Damage Signaling by Extracellular Nucleotides: A Role for Cyclic Nucleotides in Elevating Cytosolic Free Calcium?

Extracellular ATP (eATP) is now held to be a constitutive damage-associated molecular pattern (DAMP) that is released by wounding, herbivory or pathogen attack. The concentration of eATP must be tightly regulated as either depletion or overload leads to cell death. In Arabidopsis thaliana, sensing of eATP is by two plasma membrane legume-like lectin serine–threonine receptor kinases (P2K1 and P2K2), although other receptors are postulated. The transcriptional response to eATP is dominated by wound- and defense-response genes. Wounding and pathogen attack can involve the cyclic nucleotides cyclic AMP (cAMP) and cyclic GMP (cGMP) which, in common with eATP, can increase cytosolic-free Ca2+ as a second messenger. This perspective on DAMP signaling by eATP considers the possibility that the eATP pathway involves production of cyclic nucleotides to promote opening of cyclic nucleotide-gated channels and so elevates cytosolic-free Ca2+. In silico analysis of P2K1 and P2K2 reveals putative adenylyl and guanylyl kinase sequences that are the hallmarks of “moonlighting” receptors capable of cAMP and cGMP production. Further, an Arabidopsis loss of function cngc mutant was found to have an impaired increase in cytosolic-free Ca2+ in response to eATP. A link between eATP, cyclic nucleotides, and Ca2+ signaling therefore appears credible.

Download Full-text

CHOP and c-JUN up-regulate the mutant Z α1-antitrypsin, exacerbating its aggregation and liver proteotoxicity

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014307 ◽

2020 ◽

Vol 295 (38) ◽

pp. 13213-13223

Author(s):

Sergio Attanasio ◽

Rosa Ferriero ◽

Gwladys Gernoux ◽

Rossella De Cegli ◽

Annamaria Carissimo ◽

...

Keyword(s):

Liver Disease ◽

Er Stress ◽

Proteinase Inhibitors ◽

Pediatric Population ◽

Transcriptional Response ◽

Luciferase Reporter ◽

Mrna Levels ◽

Primary Role ◽

Loss Of Function ◽

Human Livers

α1-Antitrypsin (AAT) encoded by the SERPINA1 gene is an acute-phase protein synthesized in the liver and secreted into the circulation. Its primary role is to protect lung tissue by inhibiting neutrophil elastase. The Z allele of SERPINA1 encodes a mutant AAT, named ATZ, that changes the protein structure and leads to its misfolding and polymerization, which cause endoplasmic reticulum (ER) stress and liver disease through a gain-of-function toxic mechanism. Hepatic retention of ATZ results in deficiency of one of the most important circulating proteinase inhibitors and predisposes to early-onset emphysema through a loss-of-function mechanism. The pathogenetic mechanisms underlying the liver disease are not completely understood. C/EBP-homologous protein (CHOP), a transcription factor induced by ER stress, was found among the most up-regulated genes in livers of PiZ mice that express ATZ and in human livers of patients homozygous for the Z allele. Compared with controls, juvenile PiZ/Chop−/− mice showed reduced hepatic ATZ and a transcriptional response indicative of decreased ER stress by RNA-Seq analysis. Livers of PiZ/Chop−/− mice also showed reduced SERPINA1 mRNA levels. By chromatin immunoprecipitations and luciferase reporter–based transfection assays, CHOP was found to up-regulate SERPINA1 cooperating with c-JUN, which was previously shown to up-regulate SERPINA1, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. In summary, CHOP and c-JUN up-regulate SERPINA1 transcription and play an important role in hepatic disease by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.

Download Full-text

TRMmaintenance is regulated by tissue damage via P2RX7

Science Immunology ◽

10.1126/sciimmunol.aau1022 ◽

2018 ◽

Vol 3 (30) ◽

pp. eaau1022 ◽

Cited By ~ 33

Author(s):

Regina Stark ◽

Thomas H. Wesselink ◽

Felix M. Behr ◽

Natasja A. M. Kragten ◽

Ramon Arens ◽

...

Keyword(s):

T Cells ◽

Cell Death ◽

Tissue Damage ◽

Extracellular Nucleotides ◽

Critical Pathway ◽

Rna Profiling ◽

Molecular Pattern ◽

History Of ◽

Circulating T Cells

Tissue-resident memory T cells (TRM) are noncirculating immune cells that contribute to the first line of local defense against reinfections. Their location at hotspots of pathogen encounter frequently exposes TRM to tissue damage. This history of danger-signal exposure is an important aspect of TRM-mediated immunity that has been overlooked so far. RNA profiling revealed that TRM from liver and small intestine express P2RX7, a damage/danger-associated molecular pattern (DAMP) receptor that is triggered by extracellular nucleotides (ATP, NAD+). We confirmed that P2RX7 protein was expressed in CD8+ TRM but not in circulating T cells (TCIRC) across different infection models. Tissue damage induced during routine isolation of liver lymphocytes led to P2RX7 activation and resulted in selective cell death of TRM. P2RX7 activation in vivo by exogenous NAD+ led to a specific depletion of TRM while retaining TCIRC. The effect was absent in P2RX7-deficient mice and after P2RX7 blockade. TCR triggering down-regulated P2RX7 expression and made TRM resistant to NAD-induced cell death. Physiological triggering of P2RX7 by sterile tissue damage during acetaminophen-induced liver injury led to a loss of previously acquired pathogen-specific local TRM in wild-type but not in P2RX7 KO T cells. Our results highlight P2RX7-mediated signaling as a critical pathway for the regulation of TRM maintenance. Extracellular nucleotides released during infection and tissue damage could deplete TRM locally and free niches for new and infection-relevant specificities. This suggests that the recognition of tissue damage promotes persistence of antigen-specific over bystander TRM in the tissue niche.

Download Full-text

Deficiency in the double-stranded RNA binding protein HYPONASTIC LEAVES1 increases sensitivity to the endoplasmic reticulum stress inducer tunicamycin in Arabidopsis

BMC Research Notes ◽

10.1186/s13104-019-4623-3 ◽

2019 ◽

Vol 12 (1) ◽

Author(s):

Rikako Hirata ◽

Kei-ichiro Mishiba ◽

Nozomu Koizumi ◽

Yuji Iwata

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Stress Responses ◽

Rna Binding ◽

Transcriptional Response ◽

Mirna Biogenesis ◽

Loss Of Function ◽

Wild Type ◽

Protein Coding ◽

And Function

Abstract Objective microRNA (miRNA) is a small non-coding RNA that regulates gene expression by sequence-dependent binding to protein-coding mRNA in eukaryotic cells. In plants, miRNA plays important roles in a plethora of physiological processes, including abiotic and biotic stress responses. The present study was conducted to investigate whether miRNA-mediated regulation is important for the endoplasmic reticulum (ER) stress response in Arabidopsis. Results We found that hyl1 mutant plants are more sensitive to tunicamycin, an inhibitor of N-linked glycosylation that causes ER stress than wild-type plants. Other miRNA-related mutants, se and ago1, exhibited similar sensitivity to the wild-type, indicating that the hypersensitive phenotype is attributable to the loss-of-function of HYL1, rather than deficiency in general miRNA biogenesis and function. However, the transcriptional response of select ER stress-responsive genes in hyl1 mutant plants was indistinguishable from that of wild-type plants, suggesting that the loss-of-function of HYL1 does not affect the ER stress signaling pathways.

Download Full-text

Mechanisms of cytosolic calcium elevation in plants: the role of ion channels, calcium extrusion systems and NADPH oxidase-mediated 'ROS-Ca2+ Hub'

Functional Plant Biology ◽

10.1071/fp16420 ◽

2018 ◽

Vol 45 (2) ◽

pp. 9 ◽

Cited By ~ 49

Author(s):

Vadim Demidchik ◽

Sergey Shabala

Keyword(s):

Calcium Influx ◽

Gene Families ◽

Cytosolic Calcium ◽

Recent Experimental Data ◽

Free Calcium ◽

Cyclic Nucleotide Gated Channels ◽

Physiological Reactions ◽

Calcium Extrusion ◽

Calcium Elevation

Elevation in the cytosolic free calcium is crucial for plant growth, development and adaptation. Calcium influx into plant cells is mediated by Ca2+ depolarisation-activated, hyperpolarisation-activated and voltage-independent Ca2+-permeable channels (DACCs, HACCs and VICCs respectively). These channels are encoded by the following gene families: (1) cyclic nucleotide-gated channels (CNGCs), (2) ionotropic glutamate receptors (GLRs), (3) annexins, (4) ‘mechanosensitive channels of small (MscS) conductance’-like channels (MSLs), (5) ‘mid1-complementing activity’ channels (MCAs), Piezo channels, and hyperosmolality-induced [Ca2+]cyt. channel 1 (OSCA1). Also, a ‘tandem-pore channel1’ (TPC1) catalyses Ca2+ efflux from the vacuole in response to the plasma membrane-mediated Ca2+ elevation. Recent experimental data demonstrated that Arabidopsis thaliana (L.) Heynh. CNGCs 2, 5–10, 14, 16 and 18, GLRs 1.2, 3.3, 3.4, 3.6 and 3.7, TPC1, ANNEXIN1, MSL9 and MSL10,MCA1 and MCA2, OSCA1, and some their homologues counterparts in other species, are responsible for Ca2+ currents and/or cytosolic Ca2+ elevation. Extrusion of Ca2+ from the cytosol is mediated by Ca2+-ATPases and Ca2+/H+ exchangers which were recently examined at the level of high resolution crystal structure. Calcium-activated NADPH oxidases and reactive oxygen species (ROS)-activated Ca2+ conductances form a self-amplifying ‘ROS-Ca2+hub’, enhancing and transducing Ca2+ and redox signals. The ROS-Ca2+ hub contributes to physiological reactions controlled by ROS and Ca2+, demonstrating synergism and unity of Ca2+ and ROS signalling mechanisms.

Download Full-text

Familial Hyperparathyroidism

Frontiers in Endocrinology ◽

10.3389/fendo.2021.623667 ◽

2021 ◽

Vol 12 ◽

Author(s):

Jenny E. Blau ◽

William F. Simonds

Keyword(s):

Serum Calcium ◽

Mineral Metabolism ◽

Elevated Serum ◽

Tumor Development ◽

Parathyroid Glands ◽

Free Calcium ◽

Target Cells ◽

Renal Tubules ◽

Loss Of Function ◽

Endocrine Organs

Regulation of the serum calcium level in humans is achieved by the endocrine action of parathyroid glands working in concert with vitamin D and a set of critical target cells and tissues including osteoblasts, osteoclasts, the renal tubules, and the small intestine. The parathyroid glands, small highly vascularized endocrine organs located behind the thyroid gland, secrete parathyroid hormone (PTH) into the systemic circulation as is needed to keep the serum free calcium concentration within a tight physiologic range. Primary hyperparathyroidism (HPT), a disorder of mineral metabolism usually associated with abnormally elevated serum calcium, results from the uncontrolled release of PTH from one or several abnormal parathyroid glands. Although in the vast majority of cases HPT is a sporadic disease, it can also present as a manifestation of a familial syndrome. Many benign and malignant sporadic parathyroid neoplasms are caused by loss-of-function mutations in tumor suppressor genes that were initially identified by the study of genomic DNA from patients who developed HPT as a manifestation of an inherited syndrome. Somatic and inherited mutations in certain proto-oncogenes can also result in the development of parathyroid tumors. The clinical and genetic investigation of familial HPT in kindreds found to lack germline variants in the already known HPT-predisposition genes represents a promising future direction for the discovery of novel genes relevant to parathyroid tumor development.

Download Full-text

Differential Regulation by Cyclic Nucleotides of the CNGA4 and CNGB1b Subunits in Olfactory Cyclic Nucleotide-Gated Channels

Science Signaling ◽

10.1126/scisignal.2003110 ◽

2012 ◽

Vol 5 (232) ◽

pp. ra48-ra48 ◽

Cited By ~ 17

Author(s):

V. Nache ◽

T. Zimmer ◽

N. Wongsamitkul ◽

R. Schmauder ◽

J. Kusch ◽

...

Keyword(s):

Cyclic Nucleotides ◽

Cyclic Nucleotide ◽

Differential Regulation ◽

Cyclic Nucleotide Gated Channels

Download Full-text

Modulation of endothelial cell migration by extracellular nucleotides

Thrombosis and Haemostasis ◽

10.1160/th04-09-0576 ◽

2005 ◽

Vol 93 (04) ◽

pp. 735-742 ◽

Cited By ~ 73

Author(s):

Laurie Erb ◽

Katarzyna Koziak ◽

Robert Jarzyna ◽

Marcia Wink ◽

Olaf Guckelberger ◽

...

Keyword(s):

Cell Migration ◽

Endothelial Cell ◽

P2 Receptors ◽

Cellular Adhesion ◽

Extracellular Nucleotides ◽

Endothelial Cell Migration ◽

Free Calcium ◽

Receptor Subtypes ◽

Dependent Manner ◽

Cell Functions

SummaryExtracellular nucleotides bind to type-2 purinergic/pyrimidinergic (P2) receptors that mediate various responses, such as cell activation, proliferation and apoptosis, implicated in inflammatory processes. The role of P2 receptors and their associated signal transduction pathways in endothelial cell responses has not been fully investigated. Here, it is shown that stimulation of human umbilical vein endothelial cells (HUVEC) with extracellular ATP or UTP increased intracellular free calcium ion concentrations ([Ca2+]i), induced phosphorylation of focal adhesion kinase (FAK), p130cas and paxillin, and caused cytoskeletal rearrangements with consequent cell migration. Furthermore, UTP increased migration of HUVEC in a phosphatidylinositol 3-kinase (PI3-K)-dependent manner. BAPTA or thapsigargin inhibited the extracellular nucleotide-induced increase in [Ca2+]i, a response crucial for both FAK phosphorylation and cell migration. Furthermore, long-term exposure of HUVEC to ATP and UTP, agonists of the G protein-coupled P2Y2 and P2Y4 receptor subtypes, caused upregulation of αv integrin expression, a cell adhesion molecule known to directly interact with P2Y2 receptors. Our results suggest that extracellular nucleotides modulate signaling pathways in HUVEC influencing cell functions, such as cytoskeletal changes, cellular adhesion and motility, typically associated with integrin-activation and the action of growth factors. We propose that P2Y2 and possibly P2Y4 receptors mediate those responses that are important in vascular inflammation, atherosclerosis and angiogenesis.

Download Full-text