-interacting protein kinases (CIPKs), CIPK3, -9, -23, and -26, as functionally overlapping components downstream of CBL2/3 in the signaling pathway that facilitates Mg2+ homeostasis. The cipk3 cipk9 cipk23 cipk26 quadruple mutant, like the cbl2 cbl3 double mutant, was hypersensitive to high-Mg conditions; furthermore, CIPK3/9/23/26 physically interacted with CBL2/3 at the vacuolar membrane. Our results thus provide evidence that CBL2/3 and CIPK3/9/23/26 constitute a multivalent interacting network that regulates the vacuolar sequestration of Mg2+, thereby protecting plants from Mg2+ toxicity.

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Vacuolar Proton Pyrophosphatase Is Required for High Magnesium Tolerance in Arabidopsis

International Journal of Molecular Sciences ◽

10.3390/ijms19113617 ◽

2018 ◽

Vol 19 (11) ◽

pp. 3617 ◽

Cited By ~ 4

Author(s):

Yang Yang ◽

Ren-Jie Tang ◽

Baicong Mu ◽

Ali Ferjani ◽

Jisen Shi ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Elevated Level ◽

Proton Translocation ◽

Plant Cells ◽

Wild Type ◽

Growth Defects ◽

Essential Nutrient ◽

Pyrophosphatase Activity ◽

Mg Content ◽

Severe Growth

Magnesium (Mg2+) is an essential nutrient in all organisms. However, high levels of Mg2+ in the environment are toxic to plants. In this study, we identified the vacuolar-type H+-pyrophosphatase, AVP1, as a critical enzyme for optimal plant growth under high-Mg conditions. The Arabidopsis avp1 mutants displayed severe growth retardation, as compared to the wild-type plants upon excessive Mg2+. Unexpectedly, the avp1 mutant plants retained similar Mg content to wild-type plants under either normal or high Mg conditions, suggesting that AVP1 may not directly contribute to Mg2+ homeostasis in plant cells. Further analyses confirmed that the avp1 mutant plants contained a higher pyrophosphate (PPi) content than wild type, coupled with impaired vacuolar H+-pyrophosphatase activity. Interestingly, expression of the Saccharomyces cerevisiae cytosolic inorganic pyrophosphatase1 gene IPP1, which facilitates PPi hydrolysis but not proton translocation into vacuole, rescued the growth defects of avp1 mutants under high-Mg conditions. These results provide evidence that high-Mg sensitivity in avp1 mutants possibly resulted from elevated level of cytosolic PPi. Moreover, genetic analysis indicated that mutation of AVP1 was additive to the defects in mgt6 and cbl2 cbl3 mutants that are previously known to be impaired in Mg2+ homeostasis. Taken together, our results suggest AVP1 is required for cellular PPi homeostasis that in turn contributes to high-Mg tolerance in plant cells.

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The Intermolecular Interaction of Ephexin4 Leads to Autoinhibition by Impeding Binding of RhoG

Cells ◽

10.3390/cells7110211 ◽

2018 ◽

Vol 7 (11) ◽

pp. 211 ◽

Cited By ~ 1

Author(s):

Kwanhyeong Kim ◽

Juyeon Lee ◽

Hyunji Moon ◽

Sang-Ah Lee ◽

Deokhwan Kim ◽

...

Keyword(s):

Intermolecular Interaction ◽

Apoptotic Cells ◽

Nucleotide Exchange ◽

Wild Type ◽

Interacting Protein ◽

Cellular Processes ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor ◽

And Migration ◽

Conserved Residue

Ephexin4 is a guanine nucleotide-exchange factor (GEF) for RhoG and is involved in various RhoG-related cellular processes such as phagocytosis of apoptotic cells and migration of cancer cells. Ephexin4 forms an oligomer via an intermolecular interaction, and its GEF activity is increased in the presence of Elmo, an Ephexin4-interacting protein. However, it is uncertain if and how Ephexin4 is autoinhibited. Here, using an Ephexin4 mutant that abrogated the intermolecular interaction, we report that this interaction impeded binding of RhoG to Ephexin4 and thus inhibited RhoG activation. Mutation of the glutamate residue at position 295, which is a highly conserved residue located in the region of Ephexin4 required for the intermolecular interaction, to alanine (Ephexin4E295A) disrupted the intermolecular interaction and increased binding of RhoG, resulting in augmented RhoG activation. In addition, phagocytosis of apoptotic cells and formation of membrane ruffles were increased more by expression of Ephexin4E295A than by expression of wild-type Ephexin4. Taken together, our data suggest that Ephexin4 is autoinhibited through its intermolecular interaction, which impedes binding of RhoG.

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Gene Targeting Reveals a Crucial Role forMTG8 in the Gut

Molecular and Cellular Biology ◽

10.1128/mcb.21.16.5658-5666.2001 ◽

2001 ◽

Vol 21 (16) ◽

pp. 5658-5666 ◽

Cited By ~ 49

Author(s):

Franco Calabi ◽

Richard Pannell ◽

Gordana Pavloska

Keyword(s):

Myeloid Leukemia ◽

Essential Role ◽

Transcriptional Regulators ◽

Wild Type ◽

Exon 2 ◽

Growth Impairment ◽

Cellular Processes ◽

Insertional Inactivation ◽

Severe Growth ◽

Insight Into

ABSTRACT The MTG8 (ETO) locus is involved in a reciprocal exchange with runx1 in the t(8;21) of acute myeloid leukemia. It is a member of a small gene family encoding transcriptional regulators that interact with corepressors and histone deacetylase. However, the physiologic cellular processes controlled byMTG8 are not known. In order to gain an insight into the latter, we have generated mutant mice with an insertional inactivation at the locus, which disrupts transcription of exon 2. The postnatal viability of homozygous mutants was greatly reduced. In approximately 25% the midgut was missing, whereas practically all pups surviving past the first 2 days showed severe growth impairment, which was likely due to a gross disruption of the gut architecture. The latter phenotype could be traced back to late embryonic development. No difference in gut cell differentiation or proliferation was found compared to wild-type littermates. Levels of factors known to be involved in gut morphogenesis were also unchanged. MTG8 is expressed in the outermost layers of the developing gut from at least E9.5. Thus,MTG8 plays a novel, essential role in the gastrointestinal system.

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miR-125b enhances metastasis and progression of cancer via the TXNIP and HIF1α pathway in pancreatic cancer

Cancer Biomarkers ◽

10.3233/cbm-203112 ◽

2021 ◽

pp. 1-12

Author(s):

Pengli Wang ◽

Dan Zheng ◽

Hongyang Qi ◽

Qi Gao

Keyword(s):

Pancreatic Cancer ◽

Hypoxia Inducible Factor ◽

Immunofluorescence Assay ◽

Luciferase Assay ◽

Interacting Protein ◽

Over Expression ◽

Thioredoxin Interacting Protein ◽

Cellular Processes ◽

And Migration

BACKGROUND: MicroRNAs (miRNAs) play potential role in the development of various types of cancer conditions including pancreatic cancer (PC) targeting several cellular processes. Present study was aimed to evaluate function of miR-125b and the mechanism involved in PC. METHODS: Cell migration, MTT and BrdU study was done to establish the migration capability, cell viability and cell proliferation respectively. Binding sites for miR-125b were recognized by luciferase assay, expression of protein by western blot and immunofluorescence assay. In vivo study was done by BALB/c nude xenograft mice for evaluating the function of miR-125b. RESULTS: The study showed that expression of miR-125b was elevated in PC cells and tissues, and was correlated to proliferation and migration of cells. Also, over-expression of miR-125b encouraged migration, metastasis and proliferation of BxPC-3 cells, the suppression reversed it. We also noticed that thioredoxin-interacting protein (TXNIP) was the potential target of miR-125b. The outcomes also suggested that miR-125b governed the expression of TXNIP inversely via directly attaching to the 3′-UTR activating hypoxia-inducible factor 1α (HIF1α). Looking into the relation between HIF1α and TXNIP, we discovered that TXNIP caused the degradation and export of HIF1α by making a complex with it. CONCLUSION: The miR-125b-TXNIP-HIF1α pathway may serve useful strategy for diagnosing and treating PC.

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Low ABA concentration promotes root growth and hydrotropism through relief of ABA INSENSITIVE 1-mediated inhibition of plasma membrane H+-ATPase 2

Science Advances ◽

10.1126/sciadv.abd4113 ◽

2021 ◽

Vol 7 (12) ◽

pp. eabd4113

Author(s):

Rui Miao ◽

Wei Yuan ◽

Yue Wang ◽

Irene Garcia-Maquilon ◽

Xiaolin Dang ◽

...

Keyword(s):

Plasma Membrane ◽

Root Growth ◽

Experimental System ◽

Aba Signaling ◽

Wild Type ◽

Normal Medium ◽

C Terminus ◽

Quadruple Mutant ◽

Aba Insensitive ◽

Aba Receptors

The hab1-1abi1-2abi2-2pp2ca-1 quadruple mutant (Qabi2-2) seedlings lacking key negative regulators of ABA signaling, namely, clade A protein phosphatases type 2C (PP2Cs), show more apoplastic H+ efflux in roots and display an enhanced root growth under normal medium or water stress medium compared to the wild type. The presence of low ABA concentration (0.1 micromolar), inhibiting PP2C activity via monomeric ABA receptors, enhances root apoplastic H+ efflux and growth of the wild type, resembling the Qabi2-2 phenotype in normal medium. Qabi2-2 seedlings also demonstrate increased hydrotropism compared to the wild type in obliquely-oriented hydrotropic experimental system, and asymmetric H+ efflux in root elongation zone is crucial for root hydrotropism. Moreover, we reveal that Arabidopsis ABA-insensitive 1, a key PP2C in ABA signaling, interacts directly with the C terminus of Arabidopsis plasma membrane H+-dependent adenosine triphosphatase 2 (AHA2) and dephosphorylates its penultimate threonine residue (Thr947), whose dephosphorylation negatively regulates AHA2.

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Glucocorticoid Receptor Phosphorylation Differentially Affects Target Gene Expression

Molecular Endocrinology ◽

10.1210/me.2007-0219 ◽

2008 ◽

Vol 22 (8) ◽

pp. 1754-1766 ◽

Cited By ~ 157

Author(s):

Weiwei Chen ◽

Thoa Dang ◽

Raymond D. Blind ◽

Zhen Wang ◽

Claudio N. Cavasotto ◽

...

Keyword(s):

Glucocorticoid Receptor ◽

Transcriptional Activation ◽

Leucine Zipper ◽

Target Genes ◽

Divalent Cations ◽

Phosphorylation Site ◽

Transcriptional Response ◽

Receptor Occupancy ◽

Wild Type ◽

Interacting Protein

Abstract The glucocorticoid receptor (GR) is phosphorylated at multiple sites within its N terminus (S203, S211, S226), yet the role of phosphorylation in receptor function is not understood. Using a range of agonists and GR phosphorylation site-specific antibodies, we demonstrated that GR transcriptional activation is greatest when the relative phosphorylation of S211 exceeds that of S226. Consistent with this finding, a replacement of S226 with an alanine enhances GR transcriptional response. Using a battery of compounds that perturb different signaling pathways, we found that BAPTA-AM, a chelator of intracellular divalent cations, and curcumin, a natural product with antiinflammatory properties, reduced hormone-dependent phosphorylation at S211. This change in GR phosphorylation was associated with its decreased nuclear retention and transcriptional activation. Molecular modeling suggests that GR S211 phosphorylation promotes a conformational change, which exposes a novel surface potentially facilitating cofactor interaction. Indeed, S211 phosphorylation enhances GR interaction with MED14 (vitamin D receptor interacting protein 150). Interestingly, in U2OS cells expressing a nonphosphorylated GR mutant S211A, the expression of IGF-binding protein 1 and interferon regulatory factor 8, both MED14-dependent GR target genes, was reduced relative to cells expressing wild-type receptor across a broad range of hormone concentrations. In contrast, the induction of glucocorticoid-induced leucine zipper, a MED14-independent GR target, was similar in S211A- and wild-type GR-expressing cells at high hormone levels, but was reduced in S211A cells at low hormone concentrations, suggesting a link between GR phosphorylation, MED14 involvement, and receptor occupancy. Phosphorylation also affected the magnitude of repression by GR in a gene-selective manner. Thus, GR phosphorylation at S211 and S226 determines GR transcriptional response by modifying cofactor interaction. Furthermore, the effect of GR S211 phosphorylation is gene specific and, in some cases, dependent upon the amount of activated receptor.

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Characterization of Plasmodium falciparum NEDD8 and identification of cullins as its substrates

10.1101/2020.07.21.213488 ◽

2020 ◽

Author(s):

Manish Bhattacharjee ◽

Navin Adhikari ◽

Renu Sudhakar ◽

Zeba Rizvi ◽

Divya Das ◽

...

Keyword(s):

Mass Spectrometry ◽

Plasmodium Falciparum ◽

Western Blot ◽

Wild Type ◽

Malaria Parasites ◽

Post Translational Modifications ◽

Functional Conservation ◽

Cellular Processes ◽

Physiological Substrates

ABSTRACTA variety of post-translational modifications of Plasmodium falciparum proteins, including phosphorylation and ubiquitination, are shown to have key regulatory roles. The neural precursor cell expressed developmentally downregulated protein 8 (NEDD8) is a ubiquitin-like modifier of cullin-RING E3 ubiquitin ligases, which regulate diverse cellular processes, including the cell-cycle. Although neddylation pathway is conserved in eukaryotes, it is yet to be characterized in Plasmodium and related apicomplexan parasites. Towards studying the neddylation pathway in malaria parasites, we characterized P. falciparum NEDD8 (PfNEDD8) and identified cullins as its physiological substrates. PfNEDD8 is a 76 amino acid residue protein without the C-terminal tail, indicating that it can be readily conjugated. The wild type and mutant (Gly75Gly76 mutated to Ala75Ala76) PfNEDD8 were expressed in P. falciparum. Western blot of wild type PfNEDD8-expressing parasites indicated multiple high molecular weight conjugates, which were absent in the parasites expressing the mutant, indicating conjugation of NEDD8 to proteins through Gly76. Immunoprecipitation followed by mass spectrometry of wild type PfNEDD8-expressing parasites identified several proteins, including two putative cullins. Furthermore, we expressed PfNEDD8 in mutant S. cerevisiae strains that lacked endogenous NEDD8 (Δrub1) or NEDD8 conjugating E2 enzyme (ΔUbc12). The western blot of complemented strains and mass spectrometry of PfNEDD8 immunoprecipitate showed conjugation of PfNEDD8 to S. cerevisiae cullin cdc53, demonstrating functional conservation and cullins as the physiological substrates of PfNEDD8. The characterization of PfNEDD8 and identification of cullins as its substrates make ground for investigation of specific roles and drug target potential of neddylation pathway in malaria parasites.

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Arabidopsis ALIX is required for the endosomal localization of the deubiquitinating enzyme AMSH3

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1510516112 ◽

2015 ◽

Vol 112 (40) ◽

pp. E5543-E5551 ◽

Cited By ~ 32

Author(s):

Kamila Kalinowska ◽

Marie-Kristin Nagel ◽

Kaija Goodman ◽

Laura Cuyas ◽

Franziska Anzenberger ◽

...

Keyword(s):

Cellular Level ◽

Deubiquitinating Enzymes ◽

Interacting Protein ◽

Endosomal Sorting ◽

Cellular Processes ◽

Late Endosomes ◽

Knockout Mutants ◽

Important Regulator

Ubiquitination is a signal for various cellular processes, including for endocytic degradation of plasma membrane cargos. Ubiquitinating as well as deubiquitinating enzymes (DUBs) can regulate these processes by modifying the ubiquitination status of target protein. Although accumulating evidence points to the important regulatory role of DUBs, the molecular basis of their regulation is still not well understood. Associated molecule with the SH3 domain of signal transduction adaptor molecule (STAM) (AMSH) is a conserved metalloprotease DUB in eukaryotes. AMSH proteins interact with components of the endosomal sorting complex required for transport (ESCRT) and are implicated in intracellular trafficking. To investigate how the function of AMSH is regulated at the cellular level, we carried out an interaction screen for the Arabidopsis AMSH proteins and identified the Arabidopsis homolog of apoptosis-linked gene-2 interacting protein X (ALIX) as a protein interacting with AMSH3 in vitro and in vivo. Analysis of alix knockout mutants in Arabidopsis showed that ALIX is essential for plant growth and development and that ALIX is important for the biogenesis of the vacuole and multivesicular bodies (MVBs). Cell biological analysis revealed that ALIX and AMSH3 colocalize on late endosomes. Although ALIX did not stimulate AMSH3 activity in vitro, in the absence of ALIX, AMSH3 localization on endosomes was abolished. Taken together, our data indicate that ALIX could function as an important regulator for AMSH3 function at the late endosomes.

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FGF signalling is required for differentiation-induced cytoskeletal reorganisation and formation of actin-based processes by podocytes

Journal of Cell Science ◽

10.1242/jcs.114.18.3359 ◽

2001 ◽

Vol 114 (18) ◽

pp. 3359-3366 ◽

Cited By ~ 1

Author(s):

Gary Davidson ◽

Rosanna Dono ◽

Rolf Zeller

Keyword(s):

Cell Differentiation ◽

Actin Cytoskeleton ◽

Mutant Mouse ◽

Wild Type Mouse ◽

Wild Type ◽

General Role ◽

Cellular Processes ◽

Cells In Culture ◽

Fgf Signalling

To examine the potential role of fibroblast growth factor (FGF) signalling during cell differentiation, we used conditionally immortalised podocyte cells isolated from kidneys of Fgf2 mutant and wild-type mice. Wild-type mouse podocyte cells upregulate FGF2 expression when differentiating in culture, as do maturing podocytes in vivo. Differentiating wild-type mouse podocyte cells undergo an epithelial to mesenchymal-like transition, reorganise their actin cytoskeleton and extend actin-based cellular processes; all of these activities are similar to the activity of podocytes in vivo. Molecular analysis of Fgf2 mutant mouse podocyte cells reveals a general disruption of FGF signalling as expression of Fgf7 and Fgf10 are also downregulated. These FGF mutant mouse podocyte cells in culture fail to activate mesenchymal markers and their post-mitotic differentiation is blocked. Furthermore, mutant mouse podocyte cells in culture fail to reorganise their actin cytoskeleton and form actin-based cellular processes. These studies show that FGF signalling is required by cultured podocytes to undergo the epithelial to mesenchymal-like changes necessary for terminal differentiation. Together with other studies, these results point to a general role for FGF signalling in regulating cell differentiation and formation of actin-based cellular processes during morphogenesis.

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Relevance of STK11 Mutations Regarding Immune Cell Infiltration, Drug Sensitivity, and Cellular Processes in Lung Adenocarcinoma

Frontiers in Oncology ◽

10.3389/fonc.2020.580027 ◽

2020 ◽

Vol 10 ◽

Author(s):

Zhenqing Li ◽

Bo Ding ◽

Jianxun Xu ◽

Kai Mao ◽

Pengfei Zhang ◽

...

Keyword(s):

Lung Adenocarcinoma ◽

Drug Sensitivity ◽

Immune Cell ◽

Differentially Expressed ◽

Cell Infiltration ◽

Immune Cell Infiltration ◽

Wild Type ◽

Serine Threonine Kinase ◽

Threonine Kinase ◽

Cellular Processes

Serine/threonine kinase 11 (STK11) is one member of the serine/threonine kinase family, which is involved in regulating cell polarity, apoptosis, and DNA damage repair. In lung adenocarcinoma (LUAD), it can play as one tumor suppressor and always be mutated. In this study, we aimed to assess the relevance of STK11 mutations in LUAD, in which we also studied the correlation among immune cell infiltration, drug sensitivity, and cellular processes. By performing the bioinformatics analysis of the Cancer Genome Atlas (TCGA) about LUAD patients, we found that the mutation efficiency of STK11 mutations is about 19%. Additionally, the differentially expressed gene analysis showed that there were 746 differentially expressed genes (DEGs) between LUAD patients with and without STK11 mutations. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis showed that the DEGs were enriched in various tumorigenesis signaling pathways and metabolic processes. Among these DEGs, the top ranking 21 genes were found that they were more frequently mutated in the STK11 mutation group than in the wild-type group (p-value<0.01). Finally, the LUAD patients with STK11 mutations suffered the worse immune cell infiltration levels than the LUAD patients with wild-type. The STK11 gene copy number was correlated with immune cell infiltration. Aiming to develop the therapeutic drugs, we performed Genomics of Drug Sensitivity in Cancer (GDSC) data to identify the potential therapeutic candidate and the results showed that Nutlin-3a(-) may be a sensitive drug for LUAD cases harboring STK11 mutations. The specific genes and pathways shown to be associated with LUAD cases involving STK11 mutations may serve as targets for individualized LUAD treatment.

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