Calcium signalling and calcium channels: evolution and general principles

Complement Component C5a and Fungal Pathogen Induce Diverse Responses through Crosstalk between Transient Receptor Potential Channel (TRPs) Subtypes in Human Conjunctival Epithelial Cells

The conjunctiva has immune-responsive properties to protect the eye from infections. Its innate immune system reacts against external pathogens, such as fungi. The complement factor C5a is an important contributor to the initial immune response. It is known that activation of transient-receptor-potential-vanilloid 1 (TRPV1) and TRP-melastatin 8 (TRPM8) channels is involved in different immune reactions and inflammation in the human body. The aim of this study was to determine if C5a and mucor racemosus e voluminae cellulae (MR) modulate Ca2+-signaling through changes in TRPs activity in human conjunctival epithelial cells (HCjECs). Furthermore, crosstalk was examined between C5a and MR in mediating calcium regulation. Intracellular Ca2+-concentration ([Ca2+]i) was measured by fluorescence calcium imaging, and whole-cell currents were recorded using the planar-patch-clamp technique. MR was used as a purified extract. Application of C5a (0.05-50 ng/mL) increased both [Ca2+]i and whole-cell currents, which were suppressed by either the TRPV1-blocker AMG 9810 or the TRPM8-blocker AMTB (both 20 µM). The N-terminal peptide C5L2p (20-50 ng/mL) blocked rises in [Ca2+]i induced by C5a. Moreover, the MR-induced rise in Ca2+-influx was suppressed by AMG 9810 and AMTB, as well as 0.05 ng/mL C5a. In conclusion, crosstalk between C5a and MR controls human conjunctival cell function through modulating interactions between TRPV1 and TRPM8 channel activity.

Molecular and gene expression analyses of chicken oncomodulin and their association with breast myopathies in broilers

Oncomodulins (OCMs), also known as non-α-parvalbumins, are small molecules known for their high-affinity binding of Ca2+ ions. They play crucial roles as Ca2+ buffers and participate in signaling pathways within muscle and neuron cells. In chickens, 3 oncomodulin molecules have been identified at the protein level and are named chicken oncomodulin 1 (OCM1), -3 (OCM3), and alpha-parvalbumin (PVALB). OCM4 was newly assigned by genome annotation. A gene cluster containing OCM1, OCM3, and OCM4 is located in chromosome 14, while a single gene of PVALB is on chromosome 1. The Ca2+ signaling pathway may be a potential contributor to the onset of chicken breast myopathies. However, chicken OCMs have not been extensively studied in muscle tissues. In this study, the genetic specifications, tissue-specific and differential expression of OCM1, OCM3, OCM4, and PVALB in the context of chicken breast myopathies were investigated. OCM1 exhibited moderate expression in the liver, intestine, and kidney. OCM3 was highly expressed in thymus and breast muscle. A long noncoding RNA (lncRNA) transcribed from the antisense strand of the OCM3 gene was found to be expressed in liver, lung, heart, intestine, and kidney tissues. OCM4 was barely expressed in thymus, thigh-, and breast muscle. PVALB exhibited high expression across all tissues examined. Results of quantitative PCR (qPCR) indicated that the expression of OCM3 was significantly increased (4.4 ± 0.7 fold; P-value = 0.03) in woody breast (WB) muscle and even greater (8.5 ± 0.6 fold; P-value = 0.004) in WB/white striping (WS) muscles. The expression of PVALB showed no difference in WB muscle, but it was notably higher (4.6 ± 0.7 fold; P-value = 0.054) in WB/WS muscle, although statistical significance was not reached. These findings suggest that increased expression of OCM3 and PVALB may be linked to chicken breast myopathies with regard to disruption of Ca2+ buffering.

Origin, evolution, and diversification of inositol 1,4,5-trisphosphate 3-kinases in plants and animals

BACKGROUND

In Eukaryotes, inositol polyphosphates (InsPs) represent a large family of secondary messengers and play crucial roes in various cellular processes. InsPs are synthesized through a series of pohophorylation reactions catalyzed by various InsP kinases in a sequential manner. Inositol 1,4,5-trisphosphate 3-kinase (IP3 3-kinase/IP3K), one member of InsP kinase, plays important regulation roles in InsPs metabolism by specifically phosphorylating inositol 1,4,5-trisphosphate (IP3) to inositol 1,3,4,5-tetrakisphosphate (IP4) in animal cells. IP3Ks were widespread in fungi, plants and animals. However, its evolutionary history and patterns have not been examined systematically.

RESULTS

A total of 104 and 31 IP3K orthologues were identified across 57 plant genomes and 13 animal genomes, respectively. Phylogenetic analyses indicate that IP3K originated in the common ancestor before the divergence of fungi, plants and animals. In most plants and animals, IP3K maintained low-copy numbers suggesting functional conservation during plant and animal evolution. In Brassicaceae and vertebrate, IP3K underwent one and two duplication events, respectively, resulting in multiple gene copies. Whole-genome duplication (WGD) was the main mechanism for IP3K duplications, and the IP3K duplicates have experienced functional divergence. Finally, a hypothetical evolutionary model for the IP3K proteins is proposed based on phylogenetic theory.

CONCLUSION

Our study reveals the evolutionary history of IP3K proteins and guides the future functions of animal, plant, and fungal IP3K proteins.

Hypothesis paper: the development of a regulatory layer in P2B autoinhibited Ca2+-ATPases may have facilitated plant terrestrialization and animal multicellularization

With the appearance of plants and animals, new challenges emerged. These multicellular eukaryotes had to solve for example the difficulties of multifaceted communication between cells and adaptation to new habitats. In this paper, we are looking for one piece of the puzzle that made the development of complex multicellular eukaryotes possible with a focus on regulation of P2B autoinhibited Ca²⁺-ATPases. P2B ATPases pump Ca²⁺ out of the cytosol at the expense of ATP hydrolysis, and thereby maintain a steep gradient between the extra- and intracytosolic compartments which is utilized for Ca²⁺-mediated rapid cell signaling. The activity of these enzymes is regulated by a calmodulin (CaM)-responsive autoinhibitory region, which can be located in either termini of the protein, at the C-terminus in animals and at the N-terminus in plants. When the cytoplasmic Ca²⁺ level reaches a threshold, the CaM/Ca²⁺ complex binds to a calmodulin-binding domain (CaMBD) in the autoinhibitor, which leads to the upregulation of pump activity. In animals, protein activity is also controlled by acidic phospholipids that bind to a cytosolic portion of the pump. Here, we analyze the appearance of CaMBDs and the phospholipid-activating sequence and show that their evolution in animals and plants was independent. Furthermore, we hypothesize that different causes may have initiated the appearance of these regulatory layers: in animals, it is linked to the appearance of multicellularity, while in plants it co-occurs with their water-to-land transition.

Exaptation and Evolutionary Adaptation in Nociceptor Mechanisms Driving Persistent Pain

BACKGROUND

Several evolutionary explanations have been proposed for why chronic pain is a major clinical problem. One is that some mechanisms important for driving chronic pain, while maladaptive for modern humans, were adaptive because they enhanced survival. Evidence is reviewed for persistent nociceptor hyperactivity (PNH), known to promote chronic pain in rodents and humans, being an evolutionarily adaptive response to significant bodily injury, and primitive molecular mechanisms related to cellular injury and stress being exapted (co-opted or repurposed) to drive PNH and consequent pain.

SUMMARY

PNH in a snail (Aplysia californica), squid (Doryteuthis pealeii), fruit fly (Drosophila melanogaster), mice, rats, and humans has been documented as long-lasting enhancement of action potential discharge evoked by peripheral stimuli, and in some of these species as persistent extrinsically driven ongoing activity and/or intrinsic spontaneous activity (OA and SA, respectively). In mammals, OA and SA are often initiated within the protected nociceptor soma long after an inducing injury. Generation of OA or SA in nociceptor somata may be very rare in invertebrates, but prolonged afterdischarge in nociceptor somata readily occurs in sensitized Aplysia. Evidence for the adaptiveness of injury-induced PNH has come from observations of decreased survival of injured squid exposed to predators when PNH is blocked, from plausible survival benefits of chronic sensitization after severe injuries such as amputation, and from the functional coherence and intricacy of mammalian PNH mechanisms. Major contributions of cAMP-PKA signaling (with associated calcium signaling) to the maintenance of PNH both in mammals and molluscs suggest that this ancient stress signaling system was exapted early during the evolution of nociceptors to drive hyperactivity following bodily injury. Vertebrates have retained core cAMP-PKA signaling modules for PNH while adding new extracellular modulators (e.g., opioids) and cAMP-regulated ion channels (e.g., TRPV1 and Nav1.8 channels).

KEY MESSAGES

Evidence from multiple phyla indicates that PNH is a physiological adaptation that decreases the risk of attacks on injured animals. Core cAMP-PKA signaling modules make major contributions to the maintenance of PNH in molluscs and mammals. This conserved signaling has been linked to ancient cellular responses to stress, which may have been exapted in early nociceptors to drive protective hyperactivity that can persist while bodily functions recover after significant injury.

Unveiling the Secrets of Calcium-Dependent Proteins in Plant Growth-Promoting Rhizobacteria: An Abundance of Discoveries Awaits

The role of Calcium ions (Ca2+) is extensively documented and comprehensively understood in eukaryotic organisms. Nevertheless, emerging insights, primarily derived from studies on human pathogenic bacteria, suggest that this ion also plays a pivotal role in prokaryotes. In this review, our primary focus will be on unraveling the intricate Ca2+ toolkit within prokaryotic organisms, with particular emphasis on its implications for plant growth-promoting rhizobacteria (PGPR). We undertook an in silico exploration to pinpoint and identify some of the proteins described in the existing literature, including prokaryotic Ca2+ channels, pumps, and exchangers that are responsible for regulating intracellular Calcium concentration ([Ca2+]i), along with the Calcium-binding proteins (CaBPs) that play a pivotal role in sensing and transducing this essential cation. These investigations were conducted in four distinct PGPR strains: Pseudomonas chlororaphis subsp. aurantiaca SMMP3, P. donghuensis SVBP6, Pseudomonas sp. BP01, and Methylobacterium sp. 2A, which have been isolated and characterized within our research laboratories. We also present preliminary experimental data to evaluate the influence of exogenous Ca2+ concentrations ([Ca2+]ex) on the growth dynamics of these strains.

Altered TRPM7-Dependent Calcium Influx in Natural Killer Cells of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disabling multisystemic condition. The pathomechanism of ME/CFS remains unestablished; however, impaired natural killer (NK) cell cytotoxicity is a consistent feature of this condition. Calcium (Ca²⁺) is crucial for NK cell effector functions. Growing research recognises Ca²⁺ signalling dysregulation in ME/CFS patients and implicates transient receptor potential ion channel dysfunction. TRPM7 (melastatin) was recently considered in the pathoaetiology of ME/CFS as it participates in several Ca²⁺-dependent processes that are central to NK cell cytotoxicity which may be compromised in ME/CFS. TRPM7-dependent Ca²⁺ influx was assessed in NK cells isolated from n = 9 ME/CFS patients and n = 9 age- and sex-matched healthy controls (HCs) using live cell fluorescent imaging techniques. Slope (p < 0.05) was significantly reduced in ME/CFS patients compared with HCs following TRPM7 activation. Half-time of maximal response (p < 0.05) and amplitude (p < 0.001) were significantly reduced in the HCs compared with the ME/CFS patients following TRPM7 desensitisation. Findings from this investigation suggest that TRPM7-dependent Ca²⁺ influx is reduced with agonism and increased with antagonism in ME/CFS patients relative to the age- and sex-matched HCs. The outcomes reported here potentially reflect TRPM3 dysfunction identified in this condition suggesting that ME/CFS is a TRP ion channelopathy.

Structural Analysis and Diversity of Calmodulin-Binding Domains in Membrane and Intracellular Ca2+-ATPases

The plasma membrane and autoinhibited Ca²⁺-ATPases contribute to the Ca²⁺ homeostasis in a wide variety of organisms. The enzymatic activity of these pumps is stimulated by calmodulin, which interacts with the target protein through the calmodulin-binding domain (CaMBD). Most information about this region is related to all calmodulin modulated proteins, which indicates general chemical properties and there is no established relation between Ca²⁺ pump sequences and taxonomic classification. Thus, the aim of this study was to perform an in silico analysis of the CaMBD from several Ca²⁺-ATPases, in order to determine their diversity and to detect specific patterns and amino acid selection in different species. Patterns related to potential and confirmed CaMBD were detected using sequences retrieved from the literature. The occurrence of these patterns was determined across 120 sequences from 17 taxonomical classes, which were analyzed by a phylogenetic tree to establish phylogenetic groups. Predicted physicochemical characteristics including hydropathy and net charge were calculated for each group of sequences. 22 Ca²⁺-ATPases sequences from animals, unicellular eukaryotes, and plants were retrieved from bioinformatic databases. These sequences allow us to establish the Patterns 1(GQILWVRGLTRLQTQ), 3(KNPSLEALQRW), and 4(SRWRRLQAEHVKK), which are present at the beginning of putative CaMBD of metazoan, parasites, and land plants. A pattern 2 (IRVVNAFR) was consistently found at the end of most analyzed sequences. The amino acid preference in the CaMBDs changed depending on the phylogenetic groups, with predominance of several aliphatic and charged residues, to confer amphiphilic properties. The results here displayed show a conserved mechanism to contribute to the Ca²⁺ homeostasis across evolution and may help to detect putative CaMBDs.

Comprehensive Sequence Analysis of Parvalbumins in Fish and Their Comparison with Parvalbumins in Tetrapod Species

Parvalbumins are small molecules with important functions in Ca²⁺ signaling, but their sequence comparisons to date, especially in fish, have been relatively poor. We here, characterize sequence motifs that distinguish parvalbumin subfamilies across vertebrate species, as well as those that distinguish individual parvalbumins (orthologues) in fish, and map them to known parvalbumin structures. As already observed by others, all classes of jawed vertebrates possess parvalbumins of both the α-parvalbumin and oncomodulin subfamilies. However, we could not find convincing phylogenetic support for the common habit of classifying all non-α-parvalbumins together as "β-parvalbumins." In teleost (modern bony) fish, we here distinguish parvalbumins 1-to-10, of which the gene copy number can differ between species. The genes for α-parvalbumins (pvalb6 and pvalb7) and oncomodulins (pvalb8 and pvalb9) are well conserved between teleost species, but considerable variation is observed in their copy numbers of the non-α/non-oncomodulin genes pvalb1-to-5 and pvalb10. Teleost parvalbumins 1-to-4 are hardly distinguishable from each other and are highly expressed in muscle, and described allergens belong to this subfamily. However, in some fish species α-parvalbumin expression is also high in muscle. Pvalb5 and pvalb10 molecules form distinct lineages, the latter even predating the origin of teleosts, but have been lost in some teleost species. The present study aspires to be a frame of reference for future studies trying to compare different parvalbumins.

Role of Microglia and Astrocytes in Alzheimer’s Disease: From Neuroinflammation to Ca2+ Homeostasis Dysregulation

Alzheimer’s disease (AD) is the most common form of dementia worldwide, with a complex, poorly understood pathogenesis. Cerebral atrophy, amyloid-β (Aβ) plaques, and neurofibrillary tangles represent the main pathological hallmarks of the AD brain. Recently, neuroinflammation has been recognized as a prominent feature of the AD brain and substantial evidence suggests that the inflammatory response modulates disease progression. Additionally, dysregulation of calcium (Ca2+) homeostasis represents another early factor involved in the AD pathogenesis, as intracellular Ca2+ concentration is essential to ensure proper cellular and neuronal functions. Although growing evidence supports the involvement of Ca2+ in the mechanisms of neurodegeneration-related inflammatory processes, scant data are available on its contribution in microglia and astrocytes functioning, both in health and throughout the AD continuum. Nevertheless, AD-related aberrant Ca2+ signalling in astrocytes and microglia is crucially involved in the mechanisms underpinning neuroinflammatory processes that, in turn, impact neuronal Ca2+ homeostasis and brain function. In this light, we attempted to provide an overview of the current understanding of the interactions between the glia cells-mediated inflammatory responses and the molecular mechanisms involved in Ca2+ homeostasis dysregulation in AD.

Why antidiabetic drugs are potentially neuroprotective during the Sars-CoV-2 pandemic: The focus on astroglial UPR and calcium-binding proteins

We are living in a terrifying pandemic caused by Sars-CoV-2, in which patients with diabetes mellitus have, from the beginning, been identified as having a high risk of hospitalization and mortality. This viral disease is not limited to the respiratory system, but also affects, among other organs, the central nervous system. Furthermore, we already know that individuals with diabetes mellitus exhibit signs of astrocyte dysfunction and are more likely to develop cognitive deficits and even dementia. It is now being realized that COVID-19 incurs long-term effects and that those infected can develop several neurological and psychiatric manifestations. As this virus seriously compromises cell metabolism by triggering several mechanisms leading to the unfolded protein response (UPR), which involves endoplasmic reticulum Ca2+ depletion, we review here the basis involved in this response that are intimately associated with the development of neurodegenerative diseases. The discussion aims to highlight two aspects-the role of calcium-binding proteins and the role of astrocytes, glial cells that integrate energy metabolism with neurotransmission and with neuroinflammation. Among the proteins discussed are calpain, calcineurin, and sorcin. These proteins are emphasized as markers of the UPR and are potential therapeutic targets. Finally, we discuss the role of drugs widely prescribed to patients with diabetes mellitus, such as statins, metformin, and calcium channel blockers. The review assesses potential neuroprotection mechanisms, focusing on the UPR and the restoration of reticular Ca2+ homeostasis, based on both clinical and experimental data.

Control of Ca2+ and metabolic homeostasis by the Na+/Ca2+ exchangers (NCXs) in health and disease

Spatial and temporal control of calcium (Ca²⁺) levels is essential for the background rhythms and responses of living cells to environmental stimuli. Whatever other regulators a given cellular activity may have, localized and wider scale Ca²⁺ events (sparks, transients, and waves) are hierarchical determinants of fundamental processes such as cell contraction, excitability, growth, metabolism and survival. Different cell types express specific channels, pumps and exchangers to efficiently generate and adapt Ca²⁺ patterns to cell requirements. The Na⁺/Ca²⁺ exchangers (NCXs) in particular contribute to Ca²⁺ homeostasis by buffering intracellular Ca²⁺ loads according to the electrochemical gradients of substrate ions - i.e., Ca²⁺ and sodium (Na⁺) - and under a dynamic control of redundant regulatory processes. An interesting feature of NCX emerges from the strict relationship that connects transporter activity with cell metabolism: on the one hand NCX operates under constant control of ATP-dependent regulatory processes, on the other hand the ion fluxes generated through NCX provide mechanistic support for the Na⁺-driven uptake of glutamate and Ca²⁺ influx to fuel mitochondrial respiration. Proof of concept evidence highlights therapeutic potential of preserving a timed and balanced NCX activity in a growing rate of diseases (including excitability, neurodegenerative, and proliferative disorders) because of an improved ability of stressed cells to safely maintain ion gradients and mitochondrial bioenergetics. Here, we will summarize and review recent works that have focused on the pathophysiological roles of NCXs in balancing the two-way relationship between Ca²⁺ signals and metabolism.

A Narrative Review on Oral and Periodontal Bacteria Microbiota Photobiomodulation, through Visible and Near-Infrared Light: From the Origins to Modern Therapies

Photobiomodulation (PBM) consists of a photon energy transfer to the cell, employing non-ionizing light sources belonging to the visible and infrared spectrum. PBM acts on some intrinsic properties of molecules, energizing them through specific light wavelengths. During the evolution of life, semiconducting minerals were energized by sun radiation. The molecules that followed became photoacceptors and were expressed into the first proto-cells and prokaryote membranes. Afterward, the components of the mitochondria electron transport chain influenced the eukaryotic cell physiology. Therefore, although many organisms have not utilized light as an energy source, many of the molecules involved in their physiology have retained their primordial photoacceptive properties. Thus, in this review, we discuss how PBM can affect the oral microbiota through photo-energization and the non-thermal effect of light on photoacceptors (i.e., cytochromes, flavins, and iron-proteins). Sometimes, the interaction of photons with pigments of an endogenous nature is followed by thermal or photodynamic-like effects. However, the preliminary data do not allow determining reliable therapies but stress the need for further knowledge on light-bacteria interactions and microbiota management in the health and illness of patients through PBM.

A Novel Insight Into the Fate of Cardiomyocytes in Ischemia-Reperfusion Injury: From Iron Metabolism to Ferroptosis

Ischemia-reperfusion injury (IRI), critically involved in the pathology of reperfusion therapy for myocardial infarction, is closely related to oxidative stress the inflammatory response, and disturbances in energy metabolism. Emerging evidence shows that metabolic imbalances of iron participate in the pathophysiological process of cardiomyocyte IRI [also termed as myocardial ischemia-reperfusion injury (MIRI)]. Iron is an essential mineral required for vital physiological functions, including cellular respiration, lipid and oxygen metabolism, and protein synthesis. Nevertheless, cardiomyocyte homeostasis and viability are inclined to be jeopardized by iron-induced toxicity under pathological conditions, which is defined as ferroptosis. Upon the occurrence of IRI, excessive iron is transported into cells that drive cardiomyocytes more vulnerable to ferroptosis by the accumulation of reactive oxygen species (ROS) through Fenton reaction and Haber–Weiss reaction. The increased ROS production in ferroptosis correspondingly leads cardiomyocytes to become more sensitive to oxidative stress under the exposure of excess iron. Therefore, ferroptosis might play an important role in the pathogenic progression of MIRI, and precisely targeting ferroptosis mechanisms may be a promising therapeutic option to revert myocardial remodeling. Notably, targeting inhibitors are expected to prevent MIRI deterioration by suppressing cardiomyocyte ferroptosis. Here, we review the pathophysiological alterations from iron homeostasis to ferroptosis together with potential pathways regarding ferroptosis secondary to cardiovascular IRI. We also provide a comprehensive analysis of ferroptosis inhibitors and initiators, as well as regulatory genes involved in the setting of MIRI.

TypiCal but DeliCate Ca++re: Dissecting the Essence of Calcium Signaling Network as a Robust Response Coordinator of Versatile Abiotic and Biotic Stimuli in Plants

Plant growth, development, and ultimately crop productivity are largely impacted by the interaction of plants with different abiotic and biotic factors throughout their life cycle. Perception of different abiotic stresses, such as salt, cold, drought, heat, and heavy metals, and interaction with beneficial and harmful biotic agents by plants lead to transient, sustained, or oscillatory changes of [calcium ion, Ca²⁺]_cyt within the cell. Significant progress has been made in the decoding of Ca²⁺ signatures into downstream responses to modulate differential developmental and physiological responses in the whole plant. Ca²⁺ sensor proteins, mainly calmodulins (CaMs), calmodulin-like proteins (CMLs), and others, such as Ca²⁺-dependent protein kinases (CDPKs), calcineurin B-like proteins (CBLs), and calmodulin-binding transcription activators (CAMTAs) have played critical roles in coupling the specific stress stimulus with an appropriate response. This review summarizes the current understanding of the Ca²⁺ influx and efflux system in plant cells and various Ca²⁺ binding protein-mediated signal transduction pathways that are delicately orchestrated to mitigate abiotic and biotic stresses. The probable interactions of different components of Ca²⁺ sensor relays and Ca²⁺ sensor responders in response to various external stimuli have been described diagrammatically focusing on established pathways and latest developments. Present comprehensive insight into key components of the Ca²⁺ signaling toolkit in plants can provide an innovative framework for biotechnological manipulations toward crop improvability in near future.

Calenduloside E protects against myocardial ischemia-reperfusion injury induced calcium overload by enhancing autophagy and inhibiting L-type Ca2+ channels through BAG3

Calenduloside E (CE) is a saponin isolated from Aralia elata (Miq) Seem, which has anti-cardiovascular disease effects. This study aims to evaluate the anti-myocardial ischemia-reperfusion injury (MIRI) mechanisms of CE and regulation of BAG3 on calcium overload. We adopted siRNA to interfere with BAG3 expression in H9c2 cardiomyocytes and used adenovirus to interfere with BAG3 expression (Ad-BAG3) in primary neonatal rat cardiomyocytes (PNRCMs) to clarify the role of BAG3 in mitigating MIRI by CE. The results showed that CE reduced calcium overload, and Ad-BAG3 had a significant regulatory effect on L-type Ca²⁺ channels (LTCC) but no effects on other calcium-related proteins. And BAG3 and LTCC were colocalized in myocardial tissue and BAG3 inhibited LTCC expression. Surprisingly, CE had no regulatory effect on LTCC mRNA, but CE promoted LTCC degradation through the autophagy-lysosomal pathway rather than the ubiquitination-protease pathway. Autophagy inhibitor played a negative regulation of cardiomyocyte contraction rhythm and field potential signals. Ad-BAG3 inhibited autophagy by regulating the expression of autophagy-related proteins and autophagy agonist treatment suppressed calcium overload. Therefore, CE promoted autophagy through BAG3, thereby regulating LTCC expression, inhibiting calcium overload, and ultimately reducing MIRI.

Metagenomics approach for Polymyxa betae genome assembly enables comparative analysis towards deciphering the intracellular parasitic lifestyle of the plasmodiophorids

Genomic knowledge of the tree of life is biased to specific groups of organisms. For example, only six full genomes are currently available in the rhizaria clade. Here, we have applied metagenomic techniques enabling the assembly of the genome of Polymyxa betae (Rhizaria, Plasmodiophorida) RES F41 isolate from unpurified zoospore holobiont and comparison with the A26-41 isolate. Furthermore, the first P. betae mitochondrial genome was assembled. The two P. betae nuclear genomes were highly similar, each with just ~10.2 k predicted protein coding genes, ~3% of which were unique to each isolate. Extending genomic comparisons revealed a greater overlap with Spongospora subterranea than with Plasmodiophora brassicae, including orthologs of the mammalian cation channel sperm-associated proteins, raising some intriguing questions about zoospore physiology. This work validates our metagenomics pipeline for eukaryote genome assembly from unpurified samples and enriches plasmodiophorid genomics; providing the first full annotation of the P. betae genome.

Calcium (Ca2+)-regulated exopolysaccharide biosynthesis in probiotic Lactobacillus plantarum K25 as analyzed by an omics approach

Exopolysaccharide (EPS)-producing lactic acid bacteria have been widely used in dairy products, but how calcium, the main metal ion component in milk, regulates the EPS biosynthesis in lactic acid bacteria is not clear. In this study, the effect of Ca²⁺ on the biosynthesis of EPS in the probiotic Lactobacillus plantarum K25 was studied. The results showed that addition of CaCl₂ at 20 mg/L in a semi-defined medium did not affect the growth of strain K25, but it increased the EPS yield and changed the microstructure of the polymer. The presence of Ca²⁺ also changed the monosaccharide composition of the EPS with decreased high molecular weight components and more content of rhamnose, though the functional groups of the polymer were not altered as revealed by Fourier transform infrared spectral analysis. These were further confirmed by analysis of the mRNA expression of cps genes, 9 of which were upregulated by Ca²⁺, including cps4F and rfbD associated with EPS biosynthesis with rhamnose. Proteomics analysis showed that Ca²⁺ upregulated most of the proteins related to carbon transport and metabolism, fatty acid synthesis, amino acid synthesis, ion transport, UMP synthesis. Specially, the increased expression of MelB, PtlIIBC, EIIABC, PtlIIC, PtlIID, Bgl, GH1, MalFGK, DhaK, and FBPase provided substrates for the EPS synthesis. Meanwhile, metabolomics analysis revealed significant change of the small molecular metabolites in tricarboxylic acid cycle, glucose metabolism and propionic acid metabolism. Among them the content of active small molecules such as polygalitol, lyxose, and 5-phosphate ribose increased, facilitating the EPS biosynthesis. Furthermore, Ca²⁺ activated HipB signaling pathway to inhibit the expression of manipulator repressor such as ArsR, LytR/AlgR, IscR, and RafR, and activated the expression of GntR to regulate the EPS synthesis genes. This study provides a basis for understanding the overall change of metabolic pathways related to the EPS biosynthesis in L. plantarum K25 in response to Ca²⁺, facilitating exploitation of its EPS-producing potential for application in probiotic dairy products.

Saponins in Chinese Herbal Medicine Exerts Protection in Myocardial Ischemia-Reperfusion Injury: Possible Mechanism and Target Analysis

Myocardial ischemia is a high-risk disease among middle-aged and senior individuals. After thrombolytic therapy, heart tissue can potentially suffer further damage, which is called myocardial ischemia-reperfusion injury (MIRI). At present, the treatment methods and drugs for MIRI are scarce and cannot meet the current clinical needs. The mechanism of MIRI involves the interaction of multiple factors, and the current research hotspots mainly include oxidative stress, inflammation, calcium overload, energy metabolism disorders, pyroptosis, and ferroptosis. Traditional Chinese medicine (TCM) has multiple targets and few toxic side effects; clinical preparations containing Panax ginseng C. A. Mey., Panax notoginseng (Burk.) F. H. Chen, Aralia chinensis L., cardioprotection, and other Chinese herbal medicines have been used to treat patients with coronary heart disease, angina pectoris, and other cardiovascular diseases. Studies have shown that saponins are the main active substances in TCMs containing Panax ginseng C. A. Mey., Panax notoginseng (Burk.) F. H. Chen, Aralia chinensis L., and Radix astragali. In the present review, we sorted the saponin components with anti-MIRI effects and their regulatory mechanisms. Each saponin can play a cardioprotective role via multiple mechanisms, and the signaling pathways involved in different saponins are not the same. We found that more active saponins in Panax ginseng C. A. Mey. are mainly dammar-type structures and have a strong regulatory effect on energy metabolism. The highly active saponin components of Aralia chinensis L. are oleanolic acid structures, which have significant regulatory effects on calcium homeostasis. Therefore, saponins in Chinese herbal medicine provide a broad application prospect for the development of highly effective and low-toxicity anti-MIRI drugs.

Mitochondrial calcium in command of juggling myriads of cellular functions

The puzzling traits related to the evolutionary aspect of mitochondria, still positions the mitochondrion at the center of the research. The theory of endosymbiosis popularized by Lynn Margulis in 1967 gained prominence wherein the mitochondrion is believed to have emerged as a prokaryote and later integrated into the eukaryotic system. This semi-autonomous organelle has bagged two responsible but perilous cellular functions: a) energy metabolism, and b) calcium buffering, though both are interdependent. While most of the mitochondrial functions are saliently regulated by calcium ions, the calcium buffering role of mitochondria decides the cellular fate. Though calcium overload in few mitochondria makes them dysfunctional at the early stage of cellular stress, this doesn't lead to sudden cell death due to critical checkpoints like mitophagy, mitochondrial fusion, etc. Thus, mitochondrion juggles with multiple crucial cellular functions with its calcium buffering skill.

Calenduloside E suppresses calcium overload by promoting the interaction between L-type calcium channels and Bcl2-associated athanogene 3 to alleviate myocardial ischemia/reperfusion injury

Introduction

Intracellular calcium overload is an important contributor to myocardial ischemia/reperfusion (MI/R) injury. Total saponins of the traditional Chinese medicinal plant Aralia elata (Miq.) Seem. (AS) are beneficial for treating MI/R injury, and Calenduloside E (CE) is the main active ingredient of AS.

Objectives

This study aimed to investigate the effects of CE on MI/R injury and determine its specific regulatory mechanisms.

Methods

To verify whether CE mediated cardiac protection in vivo and in vitro, we performed MI/R surgery in SD rats and subjected neonatal rat ventricular myocytes (NRVMs) to hypoxia-reoxygenation (HR). CE’s cardioprotective against MI/R injury was detected by Evans blue/TTC staining, echocardiography, HE staining, myocardial enzyme levels. Impedance and field potential recording, and patch-clamp techniques of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to detect the function of L-type calcium channels (LTCC). The mechanisms underlying between CE and LTCC was studied through western blot, immunofluorescence, and immunohistochemistry. Drug affinity responsive target stability (DARTS) and co-immunoprecipitation (co-IP) used to further clarify the effect of CE on LTCC and BAG3.

Results

We found that CE protected against MI/R injury by inhibiting calcium overload. Furthermore, CE improved contraction and field potential signals of hiPSC-CMs and restored sarcomere contraction and calcium transient of adult rat ventricular myocytes (ARVMs). Moreover, patch-clamp data showed that CE suppressed increased L-type calcium current (I_Ca,L) caused by LTCC agonist, proving that CE could regulate calcium homeostasis through LTCC. Importantly, we found that CE promoted the interaction between LTCC and Bcl2-associated athanogene 3 (BAG3) by co-IP and DARTS.

Conclusion

Our results demonstrate that CE enhanced LTCC-BAG3 interaction to reduce MI/R induced-calcium overload, exerting a cardioprotective effect.

Calcium signaling is involved in diverse cellular processes in fungi

Calcium (Ca²⁺) is a universal signalling molecule of life. The Ca²⁺ signalling is an evolutionarily conserved process from prokaryotes to eukaryotes. Ca²⁺ at high concentration is deleterious to the cell; therefore, cell maintains a low resting level of intracellular free Ca²⁺ concentration ([Ca²⁺]_c). The resting [Ca²⁺]_c is tightly regulated, and a transient increase of the [Ca²⁺]_c initiates a signalling cascade in the cell. Ca²⁺ signalling plays an essential role in various processes, including growth, development, reproduction, tolerance to stress conditions, and virulence in fungi. In this review, we describe the evolutionary aspects of Ca²⁺ signalling and cell functions of major Ca²⁺ signalling proteins in different fungi.

Direct monitoring of ER Ca2+ dynamics reveals that Ca2+ entry induces ER-Ca2+ release in astrocytes

Excitability in astroglia is controlled by Ca²⁺ fluxes from intracellular organelles, mostly from the endoplasmic reticulum (ER). Astrocytic ER possesses inositol 1,4,5-trisphosphate receptors (InsP₃R) that can be activated upon stimulation through a vast number of metabotropic G-protein-coupled receptors. By contrast, the role of Ca²⁺-gated Ca²⁺ release channels is less explored in astroglia. Here we address this process by monitoring Ca²⁺ dynamics directly in the cytosol and the ER of astroglial cells. Cultured astrocytes exhibited spontaneous and high-K-evoked cytosolic Ca²⁺ transients, both of them reversibly abolished by external Ca²⁺ removal, addition of plasma membrane channel blockers or ER Ca²⁺ depletion with SERCA inhibitors. Resting astrocyte [Ca²⁺]_ER averaged 400 μM and maximal stimulation with ATP provoked a complete and reversible ER discharge. Direct monitoring of Ca²⁺ in the lumen of ER showed that high-K induced a Ca²⁺ release from the ER, and its amplitude was proportional to the [K]. Furthermore, by combining the low affinity GAP3 indicator targeted to the ER with the high affinity cytosolic Rhod-2, we simultaneously imaged ER- and cytosolic-Ca²⁺ signals, in astrocytes in culture and in situ. Plasma membrane Ca²⁺ entry triggered a fast ER Ca²⁺ release coordinated with an increase in cytosolic Ca²⁺. Thus, we identify a Ca²⁺-induced Ca²⁺-release (CICR) mechanism that is likely to participate in spontaneous astroglial oscillations, providing a graded amplification of the cytosolic Ca²⁺ signal.

Hydration Mimicry by Membrane Ion Channels

Ions transiting biomembranes might pass readily from water through ion-specific membrane proteins if these protein channels provide environments similar to the aqueous solution hydration environment. Indeed, bulk aqueous solution is an important reference condition for the ion permeation process. Assessment of this hydration mimicry concept depends on understanding the hydration structure and free energies of metal ions in water in order to provide a comparison for the membrane channel environment. To refine these considerations, we review local hydration structures of ions in bulk water and the molecular quasi-chemical theory that provides hydration free energies. In doing so, we note some current views of ion binding to membrane channels and suggest new physical chemical calculations and experiments that might further clarify the hydration mimicry concept.

Functional Innovation in the Evolution of the Calcium-Dependent System of the Eukaryotic Endoplasmic Reticulum

The origin of eukaryotes was marked by the emergence of several novel subcellular systems. One such is the calcium (Ca²⁺)-stores system of the endoplasmic reticulum, which profoundly influences diverse aspects of cellular function including signal transduction, motility, division, and biomineralization. We use comparative genomics and sensitive sequence and structure analyses to investigate the evolution of this system. Our findings reconstruct the core form of the Ca²⁺-stores system in the last eukaryotic common ancestor as having at least 15 proteins that constituted a basic system for facilitating both Ca²⁺ flux across endomembranes and Ca²⁺-dependent signaling. We present evidence that the key EF-hand Ca²⁺-binding components had their origins in a likely bacterial symbiont other than the mitochondrial progenitor, whereas the protein phosphatase subunit of the ancestral calcineurin complex was likely inherited from the asgard archaeal progenitor of the stem eukaryote. This further points to the potential origin of the eukaryotes in a Ca²⁺-rich biomineralized environment such as stromatolites. We further show that throughout eukaryotic evolution there were several acquisitions from bacteria of key components of the Ca²⁺-stores system, even though no prokaryotic lineage possesses a comparable system. Further, using quantitative measures derived from comparative genomics we show that there were several rounds of lineage-specific gene expansions, innovations of novel gene families, and gene losses correlated with biological innovation such as the biomineralized molluscan shells, coccolithophores, and animal motility. The burst of innovation of new genes in animals included the wolframin protein associated with Wolfram syndrome in humans. We show for the first time that it contains previously unidentified Sel1, EF-hand, and OB-fold domains, which might have key roles in its biochemistry.

The Role of Mitochondrial Calcium Signaling in the Pathophysiology of Cancer Cells

The pioneering work of Richard Altman on the presence of mitochondria in cells set in motion a field of research dedicated to uncovering the secrets of the mitochondria. Despite limitations in studying the structure and function of the mitochondria, advances in our understanding of this organelle prompted the development of potential treatments for various diseases, from neurodegenerative conditions to muscular dystrophy and cancer. As the powerhouses of the cell, the mitochondria represent the essence of cellular life and as such, a selective advantage for cancer cells. Much of the function of the mitochondria relies on Ca²⁺ homeostasis and the presence of effective Ca²⁺ signaling to maintain the balance between mitochondrial function and dysfunction and subsequently, cell survival. Ca²⁺ regulates the mitochondrial respiration rate which in turn increases ATP synthesis, but too much Ca²⁺ can also trigger the mitochondrial apoptosis pathway; however, cancer cells have evolved mechanisms to modulate mitochondrial Ca²⁺ influx and efflux in order to sustain their metabolic demand and ensure their survival. Therefore, targeting the mitochondrial Ca²⁺ signaling involved in the bioenergetic and apoptotic pathways could serve as potential approaches to treat cancer patients. This chapter will review the role of Ca²⁺ signaling in mediating the function of the mitochondria and its involvement in health and disease with special focus on the pathophysiology of cancer.

Mitonuclear conflict and cooperation govern the integration of genotypes, phenotypes and environments

The mitonuclear genome is the most successful co-evolved mutualism in the history of life on Earth. The cross-talk between the mitochondrial and nuclear genomes has been shaped by conflict and cooperation for more than 1.5 billion years, yet this system has adapted to countless genomic reorganizations by each partner, and done so under changing environments that have placed dramatic biochemical and physiological pressures on evolving lineages. From putative anaerobic origins, mitochondria emerged as the defining aerobic organelle. During this transition, the two genomes resolved rules for sex determination and transmission that made uniparental inheritance the dominant, but not a universal pattern. Mitochondria are much more than energy-producing organelles and play crucial roles in nutrient and stress signalling that can alter how nuclear genes are expressed as phenotypes. All of these interactions are examples of genotype-by-environment (GxE) interactions, gene-by-gene (GxG) interactions (epistasis) or more generally context-dependent effects on the link between genotype and phenotype. We provide evidence from our own studies in Drosophila, and from those of other systems, that mitonuclear interactions—either conflicting or cooperative—are common features of GxE and GxG. We argue that mitonuclear interactions are an important model for how to better understand the pervasive context-dependent effects underlying the architecture of complex phenotypes. Future research in this area should focus on the quantitative genetic concept of effect size to place mitochondrial links to phenotype in a proper context.

This article is part of the theme issue ‘Linking the mitochondrial genotype to phenotype: a complex endeavour’.

Role for calcium signaling in manganese neurotoxicity

BACKGROUND

Calcium is an essential macronutrient that is involved in many cellular processes. Homeostatic control of intracellular levels of calcium ions [Ca²⁺] is vital to maintaining cellular structure and function. Several signaling molecules are involved in regulating Ca²⁺ levels in cells and perturbation of calcium signaling processes is implicated in several neurodegenerative and neurologic conditions. Manganese [Mn] is a metal which is essential for basic physiological functions. However, overexposure to Mn from environmental contamination and workplace hazards is a global concern. Mn overexposure leads to its accumulation in several human organs particularly the brain. Mn accumulation in the brain results in a manganism, a Parkinsonian-like syndrome. Additionally, Mn is a risk factor for several neurodegenerative diseases including Parkinson's disease and Alzheimer's disease. Mn neurotoxicity also affects several neurotransmitter systems including dopaminergic, cholinergic and GABAergic. The mechanisms of Mn neurotoxicity are still being elucidated.

AIM

The review will highlight a potential role for calcium signaling molecules in the mechanisms of Mn neurotoxicity.

CONCLUSION

Ca²⁺ regulation influences the neurodegenerative process and there is possible role for perturbed calcium signaling in Mn neurotoxicity. Mechanisms implicated in Mn-induced neurodegeneration include oxidative stress, generation of free radicals, and apoptosis. These are influenced by mitochondrial integrity which can be dependent on intracellular Ca²⁺ homeostasis. Nevertheless, further elucidation of the direct effects of calcium signaling dysfunction and calcium-binding proteins activities in Mn neurotoxicity is required.

Transcriptome analysis reveals corresponding genes and key pathways involved in heat stress in Hu sheep

Heat stress (HS) seriously affects animal performance. In view of global warming, it is essential to understand the regulatory mechanisms by which animals adapt to heat stress. In this study, our aim was to explore the genes and pathways involved in heat stress in sheep. To this end, we used transcriptome analysis to understand the molecular responses to heat stress and thereby identify means to protect sheep from heat shock. To obtain an overview of the effects of heat stress on sheep, we used the hypothalamus for transcriptome sequencing and identified differentially expressed genes (DEGs; false discovery rate (FDR) < 0.01; fold change > 2) during heat stress. A total of 1423 DEGs (1122 upregulated and 301 downregulated) were identified and classified into Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Heat stress triggered dramatic and complex alterations in gene expression in the hypothalamus. We hypothesized that heat stress induced apoptosis and dysfunction in cells and vital organs and affected growth, development, reproduction, and circadian entrainment via the calcium signaling pathway, which influences ribosome assembly and function. Real-time PCR was used to evaluate the expression of the genes regulating important biological functions or whose expression profiles were significantly changed after acute heat stress (FDR < 0.01; fold change > 4), and the results showed that the expression patterns of these genes were consistent with the results of transcriptome sequencing, indicating that the credibility of the sequencing results. Our data indicated that heat stress induced calcium dyshomeostasis, blocked biogenesis, caused ROS accumulation, impaired the antioxidant system and innate defense, and induced apoptosis through the P53 signaling pathway activated by PEG3, decreased growth and development, and enhanced organ damage. These data is very important and helpful to elucidate the molecular mechanism of heat stress and finally to find ways to deal with heat stress damage in sheep.

Developmental Aspects of Glucose and Calcium Availability on the Persistence of Memory Function Over the Lifespan

An important aspect concerning the underlying nature of memory function is an understanding of how memories are acquired and lost. The stability, and ultimate demise, of memory over the lifespan of an organism remains a critical topic in determining the neurobiological mechanisms that mediate memory representations. This has important implications for the elucidation and treatment of neurodegenerative diseases such as Alzheimer's disease (AD). One important question in the context of preserving functional plasticity over the lifespan is the determination of the neurobiological structural and functional changes that contribute to the formation of memory during the juvenile time frame that might provide protection against later memory dysfunction by promoting the establishment of redundant neural pathways. The main question being, if memory formation during the juvenile period does strengthen and preserve memory stability over the lifespan, what are the neurobiological structural or functional substrates that mediate this effect? One neural attribute whose function may be altered with early life experience and provide a mechanism to preserve memory through the lifespan is glucose transport-linked calcium (Ca2+) buffering. Because peak increases in glucose utilization overlap with a timeframe during which spatial training can enhance later memory processing, it might be the case that learning-associated changes in glucose utilization would provide an important neural functional change to preserve memory function throughout the lifespan. The glucose transporters are proteins that are reduced in AD pathology and there is evidence that glucose reductions can impair Ca2+ buffering. In the absence of an appropriate supply of ATP, provided via glucose transport and glycolysis, Ca2+ levels can rise leading to neural vulnerability with ensuing pathological outcomes. In this review, we explore the hypothesis that enhancing glucose utilization with spatial training during the preadolescent period will provide a functional enhancement that regulates glucose-dependent Ca2+ signaling during aging or neurodegeneration and provide essential neural resources to preserve functional plasticity and memory function.

Phosphate Starvation Alters Abiotic-Stress-Induced Cytosolic Free Calcium Increases in Roots

Phosphate (Pi) deficiency strongly limits plant growth, and plant roots foraging the soil for nutrients need to adapt to optimize Pi uptake. Ca²⁺ is known to signal in root development and adaptation but has to be tightly controlled, as it is highly toxic to Pi metabolism. Under Pi starvation and the resulting decreased cellular Pi pool, the use of cytosolic free Ca²⁺ ([Ca²⁺]_cyt) as a signal transducer may therefore have to be altered. Employing aequorin-expressing Arabidopsis (Arabidopsis thaliana), we show that Pi starvation, but not nitrogen starvation, strongly dampens the [Ca²⁺]_cyt increases evoked by mechanical, salt, osmotic, and oxidative stress as well as by extracellular nucleotides. The altered root [Ca²⁺]_cyt response to extracellular ATP manifests during seedling development under chronic Pi deprivation but can be reversed by Pi resupply. Employing ratiometric imaging, we delineate that Pi-starved roots have a normal response to extracellular ATP at the apex but show a strongly dampened [Ca²⁺]_cyt response in distal parts of the root tip, correlating with high reactive oxygen species levels induced by Pi starvation. Excluding iron, as well as Pi, rescues this altered [Ca²⁺]_cyt response and restores reactive oxygen species levels to those seen under nutrient-replete conditions. These results indicate that, while Pi availability does not seem to be signaled through [Ca²⁺]_cyt, Pi starvation strongly affects stress-induced [Ca²⁺]_cyt signatures. These data reveal how plants can integrate nutritional and environmental cues, adding another layer of complexity to the use of Ca²⁺ as a signal transducer.

Facts and conjectures on calmodulin and its cousin proteins, parvalbumin and troponin C

This review aims at giving a rational frame to understand the diversity of EF hand containing calcium binding proteins and their roles, with special focus on three members of this huge protein family, namely calmodulin, troponin C and parvalbumin. We propose that these proteins are members of structured macromolecular complexes, termed calcisomes, which constitute building devices allowing treatment of information within eukaryotic cells and namely calcium signals encoding and decoding, as well as control of cytosolic calcium levels in resting cells. Calmodulin is ubiquitous, present in all eukaryotic cells, and pleiotropic. This may be explained by its prominent role in regulating calcium movement in and out of the cell, thus maintaining calcium homeostasis which is fundamental for cell survival. The protein is further involved in decoding transient calcium signals associated with calcium movements after cell stimulation. We will show that the specificity of calmodulin's actions may be more easily explained if one considers its role in the light of calcisomes. Parvalbumin should not be considered as a simple intracellular calcium buffer. It is also a key factor for regulating calcium homeostasis in specific cells that need a rapid retrocontrol of calcium transients, such as fast muscle fibers. Finally, we propose that troponin C, with its four calcium binding domains distributed between two lobes presenting different calcium binding kinetics, exhibits all the characteristics needed to trigger and then post modulate muscle contraction and thus appears as a typical Feed Forward Loop system. If the present conjectures prove accurate, the way will be paved for a new pharmacology targeting the cell calcium signaling machinery. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

The Evolution of Calcium-Based Signalling in Plants

The calcium-based intracellular signalling system is used ubiquitously to couple extracellular stimuli to their characteristic intracellular responses. It is becoming clear from genomic and physiological investigations that while the basic elements in the toolkit are common between plants and animals, evolution has acted in such a way that, in plants, some components have diversified with respect to their animal counterparts, while others have either been lost or have never evolved in the plant lineages. In comparison with animals, in plants there appears to have been a loss of diversity in calcium-influx mechanisms at the plasma membrane. However, the evolution of the calcium-storing vacuole may provide plants with additional possibilities for regulating calcium influx into the cytosol. Among the proteins that are involved in sensing and responding to increases in calcium, plants possess specific decoder proteins that are absent from the animal lineage. In seeking to understand the selection pressures that shaped the plant calcium-signalling toolkit, we consider the evolution of fast electrical signalling. We also note that, in contrast to animals, plants apparently do not make extensive use of cyclic-nucleotide-based signalling. It is possible that reliance on a single intracellular second-messenger-based system, coupled with the requirement to adapt to changing environmental conditions, has helped to define the diversity of components found in the extant plant calcium-signalling toolkit.

A superior bright NIR luminescent nanoparticle preparation and indicating calcium signaling detection in cells and small animals

BACKGROUND

Near-field fluorescence (NFF) effects were employed to develop a novel near-infrared (NIR) luminescent nanoparticle (LNP) with superior brightness. The LNP is used as imaging contrast agent for cellular and small animal imaging and furthermore suggested to use for detecting voltage-sensitive calcium in living cells and animals with high sensitivity.

RESULTS

NIR Indocyanine green (ICG) dye was conjugated with human serum albumin (HSA) followed by covalently binding to gold nanorod (AuNR). The AuNR displayed dual plasmons from transverse and longitudinal axis, and the longitudinal plasmon was localized at the NIR region which could efficiently couple with the excitation and emission of ICG dye leading to a largely enhanced NFF. The enhancement factor was measured to be about 16-fold using both ensemble and single nanoparticle spectral methods. As an imaging contrast agent, the ICG-HSA-Au complex (abbreviate as ICG-Au) was conjugated on HeLa cells and fluorescence cell images were recorded on a time-resolved confocal microscope. The emission signals of ICG-Au complexes were distinctly resolved as the individual spots that were observed over the cellular backgrounds due to their strong brightness as well as shortened lifetime. The LNPs were also tested to have a low cytotoxicity. The ICG-Au complexes were injected below the skin surface of mouse showing emission spots 5-fold brighter than those from the same amount of free ICG-HSA conjugates.

CONCLUSIONS

Based on the observations in this research, the excitation and emission of NIR ICG dyes were found to be able to sufficiently couple with the longitudinal plasmon of AuNRs leading to a largely enhanced NFF. Using the LNP with super-brightness as a contrast agent, the ICG-Au complex could be resolved from the background in the cell and small animal imaging. The novel NIR LNP has also a great potential for detection of voltage-gated calcium concentration in the cell and living animal with a high sensitivity.

Calcium as a signal integrator in developing epithelial tissues

Decoding how tissue properties emerge across multiple spatial and temporal scales from the integration of local signals is a grand challenge in quantitative biology. For example, the collective behavior of epithelial cells is critical for shaping developing embryos. Understanding how epithelial cells interpret a diverse range of local signals to coordinate tissue-level processes requires a systems-level understanding of development. Integration of multiple signaling pathways that specify cell signaling information requires second messengers such as calcium ions. Increasingly, specific roles have been uncovered for calcium signaling throughout development. Calcium signaling regulates many processes including division, migration, death, and differentiation. However, the pleiotropic and ubiquitous nature of calcium signaling implies that many additional functions remain to be discovered. Here we review a selection of recent studies to highlight important insights into how multiple signals are transduced by calcium transients in developing epithelial tissues. Quantitative imaging and computational modeling have provided important insights into how calcium signaling integration occurs. Reverse-engineering the conserved features of signal integration mediated by calcium signaling will enable novel approaches in regenerative medicine and synthetic control of morphogenesis.

Of poisons and parasites-the defensive role of tetrodotoxin against infections in newts

Classical research on animal toxicity has focused on the role of toxins in protection against predators, but recent studies suggest these same compounds can offer a powerful defense against parasites and infectious diseases. Newts in the genus Taricha are brightly coloured and contain the potent neurotoxin, tetrodotoxin (TTX), which is hypothesized to have evolved as a defense against vertebrate predators such as garter snakes. However, newt populations often vary dramatically in toxicity, which is only partially explained by predation pressure. The primary aim of this study was to evaluate the relationships between TTX concentration and infection by parasites. By systematically assessing micro- and macroparasite infections among 345 adult newts (sympatric populations of Taricha granulosa and T. torosa), we detected 18 unique taxa of helminths, fungi, viruses and protozoans. For both newt species, per-host concentrations of TTX, which varied from undetectable to >60 μg/cm² skin, negatively predicted overall parasite richness as well as the likelihood of infection by the chytrid fungus, Batrachochytrium dendrobatidis, and ranavirus. No such effect was found on infection load among infected hosts. Despite commonly occurring at the same wetlands, T. torosa supported higher parasite richness and average infection load than T. granulosa. Host body size and sex (females > males) tended to positively predict infection levels in both species. For hosts in which we quantified leucocyte profiles, total white blood cell count correlated positively with both parasite richness and total infection load. By coupling data on host toxicity and infection by a broad range of micro- and macroparasites, these results suggest that-alongside its effects on predators-tetrodotoxin may help protect newts against parasitic infections, highlighting the importance of integrative research on animal chemistry, immunological defenses and natural enemy ecology.

Cyanobacterial formation of intracellular Ca-carbonates in undersaturated solutions

Cyanobacteria have long been thought to induce the formation of Ca-carbonates as secondary by-products of their metabolic activity, by shifting the chemical composition of their extracellular environment to conditions favoring mineral precipitation. Some cyanobacterial species forming Ca-carbonates intracellularly were recently discovered. However, the environmental conditions under which this intracellular biomineralization process can occur and the impact of cyanobacterial species forming Ca-carbonates intracellularly on extracellular carbonatogenesis are not known. Here, we show that these cyanobacteria can form Ca-carbonates intracellularly while growing in extracellular solutions undersaturated with respect to all Ca-carbonate phases, that is, conditions thermodynamically unfavorable to mineral precipitation. This shows that intracellular Ca-carbonate biomineralization is an active process; that is, it costs energy provided by the cells. The cost of energy may be due to the active accumulation of Ca intracellularly. Moreover, unlike cyanobacterial strains that have been usually considered before by studies on Ca-carbonate biomineralization, cyanobacteria forming intracellular carbonates may slow down or hamper extracellular carbonatogenesis, by decreasing the saturation index of their extracellular solution following the buffering of the concentration of extracellular calcium to low levels.

Dopamine elevates and lowers astroglial Ca2+ through distinct pathways depending on local synaptic circuitry

Whilst astrocytes in culture invariably respond to dopamine with cytosolic Ca²⁺ rises, the dopamine sensitivity of astroglia in situ and its physiological roles remain unknown. To minimize effects of experimental manipulations on astroglial physiology, here we monitored Ca²⁺ in cells connected via gap junctions to astrocytes loaded whole‐cell with cytosolic indicators in area CA1 of acute hippocampal slices. Aiming at high sensitivity of [Ca²⁺] measurements, we also employed life‐time imaging of the Ca²⁺ indicator Oregon Green BAPTA‐1. We found that dopamine triggered a dose‐dependent, bidirectional Ca²⁺ response in stratum radiatum astroglia, a jagged elevation accompanied and followed by below‐baseline decreases. The elevation depended on D1/D2 receptors and engaged intracellular Ca²⁺ storage and removal whereas the dopamine‐induced [Ca²⁺] decrease involved D2 receptors only and was sensitive to Ca²⁺ channel blockade. In contrast, the stratum lacunosum moleculare astroglia generated higher‐threshold dopamine‐induced Ca²⁺ responses which did not depend on dopamine receptors and were uncoupled from the prominent inhibitory action of dopamine on local perforant path synapses. Our findings thus suggest that a single neurotransmitter—dopamine—could either elevate or decrease astrocyte [Ca²⁺] depending on the receptors involved, that such actions are specific to the regional neural circuitry and that they may be causally uncoupled from dopamine actions on local synapses. The results also indicate that [Ca²⁺] elevations commonly detected in astroglia can represent the variety of distinct mechanisms acting on the microscopic scale. GLIA 2017;65:447–459

A calcium sensor - protein kinase signaling module diversified in plants and is retained in all lineages of Bikonta species

Calcium (Ca²⁺) signaling is a universal mechanism of signal transduction and involves Ca²⁺ signal formation and decoding of information by Ca²⁺ binding proteins. Calcineurin B-like proteins (CBLs), which upon Ca²⁺ binding activate CBL-interacting protein kinases (CIPKs) regulate a multitude of physiological processes in plants. Here, we combine phylogenomics and functional analyses to investigate the occurrence and structural conservation of CBL and CIPK proteins in 26 species representing all major clades of eukaryotes. We demonstrate the presence of at least singular CBL-CIPK pairs in representatives of Archaeplastida, Chromalveolates and Excavates and their general absence in Opisthokonta and Amoebozoa. This denotes CBL-CIPK complexes as evolutionary ancient Ca²⁺ signaling modules that likely evolved in the ancestor of all Bikonta. Furthermore, we functionally characterize the CBLs and CIPK from the parabasalid human pathogen Trichomonas vaginalis. Our results reveal strict evolutionary conservation of functionally important structural features, preservation of biochemical properties and a remarkable cross-kingdom protein-protein interaction potential between CBLs and CIPKs from Arabidopsis thaliana and T. vaginalis. Together our findings suggest an ancient evolutionary origin of a functional CBL-CIPK signaling module close to the root of eukaryotic evolution and provide insights into the initial evolution of signaling networks and Ca²⁺ signaling specificity.

Evolution of the Calcium-Based Intracellular Signaling System

To progress our understanding of molecular evolution from a collection of well-studied genes toward the level of the cell, we must consider whole systems. Here, we reveal the evolution of an important intracellular signaling system. The calcium-signaling toolkit is made up of different multidomain proteins that have undergone duplication, recombination, sequence divergence, and selection. The picture of evolution, considering the repertoire of proteins in the toolkit of both extant organisms and ancestors, is radically different from that of other systems. In eukaryotes, the repertoire increased in both abundance and diversity at a far greater rate than general genomic expansion. We describe how calcium-based intracellular signaling evolution differs not only in rate but in nature, and how this correlates with the disparity of plants and animals.

From damage response to action potentials: early evolution of neural and contractile modules in stem eukaryotes

Eukaryotic cells convert external stimuli into membrane depolarization, which in turn triggers effector responses such as secretion and contraction. Here, we put forward an evolutionary hypothesis for the origin of the depolarization-contraction-secretion (DCS) coupling, the functional core of animal neuromuscular circuits. We propose that DCS coupling evolved in unicellular stem eukaryotes as part of an 'emergency response' to calcium influx upon membrane rupture. We detail how this initial response was subsequently modified into an ancient mechanosensory-effector arc, present in the last eukaryotic common ancestor, which enabled contractile amoeboid movement that is widespread in extant eukaryotes. Elaborating on calcium-triggered membrane depolarization, we reason that the first action potentials evolved alongside the membrane of sensory-motile cilia, with the first voltage-sensitive sodium/calcium channels (Nav/Cav) enabling a fast and coordinated response of the entire cilium to mechanosensory stimuli. From the cilium, action potentials then spread across the entire cell, enabling global cellular responses such as concerted contraction in several independent eukaryote lineages. In animals, this process led to the invention of mechanosensory contractile cells. These gave rise to mechanosensory receptor cells, neurons and muscle cells by division of labour and can be regarded as the founder cell type of the nervous system.

Sigma-1 receptors and animal studies centered on pain and analgesia

INTRODUCTION

Neuropathic pain is difficult to relieve with standard analgesics and tends to be resistant to opioid therapy. Sigma-1 receptors activated during neuropathic injury may sustain pain. Neuropathic injury activates sigma-1 receptors, which results in activation of various kinases, modulates the activity of multiple ion channels, ligand activated ion channels and voltage-gated ion channels; alters monoamine neurotransmission and dampens opioid receptors G-protein activation. Activation of sigma-1 receptors tonically inhibits opioid receptor G-protein activation and thus dampens analgesic responses. Therefore, sigma-1 receptor antagonists are potential analgesics for neuropathic and adjuvants to opioid therapy.

AREAS COVERED

This article reviews the importance of sigma-1 receptors as pain generators in multiple animal models in order to illustrate both the importance of these unique receptors in pathologic pain and the potential benefits to sigma-1 receptor antagonists as analgesics.

EXPERT OPINION

Sigma-1 receptor antagonists have a great potential as analgesics for acute neuropathic injury (herpes zoster, acute postoperative pain and chemotherapy induced neuropathy) and may, as an additional benefit, prevent the development of chronic neuropathic pain. Antagonists are potentially effective as adjuvants to opioid therapy when used early to prevent analgesic tolerance. Drug development is complicated by the complexity of sigma-1 receptor pharmacodynamics and its multiple targets, the lack of a specific sigma-1 receptor antagonist, and potential side effects due to on-target toxicities (cognitive impairment, depression).

Inhibition of glutamate regulated calcium entry into leukemic megakaryoblasts reduces cell proliferation and supports differentiation

Human megakaryocytes release glutamate and express glutamate-gated Ca(2+)-permeable N-methyl-D-aspartate receptors (NMDARs) that support megakaryocytic maturation. While deregulated glutamate pathways impact oncogenicity in some cancers, the role of glutamate and NMDARs in megakaryocytic malignancies remains unknown. The aim of this study was to determine if NMDARs participate in Ca(2+) responses in leukemic megakaryoblasts and if so, whether modulating NMDAR activity could influence cell growth. Three human cell lines, Meg-01, Set-2 and K-562 were used as models of leukemic megakaryoblasts. NMDAR components were examined in leukemic cells and human bone marrow, including in megakaryocytic disease. Well-established NMDAR modulators (agonists and antagonists) were employed to determine NMDAR effects on Ca(2+) flux, cell viability, proliferation and differentiation. Leukemic megakaryoblasts contained combinations of NMDAR subunits that differed from normal bone marrow and the brain. NMDAR agonists facilitated Ca(2+) entry into Meg-01 cells, amplified Ca(2+) responses to adenosine diphosphate (ADP) and promoted growth of Meg-01, Set-2 and K-562 cells. Low concentrations of NMDAR inhibitors (riluzole, memantine, MK-801 and AP5; 5-100μM) were weakly cytotoxic but mainly reduced cell numbers by suppressing proliferation. The use-dependent NMDAR inhibitor, memantine (100μM), reduced numbers and proliferation of Meg-01 cells to less than 20% of controls (IC50 20μM and 36μM, respectively). In the presence of NMDAR inhibitors cells acquired morphologic and immunophenotypic features of megakaryocytic differentiation. In conclusion, NMDARs provide a novel pathway for Ca(2+) entry into leukemic megakaryoblasts that supports cell proliferation but not differentiation. NMDAR inhibitors counteract these effects, suggesting a novel opportunity to modulate growth of leukemic megakaryoblasts.

Tracing the Evolutionary History of Inositol, 1, 4, 5-Trisphosphate Receptor: Insights from Analyses of Capsaspora owczarzaki Ca2+ Release Channel Orthologs

Cellular Ca(2+) homeostasis is tightly regulated and is pivotal to life. Inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) are the major ion channels that regulate Ca(2+) release from intracellular stores. Although these channels have been extensively investigated in multicellular organisms, an appreciation of their evolution and the biology of orthologs in unicellular organisms is largely lacking. Extensive phylogenetic analyses reveal that the IP3R gene superfamily is ancient and diverged into two subfamilies, IP3R-A and IP3R-B/RyR, at the dawn of Opisthokonta. IP3R-B/RyR further diversified into IP3R-B and RyR at the stem of Filozoa. Subsequent evolution and speciation of Holozoa is associated with duplication of IP3R-A and RyR genes, and loss of IP3R-B in the vertebrate lineages. To gain insight into the properties of IP3R important for the challenges of multicellularity, the IP3R-A and IP3R-B family orthologs were cloned from Capsaspora owczarzaki, a close unicellular relative to Metazoa (designated as CO.IP3R-A and CO.IP3R-B). Both proteins were targeted to the endoplasmic reticulum. However, CO.IP3R-A, but strikingly not CO.IP3R-B, bound IP3, exhibited robust Ca(2+) release activity and associated with mammalian IP3Rs. These data indicate strongly that CO.IP3R-A as an exemplar of ancestral IP3R-A orthologs forms bona fide IP3-gated channels. Notably, however, CO.IP3R-A appears not to be regulated by Ca(2+), ATP or Protein kinase A-phosphorylation. Collectively, our findings explore the origin, conservation, and diversification of IP3R gene families and provide insight into the functionality of ancestral IP3Rs and the added specialization of these proteins in Metazoa.

Crosstalk Among Disrupted Glutamatergic and Cholinergic Homeostasis and Inflammatory Response in Mechanisms Elicited by Proline in Astrocytes

Hyperprolinemias are inherited disorder of proline (Pro) metabolism. Patients affected may present neurological manifestations, but the mechanisms of neural excitotoxicity elicited by hyperprolinemia are far from being understood. Considering that the astrocytes are important players in neurological disorders, the aim of the present work was to study the effects 1 mM Pro on glutamatergic and inflammatory parameters in cultured astrocytes from cerebral cortex of rats, exploring some molecular mechanisms underlying the disrupted homeostasis of astrocytes exposed to this toxic Pro concentration. We showed that cortical astrocytes of rats exposed to 1 mM Pro presented significantly elevated extracellular glutamate and glutamine levels, suggesting glutamate excitotoxicity. The excess of glutamate elicited by Pro together with increased glutamate uptake and upregulated glutamine synthetase (GS) activity supported misregulated glutamate homeostasis in astrocytic cells. High Pro levels also induced production/release of pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. We also evidenced misregulation of cholinergic anti-inflammatory system with increased acetylcholinesterase (AChE) activity and decreased acetylcholine (ACh) levels, contributing to the inflammatory status in Pro-treated astrocytes. Our findings highlighted a crosstalk among disrupted glutamate homeostasis, cholinergic mechanisms, and inflammatory cytokines, since ionotropic (DL-AP5 and CNQX) and metabotropic (MCPG and MPEP) glutamate antagonists were able to restore the extracellular glutamate and glutamine levels; downregulate TNFα and IL6 production/release, modulate GS and AChE activities; and restore ACh levels. Otherwise, the non-steroidal anti-inflammatory drugs nimesulide, acetylsalicylic acid, ibuprofen, and diclofenac sodium decreased the extracellular glutamate and glutamine levels, downregulated GS and AChE activities, and restored ACh levels in Pro-treated astrocytes. Altogether, our results evidence that the vulnerability of metabolic homeostasis in cortical astrocytes might have important implications in the neurotoxicity of Pro.

Insights into the early evolution of animal calcium signaling machinery: a unicellular point of view

The basic principles of Ca(2+) regulation emerged early in prokaryotes. Ca(2+) signaling acquired more extensive and varied functions when life evolved into multicellular eukaryotes with intracellular organelles. Animals, fungi and plants display differences in the mechanisms that control cytosolic Ca(2+) concentrations. The aim of this review is to examine recent findings from comparative genomics of Ca(2+) signaling molecules in close unicellular relatives of animals and in common unicellular ancestors of animals and fungi. Also discussed are the evolution and origins of the sperm-specific CatSper channel complex, cation/Ca(2+) exchangers and four-domain voltage-gated Ca(2+) channels. Newly identified evolutionary evidence suggests that the distinct Ca(2+) signaling machineries in animals, plants and fungi likely originated from an ancient Ca(2+) signaling machinery prior to early eukaryotic radiation.

Early evolution of the eukaryotic Ca2+ signaling machinery: conservation of the CatSper channel complex

Calcium signaling is one of the most extensively employed signal transduction mechanisms in life. As life evolved into increasingly complex organisms, Ca(2+) acquired more extensive and varied functions. Here, we compare genes encoding proteins that govern Ca(2+) entry and exit across cells or organelles within organisms of early eukaryotic evolution into fungi, plants, and animals. Recent phylogenomics analyses reveal a complex Ca(2+) signaling machinery in the apusozoan protist Thecamonas trahens, a putative unicellular progenitor of Opisthokonta. We compare T. trahens Ca(2+) signaling to that in a marine bikont protist, Aurantiochytrium limacinum, and demonstrate the conservation of key Ca(2+) signaling molecules in the basally diverging alga Cyanophora paradoxa. Particularly, our findings reveal the conservation of the CatSper channel complex in Au. limacinum and C. paradoxa, suggesting that the CatSper complex likely originated from an ancestral Ca(2+) signaling machinery at the root of early eukaryotic evolution prior to the unikont/bikont split.