Rapid shuttling of NF-AT in discrimination of Ca2+ signals and immunosuppression

Timmerman, Luika; Clipstone, Neil A.; Ho, Steffan N.; Northrop, Jeffrey P.; Crabtree, Gerald R.

doi:10.1038/383837a0

Cited by 498 publications

(385 citation statements)

References 28 publications

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“…Figure 5a shows the distribution before (left panel), and 5 minutes after (right panel), ionomycin addition. This observed translocation of CaM is consistent with previously reported nuclear enrichment of CaM in other cell types [12,27,31,32]. Figure 5b shows that the CaM translocation to the nucleus is reversible when a transient calcium signal is applied.…”

Section: Calmodulin Rapidly Exchanges Between Nucleus and Cytosol At supporting

confidence: 92%

“…The faster equilibration time of the two proteins at high calcium concentration may reflect calcium-induced differences in nuclear pore permeability. Independently of the free calcium concentration, the measured exchange times are more rapid than those reported for active nuclear transport of CaM-binding proteins [31,32]. This suggests that the relatively small sizes of GFP and CaM allow these proteins to equilibrate between the nucleus and cytosol by diffusion.…”

Section: Calmodulin Rapidly Exchanges Between Nucleus and Cytosol At mentioning

confidence: 77%

“…Although earlier studies suggested that CaM can be actively transported into the nucleus along with calcineurin [32], Ca 2+ -CaM kinase II isoforms [38], or possibly by other processes [14], the small size of CaM (17 kDa) makes it likely that the flux of CaM between nucleus and cytosol is mainly by diffusion. A diffusion or facilitated diffusion mechanism has been suggested previously from nuclear CaM influx and efflux studies which used permeabilized cells combined with blockers of active transport and externally added CaM sinks [12,16].…”

Section: Molecular Mechanism For the Control Of The Nuclear Free Ca 2mentioning

confidence: 99%

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Mobilization of late-endosomal cholesterol is inhibited by Rab guanine nucleotide dissociation inhibitor

et al. 2000

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Background: Many targets of calcium signaling pathways are activated or inhibited by binding the Ca 2+ -liganded form of calmodulin (Ca 2+ -CaM). Here, we test the hypothesis that local Ca 2+ -CaM-regulated signaling processes can be selectively activated by local intracellular differences in free Ca 2+ -CaM concentration.Results: Energy-transfer confocal microscopy of a fluorescent biosensor was used to measure the difference in the concentration of free Ca 2+ -CaM between nucleus and cytoplasm. Strikingly, short receptor-induced calcium spikes produced transient increases in free Ca 2+ -CaM concentration that were of markedly higher amplitude in the cytosol than in the nucleus. In contrast, prolonged increases in calcium led to equalization of the nuclear and cytosolic free Ca 2+ -CaM concentrations over a period of minutes. Photobleaching recovery and translocation measurements with fluorescently labeled CaM showed that equalization is likely to be the result of a diffusion-mediated net translocation of CaM into the nucleus. The driving force for equalization is a higher Ca 2+ -CaM-buffering capacity in the nucleus compared with the cytosol, as the direction of the free Ca 2+ -CaM concentration gradient and of CaM translocation could be reversed by expressing a Ca 2+ -CaM-binding protein at high concentration in the cytosol.Conclusions: Subcellular differences in the distribution of Ca 2+ -CaM-binding proteins can produce gradients of free Ca 2+ -CaM concentration that result in a net translocation of CaM. This provides a mechanism for dynamically regulating local free Ca 2+ -CaM concentrations, and thus the local activity of Ca 2+ -CaM targets. Free Ca 2+ -CaM signals in the nucleus remain low during brief or low-frequency calcium spikes, whereas high-frequency spikes or persistent increases in calcium cause translocation of CaM from the cytoplasm to the nucleus, resulting in similar concentrations of nuclear and cytosolic free Ca 2+ -CaM.

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Section: Calmodulin Rapidly Exchanges Between Nucleus and Cytosol At supporting

confidence: 92%

Section: Calmodulin Rapidly Exchanges Between Nucleus and Cytosol At mentioning

confidence: 77%

Section: Molecular Mechanism For the Control Of The Nuclear Free Ca 2mentioning

confidence: 99%

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Mobilization of late-endosomal cholesterol is inhibited by Rab guanine nucleotide dissociation inhibitor

et al. 2000

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“…PP-2B dephosphorylates (on multiples serines) the transcription complex NFAT, exposing its nuclear localization signal (Crabtree, 2001;Rao et al, 1997). The dephosphorylated NFAT complex is maintained in the nucleus as long as Ca 2+ concentrations are elevated, thus keeping PP-2B in the activated state (Timmerman et al, 1996). Inhibition of PP-2B by cyclosporin or FK506 (tacrolimus) decreases GLP-1-induced insulin transcription via suppression of binding of NFAT to the insulin promoter region (see section 5.2).…”

Section: Calcium/calmodulin Pathwaymentioning

confidence: 99%

Mechanisms of action of glucagon-like peptide 1 in the pancreas

Doyle

Egan

2007

Pharmacology & Therapeutics

576

465

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Glucagon-like peptide-1 is a hormone that is encoded in the proglucagon gene. It is mainly produced in enteroendocrine L cells of the gut and is secreted into the blood stream when food containing fat, protein hydrolysate and/or glucose enters the duodenum. Its particular effects on insulin and glucagon secretion have generated a flurry of research activity over the past twenty years culminating in a naturally occurring GLP-1 receptor agonist, exendin-4, now being used to treat type 2 diabetes. GLP-1 engages a specific G-protein coupled receptor that is present in tissues other than the pancreas (brain, kidney, lung, heart, major blood vessels). The most widely studied cell activated by GLP-1 is the insulin-secreting beta cell where its defining action is augmentation of glucose-induced insulin secretion. Upon GLP-1 receptor activation, adenylyl cyclase is activated and cAMP generated, leading, in turn, to cAMP-dependent activation of second messenger pathways, such as the PKA and Epac pathways. As well as short-term effects of enhancing glucose-induced insulin secretion, continuous GLP-1 receptor activation also increases insulin synthesis, and beta cell proliferation and neogenesis. Although these latter effects cannot be currently monitored in humans, there are substantial improvements in glucose tolerance and increases in both first phase and plateau phase insulin secretory responses in type 2 diabetic patients treated with exendin-4. This review we will focus on the effects resulting from GLP-1 receptor activation in islets of Langerhans

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“…Once activated, NFAT proteins translocate into the nucleus, bind to regulatory elements of NFAT target genes, interact with other nuclear proteins and control transcription. When calcineurin is inactivated by a decrease in free Ca 2+ level, NFAT factors are rapidly re-phosphorylated and exported from the nucleus to the cytoplasm [6].…”

Section: Introductionmentioning

confidence: 99%

Inhibition of calcineurin‐NFAT signaling by the pyrazolopyrimidine compound NCI3

et al. 2007

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Dephosphorylation of NFAT by the Ca 2+ -calmodulin-dependent Ser/Thr protein phosphatase calcineurin is a bottleneck of T cell receptor-dependent activation of T cells. In dimeric complexes with immunophilins, the immunosuppressants cyclosporine A (CsA) and tacrolimus (FK506) block this process by inhibition of the enzymatic activity of calcineurin. We have identified the pyrazolopyrimidine compound NCI3 as a novel inhibitor of calcineurin-NFAT signaling. Similar to CsA and FK506, NCI3 inhibits dephosphorylation and nuclear translocation of NFAT, IL-2 production and proliferation of stimulated human primary T cells with IC 50 values from 2 to 4.5 lM. However, contrary to CsA and FK506, NCI3 neither blocks calcineurin`s phosphatase activity nor requires immunophilins for inhibiting NFAT activation. Our data suggest that NCI3 binds to calcineurin and causes an allosteric change interfering with NFAT dephosphorylation in vivo but not in vitro. NCI3 acts not only on the endogenous calcineurin but also on a C-terminally truncated, constitutively active version of calcineurin. The novel inhibitor described herein will be useful in better defining the cellular regulation of calcineurin activation and may serve as a lead for the development of a new type of immunosuppressants acting not by direct inhibition of the calcineurin phosphatase activity.

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Rapid shuttling of NF-AT in discrimination of Ca2+ signals and immunosuppression

Cited by 498 publications

References 28 publications

Mobilization of late-endosomal cholesterol is inhibited by Rab guanine nucleotide dissociation inhibitor

Mobilization of late-endosomal cholesterol is inhibited by Rab guanine nucleotide dissociation inhibitor

Mechanisms of action of glucagon-like peptide 1 in the pancreas

Inhibition of calcineurin‐NFAT signaling by the pyrazolopyrimidine compound NCI3

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