Cell calcium最新文献

The central nervous system (CNS) is constantly surveilled by microglia, highly motile and dynamic cells deputed to act as the first line of immune defense in the brain and spinal cord. Alterations in the homeostasis of the CNS are detected by microglia that respond by extending their processes or – following major injuries – by migrating toward the affected area. Understanding the mechanisms controlling directed cell migration of microglia is crucial to dissect their responses to neuroinflammation and injury. We used a combination of pharmacological and genetic approaches to explore the involvement of calcium (Ca²⁺) signaling in the directed migration of human induced pluripotent stem cell (iPSC)-derived microglia challenged with a purinergic stimulus. This approach mimics cues originating from injury of the CNS. Unexpectedly, simultaneous imaging of microglia migration and intracellular Ca²⁺ changes revealed that this phenomenon does not require Ca²⁺ signals generated from the endoplasmic reticulum (ER) and store-operated Ca²⁺ entry (SOCE) pathways. Instead, we find evidence that human microglial chemotaxis to purinergic signals is mediated by cyclic AMP in a Ca²⁺-independent manner. These results challenge prevailing notions, with important implications in neurological conditions characterized by perturbation in Ca²⁺ homeostasis.

The primary role of pancreatic ductal HCO₃⁻ secretion is to prevent premature activation of digestive enzymes and to provide a vehicle for the delivery of enzymes to the duodenum. In addition, HCO₃⁻is responsible for the neutralization of gastric juice and protect against the formation of protein plugs and viscous mucus. Due to this multifaceted role of HCO₃⁻ in the pancreas, its altered functioning can greatly contribute to the development of various exocrine diseases. It is well known that the exocrine and endocrine pancreas interact lively with each other, but not all details of this relationship are known. An interesting finding of a recent study by Jo-Watanabe et al. is that the G protein-coupled oestrogen receptor, GPR30, which is expressed in the endocrine pancreas, can be also activated by HCO₃⁻. This raises the possibility that ductal cells play a key role not only in the exocrine pancreas, but presumably also in endocrine function through HCO₃⁻ secretion.

Many studies have focused on identifying the signaling pathway by which addition of glucose triggers post-translational activation of the plasma membrane H⁺-ATPase in yeast. They have revealed that calcium signaling is involved in the regulatory pathway, supported for instance by the phenotype of mutants inARG82 that encodes an inositol kinase that phosphorylates inositol triphosphate (IP₃). Strong glucose-induced calcium signaling, and high glucose-induced plasma membrane H⁺-ATPase activation have been observed in a specific yeast strain with the PJ genetic background. In this study, we have applied pooled-segregant whole genome sequencing, QTL analysis and a new bioinformatics methodology for determining SNP frequencies to identify the cause of this discrepancy and possibly new components of the signaling pathway. This has led to the identification of an STT4 allele with 6 missense mutations as a major causative allele, further supported by the observation that deletion of STT4 in the inferior parent caused a similar increase in glucose-induced plasma membrane H⁺-ATPase activation. However, the effect on calcium signaling was different indicating the presence of additional relevant genetic differences between the superior and reference strains. Our results suggest that phosphatidylinositol-4-phosphate might play a role in the glucose-induced activation of plasma membrane H⁺-ATPase by controlling intracellular calcium release through the modulation of the activity of phospholipase C.

Anoctamin 1 (ANO1) binds to transient receptor potential (TRP) channels (protein-protein interaction) and then is activated by TRP channels (functional interaction). TRP channels are non-selective cation channels that are expressed throughout the body and play roles in multiple physiological functions. Studies on TRP channels increased after the identification of TRP vanilloid 1 (TRPV1) in 1997. Calcium-activated chloride channel anoctamin 1 (ANO1, also called TMEM16A and DOG1) was identified in 2008. ANO1 plays a major role in TRP channel-mediated functions, as first shown in 2014 with the demonstration of a protein-protein interaction between TRPV4 and ANO1. In cells that co-express TRP channels and ANO1, calcium entering cells through activated TRP channels causes ANO1 activation. Therefore, in many tissues, the physiological functions related to TRP channels are modulated through chloride flux associated with ANO1 activation. In this review, we summarize the latest understanding of TRP-ANO1 interactions, particularly interaction of ANO1 with TRPV4, TRP canonical 6 (TRPC6), TRPV3, TRPV1, and TRPC2 in the salivary glands, blood vessels, skin keratinocytes, primary sensory neurons, and vomeronasal organs, respectively.

In cardiac myocytes, the type 2a sarco/endoplasmic reticulum Ca-ATPase (SERCA2a) plays a key role in intracellular Ca regulation. Due to its critical role in heart function, SERCA2a activity is tightly regulated by different mechanisms, including micropeptides. While phospholamban (PLB) is a well-known SERCA2a inhibitor, dwarf open reading frame (DWORF) is a recently identified SERCA2a activator. Since PLB phosphorylation is the most recognized mechanism of SERCA2a activation during adrenergic stress, we studied whether PLB phosphorylation also affects SERCA2a regulation by DWORF. By using confocal Ca imaging in a HEK293 expressing cell system, we analyzed the effect of the co-expression of PLB and DWORF using a bicistronic construct on SERCA2a-mediated Ca uptake. Under these conditions of matched expression of PLB and DWORF, we found that SERCA2a inhibition by non-phosphorylated PLB prevails over DWORF activating effect. However, when PLB is phosphorylated at PKA and CaMKII sites, not only PLB's inhibitory effect was relieved, but SERCA2a was effectively activated by DWORF. Förster resonance energy transfer (FRET) analysis between SERCA2a and DWORF showed that DWORF has a higher relative affinity for SERCA2a when PLB is phosphorylated. Thus, SERCA2a regulation by DWORF responds to the PLB phosphorylation status, suggesting that DWORF might contribute to SERCA2a activation during conditions of adrenergic stress.

Animal and human studies have suggested that sex steroids have calciotropic actions, and it has been proposed that follicle-stimulating hormone (FSH) may exert direct effects on bone. Here, we demonstrate the expression of the receptor for Luteinizing hormone (LH) and human choriogonadotropin (hCG), LHCGR, in human kidney tissue, suggesting a potential influence on calcium homeostasis. To investigate the role of LHCGR agonist on calcium homeostasis in vivo, we conducted studies in male mice and human subjects. Male mice were treated with luteinizing hormone (LH), and human extrapolation was achieved by injecting 5000 IU hCG once to healthy men or men with hypergonadotropic or hypogonadotropic hypogonadism. In mice, LH treatment significantly increased urinary calcium excretion and induced a secondary increase in serum parathyroid hormone (PTH). Similarly, hCG treatment in healthy men led to a significant increase in urinary calcium excretion, serum PTH levels, and 1,25 (OH)₂D₃, while calcitonin, and albumin levels were reduced, possibly to avoid development of persistent hypocalcemia. Still, the rapid initial decline in ionized calcium coincided with a significant prolongation of the cardiac QTc-interval that normalized over time. The observed effects may be attributed to LH/hCG-receptor (LHCGR) activation, considering the presence of LHCGR expression in human kidney tissue, and the increase in sex steroids occurred several hours after the changes in calcium homeostasis. Our translational study shed light on the intricate relationship between gonadotropins, sex hormones and calcium, suggesting that LHCGR may be influencing calcium homeostasis directly or indirectly.

Calcium (Ca²⁺) signalling acts a pleiotropic message within the cell that is decoded by the mitochondria through a sophisticated ion channel known as the Mitochondrial Ca²⁺ Uniporter (MCU) complex. Under physiological conditions, mitochondrial Ca²⁺ signalling is crucial for coordinating cell activation with energy production. Conversely, in pathological scenarios, it can determine the fine balance between cell survival and death. Over the last decade, significant progress has been made in understanding the molecular bases of mitochondrial Ca²⁺ signalling. This began with the elucidation of the MCU channel components and extended to the elucidation of the mechanisms that regulate its activity. Additionally, increasing evidence suggests molecular mechanisms allowing tissue-specific modulation of the MCU complex, tailoring channel activity to the specific needs of different tissues or cell types. This review aims to explore the latest evidence elucidating the regulation of the MCU complex, the molecular factors controlling the tissue-specific properties of the channel, and the physiological and pathological implications of mitochondrial Ca²⁺ signalling in different tissues.

The meticulous regulation of ER calcium (Ca²⁺) homeostasis is indispensable for the proper functioning of numerous cellular processes. Disrupted ER Ca²⁺ balance is implicated in diverse diseases, underscoring the need for a systematic exploration of its regulatory factors in cells. Our recent genomic-scale screen identified a scaffolding protein A-kinase anchoring protein 9 (AKAP9) as a regulator of ER Ca²⁺ levels, but the underlying molecular mechanisms remain elusive. Here, we reveal that Yotiao, the smallest splicing variant of AKAP9 decreased ER Ca²⁺ content in animal cells. Additional testing using a combination of Yotiao truncations, knock-out cells and pharmacological tools revealed that, Yotiao does not require most of its interactors, including type 1 inositol 1,4,5-trisphosphate receptors (IP₃R1), protein kinase A (PKA), protein phosphatase 1 (PP1), adenylyl cyclase type 2 (AC2) and so on, to reduce ER Ca²⁺ levels. However, adenylyl cyclase type 9 (AC9), which is known to increases its cAMP generation upon interaction with Yotiao for the modulation of potassium channels, plays an essential role for Yotiao's ER-Ca²⁺-lowering effect. Mechanistically, Yotiao may work through AC9 to act on Orai1-C terminus and suppress store operated Ca²⁺ entry, resulting in reduced ER Ca²⁺ levels. These findings not only enhance our comprehension of the interplay between Yotiao and AC9 but also contribute to a more intricate understanding of the finely tuned mechanisms governing ER Ca²⁺ homeostasis.