Synergistic effects of putative Ca2+-binding sites of calmodulin in fungal development, temperature stress and virulence of Aspergillus fumigatus

In pathogenic fungi, calcium-calmodulin-dependent serine-threonine-specific phosphatase calcineurin is involved in morphogenesis and virulence. Therefore, calcineurin and its tightly related protein complexes are attractive antifungal drug targets. However, there is limited knowledge available on the relationship between in vivo Ca2+-binding sites of calmodulin (CaM) and its functions in regulating stress responses, morphogenesis, and pathogenesis. In the current study, we demonstrated that calmodulin is required for hyphal growth, conidiation, and virulence in the human fungal pathogen, Aspergillus fumigatus. Site-directed mutations of calmodulin revealed that a single Ca2+-binding site mutation had no significant effect on A. fumigatus hyphal development, but multiple Ca2+-binding site mutations exhibited synergistic effects, especially when cultured at 42 °C, indicating that calmodulin function in response to temperature stress depends on its Ca2+-binding sites. Western blotting implied that mutations in Ca2+-binding sites caused highly degraded calmodulin fragments, suggesting that the loss of Ca2+-binding sites results in reduced protein stability. Moreover, normal intracellular calcium homeostasis and the nuclear translocation of the transcriptional factor CrzA are dependent on Ca2+-binding sites of AfCaM, demonstrating that Ca2+-binding sites of calmodulin are required for calcium signalling and its major transcription factor CrzA. Importantly, in situ mutations for four Ca2+-binding sites of calmodulin resulted in an almost complete loss of virulence in the Galleria mellonella wax moth model. This study shed more light on the functional characterization of putative calcium-binding sites of calmodulin in the morphogenesis and virulence of A. fumigatus, which enhances our understanding of calmodulin biological functions in cells of opportunistic fungal pathogens.

Potential inhibitory effect of geraniol isolated from lemongrass (Cymbopogon commutatus Stapf) on tilmicosin-induced oxidative stress in cardiac tissue

An experimental study has been conducted to investigate the efficacy of geraniol (GNL) isolated from lemomgrass in protecting against cardiac toxicity induced by tilmicosin (TIL) in albino mice. Compared to TIL-treated mice, those supplemented with GNL had a thicker left ventricular wall and a smaller ventricular cavity. Studies of TIL animals treated with GNL showed that their cardiomyocytes had markedly changed in diameter and volume, along with a reduction in numerical density. After TIL induction, animals showed a significant increase in the protein expression of TGF-β1, TNF-α, nuclear factor kappa B (NF-kB), by 81.81, 73.75 and 66.67%, respectively, and hypertrophy marker proteins ANP, BNP, and calcineurin with respective percentages of 40, 33.34 and 42.34%. Interestingly, GNL significantly decreased the TGF-β1, TNF-α, NF-kB, ANP, BNP, and calcineurin levels by 60.94, 65.13, 52.37, 49.73, 44.18 and 36.84%, respectively. As observed from histopathology and Masson's trichrome staining, supplementation with GNL could rescue TIL-induced cardiac hypertrophy. According to these results, GNL may protect the heart by reducing hypertrophy in mice and modulating biomarkers of fibrosis and apoptosis.

A snake cathelicidin enhances transcription factor EB-mediated autophagy and alleviates ROS-induced pyroptosis after ischaemia-reperfusion injury of island skin flaps

BACKGROUND AND PURPOSE

Ischaemia-reperfusion (I/R) injury is a major contributor to skin flap necrosis, which presents a challenge in achieving satisfactory therapeutic outcomes. Previous studies showed that cathelicidin-BF (BF-30) protects tissues from I/R injury. In this investigation, BF-30 was synthesized and its role and mechanism in promoting survival of I/R-injured skin flaps explored.

EXPERIMENTAL APPROACH

Survival rate analysis and laser Doppler blood flow analysis were used to evaluate I/R-injured flap viability. Western blotting, immunofluorescence, TdT-mediated dUTP nick end labelling (TUNEL) and dihydroethidium were utilized to examine the levels of apoptosis, pyroptosis, oxidative stress, transcription factor EB (TFEB)-mediated autophagy and molecules related to the adenosine 5'-monophosphate-activated protein kinase (AMPK)-transient receptor potential mucolipin 1 (TRPML1)-calcineurin signalling pathway.

KEY RESULTS

The outcomes revealed that BF-30 enhanced I/R-injured island skin flap viability. Autophagy, oxidative stress, pyroptosis and apoptosis were related to the BF-30 capability to enhance I/R-injured flap survival. Improved autophagy flux and tolerance to oxidative stress promoted the inhibition of apoptosis and pyroptosis in vascular endothelial cells. Activation of TFEB increased autophagy and inhibited endothelial cell oxidative stress in I/R-injured flaps. A reduction in TFEB level led to a loss of the protective effect of BF-30, by reducing autophagy flux and increasing the accumulation of reactive oxygen species (ROS) in endothelial cells. Additionally, BF-30 modulated TFEB activity via the AMPK-TRPML1-calcineurin signalling pathway.

CONCLUSION AND IMPLICATIONS

BF-30 promotes I/R-injured skin flap survival by TFEB-mediated up-regulation of autophagy and inhibition of oxidative stress, which may have possible clinical applications.

Novel peptides from sea cucumber intestines hydrolyzed by neutral protease alleviate exercise-induced fatigue via upregulating the glutaminemediated Ca2+ /Calcineurin signaling pathway in mice

Sea cucumber intestines are considered a valuable resource in the sea cucumber processing industry due to their balanced amino acid composition. Studies have reported that peptides rich in glutamate and branched-chain amino acids have anti-fatigue properties. However, the function of the sea cucumber intestine in reducing exercise-induced fatigue remains unclear. In this study, we enzymatically hydrolyzed low molecular weight peptides from sea cucumber intestines (SCIP) and administered SCIP orally to mice to examine its effects on exercise-induced fatigue using swimming and pole-climbing exhaustion experiments. The results revealed that supplementation with SCIP significantly prolonged the exhaustion time of swimming in mice, decreased blood lactate and urea nitrogen levels, and increased liver and muscle glycogen levels following a weight-loaded swimming test. Immunofluorescence analysis indicated a notable increase the proportion of slow-twitch muscle fiber and a significant decrease the proportion of fast-twitch muscle fiber following SCIP supplementation. Furthermore, SCIP upregulated mRNA expression levels of Ca2+ /Calcineurin upstream and downstream regulators, thereby contributing to the promotion of skeletal muscle fiber type conversion. This study presents the initial evidence establishing SCIP as a potential enhancer of skeletal muscle fatigue resistance, consequently providing a theoretical foundation for the valuable utilization of sea cucumber intestines.

Shikonin reactivates TSGs GADD45B and PPP3CC to block NSCLC cell proliferation and migration through JNK/P38/MAPK signaling pathways

BACKGROUND

Shikonin, a natural naphthoquinone compound extracted from the Chinese traditional herbal medicine "Lithospermum erythrorhizon", possesses antitumor activity against various cancer types. Tumor-suppressor genes (TSGs) negatively regulate cell growth, proliferation, and differentiation, thereby inhibiting tumor formation. However, the molecular mechanism of action of shikonin on TSGs in non-small-cell lung cancer (NSCLC) remains unclear.

METHODS

The inhibitory effect of shikonin on the proliferation and migration abilities of lung cancer cells were measured by Cell Counting Kit 8 (CCK8) and wound healing assays. The alteration of genes by shikonin treatment was detected by mRNA high-throughput sequencing and further confirmed by qPCR and western blotting experiments. The dominant functions of the upregulated genes were analyzed by GO and KEGG profiling.

RESULTS

Shikonin inhibited the proliferation and migration of A549 and H1299 NSCLC cells in a dose-dependent manner. mRNA high-throughput sequencing revealed a total of 1794 upregulated genes in shikonin-treated NSCLC cells. Moreover, bioinformatic analysis of GO and KEGG profiling revealed that the up-regulated genes were mostly involved in the JNK/P38/MAPK signaling pathway, among which the expression of GADD45B and PPP3CC was significantly enhanced. Finally, we confirmed that GADD45B and PPP3CC were indeed upregulated in JNK/P38/MAPK pathway.

CONCLUSIONS

Taken together, these results suggested that shikonin might affect the expression of GADD45B and PPP3CC through the JNK/P38/MAPK pathway, therefore exerting an inhibitory effect on the proliferation and migration of cancer cells. To our knowledge, this is the first study reporting the role of shikonin in upregulating TSGs to activate the JNK/P38/MAPK signaling pathways in NSCLC.

Melatonin inhibits Japanese encephalitis virus replication and neurotoxicity via calcineurin-autophagy pathways

BACKGROUND

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that has no specific treatment except for supportive medical care. JEV is a neurotropic virus that affects the nervous system and triggers inflammation in the brain.

METHODS

Melatonin is used as a sleep-inducing agent in neurophysiology and may serve as a protective agent against neurological and neurodegenerative diseases. Herein, we investigated the effects of melatonin and the critical roles of the serine/threonine protein phosphatase calcineurin during JEV infection in SK-N-SH neuroblastoma cells.

RESULTS

Melatonin treatment decreased JEV replication and JEV-mediated neurotoxicity. Calcineurin activity was increased by JEV infection and inhibited by melatonin treatment. Through calcineurin regulation, melatonin decreased the JEV-mediated neuroinflammatory response and attenuated JEV-induced autophagy.

CONCLUSIONS

Calcineurin inactivation has a protective effect in JEV-infected neuronal cells, and melatonin is a novel resource for the development of anti-JEV agents.

Endothelin-1 acutely increases nitric oxide production via the calcineurin mediated dephosphorylation of Caveolin-1

Endothelin (ET)-1 is an endothelial-derived peptide that exerts biphasic effects on nitric oxide (NO) levels in endothelial cells such that acute exposure stimulates-while sustained exposure attenuates-NO production. Although the mechanism involved in the decrease in NO generation has been identified but the signaling involved in the acute increase in NO is still unresolved. This was the focus of this study. Our data indicate that exposing pulmonary arterial endothelial cells (PAEC) to ET-1 led to an increase in NO for up to 30min after which levels declined. These effects were attenuated by ET receptor antagonists. The increase in NO correlated with significant increases in pp60Src activity and increases in eNOS phosphorylation at Tyr83 and Ser1177. The ET-1 mediated increase in phosphorylation and NO generation were attenuated by the over-expression of a pp60Src dominant negative mutant. The increase in pp60Src activity correlated with a reduction in the interaction of Caveolin-1 with pp60Src and the calcineurin-mediated dephosphorylation of caveolin-1 at three previously unidentified sites: Thr91, Thr93, and Thr95. The calcineurin inhibitor, Tacrolimus, attenuated the acute increase in pp60Src activity induced by ET-1 and a calcineurin siRNA attenuated the ET-1 mediated increase in eNOS phosphorylation at Tyr83 and Ser1177 as well as the increase in NO. By using a Caveolin-1 celluSpot peptide array, we identified a peptide targeting a sequence located between aa 41-56 as the pp60Src binding region. This peptide fused to the TAT sequence was found to decrease caveolin-pp60Src interaction, increased pp60Src activity, increased eNOS pSer1177 and NO levels in PAEC and induce vasodilation in isolated aortic rings in wildtype but not eNOS knockout mice. Together, our data identify a novel mechanism by which ET-1 acutely increases NO via a calcineurin-mediated dephosphorylation of caveolin-1 and the subsequent stimulation of pp60Src activity, leading to increases in phosphorylation of eNOS at Tyr83 and Ser1177.

Investigation of the effects of urotensin II receptors in LPS-induced inflammatory response in HUVEC cell line through calcineurin/NFATc/IL-2 pathway

PURPOSE

The effect of urotensin II (U-II), a powerful endogenous vasoconstrictor substance, on the immune system and its mediators is very important. It was herein aimed to demonstrate the possible relationship between the calcineurin/nuclear factor of activated T-cells cytoplasmic 1/interleukin-2 (CaN/NFATc/IL-2) pathway and urotensin receptors (UTRs) in inflammatory response due to lipopolysaccharide (LPS).

METHODS

An LPS-induced inflammation model was used on the human umbilical vein endothelial cells (HUVEC) cell line and drugs were applied accordingly, forming the following groups: Control Group, LPS Group, Agonist Group (10-8 ​M U-II), Antagonist Group (10-6 ​M palosuran), Tacrolimus (TAC) Group (10 ​ng/mL FK-506), Agonist ​+ ​TAC Group, and Antagonist ​+ ​TAC Group. Gene expression analyses were performed using real-time polymerase chain reaction (RT-PCR).

RESULTS

In the analysis of the cell viability at 48 and 72 ​h, there was a decrease in the Agonist Group, while in the Agonist ​+ ​TAC Group, the cell viability increased. In the Antagonist Group, cell viability was maintained when compared to the LPS Group, while in the TAC Group, this effect was reduced. The mRNA expression levels of UTR, CaN, NFATc, IL-2 receptor (IL-2R), IL-6 and nuclear factor kappa B (NF-κB) were higher in the LPS Group than in the Control Group, and even the UTR, CaN, NFATc, IL-2R were higher with agonist administration. This effect of the agonist was shown to be completely mitigated in the presence of the CaN inhibitor.

CONCLUSION

U-II and its receptors can perform key functions regarding the endothelial cell damage via the CaN/NFATc/IL-2 pathway.

HIV-1 gp120 protein promotes HAND through the calcineurin pathway activation

For over two decades, highly active antiretroviral therapy (HAART) was able to help prolong the life expectancy of people living with HIV-1 (PLWH) and eliminate the virus to an undetectable level. However, an increased prevalence of HIV- associated neurocognitive disorders (HAND) was observed. These symptoms range from neuronal dysfunction to cell death. Among the markers of neuronal deregulation, we cite the alteration of synaptic plasticity and neuronal communications. Clinically, these dysfunctions led to neurocognitive disorders such as learning alteration and loss of spatial memory, which promote premature brain aging even in HAART-treated patients. In support of these observations, we showed that the gp120 protein deregulates miR-499-5p and its downstream target, the calcineurin (CaN) protein. The gp120 protein also promotes the accumulation of calcium (Ca2+) and reactive oxygen species (ROS) inside the neurons leading to the activation of CaN and the inhibition of miR-499-5p. gp120 protein also caused mitochondrial fragmentation and changes in shape and size. The use of mimic miR-499 restored mitochondrial functions, appearance, and size. These results demonstrated the additional effect of the gp120 protein on neurons through the miR-499-5p/calcineurin pathway.

Neonatal sevoflurane exposure induces long-term changes in dendritic morphology in juvenile rats and mice

General anesthetics are potent neurotoxins when given during early development, causing apoptotic deletion of substantial number of neurons and persistent neurocognitive and behavioral deficits in animals and humans. The period of intense synaptogenesis coincides with the peak of susceptibility to deleterious effects of anesthetics, a phenomenon particularly pronounced in vulnerable brain regions such as subiculum. With steadily accumulating evidence confirming that clinical doses and durations of anesthetics may permanently alter the physiological trajectory of brain development, we set out to investigate the long-term consequences on dendritic morphology of subicular pyramidal neurons and expression on genes regulating the complex neural processes such as neuronal connectivity, learning, and memory. Using a well-established model of anesthetic neurotoxicity in rats and mice neonatally exposed to sevoflurane, a volatile general anesthetic commonly used in pediatric anesthesia, we report that a single 6 h of continuous anesthesia administered at postnatal day (PND) 7 resulted in lasting dysregulation in subicular mRNA levels of cAMP responsive element modulator (Crem), cAMP responsive element-binding protein 1 (Creb1), and Protein phosphatase 3 catalytic subunit alpha, a subunit of calcineurin (Ppp3ca) (calcineurin) when examined during juvenile period at PND28. Given the critical role of these genes in synaptic development and neuronal plasticity, we deployed a set of histological measurements to investigate the implications of anesthesia-induced dysregulation of gene expression on morphology and complexity of surviving subicular pyramidal neurons. Our results indicate that neonatal exposure to sevoflurane induced lasting rearrangement of subicular dendrites, resulting in higher orders of complexity and increased branching with no significant effects on the soma of pyramidal neurons. Correspondingly, changes in dendritic complexity were paralleled by the increased spine density on apical dendrites, further highlighting the scope of anesthesia-induced dysregulation of synaptic development. We conclude that neonatal sevoflurane induced persistent genetic and morphological dysregulation in juvenile rodents, which could indicate heightened susceptibility toward cognitive and behavioral disorders we are beginning to recognize as sequelae of early-in-life anesthesia.

The calcium-calcineurin and high-osmolarity glycerol pathways co-regulate tebuconazole sensitivity and pathogenicity in Fusarium graminearum

The calcium-calcineurin and high-osmolarity glycerol (HOG) pathways play crucial roles in fungal development, pathogenicity, and in responses to various environmental stresses. However, interaction of these pathways in regulating fungicide sensitivity remains largely unknown in phytopathogenic fungi. In this study, we investigated the function of the calcium-calcineurin signalling pathway in Fusarium graminearum, the causal agent of Fusarium head blight. Inhibitors of Ca²⁺ and calcineurin enhanced antifungal activity of tebuconazole (an azole fungicide) against F. graminearum. Deletion of the putative downstream transcription factor FgCrz1 resulted in significantly increased sensitivity of F. graminearum to tebuconazole. FgCrz1-GFP was translocated to the nucleus upon tebuconazole treatment in a calcineurin-dependent manner. In addition, deletion of FgCrz1 increased the phosphorylation of FgHog1 in response to tebuconazole. Moreover, the calcium-calcineurin and HOG signalling pathways exhibited synergistic effect in regulating pathogenicity and sensitivity of F. graminearum to tebuconazole and multiple other stresses. RNA-seq data revealed that FgCrz1 regulated expression of a set of non-CYP51 genes that are associated with tebuconazole sensitivity, including multidrug transporters, membrane lipid biosynthesis and metabolism, and cell wall organization. Our findings demonstrate that the calcium-calcineurin and HOG pathways act coordinately to orchestrate tebuconazole sensitivity and pathogenicity in F. graminearum, which may provide novel insights in management of Fusarium disease.

The calcium sensor CBL7 is required for Serendipita indica-induced growth stimulation in Arabidopsis thaliana, controlling defense against the endophyte and K+ homoeostasis in the symbiosis

Calcium is an important second messenger in plants. The activation of Ca²⁺ signalling cascades is critical in the activation of adaptive processes in response to environmental stimuli. Root colonization by the growth promoting endophyte Serendipita indica involves the increase of cytosolic Ca²⁺ levels in Arabidopsis thaliana. Here, we investigated transcriptional changes in Arabidopsis roots during symbiosis with S. indica. RNA-seq profiling disclosed the induction of Calcineurin B-like 7 (CBL7) during early and later phases of the interaction. Consistently, reverse genetic evidence highlighted the functional relevance of CBL7 and tested the involvement of a CBL7-CBL-interacting protein kinase 13 signalling pathway. The loss-of-function of CBL7 abolished the growth promoting effect and affected root colonization. The transcriptomics analysis of cbl7 revealed the involvement of this Ca²⁺ sensor in activating plant defense responses. Furthermore, we report on the contribution of CBL7 to potassium transport in Arabidopsis. We analysed K⁺ contents in wild-type and cbl7 plants and observed a significant increase of K⁺ in roots of cbl7 plants, while shoot tissues demonstrated K⁺ depletion. Taken together, our work associates CBL7 with an important role in the mutual interaction between Arabidopsis and S. indica and links CBL7 to K⁺ transport.

Crucial role of Ca2+ /CN signalling pathway in the antifungal activity of disenecioyl-cis-khellactone against Botrytis cinerea

BACKGROUND

Botrytis cinerea causes grey mould and is one of the most destructive fungal pathogens affecting important fruit and vegetable crops. In preliminary studies, we found that disenecioyl-cis-khellactone (DK) had strong antifungal activity against several fungi species including B. cinerea [half maximal effective concentration (EC₅₀ ) = 11.0 μg mL^-1 ]. In this study, we aimed to further evaluate the antifungal activity of DK against B. cinerea and determine the role of calcium ion/calcineurin (Ca²⁺ /CN) signalling pathway on its antifungal effect.

RESULTS

DK was effective against B. cinerea in both in vitro and in vivo assays. Exogenous Ca²⁺ reduced the antifungal activity of DK. The combination of DK and cyclosporine A (CsA) did not exhibit an additive effect against B. cinerea. In contrast to CsA, DK reduced the intracellular Ca²⁺ concentration in B. cinerea. DK bound to calcineurin A (cnA) and up-regulated the expression of PMC1 and PMR1 genes. Moreover, DK sensitivity of △bccnA significantly decreased compared with that of Bc05.10 strain.

CONCLUSION

DK is a promising lead compound for developing fungicides against B. cinerea. The Ca²⁺ /CN signalling pathway plays a crucial role in the DK antifungal activity, and cnA is one of the targets of DK against B. cinerea. DK directly reacts with cnA, which up-regulates the transcription of Ca²⁺ /CN-dependent target genes PMC1 and PMR1, decreasing the intracellular Ca²⁺ concentration and disturbing the intracellular Ca²⁺ balance, leading to cell death. © 2022 Society of Chemical Industry.

Phillygenin ameliorates nonalcoholic fatty liver disease via TFEB-mediated lysosome biogenesis and lipophagy

BACKGROUND

Lipophagy is an autophagic process, which delivers the intracellular lipid droplets to the lysosomes for degradation. Recent studies revealed that the impairment of lysosomal biogenesis and autophagic flux led to dysregulation of lipophagy in hepatocytes, which exacerbated the development of nonalcoholic fatty liver disease (NAFLD). Therefore, agents restoring autophagic flux and lipophagy in hepatocytes may have therapeutic potential against this increasingly prevalent disease. Phillygenin (PHI), a lignin extracted from Forsythia suspense, exerts hepatoprotective and anti-inflammatory effects. However, the effect of PHI on NAFLD remains unknown.

PURPOSE

This study aimed to investigate the protective effect of PHI on NAFLD and elucidate the underlying mechanism.

METHODS

The effects of PHI were examined in palmitate (PA)-stimulated AML12 cells and primary hepatocytes, as well as in NAFLD mice induced by a high-fat diet (HFD). We also used transcription factor EB (TFEB) knockdown hepatocytes and hepatocyte-specific TFEB knockout (TFEB^Δhep) mice for mechanistic studies. In vivo and in vitro studies were performed using western blots, immunofluorescence techniques, and transmission electron microscopy.

RESULTS

Our results indicated that autophagic flux and lysosome biogenesis in PA-stimulated hepatocytes were impaired. PHI alleviated lipid deposition by increasing lysosomal biogenesis and autophagic flux. It also stimulated the release of endoplasmic reticulum Ca²⁺ to activate calcineurin, which regulated TFEB dephosphorylation and nuclear translocation, and promoted lysosomal biogenesis. In addition, PHI blocked the NLRP3 inflammasome pathway and improved hepatocyte inflammation in an autophagy-dependent manner. Consistent with the in vitro results, PHI improved hepatic steatosis and inflammation in HFD mice, but these beneficial effects were eliminated in hepatocyte-specific TFEB knockout mice.

CONCLUSION

Despite PHI has been reported to have anti-hepatic fibrosis effects, whether it has a hepatoprotective effects against NAFLD and the underlying molecular mechanism remain unclear. Herein, we found that PHI restored lipophagy and suppressed lipid accumulation and inflammation by regulating the Ca²⁺-calcineurin-TFEB axis in hepatocytes. Thus, PHI represents a therapeutic candidate for the treatment of NAFLD.

TRIM72 exerts antitumor effects in breast cancer and modulates lactate production and MCT4 promoter activity by interacting with PPP3CA

A hypoxic tumor microenvironment (TME) promotes cancer progression, yet its value as a therapeutic target remains underexploited. Tripartite motif-containing 72 (TRIM72) may protect cells against various stresses including hypoxia. Recently, low TRIM72 expression has been implicated in cancer progression. However, the biological role and molecular mechanism of TRIM72 in breast cancer (BC) remain unclear. Herein, we analyzed the TRIM72 expression in BC tissue and cell lines by western blot (WB) and quantitative reverse transcription-PCR. We established the overexpression of TRIM72 using plasmids and lentiviral-mediated upregulation, as well as downregulation of protein phosphatase 3 catalytic subunit alpha (PPP3CA) by siRNA. The tumor-suppressive roles of TRIM72 were assessed on BT549 and MDA-MB-231 cells by MTS, Transwell, and flow cytometry assays in vitro and in xenografted tumors in vivo. The molecular mechanism of TRIM72 was investigated by luciferase reporter and co-immunoprecipitation (Co-IP) assay. Lactate production was measured by ELISA under hypoxic environments induced by CoCl2. Moreover, the expression of PI3K/Akt/mTOR pathway-associated proteins was detected by WB in BC cells. Results showed that TRIM72 was downregulated in BC. Overexpression of TRIM72 inhibited tumor proliferation and invasion in vitro and in a xenograft tumor model. Mechanistically, PPP3CA altered the inhibitory effects of TRIM72 on hypoxia-induced lactate production and monocarboxylate transporter 4-promoter activity, as well as the effect of the PI3K/Akt/mTOR signaling pathway. Our study suggests that TRIM72 modulates the TME and plays tumor-suppressive roles in BC progression. Therefore, TRIM72 may serve as a potential therapeutic target in BC.

Inhibition of Calcium Signaling Prevents Exhaustion and Enhances Anti-Leukemia Efficacy of CAR-T Cells via SOCE-Calcineurin-NFAT and Glycolysis Pathways

Chimeric antigen receptor (CAR) T cells are potent agents for recognizing and eliminating tumors, and have achieved remarkable success in the treatment of patients with refractory leukemia and lymphoma. However, dysfunction of T cells, including exhaustion, is an inevitable obstacle for persistent curative effects. Here, the authors initially found that calcium signaling is hyperactivated via sustained tonic signaling in CAR-T cells. Next, it is revealed that the store-operated calcium entry (SOCE) inhibitor BTP-2, but not the calcium chelator BAPTA-AM, markedly diminishes CAR-T cell exhaustion and terminal differentiation of CAR-T cells in both tonic signaling and tumor antigen exposure models. Furthermore, BTP-2 pretreated CAR-T cells show improved antitumor potency and prolonged survival in vivo. Mechanistically, transcriptome and metabolite analyses reveal that treatment with BTP-2 significantly downregulate SOCE-calcineurin-nuclear factor of activated T-cells (NFAT) and glycolysis pathways. Together, the results indicate that modulating the SOCE-calcineurin-NFAT pathway in CAR-T cells renders them resistant to exhaustion, thereby yielding CAR products with enhanced antitumor potency.

Calcineurin inhibition blocks within-, but not between-session fear extinction in mice

Memory extinction involves the formation of a new associative memory that inhibits a previously conditioned association. Nonetheless, it could also depend on weakening of the original memory trace if extinction is assumed to have multiple components. The phosphatase calcineurin (CaN) has been described as being involved in extinction but not in the initial consolidation of fear learning. With this in mind, we set to study whether CaN could have different roles in distinct components of extinction. Systemic treatment with the CaN inhibitors cyclosporin A (CsA) or FK-506, as well as i.c.v. administration of CsA, blocked within-session, but not between-session extinction or initial learning of contextual fear conditioning. Similar effects were found in multiple-session extinction of contextual fear conditioning and in auditory fear conditioning, indicating that CaN is involved in different types of short-term extinction. Meanwhile, inhibition of protein synthesis by cycloheximide (CHX) treatment did not affect within-session extinction, but disrupted fear acquisition and slightly impaired between-session extinction. Our results point to a dissociation of within- and between-session extinction of fear conditioning, with the former being more dependent on CaN activity and the latter on protein synthesis. Moreover, the modulation of within-session extinction did not affect between-session extinction, suggesting that these components are at least partially independent.

Calcineurin and CRTC2 mediate FSH and TGFβ1 upregulation of Cyp19a1 and Nr5a in ovary granulosa cells

Estrogens are essential for female reproduction and overall well-being, and estrogens in the circulation are largely synthesized in ovarian granulosa cells. Using primary cultures of ovarian granulosa cells from gonadotropin-primed immature rats, we have recently discovered that pituitary FSH and ovarian cytokine transforming growth factor beta 1 (TGFβ1) induce calcineurin-mediated dephosphorylation-activation of cAMP-response element-binding protein (CREB)-regulated transcription coactivator (CRTC2) to modulate the expression of Star, Cyp11a1, and Hsd3b leading to increased production of progesterone. This study explored the role of calcineurin and CRTC2 in FSH and TGFβ1 regulation of Cyp19a1 expression in granulosa cells. Ovarian granulosa cells treated with FSH displayed increased aromatase protein at 24  h post-treatment, which subsided by 48  h, while TGFβ1 acting through its type 1 receptor augmented the action of FSH with a greater and longer effects. It is known that the ovary-specific Cyp19a1 PII-promoter contains crucial response elements for CREB and nuclear receptor NR5A subfamily liver receptor homolog 1 (LRH1/NR5A2) and steroidogenic factor 1 (SF1/NR5A1), and that the Nr5a2 promoter also has a potential CREB-binding site. Herein, we demonstrate that FSH+TGFβ1 increased LRH1 and SF1 protein levels, and their binding to the Cyp19a1 PII-promoter evidenced, determined by chromatin immunoprecipitation analysis. Moreover, pretreatment with calcineurin auto-inhibitory peptide (CNI) abolished the FSH+TGFβ1-upregulated but not FSH-upregulated aromatase activity at 48  h, and the corresponding mRNA changes in Cyp19a1, and Nr5a2 and Nr5a1 at 24  h. In addition, FSH and TGFβ1 increased CRTC2 binding to the Cyp19a1 PII-promoter and Nr5a2 promoter at 24  h, with CREB bound constitutively. In summary, the results of this study indicate that calcineurin and CRTC2 have important roles in mediating FSH and TGFβ1 collateral upregulation of Cyp19a1 expression together with its transcription regulators Nr5a2 and Nr5a1 in ovarian granulosa cells.

[Calcineurin subunit B is not an effective adjuvant when combined with a novel HBV protein particle vaccine]

To compare different adjuvant formulation and explore the impact of Calcineurin B subunit(CnB) as adjuvant with a novel HBV protein particle (HBSS1) vaccine in mice, female C57BL/6 mice were immunized HBSS1 with Al(OH)3 only, or a normal dose (5 μg) CnB only, or (CnB+ Al(OH)3) mixture as the adjuvant. All immunized groups were primed twice at 4-week intervals; followed by boosting with recombinant adenoviral based HBV vaccine(rAdSS1) at 10-week intervals. We detected the antigen specific humoral response in mice, including total IgG antibody and IgG subtyping. Then, we characterized the specific cell-mediated immune (CMI) response by detection of γ-interferon secreting splenocytes after stimulaton with S or PreS1 peptide pools. No enhancement of immunity was found among the mice with 5 μg of CnB alone or combined with Al(OH), adjuvanted vaccine,which could not induce higher level of anti-PreS1 and anti-S antibodies and CMI than that of HBSS1 alone or Al(OH)3 adjuvanted vaccines. We concluded that CnB is not an effective adjuvant for a novel HBV subunit vaccine.

Effects of arsenite and UVA-1 radiation on calcineurin signaling

Calcineurin is a Ca(2+)-dependent serine/threonine phosphatase and the target of the immunosuppressive drugs cyclosporin and tacrolimus, which are used in transplant recipients to prevent rejection. Unfortunately, the therapeutic use of this drugs is complicated by a high incidence of skin malignancy, which has set off a number of studies into the role of calcineurin signaling in skin, particularly with respect to cell cycle control and DNA repair. Both UVA1 radiation and arsenic species are known to promote skin cancer development via production of reactive oxygen species. In light of the well-documented sensitivity of calcineurin to oxidative stress, we examined and compared the effects of UVA1 and arsenite on calcineurin signaling. In this paper, we show that physiologically relevant doses of UVA1 radiation and low micromolar concentrations of arsenite strongly inhibit calcineurin phosphatase activity in Jurkat and skin cells and decrease NFAT nuclear translocation in Jurkat cells. The effects on calcineurin signaling could be partly prevented by inhibition of NADPH oxidase in Jurkat cells or increased dismutation of superoxide in Jurkat and skin cells. In addition, both UVA1 and arsenite decreased NF-κB activity, although at lower concentrations, arsenite enhanced NF-κB activity. These data indicate that UVA1 and arsenite affect a signal transduction route of growingly acknowledged importance in skin and that calcineurin may serve as a potential link between ROS exposure and impaired tumor suppression.

Gene expression is differently affected by pimecrolimus and betamethasone in lesional skin of atopic dermatitis

BACKGROUND

Topical corticosteroids and calcineurin inhibitors are well-known treatments of atopic dermatitis (AD) but differ in their efficacy and side effects. We recently showed that betamethasone valerate (BM) although clinically more efficient impaired skin barrier repair in contrast to pimecrolimus in AD.

OBJECTIVE

This study elucidates the mode of action of topical BM and pimecrolimus cream in AD.

METHODS

Lesional AD skin samples after topical treatment with either BM or pimecrolimus were subjected to gene expression profile analysis.

RESULTS

Betamethasone valerate resulted in a significant reduction in mRNA levels of genes encoding markers of immune cells and inflammation, dendritic cells, T cells, cytokines, chemokines, and serine proteases, whereas pimecrolimus exerted minor effects only. This corroborates the clinical finding that BM reduces inflammation more effectively than pimecrolimus. Genes encoding molecules important for skin barrier function were differently affected. Both BM and pimecrolimus normalized the expression of filaggrin and loricrin. BM, but not pimecrolimus, significantly reduced the expression of rate-limiting enzymes for lipid synthesis and the expression of involucrin and small proline-rich proteins, which covalently bind ceramides. This may explain the lack of restoration of functional stratum corneum layers observed after BM treatment.

CONCLUSION

The gene expression profiles are consistent with our previous findings that corticosteroids may exert a more potent anti-inflammatory effect but may impair the restoration of the skin barrier. Corticosteroids are still the main treatment for severe and acutely exacerbated AD; pimecrolimus may be preferable for long-term treatment and stabilization.

DYRK1A is a novel negative regulator of cardiomyocyte hypertrophy

Activation of the phosphatase calcineurin and its downstream targets, transcription factors of the NFAT family, results in cardiomyocyte hypertrophy. Recently, it has been shown that the dual specificity tyrosine (Y) phosphorylation-regulated kinase 1A (DYRK1A) is able to antagonize calcineurin signaling by directly phosphorylating NFATs. We thus hypothesized that DYRK1A might modulate the hypertrophic response of cardiomyocytes. In a model of phenylephrine-induced hypertrophy, adenovirus-mediated overexpression of DYKR1A completely abrogated the hypertrophic response and significantly reduced the expression of the natriuretic peptides ANF and BNP. Furthermore, DYRK1A blunted cardiomyocyte hypertrophy induced by overexpression of constitutively active calcineurin and attenuated the induction of the hypertrophic gene program. Conversely, knockdown of DYRK1A, utilizing adenoviruses encoding for a specific synthetic miRNA, resulted in an increase in cell surface area accompanied by up-regulation of ANF- mRNA. Similarly, treatment of cardiomyocytes with harmine, a specific inhibitor of DYRK1A, revealed cardiomyocyte hypertrophy on morphological and molecular level. Moreover, constitutively active calcineurin led to robust induction of an NFAT-dependent luciferase reporter, whereas DYRK1A attenuated calcineurin-induced reporter activation in cardiomyocytes. Conversely, both knockdown and pharmacological inhibition of DYRK1A significantly augmented the effect of calcineurin in this assay. In summary, we identified DYRK1A as a novel negative regulator of cardiomyocyte hypertrophy. Mechanistically, this effect appears to be mediated via inhibition of NFAT transcription factors.

Digital NFATc2 activation per cell transforms graded T cell receptor activation into an all-or-none IL-2 expression

The expression of interleukin-2 (IL-2) is a key event in T helper (Th) lymphocyte activation, controlling both, the expansion and differentiation of effector Th cells as well as the activation of regulatory T cells. We demonstrate that the strength of TCR stimulation is translated into the frequency of memory Th cells expressing IL-2 but not into the amount of IL-2 per cell. This molecular switch decision for IL-2 expression per cell is located downstream of the cytosolic Ca²⁺ level. Here we show that in a single activated Th cell, NFATc2 activation is digital but NF-κB activation is graded after graded T cell receptor (TCR) signaling. Subsequently, NFATc2 translocates into the nucleus in an all-or-none fashion per cell, transforming the strength of TCR-stimulation into the number of nuclei positive for NFATc2 and IL-2 transcription. Thus, the described NFATc2 switch regulates the number of Th cells actively participating in an immune response.

Cooperation of calcineurin and ERK for UTP-induced IL-6 production in HaCaT keratinocytes

UTP causes IL-6 production in HaCaT keratinocytes, which is partially inhibited by PD98059, a mitogen-activated protein kinase kinase (MEK) inhibitor, suggesting that a pathway other than the extracellular signal-regulated kinase (ERK) pathway is involved in the production. In the present study, we examined the involvement of calcineurin in the UTP-induced interleukin (IL)-6 production in HaCaT keratinocytes. FK506 and cyclosporine A, calcineurin inhibitors, partially inhibited UTP-induced IL-6 mRNA expression and protein production. In addition, combined application of FK506 and PD98059 synergistically inhibited the UTP-induced IL-6 production. These results suggest that ERK and calcineurin are cooperatively involved in UTP-induced IL-6 production.

Bacterial superantigen TSST-1 attenuates suppressive efficacy of glucocorticoids and calcineurin inhibitors against blastogenesis of peripheral blood mononuclear cells from patients with chronic renal failure on hemodialysis treatment

BACKGROUND

Many cases of patients with chronic renal failure (CRF) on hemodialysis are known to be infected with Staphylococcus aureus (S. aureus) from the sites of blood vessel puncture for hemodialysis and the custody of the vascular access catheter. S. aureus produces superantigens, such as toxic shock syndrome toxin-1 (TSST-1), which may influence the sensitivity of peripheral-blood mononuclear cells (PBMCs) to immunosuppressive drugs after they are received postrenal transplantation.

METHODS

We examined the drug-sensitivities of PBMCs stimulated with TSST-1 in 18 CRF patients on hemodialysis. PBMCs were isolated from venous blood before hemodialysis, and were cultured in the presence of concanavalin A (ConA) or TSST-1 and serial concentrations of the drugs. In vitro drug concentrations giving 50% inhibition (IC(50)) of PBMC blastogenesis were calculated. INF-gamma and IL-4 in supernatants of cultured PBMCs were measured with ELISA.

RESULTS

The median (range) IC(50) values (ng/ml) for four drugs; tacrolimus, cyclosporine, methylprednisolone, and prednisolone, evaluated in ConA-stimulated PBMCs of CRF patients were 0.04 ng/ml (0.03-0.21), 3.0 (0.1-15.1), 3.0 (1-104), and 16.2 (5.9-35.4), respectively. The values for the four drugs evaluated in TSST-1-stimulated PBMCs were 0.22 (0.08-0.36), 18.9 (5.1-38.2), 328.3 (1.9-1000), and 150.9 (94.7-880), respectively, which were significantly higher than those evaluated in the ConA-stimulated PBMCs (p=0.003-0.023). Amounts of INF-gamma and IL-4 produced from cells were not significantly different between the ConA-or TSST-1-stimulated PBMCs in the presence or absence of immunosuppressive drugs.

CONCLUSION

These observations raise the possibility that TSST-1 induced by S. aureus infection attenuates the clinical efficacy of glucocorticoids and calcineurin inhibitors in CRF patients after renal transplantation. Furthermore, INF-gamma and IL-4 related pathways appear not to play major roles in the TSST-1-induced attenuation of the drug sensitivities.

Calcineurin regulates skeletal muscle metabolism via coordinated changes in gene expression

The metabolic property of skeletal muscle adapts in response to an increased physiological demand by altering substrate utilization and gene expression. The calcium-regulated serine/threonine protein phosphatase calcineurin has been implicated in the transduction of motor neuron signals to alter gene expression programs in skeletal muscle. We utilized transgenic mice that overexpress an activated form of calcineurin in skeletal muscle (MCK-CnA*) to investigate the impact of calcineurin activation on metabolic properties of skeletal muscle. Activation of calcineurin increased glucose incorporation into glycogen and lipid oxidation in skeletal muscle. Activated calcineurin suppressed skeletal muscle glucose oxidation and increased lactate release. The enhancement in lipid oxidation was supported by increased expression of genes for lipid metabolism and mitochondrial oxidative phosphorylation. In a reciprocal fashion, several genes of glycolysis were down-regulated, whereas pyruvate dehydrogenase kinase 4 was markedly induced. This expression pattern was associated with decreased glucose utilization and enhanced glycogen storage. The peroxisome proliferator-activated receptors (PPARs) and PPARgamma coactivator 1alpha (PGC1alpha) are transcription regulators for the expression of metabolic and mitochondrial genes. Consistent with changes in the gene-regulatory program, calcineurin promoted the expression of PPARalpha, PPARdelta, and PPARgamma coactivator 1alpha in skeletal muscle. These results provide evidence that calcineurin-mediated skeletal muscle reprogramming induces the expression of several transcription regulators that coordinate changes in the expression of genes for lipid and glucose metabolism, which in turn alters energy substrate utilization in skeletal muscle.

Calcineurin increases cardiac transient outward K+ currents via transcriptional up-regulation of Kv4.2 channel subunits

Fast transient outward potassium currents (I(to,f)) are critical determinants of regional heterogeneity of cardiomyocyte repolarization as well as cardiomyocyte contractility. Additionally, I(to,f) densities are markedly down-regulated in cardiac hypertrophy and heart disease, conditions associated with activation of the serine/threonine phosphatase calcineurin (Cn). In this study, we investigated the regulation of I(to,f) expression by Cn in cultured neonatal rat ventricular myocytes (NRVMs) with and without alpha(1)-adrenoreceptor stimulation with phenylephrine (PE). Overexpression of constitutively active Cn in NRVMs induced hypertrophy and caused profound increases in I(to,f) density as well as Kv4.2 mRNA and protein expression and promoter activity, without affecting Kv4.3 or KChIP2 levels. The effects of Cn on hypertrophy, I(to,f), and Kv4.2 transcription were associated with NFAT activation and were abrogated by NFAT inhibition. Despite activating Cn and inducing hypertrophy in NRVMs, PE resulted in profound down-regulation of I(to,f) densities as well as Kv4.2, Kv4.3, and KChIP2 expression. Although hypertrophy and NFAT activation were inhibited by the Cn inhibitory peptide CAIN, I(to,f) and Kv4.2 expression were further reduced by CAIN, whereas Cn overexpression eliminated PE-induced reductions in I(to,f) and Kv4.2 expression without affecting Kv4.3 or KChIP2 levels. We conclude that Cn increases cardiac I(to,f) densities by positively regulating Kv4.2 gene transcription. Consistent with this conclusion, we found that I(to,f) was increased in myocytes isolated from young mice overexpressing Cn prior to the development of heart disease. This positive regulation of Kv4.2 transcription by Cn activation is expected to minimize the reductions in I(to,f) and Kv4.2 expression observed in hypertrophic cardiomyocytes.

Studies of the anticancer effect of calcineurin B

Calcineurin (CN) is a Ca (2+)/calmodulin-stimulated protein phosphatase. It is a heterodimeric enzyme consisting of a catalytic subunit (CN A) and a Ca2+ -binding regulatory subunit (CN B), which plays an important role in the human immune system. Its regulatory subunit, CN B, on its own, was found to have a remarkable anticancer effect in mice. To clarify the basis of this action the in vivo and in vitro effect of CN B on several types of mice immunocytes was investigated. The phagocytic activity of peritoneal macrophages of both normal mice and mice bearing S 180 solid tumors increased when CN B was injected daily. In vitro examination using a modified MTT assay and an [3H] incorporation assay showed that the cytotoxicity of peritoneal macrophages was increased substantially. CN B also increased the natural killer activity of murine spleen lymphocytes in vivo and in vitro, and synergized with concanavalin A in stimulating their proliferation. Our results indicate that CN B has a significant stimulatory action on the immune system that may partially account for its anticancer activity.

MEF2 activates a genetic program promoting chamber dilation and contractile dysfunction in calcineurin-induced heart failure

BACKGROUND

Hypertrophic growth, a risk factor for mortality in heart disease, is driven by reprogramming of cardiac gene expression. Although the transcription factor myocyte enhancer factor-2 (MEF2) is a common end point for several hypertrophic pathways, its precise cardiac gene targets and function in cardiac remodeling remain to be elucidated.

METHODS AND RESULTS

We report the existence of synergistic interactions between the nuclear factor of activated T cells and MEF2 transcription factors triggered by calcineurin signaling. To circumvent the embryonic lethality and mitochondrial deficiency associated with germ-line null mutations for MEF2C and MEF2A respectively, we used conditional transgenesis to express a dominant-negative form of MEF2 in the murine postnatal heart and combined this with magnetic resonance imaging to assess MEF2 transcriptional function in Ca2+/calcineurin-induced cardiac remodeling. Surprisingly, end-diastolic and end-systolic ventricular dimensions and contractility were normalized in the presence of severely hypertrophied left ventricular walls on MEF2 inhibition in calcineurin transgenic mice. In line, we generated lines of transgenic mice expressing MEF2A in the heart, which displayed primarily chamber dilation. Microarray profiling indicated that MEF2 promotes a gene profile functioning primarily to or at the nucleus, cytoskeletal and microtubular networks, and mitochondria.

CONCLUSIONS

These findings assign a novel function to MEF2 transcription factors in the postnatal heart, where they activate a genetic program that minimally affects cardiac growth yet promotes chamber dilation, mechanical dysfunction, and dilated cardiomyopathy.

Protein kinase C theta co-operates with calcineurin in the activation of slow muscle genes in cultured myogenic cells

Adult skeletal muscle fibers can be divided into fast and slow twitch subtypes on the basis of specific contractile and metabolic properties, and on distinctive patterns of muscle gene expression. The calcium, calmodulin-dependent protein phosphatase, calcineurin, stimulates slow fiber-specific genes (myoglobin (Mb), troponin I slow) in cultured skeletal muscle cells, as well as in transgenic mice, through the co-operation of peroxisome-proliferation-activator receptor gamma co-activator 1alpha (PGC1alpha) myocyte enhancer factor 2 (MEF2), and nuclear factor of activated T cells (NFAT) transcription factors. Specific protein kinase C isoforms have been shown to functionally co-operate with calcineurin in different cellular models. We investigated whether specific protein kinase C isoforms are involved in calcineurin-induced slow skeletal muscle gene expression. By pharmacological inhibition or exogenous expression of mutant forms, we show that protein kinase C theta (the protein kinase C isoform predominantly expressed in skeletal muscle) is required and co-operates with calcineurin in the activation of the Mb promoter, as well as in the induction of slow isoforms of myosin and troponin I expression, in cultured muscle cells. This co-operation acts primarily regulating MEF2 activity, as shown by using reporter gene expression driven by the Mb promoter mutated in the specific binding sites. MEF2 activity on the Mb promoter is known to be dependent on both PGC1alpha and inactivation of histone deacetylases (HDACs) activity. We show in this study that protein kinase C theta is required for, even though it does not co-operate in, PGC1alpha-dependent Mb activation. Importantly, protein kinase C theta regulates the HDAC5 nucleus/cytoplasm location. We conclude that protein kinase C theta ensures maximal activation of MEF2, by regulating both MEF2 transcriptional complex formation and HDACs nuclear export.

Inhibition of CD4+CD25+ regulatory T-cell function by calcineurin-dependent interleukin-2 production

CD4+CD25+ regulatory T (Treg) cells control immunologic tolerance and antitumor immune responses. Therefore, in vivo modification of Treg function by immunosuppressant drugs has broad implications for transplantation biology, autoimmunity, and vaccination strategies. In vivo bioluminescence imaging demonstrated reduced early proliferation of donor-derived luciferase-labeled conventional T cells in animals treated with Treg cells after major histocompatibility complex mismatch bone marrow transplantation. Combining Treg cells with cyclosporine A (CSA), but not rapamycin (RAPA) or mycophenolate mofetil (MMF), suppressed Treg function assessed by increased T-cell proliferation, graft-versus-host disease (GVHD) severity, and reduced survival. Expansion of Treg and FoxP3 expression within this population was lowest in conjunction with CSA, suggesting that calcineurin-dependent interleukin 2 (IL-2) production is critically required for Treg cells in vivo. The functional defect of Treg cells after CSA exposure could be reversed by exogenous IL-2. Further, the Treg plus RAPA combination preserved graft-versus-tumor (GVT) effector function against leukemia cells. Our data indicate that RAPA and MMF rather than CSA preserve function of Treg cells in pathologic immune responses such as GVHD without weakening the GVT effect.

Sirolimus in de novo heart transplant recipients with severe renal impairment

Two patients with end-stage heart failure and advanced renal dysfunction (under chronic dialysis therapy) underwent heart transplantation. In order to avoid further renal impairment, a calcineurine inhibitor-free immunosuppression regimen based on the sirolimus was used. Although temporary perioperative support with hemofiltration and dialysis was needed, both patients eventually regained a reasonable renal function with no episodes of clinical rejection and normal cardiac function at 13 and 11 months, respectively, after transplantation. Sirolimus-based immunosuppression might be an interesting alternative to calcineurine inhibitors in the management of patients with significant renal impairment.

NMDA-induced potentiation of mGluR5 is mediated by activation of protein phosphatase 2B/calcineurin

Previous reports have shown that activation of N-methyl-D-aspartate (NMDA) receptors potentiates responses to activation of the group I metabotropic glutamate receptor mGluR5 by reversing PKC-mediated desensitization of this receptor. NMDA-induced reversal of mGluR5 desensitization is dependent on activation of protein phosphatases. However, the specific protein phosphatase involved and the precise mechanism by which NMDA receptor activation reduces mGluR desensitization are not known. We have performed a series of molecular, biochemical, and genetic studies to show that NMDA-induced regulation of mGluR5 is dependent on activation of calcium-dependent protein phosphatase 2B/calcineurin (PP2B/CaN). Furthermore, we report that purified calcineurin directly dephosphorylates the C-terminal tail of mGluR5 at sites that are phosphorylated by PKC. Finally, immunoprecipitation and GST fusion protein pull-down experiments reveal that calcineurin interacts with mGluR5, suggesting that these proteins could be colocalized in a signaling complex. Taken together with previous studies, these data suggest that activation of NMDA receptors leads to activation of calcineurin and that calcineurin modulates mGluR5 function by directly dephosphorylating mGluR5 at PKC sites that are involved in desensitization of this receptor.

Calcium increases endocytotic vesicle size and accelerates membrane fission in insulin-secreting INS-1 cells

In many cells, endocytotic membrane retrieval is accelerated by Ca2+. The effect of Ca2+ on single endocytotic vesicles and fission pore kinetics was examined by measuring capacitance and conductance changes in small membrane patches of insulin-secreting INS-1 cells. In intact cells, elevation of Ca2+ by glucose stimulation induced a 1.8-fold increase in membrane internalisation. This surprisingly resulted from an increased unitary capacitance of endocytotic vesicles whereas the frequency of endocytosis was unaltered. This effect of glucose was prevented by inhibition of L- or R-type Ca2+ channels. Extracellular (pipette) Ca2+ was found to regulate endocytotic vesicle capacitance in a bimodal manner. Vesicle capacitance was increased at intermediate Ca2+ (2.6 mM), but not at high Ca2+ (10 mM). Similar results were obtained upon direct application of 100 nM and 0.5 mM Ca2+ to the intracellular surface of inside-out excised membrane patches, and in these experiments the increase in vesicle capacitance was prevented by the calcineurin inhibitor deltamethrin. Endocytotic fission pore kinetics were accelerated by Ca2+ in both the intact cells and isolated membrane patches; however, the effect in this case was neither bimodal nor deltamethrin sensitive. Membrane retrieval can therefore be upregulated by a Ca2+-dependent increase in endocytotic vesicle size and acceleration of membrane fission in insulin-secreting INS-1 cells.

Transcriptional response of Saccharomyces cerevisiae to the plasma membrane-perturbing compound chitosan

Chitosan is a plasma membrane-perturbing compound consisting of linear chains of beta-1,4-linked glucosamine residues, which at acidic pHs become positively charged. It is extensively used as an antimicrobial compound, yet its mode of action is still unresolved. Chitosan strongly affected the growth of the yeast Saccharomyces cerevisiae, the food spoilage yeast Zygosaccharomyces bailii, and two human-pathogenic yeasts, Candida albicans and Candida glabrata. Microarray analysis of yeast cells treated with sublethal concentrations of chitosan revealed induction of the environmental stress response and three more major transcriptional responses. The first was a rapid and stable Cin5p-mediated response. Cin5p/Yap4p is a transcription factor involved in various stress responses. Deletion of CIN5 led to increased chitosan sensitivity. The second was a Crz1p-mediated response, which is delayed compared to the Cin5p response. Crz1p is a transcription factor of the calcineurin pathway. Cells deleted for CRZ1 or treated with the calcineurin inhibitor FK506 became hypersensitive to chitosan, supporting the notion that the Crz1p-controlled response offers protection against chitosan. The third was a strong Rlm1p-mediated response which ran parallel in time with the Crz1p-regulated response. Rlm1p is a transcription factor of the cell wall integrity pathway, which is activated by cell wall stress. Importantly, chitosan-treated cells became more resistant to beta-1,3-glucanase, which is a well-known response to cell wall stress. We propose that the transcriptional response to chitosan may be representative of other plasma membrane-perturbing compounds.

Yapsins are a family of aspartyl proteases required for cell wall integrity in Saccharomyces cerevisiae

The yeast cell wall is a crucial extracellular organelle that protects the cell from lysis during environmental stress and morphogenesis. Here, we demonstrate that the yapsin family of five glycosylphosphatidylinositol-linked aspartyl proteases is required for cell wall integrity in Saccharomyces cerevisiae. Yapsin null mutants show hypersensitivity to cell wall perturbation, and both the yps1Delta2Delta mutant and the quintuple yapsin mutant (5ypsDelta) undergo osmoremedial cell lysis at 37 degrees C. The cell walls of both 5ypsDelta and yps1Delta2Delta mutants have decreased amounts of 1,3- and 1,6-beta-glucan. Although there is decreased incorporation of both 1,3- and 1,6-beta-glucan in the 5ypsDelta mutant in vivo, in vitro specific activity of both 1,3- and 1,6-beta-glucan synthesis is similar to wild type, indicating that the yapsins affect processes downstream of glucan synthesis and that the yapsins may be involved in the incorporation or retention of cell wall glucan. Presumably as a response to the significant alterations in cell wall composition, the cell wall integrity mitogen-activated kinase signaling cascade (PKC1-MPK pathway) is basally active in 5ypsDelta. YPS1 expression is induced during cell wall stress and remodeling in a PKC1-MPK1-dependent manner, indicating that Yps1p is a direct, and important, output of the cell wall integrity response. The Candida albicans (SAP9) and Candida glabrata (CgYPS1) homologues of YPS1 complement the phenotypes of the yps1Delta mutant. Taken together, these data indicate that the yapsins play an important role in glucan homeostasis in S. cerevisiae and that yapsin homologues may play a similar role in the pathogenic yeasts C. albicans and C. glabrata.

Estrogen inhibits cardiomyocyte hypertrophy in vitro. Antagonism of calcineurin-related hypertrophy through induction of MCIP1

Evidence from in vivo studies suggests that some inputs to cardiac hypertrophy are opposed by the actions of estrogen. However, the mechanisms of E2 action in this respect are mainly unknown. An important pathway that is utilized by multiple hypertrophic stimuli involves the activation of the tyrosine phosphatase, calcineurin (PP2B). Here we show that 17beta-estradiol (E2) significantly prevents angiotensin II (AngII)- or endothelin-1 (ET-1)-induced new protein synthesis, skeletal muscle actin expression, and increased surface area in cultured rat cardiomyocytes. ET-1 stimulated calcineurin phosphatase activity, resulting in new protein synthesis, and both were prevented by E2. E2 induced the MCIP1 gene, an inhibitor of calcineurin activity, via phosphatidylinositol 3-kinase, transcriptional, and mRNA stability mechanisms. Small interfering RNA for MCIP1 significantly reversed both the E2 restraint of protein synthesis and the inhibition of AngII-induced calcineurin activity. AngII-induced the translocation of the hypertrophic transcription factor, NF-AT, to the nucleus of the cardiomyocyte and stimulated NF-AT transcriptional activity. Both were prevented by E2. AngII also stimulated the activation of ERK and protein kinase C, contributing to cardiac hypertrophy. E2 inhibited these pathways, related to the stimulation of atrial natriuretic peptide production and secretion. Thus, restraint of calcineurin and kinase signaling to the hypertrophic program underlie these important effects of E2.

Transient receptor potential vanilloid type 1 activation down-regulates voltage-gated calcium channels through calcium-dependent calcineurin in sensory neurons

Calcium influx through voltage-activated Ca(2+) channels (VACCs) plays a critical role in neurotransmission. Capsaicin application inhibits VACCs and desensitizes nociceptors. In this study, we determined the signaling mechanisms of the inhibitory effect of capsaicin on VACCs in primary sensory neurons. Whole-cell voltage clamp recordings were performed in acutely isolated rat dorsal root ganglion neurons. Capsaicin caused a profound decrease in the Ca(2+) current (I(Ca)) density in capsaicin-sensitive, but not -insensitive, dorsal root ganglion neurons. At 1 mum, capsaicin suppressed about 60% of N-, P/Q-, L-, and R-type I(Ca) density. Pretreatment with iodoresiniferatoxin, a specific transient receptor potential vanilloid type 1 (TRPV1) antagonist, or intracellular application of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid blocked the inhibitory effect of capsaicin on I(ca). However, neither W-7, a calmodulin blocker, nor KN-93, a CaMKII inhibitor, attenuated the inhibitory effect of capsaicin on I(Ca). Furthermore, intracellular dialysis of deltamethrin or cyclosporin A, the specific calcineurin (protein phosphatase 2B) inhibitors, but not okadaic acid (a selective protein phosphatase 1/protein phosphatase 2A inhibitor), abolished the effect of capsaicin on I(Ca). Interestingly, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, deltamethrin, cyclosporin A, and okadaic acid each alone significantly increased the I(Ca) density and caused a depolarizing shift in the voltage dependence of activation. Immunofluorescence labeling revealed that capsaicin induced a rapid internalization of Ca(V)2.2 channels on the membrane. Thus, this study provides novel information that VACCs are tonically modulated by the intracellular Ca(2+) level and endogenous phosphatases in sensory neurons. Stimulation of TRPV1 by capsaicin down-regulates VACCs by dephosphorylation through Ca(2+)-dependent activation of calcineurin.

Concentrations of cyclosporin A and FK506 that inhibit IL-2 induction in human T cells do not affect TGF-beta1 biosynthesis, whereas higher doses of cyclosporin A trigger apoptosis and release of preformed TGF-beta1

Cyclosporin A (CsA) and FK506 suppress T cell activation by inhibiting calcineurin and the calcineurin-dependent transcription factors nuclear factor of activated T cells (NFATc), which are central regulators of T cell function. It was reported that CsA up-regulated the transcription of transforming growth factor-beta1 (TGF-beta1) in lymphocytes and other cells and activated its promoter in A549 lung carcinoma cells, but the mechanisms involved are poorly understood, and it is unclear whether calcineurin plays any role. We have studied the regulation of TGF-beta1 in normal human lymphocytes and cell lines. In Jurkat T cells, the TGF-beta1 promoter was activated by calcineurin and NFATc and inhibited by CsA and FK506. However, the promoter was insensitive to both drugs in A549 cells. In human T cells preactivated with phytohemagglutinin, biosynthesis of TGF-beta1, induced by the T cell receptor (TCR) or the TGF-beta receptor, was not substantially affected by CsA and FK506 concentrations (< or = 1 microM) that effectively inhibited interleukin-2 production. However, pretreatment of fresh lymphocytes with CsA or FK506 during primary TCR stimulation reduced their production of TGF-beta1 during secondary TCR activation. Finally, high concentrations of CsA (10 microM), in the range attained in vivo in experiments in rodents, caused apoptosis in human T cells and the release of preformed, bioactive TGF-beta1. These effects are unlikely to owe to calcineurin inhibition, as they were not observed with FK506. Our results indicate that CsA and FK506 are not general inducers of TGF-beta1 biosynthesis but can cause different effects on TGF-beta1 depending on the cell type and concentrations used.

Inhibitory interactions of calcineurin (phosphatase 2B) and calmodulin on rat hippocampal NMDA receptors

Calcineurin, protein phosphatase 2B, is a calcium-binding protein that has been shown to modulate NMDA receptor activity (Regulation of NMDA channel function by endogenous Ca(2+)-dependent phosphatase. Nature 369 (1994) 235; Regulation of glycine-insensitive desensitisation of the NMDA receptor in outside-out patches. J. Neurophysiol. 71 (1994) 754; Calcineurin acts via the C-terminus of NR2A to modulate desensitization of NMDA receptors. Neuropharmacology 42 (2002) 593) and synaptic transmission (Synaptic desensitization of NMDA receptors by calcineurin. Science 267 (1995) 1510; beta-adrenergic regulation of synaptic NMDA receptors by cAMP-dependent protein kinase. Neuron 16 (1996) 415). Calmodulin, a necessary co-factor for calcineurin (Calmodulin binding by calcineurin. J. Biol. Chem. 262 (1987) 15062), has also been shown to inhibit NMDA receptor activity (Inactivation of NMDA receptors by direct interaction of calmodulin with the NR1 subunit. Cell 84 (1996) 745; Direct effects of calmodulin on NMDA receptor single-channel gating in rat hippocampal granule cells. J. Neurosci. 22 (2002) 8860) in a calcium dependent manner (Calmodulin mediates calcium-dependent inactivation of N-methyl-d-aspartate receptors. Neuron 21 (1998) 443; Interactions of calmodulin and alpha-actinin with the NR1 subunit modulate calcium-dependent inactivation of NMDA receptors. J. Neurosci. 19 (1999) 1165). In order to gain insight into the likely actions and interactions of calcineurin and calmodulin at excitatory synapses, we have investigated the effects of these two proteins on single NMDA receptor channel activity. Calcineurin and calmodulin are both known to reduce channel open time (Regulation of NMDA channel function by endogenous Ca(2+)-dependent phosphatase. Nature 369 (1994) 235; Inactivation of NMDA receptors by direct interaction of calmodulin with the NR1 subunit. Cell 84 (1996) 745), and the duration of receptor activations or superclusters. They are, therefore, predicted to shorten the synaptic current decay (Regulation of NMDA channel function by endogenous Ca(2+)-dependent phosphatase. Nature 369 (1994) 235; Direct effects of calmodulin on NMDA receptor single-channel gating in rat hippocampal granule cells. J. Neurosci. 22 (2002) 8860). In agreement with Lieberman and Mody (Regulation of NMDA channel function by endogenous Ca(2+)-dependent phosphatase. Nature 369 (1994) 235), the results of this study indicate calcineurin plus calmodulin reduces channel open time. However, this effect is not as pronounced as that observed in the presence of calmodulin alone. Calcineurin plus calmodulin was also found to increase single channel shut time. We conclude that in addition to its direct effects on single channel activity, calcineurin regulates the effects of calmodulin on NMDA receptor activity.

The calcineurin target, Crz1, functions in azole tolerance but is not required for virulence of Candida albicans

In Candida albicans, calcineurin is essential for virulence and survival during membrane perturbation by azoles. Crz1 is a proposed downstream target of calcineurin based on studies of Saccharomyces cerevisiae. However, the in vitro phenotypes of C. albicans crz1/crz1 and calcineurin mutants differ and Crz1 is not required for virulence.

Extracellular pressure stimulates colon cancer cell adhesion in vitro and to surgical wounds by Src (sarcoma protein) activation

BACKGROUND

We hypothesized that pressure stimulates colon cancer cell adhesion to surgical wounds.

METHODS

We quantitated adhesion of murine 26/51 transplantable colon cancer cells by cell counting or chromium 51-labeling. Tumor cells were added to murine surgical wounds after 30 minutes preincubation under ambient or 15 mm Hg increased pressure. Src activation was assayed by immunoblotting for phosphorylated Src and inhibited by 4-amino-5-(4chlorophenyl)-7-(t-butyl)pyrazolo-[3-4-d]pyrimidine (PP2).

RESULTS

Pressure stimulated colon 26/51 cell adhesion to murine wounds by 43% to 52% (n = 9, P <0.05 each). Pressure stimulated Src phosphorylation by 39% +/- 4% (n = 5, P = 0.004) in colon 26 cells. The Src inhibitor PP2 (20 mumol/L) did not inhibit Src phosphorylation at ambient pressure but prevented pressure stimulation of Src phosphorylation. Src blockade by PP2 did not affect basal adhesion of either tumor to murine wounds but completely blocked pressure stimulation of adhesion (n = 4, P <0.001 each).

CONCLUSIONS

Increased pressure may activate cancer adhesion to surgical wounds via Src. Src antagonists might inhibit this process.

Ca2+ Controls Functional Expression of the Cardiac K+ Transient Outward Current via the Calcineurin Pathway

The transient outward K+ current (Ito) modulates transmembrane Ca2+ influx into cardiomyocytes, which, in turn, might act on Ito. Here, we investigated whether Ca2+ modifies functional expression of Ito. Whole-cell Ito were recorded using the patch clamp technique in single right ventricular myocytes isolated from adult rats and incubated for 24 h at 37 degrees C in a serum-free medium containing various Ca2+ concentrations ([Ca2+]o). Increasing the [Ca2+]o from 0.5 to 1.0 and 2.5 mM produced a gradual decrease in Ito density without change in current kinetics. Quantitativereverse transcriptase-PCR showed that a decrease of the Kv4.2 mRNA could account for this decrease. In the acetoxymethyl ester form of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM)-loaded myocytes (a permeant Ca2+ chelator), Ito density increased significantly when cells were exposed for 24 h to either 1 or 2.5 mM [Ca2+]o. Moreover, 24-h exposure to the Ca2+ channel agonist, Bay K8644, in 1 mM [Ca2+]o induced a decrease in Ito density, whereas the Ca2+ channel antagonist, nifedipine, blunted Ito decrease in 2.5 mM [Ca2+]o. The decrease of Ito in 2.5 mM [Ca2+]o was also prevented by co-incubation with either the calmodulin inhibitor W7 or the calcineurin inhibitors FK506 or cyclosporin A. Furthermore, in myocytes incubated for 24 h with 2.5 mM [Ca2+]o, calcineurin activity was significantly increased compared with 1 mM [Ca2+]o. Our data suggest that modulation of [Ca2+]i via L-type Ca2+ channels, which appears to involve the Ca2+/calmodulin-regulated protein phosphatase calcineurin, down-regulates the functional expression of Ito. This effect might be involved in many physiological and pathological modulations of Ito channel expression in cardiac cells, as well other cell types.

Protein phosphatase 2B dephosphorylates twitchin, initiating the catch state of invertebrate smooth muscle

"Catch" is the state where some invertebrate muscles sustain high tension for long periods at low ATP hydrolysis rates. Physiological studies using muscle fibers have not yet fully provided the details of the initiation process of the catch state. The process was extensively studied by using an in vitro reconstitution assay with several phosphatase inhibitors. Actin filaments bound to thick filaments pretreated with the soluble protein fraction of muscle homogenate and Ca2+ (catch treatment) in the presence of MgATP at a low free Ca2+ concentration (the catch state). Catch treatment with > 50 microm okadaic acid, > 1 microm microcystin LR, 1 microm cyclosporin A, 1 microm FK506, or 0.2 mm calcineurin autoinhibitory peptide fragment produced almost no binding of the actin filaments, indicating protein phosphatase 2B (PP2B) was involved. Use of bovine calcineurin (PP2B) and its activator calmodulin instead of the soluble protein fraction initiated the catch state, indicating that only PP2B and calmodulin in the soluble protein fraction are essential for the initiation process. The initiation was reproduced with purified actin, myosin, twitchin, PP2B, and calmodulin. 32P autoradiography showed that only twitchin was dephosphorylated during the catch treatment with either the soluble protein fraction or bovine calcineurin and calmodulin. These results indicate that PP2B directly dephosphorylates twitchin and initiates the catch state and that no other component is required for the initiation process of the catch state.

Clinical trials: where are we now?

Clinical trials in transplantation have focused on improving outcomes and minimizing side effects associated with renal transplantation. Although immunologic tolerance, which means complete freedom from immunosuppressive drugs and maintenance of excellent long-term graft function, has seldom been achieved, in rare cases, this has been accomplished. Most current clinical trials focus on minimization of steroid use and calcineurin inhibitor use as a step toward tolerance, sometimes termed prope tolerance. Alternatively, new immunosuppressive agents are studied to assess their efficacy in preventing graft rejection with the anticipation of lesser toxicity. This review is organized in a case presentation style with actual cases from the University of Wisconsin kidney transplant experience presented as illustrations of actual scenarios in clinical trials. Lessons learned from these particular patients are then summarized with reference to the literature associated with the case. Using this format, some of the important lessons learned from clinical trials are outlined and directions for future study are noted. Clinical trials have permitted a dramatic improvement in graft survival and lowering of infectious and malignant side effects over the past 30-40 years. Nevertheless, we remain far from achieving true tolerance in patients for a variety of reasons.

Functional obstruction: the renal pelvis rules

Failure in the peristaltic mechanism that conducts urine from the kidney to the bladder can lead to hydronephrosis, a common birth defect associated with obstructive nephropathy. New animal models reveal molecular pathways important for peristalsis and point to the central role of the renal pelvis in urine transport.

c-Fos phosphorylation induced by H2O2 prevents proteasomal degradation of c-Fos in cardiomyocytes

Oxidants cause activation of the AP-1 transcription factor in cardiomyocytes. c-Fos, a component of the AP-1 transcription factor, is transiently induced by H2O2 and the induction is sensitive to the protein synthesis inhibitor cycloheximide. With high percentage gel electrophoresis, multiple c-Fos bands were resolved by Western blot analyses, indicating post-translational modification of newly synthesized c-Fos protein after H2O2 exposure. Treatment of immunoprecipitated c-Fos protein with the type 2 serine/threonine phosphatase A (PP2A) and immunoblotting of c-Fos protein with antibodies against phosphorylated serine or threonine demonstrated that c-Fos was phosphorylated at serine residues. A pharmacological inhibitor of JNKs inhibited the formation of multiple c-Fos bands without affecting c-fos transcription. The proteasomal inhibitor MG132 and Proteasome Inhibitor I extended the time course of c-Fos protein elevation. An increase in ubiquitin was detectable in c-Fos protein from H2O2-treated cells. Interestingly, treating the whole cell lysates with PP2A, but not calcineurin (i.e. PP2B), resulted in disappearance of c-Fos protein and MG132 was able to prevent this loss. H2O2 caused an elevation of PP2B and total phosphatase activity. The phosphatase inhibitor okadaic acid, but not PP2B inhibiter cypermethrin, extended the time course of c-Fos protein elevation after H2O2 exposure. These data suggest that JNK-mediated phosphorylation of newly synthesized c-Fos protects the protein from being degraded by the proteasome. PP2B independent dephosphorylation contributes to degradation of c-Fos protein during oxidative stress response of cardiomyocytes.

Differential modulation of glutamatergic and cholinergic synapses by calcineurin in hippocampal CA1 fast-spiking interneurons

How signaling molecules in inhibitory interneurons modulate and coordinate the integration of synaptic inputs remains largely unknown. We investigated the kinetics and modulation of glutamatergic and cholinergic synapses on CA1 fast-spiking interneurons in hippocampal slices by using whole-cell clamp recording. Spontaneous synaptic currents mediated by either AMPA-type glutamate or nicotinic acetylcholine receptors on the interneurons can be classified into fast, slow and fast-slow based on their duration and decay phase. Effects of calcineurin, calmodulin-dependent protein phosphatase, on these two groups of synapses were examined by infusing an autoinhibitory peptide of calcineurin (CaN-AIP) into the recording neurons. CaN-AIP enhanced the amplitude of glutamatergic fast-EPSCs, as well as both amplitude and frequency of cholinergic fast-EPSCs. No significant changes in slow-EPSCs were observed during the infusion of CaN-AIP. Our results indicate that signal transmission at synapses, which are mediated by either AMPA-type glutamate or nicotinic acetylcholine receptors, appears different in the kinetics. The selective influence of calcineurin on different synapses in fast-spiking interneurons may play an important role in coordinating thousands of synaptic inputs in order to set neuronal excitability at proper levels.

FK506 sensitizes mammalian cells to high osmolarity by modulating p38 MAP kinase activation

The immunosuppressants tacrolimus (FK506) and cyclosporin A (CsA) have increased the survival rates in organ transplantation. Both drugs inhibit the protein phosphatase calcineurin (CaN) in activated T cells, exhibiting similar side-effects. Diabetes is observed more often in FK506 than CsA therapy, probably due to inhibition of new molecular targets other than CaN. We studied FK506 toxicity in mammalian cells. FK506, but not CsA, regulated p38 activation by osmotic stress, and decreased viability in osmostressed cells. In addition, FK506 treatment strongly increased the phosphorylation of the eukaryotic initiation factor-2alpha (eIF-2alpha) subunit. eIF-2alpha phosphorylation, p38 inhibition and cell lethality were relieved by addition of excess amino acids to the medium, suggesting that amino acid availability mediated FK506 toxicity. Therefore, these FK506-dependent responses could be relevant to the non-therapeutic effects of FK506 therapy.

Calcineurin Contributes to the Enhancing Effect of Adenosine on Nerve Growth Factor-Induced Neurite Outgrowth via the Decreased Duration of p38 Mitogen-Activated Protein Kinase Phosphorylation

Adenosine enhances nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells. We found that adenosine increases NGF-induced phosphorylation of extracellular signal-regulated kinase (ERK), but decreases the duration of phosphorylation of p38 mitogen-activated protein (MAP) kinase. Therefore, we further examined the involvement of protein phosphatase in these effects of adenosine. FK506, a specific calcineurin inhibitor, inhibited the enhancing effect of adenosine on the NGF-induced neurite outgrowth and increased the duration of p38 MAP kinase phosphorylation without affecting ERK phosphorylation. These results suggest that adenosine decreases the duration of p38 MAP kinase via calcineurin activation, which contributes to the enhancement of NGF-induced neurite outgrowth.