Microbiota-dependent activation of the myeloid calcineurin-NFAT pathway inhibits B7H3- and B7H4-dependent anti-tumor immunity in colorectal cancer.

Bacterial sensing by intestinal tumor cells contributes to tumor growth through cell-intrinsic activation of the calcineurin-NFAT axis, but the role of this pathway in other intestinal cells remains unclear. Here, we found that myeloid-specific deletion of calcineurin in mice activated protective CD8+ T cell responses and inhibited colorectal cancer (CRC) growth. Microbial sensing by myeloid cells promoted calcineurin- and NFAT-dependent interleukin 6 (IL-6) release, expression of the co-inhibitory molecules B7H3 and B7H4 by tumor cells, and inhibition of CD8+ T cell-dependent anti-tumor immunity. Accordingly, targeting members of this pathway activated protective CD8+ T cell responses and inhibited primary and metastatic CRC growth. B7H3 and B7H4 were expressed by the majority of human primary CRCs and metastases, which was associated with low numbers of tumor-infiltrating CD8+ T cells and poor survival. Therefore, a microbiota-, calcineurin-, and B7H3/B7H4-dependent pathway controls anti-tumor immunity, revealing additional targets for immune checkpoint inhibition in microsatellite-stable CRC.

Calcineurin dephosphorylates topoisomerase IIß and regulates the formation of neuronal-activity-induced DNA breaks.

Neuronal activity induces topoisomerase IIß (Top2B) to generate DNA double-strand breaks (DSBs) within the promoters of neuronal early response genes (ERGs) and facilitate their transcription, and yet, the mechanisms that control Top2B-mediated DSB formation are unknown. Here, we report that stimulus-dependent calcium influx through NMDA receptors activates the phosphatase calcineurin to dephosphorylate Top2B at residues S1509 and S1511, which stimulates its DNA cleavage activity and induces it to form DSBs. Exposing mice to a fear conditioning paradigm also triggers Top2B dephosphorylation at S1509 and S1511 in the hippocampus, indicating that calcineurin also regulates Top2B-mediated DSB formation following physiological neuronal activity. Furthermore, calcineurin-Top2B interactions following neuronal activity and sites that incur activity-induced DSBs are preferentially localized at the nuclear periphery in neurons. Together, these results reveal how radial gene positioning and the compartmentalization of activity-dependent signaling govern the position and timing of activity-induced DSBs and regulate gene expression patterns in neurons.

Systematic Discovery of Short Linear Motifs Decodes Calcineurin Phosphatase Signaling.

Short linear motifs (SLiMs) drive dynamic protein-protein interactions essential for signaling, but sequence degeneracy and low binding affinities make them difficult to identify. We harnessed unbiased systematic approaches for SLiM discovery to elucidate the regulatory network of calcineurin (CN)/PP2B, the Ca2+-activated phosphatase that recognizes LxVP and PxIxIT motifs. In vitro proteome-wide detection of CN-binding peptides, in vivo SLiM-dependent proximity labeling, and in silico modeling of motif determinants uncovered unanticipated CN interactors, including NOTCH1, which we establish as a CN substrate. Unexpectedly, CN shows SLiM-dependent proximity to centrosomal and nuclear pore complex (NPC) proteins-structures where Ca2+ signaling is largely uncharacterized. CN dephosphorylates human and yeast NPC proteins and promotes accumulation of a nuclear transport reporter, suggesting conserved NPC regulation by CN. The CN network assembled here provides a resource to investigate Ca2+ and CN signaling and demonstrates synergy between experimental and computational methods, establishing a blueprint for examining SLiM-based networks.

LAMTOR1 inhibition of TRPML1-dependent lysosomal calcium release regulates dendritic lysosome trafficking and hippocampal neuronal function.

Lysosomes function not only as degradatory compartments but also as dynamic intracellular calcium ion stores. The transient receptor potential mucolipin 1 (TRPML1) channel mediates lysosomal Ca2+ release, thereby participating in multiple cellular functions. The pentameric Ragulator complex, which plays a critical role in the activation of mTORC1, is also involved in lysosomal trafficking and is anchored to lysosomes through its LAMTOR1 subunit. Here, we report that the Ragulator restricts lysosomal trafficking in dendrites of hippocampal neurons via LAMTOR1-mediated tonic inhibition of TRPML1 activity, independently of mTORC1. LAMTOR1 directly interacts with TRPML1 through its N-terminal domain. Eliminating this inhibition in hippocampal neurons by LAMTOR1 deletion or by disrupting LAMTOR1-TRPML1 binding increases TRPML1-mediated Ca2+ release and facilitates dendritic lysosomal trafficking powered by dynein. LAMTOR1 deletion in the hippocampal CA1 region of adult mice results in alterations in synaptic plasticity, and in impaired object-recognition memory and contextual fear conditioning, due to TRPML1 activation. Mechanistically, changes in synaptic plasticity are associated with increased GluA1 dephosphorylation by calcineurin and lysosomal degradation. Thus, LAMTOR1-mediated inhibition of TRPML1 is critical for regulating dendritic lysosomal motility, synaptic plasticity, and learning.

Store-Operated Ca2+ Entry Controls Clonal Expansion of T Cells through Metabolic Reprogramming.

Store-operated Ca2+ entry (SOCE) is the main Ca2+ influx pathway in lymphocytes and is essential for T cell function and adaptive immunity. SOCE is mediated by Ca2+ release-activated Ca2+ (CRAC) channels that are activated by stromal interaction molecule (STIM) 1 and STIM2. SOCE regulates many Ca2+-dependent signaling molecules, including calcineurin, and inhibition of SOCE or calcineurin impairs antigen-dependent T cell proliferation. We here report that SOCE and calcineurin regulate cell cycle entry of quiescent T cells by controlling glycolysis and oxidative phosphorylation. SOCE directs the metabolic reprogramming of naive T cells by regulating the expression of glucose transporters, glycolytic enzymes, and metabolic regulators through the activation of nuclear factor of activated T cells (NFAT) and the PI3K-AKT kinase-mTOR nutrient-sensing pathway. We propose that SOCE controls a critical "metabolic checkpoint" at which T cells assess adequate nutrient supply to support clonal expansion and adaptive immune responses.

Macromolecular Complex Including MLL3, Carabin and Calcineurin Regulates Cardiac Remodeling.

BACKGROUND: Cardiac hypertrophy is an intermediate stage in the development of heart failure. The structural and functional processes occurring in cardiac hypertrophy include extensive gene reprogramming, which is dependent on epigenetic regulation and chromatin remodeling. However, the chromatin remodelers and their regulatory functions involved in the pathogenesis of cardiac hypertrophy are not well characterized. METHODS: Protein interaction was determined by immunoprecipitation assay in primary cardiomyocytes and mouse cardiac samples subjected or not to transverse aortic constriction for 1 week. Chromatin immunoprecipitation and DNA sequencing (ChIP-seq) experiments were performed on the chromatin of adult mouse cardiomyocytes. RESULTS: We report that the calcium-activated protein phosphatase CaN (calcineurin), its endogenous inhibitory protein carabin, the STK24 (STE20-like protein kinase 3), and the histone monomethyltransferase, MLL3 (mixed lineage leukemia 3) form altogether a macromolecular complex at the chromatin of cardiomyocytes. Under basal conditions, carabin prevents CaN activation while the serine/threonine kinase STK24 maintains MLL3 inactive via phosphorylation. After 1 week of transverse aortic constriction, both carabin and STK24 are released from the CaN-MLL3 complex leading to the activation of CaN, dephosphorylation of MLL3, and in turn, histone H3 lysine 4 monomethylation. Selective cardiac MLL3 knockdown mitigates hypertrophy, and chromatin immunoprecipitation and DNA sequencing analysis demonstrates that MLL3 is de novo recruited at the transcriptional start site of genes implicated in cardiomyopathy in stress conditions. We also show that CaN and MLL3 colocalize at chromatin and that CaN activates MLL3 histone methyl transferase activity at distal intergenic regions under hypertrophic conditions. CONCLUSIONS: Our study reveals an unsuspected epigenetic mechanism of CaN that directly regulates MLL3 histone methyl transferase activity to promote cardiac remodeling.

Octopamine metabolically reprograms astrocytes to confer neuroprotection against α-synuclein.

Octopamine is a well-established invertebrate neurotransmitter involved in fight or flight responses. In mammals, its function was replaced by epinephrine. Nevertheless, it is present at trace amounts and can modulate the release of monoamine neurotransmitters by a yet unidentified mechanism. Here, through a multidisciplinary approach utilizing in vitro and in vivo models of α-synucleinopathy, we uncovered an unprecedented role for octopamine in driving the conversion from toxic to neuroprotective astrocytes in the cerebral cortex by fostering aerobic glycolysis. Physiological levels of neuron-derived octopamine act on astrocytes via a trace amine-associated receptor 1-Orai1-Ca2+-calcineurin-mediated signaling pathway to stimulate lactate secretion. Lactate uptake in neurons via the monocarboxylase transporter 2-calcineurin-dependent pathway increases ATP and prevents neurodegeneration. Pathological increases of octopamine caused by α-synuclein halt lactate production in astrocytes and short-circuits the metabolic communication to neurons. Our work provides a unique function of octopamine as a modulator of astrocyte metabolism and subsequent neuroprotection with implications to α-synucleinopathies.

Nitro-oleic acid regulates T cell activation through post-translational modification of calcineurin.

Nitro-fatty acids (NO2-FAs) are unsaturated fatty acid nitration products that exhibit anti-inflammatory actions in experimental mouse models of autoimmune and allergic diseases. These electrophilic molecules interfere with intracellular signaling pathways by reversible post-translational modification of nucleophilic amino-acid residues. Several regulatory proteins have been identified as targets of NO2-FAs, modifying their activity and promoting gene expression changes that result in anti-inflammatory effects. Herein, we report the effects of nitro-oleic acid (NO2-OA) on pro-inflammatory T cell functions, showing that 9- and 10-NOA, but not their oleic acid precursor, decrease T cell proliferation, expression of activation markers CD25 and CD71 on the plasma membrane, and IL-2, IL-4, and IFN-γ cytokine gene expressions. Moreover, we have found that NO2-OA inhibits the transcriptional activity of nuclear factor of activated T cells (NFAT) and that this inhibition takes place through the regulation of the phosphatase activity of calcineurin (CaN), hindering NFAT dephosphorylation, and nuclear translocation in activated T cells. Finally, using mass spectrometry-based approaches, we have found that NO2-OA nitroalkylates CaNA on four Cys (Cys129, 228, 266, and 372), of which only nitroalkylation on Cys372 was of importance for the regulation of CaN phosphatase activity in cells, disturbing functional CaNA/CaNB heterodimer formation. These results provide evidence for an additional mechanism by which NO2-FAs exert their anti-inflammatory actions, pointing to their potential as therapeutic bioactive lipids for the modulation of harmful T cell-mediated immune responses.

Age-Related Brain Atrophy and the Positive Effects of Behavioral Enrichment in Middle-Aged Beagles.

Aging dogs serve as a valuable preclinical model for Alzheimer's disease (AD) due to their natural age-related development of ß-amyloid (Aß) plaques, human-like metabolism, and large brains that are ideal for studying structural brain aging trajectories from serial neuroimaging. Here we examined the effects of chronic treatment with the calcineurin inhibitor (CNI) tacrolimus or the nuclear factor of activated T cells (NFAT)-inhibiting compound Q134R on age-related canine brain atrophy from a longitudinal study in middle-aged beagles (36 females, 7 males) undergoing behavioral enrichment. Annual MRI was analyzed using modern, automated techniques for region-of-interest-based and voxel-based volumetric assessments. We found that the frontal lobe showed accelerated atrophy with age, while the caudate nucleus remained relatively stable. Remarkably, the hippocampus increased in volume in all dogs. None of these changes were influenced by tacrolimus or Q134R treatment. Our results suggest that behavioral enrichment can prevent atrophy and increase the volume of the hippocampus but does not prevent aging-associated prefrontal cortex atrophy.

Novel approaches to increase synaptic resilience as potential treatments for Alzheimer's disease.

A significant proportion of brains with Alzheimer's disease pathology are obtained from patients that were cognitively normal, suggesting that differences within the brains of these individuals made them resilient to the disease. Here, we describe recent approaches that specifically increase synaptic resilience, as loss of synapses is considered to be the first change in the brains of Alzheimer's patients. We start by discussing studies showing benefit from increased expression of neurotrophic factors and protective genes. Methods that effectively make dendritic spines stronger, specifically by acting through actin network proteins, scaffolding proteins and inhibition of phosphatases are described next. Importantly, the therapeutic strategies presented in this review tackle Alzheimer's disease not by targeting plaques and tangles, but instead by making synapses resilient to the pathology associated with Alzheimer's disease, which has tremendous potential.

FOXO1 promotes cancer cell growth through MDM2-mediated p53 degradation.

FOXO1 is a transcription factor and potential tumor suppressor that is negatively regulated downstream of PI3K-PKB/AKT signaling. Paradoxically, FOXO also promotes tumor growth, but the detailed mechanisms behind this role of FOXO are not fully understood. In this study, we revealed a molecular cascade by which the Thr24 residue of FOXO1 is phosphorylated by AKT and is dephosphorylated by calcineurin, which is a Ca2+-dependent protein phosphatase. Curiously, single nucleotide somatic mutations of FOXO1 in cancer occur frequently at and near Thr24. Using a calcineurin inhibitor and shRNA directed against calcineurin, we revealed that calcineurin-mediated dephosphorylation of Thr24 regulates FOXO1 protein stability. We also found that FOXO1 binds to the promoter region of MDM2 and activates transcription, which in turn promotes MDM2-mediated ubiquitination and degradation of p53. FOXO3a and FOXO4 are shown to control p53 activity; however, the significance of FOXO1 in p53 regulation remains largely unknown. Supporting this notion, FOXO1 depletion increased p53 and p21 protein levels in association with the inhibition of cell proliferation. Taken together, these results indicate that FOXO1 is stabilized by calcineurin-mediated dephosphorylation and that FOXO1 supports cancer cell proliferation by promoting MDM2 transcription and subsequent p53 degradation.

Leishmania exploits host cAMP/EPAC/calcineurin signaling to induce an IL-33-mediated anti-inflammatory environment for the establishment of infection.

Host anti-inflammatory responses are critical for the progression of visceral leishmaniasis, and the pleiotropic cytokine interleukin (IL)-33 was found to be upregulated in infection. Here, we documented that IL-33 induction is a consequence of elevated cAMP-mediated exchange protein activated by cAMP (EPAC)/calcineurin-dependent signaling and essential for the sustenance of infection. Leishmania donovani-infected macrophages showed upregulation of IL-33 and its neutralization resulted in decreased parasite survival and increased inflammatory responses. Infection-induced cAMP was involved in IL-33 production and of its downstream effectors PKA and EPAC, only the latter was responsible for elevated IL-33 level. EPAC initiated Rap-dependent phospholipase C activation, which triggered the release of intracellular calcium followed by calcium/calmodulin complex formation. Screening of calmodulin-dependent enzymes affirmed involvement of the phosphatase calcineurin in cAMP/EPAC/calcium/calmodulin signaling-induced IL-33 production and parasite survival. Activated calcineurin ensured nuclear localization of the transcription factors, nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha required for IL-33 transcription, and we further confirmed this by chromatin immunoprecipitation assay. Administering specific inhibitors of nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha in BALB/c mouse model of visceral leishmaniasis decreased liver and spleen parasite burden along with reduction in IL-33 level. Splenocyte supernatants of inhibitor-treated infected mice further documented an increase in tumor necrosis factor alpha and IL-12 level with simultaneous decrease of IL-10, thereby indicating an overall disease-escalating effect of IL-33. Thus, this study demonstrates that cAMP/EPAC/calcineurin signaling is crucial for the activation of IL-33 and in effect creates anti-inflammatory responses, essential for infection.

Calcineurin associates with centrosomes and regulates cilia length maintenance.

Calcineurin, or protein phosphatase 2B (PP2B), the Ca2+ and calmodulin-activated phosphatase and target of immunosuppressants, has many substrates and functions that remain uncharacterized. By combining rapid proximity-dependent labeling with cell cycle synchronization, we mapped the spatial distribution of calcineurin in different cell cycle stages. While calcineurin-proximal proteins did not vary significantly between interphase and mitosis, calcineurin consistently associated with multiple centrosomal and/or ciliary proteins. These include POC5, which binds centrins in a Ca2+-dependent manner and is a component of the luminal scaffold that stabilizes centrioles. We show that POC5 contains a calcineurin substrate motif (PxIxIT type) that mediates calcineurin binding in vivo and in vitro. Using indirect immunofluorescence and ultrastructure expansion microscopy, we demonstrate that calcineurin colocalizes with POC5 at the centriole, and further show that calcineurin inhibitors alter POC5 distribution within the centriole lumen. Our discovery that calcineurin directly associates with centriolar proteins highlights a role for Ca2+ and calcineurin signaling at these organelles. Calcineurin inhibition promotes elongation of primary cilia without affecting ciliogenesis. Thus, Ca2+ signaling within cilia includes previously unknown functions for calcineurin in maintenance of cilia length, a process that is frequently disrupted in ciliopathies.

Rcn1, the fission yeast homolog of human DSCR1, regulates arsenite tolerance independently from calcineurin.

Calcineurin (CN) is a conserved Ca2+/calmodulin-dependent phosphoprotein phosphatase that plays a key role in Ca2+ signaling. Regulator of calcineurin 1 (RCAN1), also known as Down syndrome critical region gene 1 (DSCR1), interacts with calcineurin and inhibits calcineurin-dependent signaling in various organisms. Ppb1, the fission yeast calcineurin regulates Cl--homeostasis, and Ppb1 deletion induces MgCl2 hypersensitivity. Here, we characterize the conserved and novel roles of the fission yeast RCAN1 homolog rcn1+. Consistent with its role as an endogenous calcineurin inhibitor, Rcn1 overproduction reproduced the calcineurin-null phenotypes, including MgCl2 hypersensitivity and inhibition of calcineurin signaling upon extracellular Ca2+ stimuli as evaluated by the nuclear translocation and transcriptional activation of the calcineurin substrate Prz1. Notably, overexpression of rcn1+ causes hypersensitivity to arsenite, whereas calcineurin deletion induces arsenite tolerance, showing a phenotypic discrepancy between Rcn1 overexpression and calcineurin deletion. Importantly, although Rcn1 deletion induces modest sensitivities to arsenite and MgCl2 in wild-type cells, the arsenite tolerance, but not MgCl2 sensitivity, associated with Ppb1 deletion was markedly suppressed by Rcn1 deletion. Collectively, our findings reveal a previously unrecognized functional collaboration between Rcn1 and calcineurin, wherein Rcn1 not only negatively regulates calcineurin in the Cl- homeostasis, but also Rcn1 mediates calcineurin signaling to modulate arsenite cytotoxicity.

The Ca2+-dependent phosphatase calcineurin dephosphorylates TBK1 to suppress antiviral innate immunity.

Tumor necrosis factor receptor-associated factor family member-associated NF-κB activator-binding kinase 1 (TBK1) plays a key role in the induction of the type 1 interferon (IFN-I) response, which is an important component of innate antiviral defense. Viruses target calcium (Ca2+) signaling networks, which participate in the regulation of the viral life cycle, as well as mediate the host antiviral response. Although many studies have focused on the role of Ca2+ signaling in the regulation of IFN-I, the relationship between Ca2+ and TBK1 in different infection models requires further elucidation. Here, we examined the effects of the Newcastle disease virus (NDV)-induced increase in intracellular Ca2+ levels on the suppression of host antiviral responses. We demonstrated that intracellular Ca2+ increased significantly during NDV infection, leading to impaired IFN-I production and antiviral immunity through the activation of calcineurin (CaN). Depletion of Ca²+ was found to lead to a significant increase in virus-induced IFN-I production resulting in the inhibition of viral replication. Mechanistically, the accumulation of Ca2+ in response to viral infection increases the phosphatase activity of CaN, which in turn dephosphorylates and inactivates TBK1 in a Ca2+-dependent manner. Furthermore, the inhibition of CaN on viral replication was counteracted in TBK1 knockout cells. Together, our data demonstrate that NDV hijacks Ca2+ signaling networks to negatively regulate innate immunity via the CaN-TBK1 signaling axis. Thus, our findings not only identify the mechanism by which viruses exploit Ca2+ signaling to evade the host antiviral response but also, more importantly, highlight the potential role of Ca2+ homeostasis in the viral innate immune response.IMPORTANCEViral infections disrupt intracellular Ca2+ homeostasis, which affects the regulation of various host processes to create conditions that are conducive for their own proliferation, including the host immune response. The mechanism by which viruses trigger TBK1 activation and IFN-I induction through viral pathogen-associated molecular patterns has been well defined. However, the effects of virus-mediated Ca2+ imbalance on the IFN-I pathway requires further elucidation, especially with respect to TBK1 activation. Herein, we report that NDV infection causes an increase in intracellular free Ca2+ that leads to activation of the serine/threonine phosphatase CaN, which subsequently dephosphorylates TBK1 and negatively regulates IFN-I production. Furthermore, depletion of Ca2+ or inhibition of CaN activity exerts antiviral effects by promoting the production of IFN-I and inhibiting viral replication. Thus, our results reveal the potential role of Ca2+ in the innate immune response to viruses and provide a theoretical reference for the treatment of viral infectious diseases.

Cip1 tunes cell cycle arrest duration upon calcineurin activation.

Cells exposed to environmental stress arrest the cell cycle until they have adapted to their new environment. Cells adjust the length of the arrest for each unique stressor, but how they do this is not known. Here, we investigate the role of the stress-activated phosphatase calcineurin (CN) in controlling cell cycle arrest in Saccharomyces cerevisiae. We find that CN controls arrest duration through activation of the G1 cyclin­dependent kinase inhibitor Cip1. Our results demonstrate that multiple stressors trigger a G1/S arrest through Hog1-dependent down-regulation of G1 cyclin transcription. When a stressor also activates CN, this arrest is lengthened as CN prolongs Hog1-dependent phosphorylation of Cip1. Cip1 plays no role in response to stressors that activate Hog1 but not CN. These findings illustrate how stress response pathways cooperate to tailor the stress response and suggest that Cip1 functions to prolong cell cycle arrest when a cell requires additional time for adaptation.

PPP1r18 promotes tumor progression in esophageal squamous cell carcinoma by regulating the calcineurin-mediated ERK pathway.

Esophageal cancer is one of the most common malignant tumors, and the 5-year overall survival rate is only 20%. Esophageal squamous cell carcinoma (ESCC) is the primary histological type of esophageal carcinoma in China. Protein phosphatase 1 regulatory subunit 18 (PPP1r18) is one of the actin-regulatory proteins and is able to bind to protein phosphatase 1 catalytic subunit alpha (PPP1CA). Yet, little is known about the role of PPP1r18 in esophageal squamous cell carcinoma (ESCC). This study aimed to elucidate the biological functions of PPP1r18 in the ESCC progression. Clinical samples first confirmed that PPP1r18 expression was upregulated in ESCC, and PPP1r18 was correlated with tumor invasion depth, lymph node metastasis, distant metastasis, and reduced overall survival. We then observed that PPP1r18 overexpression enhanced cell proliferation in vitro and in vivo. Mechanistically, PPP1r18 regulated tumor progression of ESCC through activating the calcineurin-mediated ERK pathway, rather than binding to PPP1CA. Collectively, our results suggest that PPP1r18 promotes ESCC progression by regulating the calcineurin-mediated ERK pathway. PPP1r18 might be a potential target for the diagnosis and treatment of ESCC.

The Ycx1 protein encoded by the yeast YDL206W gene plays a role in calcium and calcineurin signaling.

Calcium is ubiquitously present in all living cells and plays important regulatory roles in a wide variety of biological processes. In yeast, many effects of calcium are mediated via the action of calcineurin, a calcium/calmodulin-dependent protein phosphatase. Proper signaling of calcium and calcineurin is important in yeast, and the calcineurin pathway has emerged as a valuable target for developing novel antifungal drugs. Here, we report a role of YDL206W in calcium and calcineurin signaling in yeast. YDL206W is an uncharacterized gene in yeast, encoding a protein with two sodium/calcium exchange domains. Disrupting the YDL206W gene leads to a diminished level of calcium-induced activation of calcineurin and a reduced accumulation of cytosolic calcium. Consistent with a role of calcineurin in regulating pheromone and cell wall integrity signaling, the ydl206wΔ mutants display an enhanced growth arrest induced by pheromone treatment and poor growth at elevated temperature. Subcellular localization studies indicate that YDL206W is localized in endoplasmic reticulum and Golgi. Together, our results reveal YDL206W as a new regulator for calcineurin signaling in yeast and suggest a role of the endoplasmic reticulum and Golgi in regulating cytosolic calcium in yeast.

CIB2 Is a Novel Endogenous Repressor of Atrial Remodeling.

BACKGROUND: Atrial fibrillation (AF) is a highly prevalent condition that can cause or exacerbate heart failure, is an important risk factor for stroke, and is associated with pronounced morbidity and death. Genes uniquely expressed in the atria are known to be essential for maintaining atrial structure and function. Atrial tissue remodeling contributes to arrhythmia recurrence and maintenance. However, the mechanism underlying atrial remodeling remains poorly understood. This study was designed to investigate whether other uncharacterized atrial specific genes play important roles in atrial physiology and arrhythmogenesis. METHODS: RNA-sequencing analysis was used to identify atrial myocyte specific and angiotensin II-responsive genes. Genetically modified, cardiomyocyte-specific mouse models (knockout and overexpression) were generated. In vivo and in vitro electrophysiological, histology, and biochemical analyses were performed to determine the consequences of CIB2 (calcium and integrin binding family member 2 protein) gain and loss of function in the atrium. RESULTS: Using RNA-sequencing analysis, we identified CIB2 as an atrial-enriched protein that is significantly downregulated in the left atria of patients with AF and mouse models of AF from angiotensin II infusion or pressure overload. Using cardiomyocyte-specific Cib2 knockout (Cib2-/-) and atrial myocyte-specific Cib2-overexpressing mouse models, we found that loss of Cib2 enhances AF occurrence, prolongs AF duration, and correlates with a significant increase in atrial fibrosis under stress. Conversely, Cib2 overexpression mitigates AF occurrence and atrial fibrosis triggered by angiotensin II stress. Mechanistically, we revealed that CIB2 competes with and inhibits CIB1-mediated calcineurin activation, thereby negating stress-induced structural remodeling and AF. CONCLUSIONS: Our data suggest that CIB2 represents a novel endogenous and atrial-enriched regulator that protects against atrial remodeling and AF under stress conditions. Therefore, CIB2 may represent a new potential target for treating AF.

Genetic deletion of astrocytic calcineurin B1 prevents cognitive impairment and neuropathology development in acute and chronic mouse models of Alzheimer's disease.

Alzheimer's disease (AD) represents an urgent yet unmet challenge for modern society, calling for exploration of innovative targets and therapeutic approaches. Astrocytes, main homeostatic cells in the CNS, represent promising cell-target. Our aim was to investigate if deletion of the regulatory CaNB1 subunit of calcineurin in astrocytes could mitigate AD-related memory deficits, neuropathology, and neuroinflammation. We have generated two, acute and chronic, AD mouse models with astrocytic CaNB1 ablation (ACN-KO). In the former, we evaluated the ability of ß-amyloid oligomers (AßOs) to impair memory and activate glial cells once injected in the cerebral ventricle of conditional ACN-KO mice. Next, we generated a tamoxifen-inducible astrocyte-specific CaNB1 knock-out in 3xTg-AD mice (indACNKO-AD). CaNB1 was deleted, by tamoxifen injection, in 11.7-month-old 3xTg-AD mice for 4.4 months. Spatial memory was evaluated using the Barnes maze; ß-amyloid plaques burden, neurofibrillary tangle deposition, reactive gliosis, and neuroinflammation were also assessed. The acute model showed that ICV injected AßOs in 2-month-old wild type mice impaired recognition memory and fostered a pro-inflammatory microglia phenotype, whereas in ACN-KO mice, AßOs were inactive. In indACNKO-AD mice, 4.4 months after CaNB1 depletion, we found preservation of spatial memory and cognitive flexibility, abolishment of amyloidosis, and reduction of neurofibrillary tangles, gliosis, and neuroinflammation. Our results suggest that ACN is crucial for the development of cognitive impairment, AD neuropathology, and neuroinflammation. Astrocyte-specific CaNB1 deletion is beneficial for both the abolishment of AßO-mediated detrimental effects and treatment of ongoing AD-related pathology, hence representing an intriguing target for AD therapy.