Calcium regulation of basic helix-loop-helix transcription factors

Hermann, Stefan; Saarikettu, Juha; Onions, Jacqueline; Hughes, Kate; Grundström, Thomas

doi:10.1016/s0143-4160(98)90112-9

Cited by 32 publications

(16 citation statements)

References 67 publications

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“…This interaction inhibits DNA binding and mediates nuclear export of the nuclear hormone receptor (6). In a similar vein, Ca 2ϩ /CaM binds to the DNA binding domain of members of the basic helix-loop-helix family of transcription factors to inhibit their interaction with DNA (14). The possibility exists that the NLS of GRK5 is itself a Ca 2ϩ /CaM-binding domain, the accessibility of which is regulated by the interaction of Ca 2ϩ /CaM with the N terminus of the enzyme.…”

Section: Vol 24 2004mentioning

confidence: 99%

G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

Johnson

Scott

Pitcher

2004

Molecular and Cellular Biology

110

117

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G protein-coupled receptor kinases (GRKs) mediate desensitization of agonist-occupied G protein-coupled receptors (GPCRs). Here we report that GRK5 contains a DNA-binding nuclear localization sequence (NLS) and that its nuclear localization is regulated by GPCR activation, results that suggest potential nuclear functions for GRK5. As assessed by fluorescence confocal microscopy, transfected and endogenous GRK5 is present in the nuclei of HEp2 cells. Mutation of basic residues in the catalytic domain of GRK5 (between amino acids 388 and 395) results in the nuclear exclusion of the mutant enzyme (GRK5 ⌬NLS ), demonstrating that GRK5 contains a functional NLS. The nuclear localization of GRK5 is subject to dynamic regulation. Calcium ionophore treatment or activation of Gq-coupled muscarinic-M3 receptors promotes the nuclear export of the kinase in a Ca 2؉ /calmodulin (Ca 2؉ /CaM)-dependent fashion. Ca 2؉ /CaM binding to the N-terminal CaM binding site of GRK5 mediates this effect. Furthermore, GRK5, but not GRK5 ⌬NLS or GRK2, binds specifically and directly to DNA in vitro. Consistent with their presence in the nuclei of transfected cells, all the GRK4, but not GRK2, subfamily members contain putative NLSs. These results suggest that the GRK4 subfamily of GRKs may play a signaling role in the nucleus and that GRK4 and GRK2 subfamily members perform divergent cellular functions.G protein-coupled receptor kinases (GRKs) comprise a family of seven serine/threonine protein kinases that phosphorylate agonist-bound, activated, G protein-coupled receptors (GPCRs). GRK-mediated GPCR phosphorylation initiates ␤-arrestin binding, receptor uncoupling from the G protein, and targeting of the ␤-arrestin-receptor complex to a clathrin-coated pit for internalization. The receptor may then be degraded or returned to the cell surface for a further round of signaling (reviewed in reference 4).Seven mammalian GRKs have been identified, which are divided into three subfamilies on the basis of sequence homology and the regulatory mechanisms controlling their activity (reviewed in reference 24): the GRK1-like subfamily, GRK1 (or rhodopsin kinase) and GRK7; the GRK2-like subfamily, GRK2 (␤-adrenergic kinase) and GRK3 (␤-adrenergic kinase 2); and the GRK4-like subfamily, GRK4, GRK5, and GRK6. Four splice variants of GRK4 (␣, ␤, ␥, and ␦) and three splice variants of GRK6 (A, B, and C) have been identified (24).GRKs are regulated by several mechanisms, including modulation of their subcellular localization, kinase activity, and expression (reviewed in reference 21). In many instances, regulation of GRK activity is subfamily specific. PKC phosphorylation results in activation of GRK2 but inhibition of GRK5 activity (21). Additionally, the three GRK subfamilies display differential affinities for calcium binding proteins. GRK1 binds Ca 2ϩ /recoverin, and GRK4␣, GRK5, and GRK6A, -B and -C bind Ca 2ϩ /calmodulin (Ca 2ϩ /CaM) with high affinity (reviewed in reference 32). In contrast, GRK2 exhibits an approximately 40-fold lower affinity for C...

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Section: Vol 24 2004mentioning

confidence: 99%

G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

Johnson

Scott

Pitcher

2004

Molecular and Cellular Biology

110

117

View full text Add to dashboard Cite

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“…CaM is a key mediator of signals by the secondary messenger Ca 2ϩ , and it has been shown to be an essential regulator of cell cycle progression, cell motility and contraction, ion homeostasis, and other fundamental cellular processes (65). CaM is also involved in the regulation of transcription (6,12,13,22), not only indirectly through CaM-dependent kinases and phosphatases, but also directly through interaction with transcription factors (10,21,47,61).…”

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confidence: 99%

Regulation of c-Rel Nuclear Localization by Binding of Ca²⁺/Calmodulin

Antonsson

Hughes

Edin

et al. 2003

Molecular and Cellular Biology

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“…However, overexpression of constitutively active variants of calmodulin-dependent kinase II or IV or calcineurin did not have any significant effect on the transcriptional activity of E12 or E47 (data not shown). Furthermore, specific inhibitors of calmodulin-dependent kinases II and IV and calcineurin did not affect ionomycin-induced inhibition of the transcriptional activity of E47 (28). Collectively, these data suggest that no calmodulin-dependent change in the phosphorylation status of E12/E47 or any other component in the E12/E47 transcription complex contributes to the Ca 2ϩ regulation of the transcriptional activity of E12/E47.…”

Section: Discussionmentioning

confidence: 80%

Calcium/Calmodulin Inhibition of Transcriptional Activity of E-proteins by Prevention of Their Binding to DNA

Saarikettu

Sveshnikova

Grundström

2004

Journal of Biological Chemistry

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The Ca 2؉ sensor protein calmodulin can interact with the DNA binding basic helix-loop-helix (bHLH) domain of E12, E47, and SEF2-1 (E2-2), which belong to the Eprotein subclass of bHLH transcription factors. This interaction inhibits the DNA binding of these bHLH proteins in vitro, and an ionophore that increases intracellular Ca 2؉ can inhibit transcriptional activation by the E-proteins. Here we have attempted to determine if these phenomena reflect a direct calmodulin-dependent inhibition of DNA binding by E-proteins in vivo. We show that calmodulin overexpression inhibits the transcriptional activity of E12, E47, and SEF2-1. We have compared calmodulin effects on DNA binding in vitro and on activation of transcription in vivo using a series of E12 mutants harboring defined alterations within the basic sequence of the bHLH domain that reduce their ability to bind calmodulin to varying degrees. We find a striking direct correlation between the ability of calmodulin to inhibit their DNA binding in vitro and the ability of overexpressed calmodulin or cellular Ca 2؉ mobilization to inhibit their transcriptional activity in vivo. Furthermore, E12 and overexpressed calmodulin were co-localized in the nucleus, and calmodulin pulldown experiments with cell extracts showed a Ca 2؉ -dependent interaction between calmodulin and E12 but not with a calmodulin inhibition-deficient E12 mutant. Chromatin immunoprecipitation showed that calmodulin overexpression leads to decreased binding of E12 and E47, but not a calmodulin inhibition-deficient E12 mutant, to the DNA recognition sequence in vivo. The data suggest that Ca 2؉ signaling can inhibit the transcriptional activities of E-proteins through direct binding of Ca 2؉ /calmodulin to the basic sequence of E-proteins, resulting in inhibition of their DNA binding.Calmodulin is a ubiquitously expressed regulator of numerous cellular processes including cell cycle progression, cell mobility and contraction, ion homeostasis, and transcription. Most target proteins bind to the Ca 2ϩ -loaded form of calmodulin. Therefore, upon signals leading to increased intracellular Ca 2ϩ concentration, calmodulin is able to bind to a new set of target proteins and modulate their activity (1). Several transcriptional regulators are direct targets for calmodulin or are regulated by calmodulin-dependent kinases or the calmodulin-dependent phosphatase calcineurin (2, 3).Basic helix-loop-helix (bHLH) 1 proteins are a large family of transcription factors that are important regulators of many cellular functions including differentiation processes such as myogenesis, hematopoiesis, and neurogenesis (4). bHLH transcription factors can be divided into several classes based on their structure, dimerization properties, function, and expression pattern. E-proteins (class I bHLH transcription factors) are encoded by three mammalian genes, E2A, SEF2-1 (also denoted E2-2), and HEB. The E2A gene encodes the alternatively spliced protein products E12 and E47 (4). E-proteins usually function as heterodimers wi...

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Calcium regulation of basic helix-loop-helix transcription factors

Cited by 32 publications

References 67 publications

G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

Regulation of c-Rel Nuclear Localization by Binding of Ca²⁺/Calmodulin

Calcium/Calmodulin Inhibition of Transcriptional Activity of E-proteins by Prevention of Their Binding to DNA

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Calcium regulation of basic helix-loop-helix transcription factors

Cited by 32 publications

References 67 publications

G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

G Protein-Coupled Receptor Kinase 5 Contains a DNA-Binding Nuclear Localization Sequence

Regulation of c-Rel Nuclear Localization by Binding of Ca2+/Calmodulin

Calcium/Calmodulin Inhibition of Transcriptional Activity of E-proteins by Prevention of Their Binding to DNA

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Regulation of c-Rel Nuclear Localization by Binding of Ca²⁺/Calmodulin