JNK suppresses melanogenesis by interfering with CREB-regulated transcription coactivator 3-dependent MITF expression

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Abstract

Melanogenesis is a critical self-defense mechanism against ultraviolet radiation (UVR)-induced skin damage and carcinogenesis; however, dysregulation of melanin production and distribution causes skin-disfiguring pigmentary disorders. Melanogenesis is initiated by UVR-induced cAMP generation and ensuing activation of transcription factor CREB, which induces expression of the master melanogenic regulator MITF. Recent studies have demonstrated that recruitment of CRTCs to the CREB transcription complex is also required for UVR-stimulated melanogenesis. Therefore, modulation of cAMP-CRTC/CREB-MITF signaling may be a useful therapeutic strategy for UVR-associated skin pigmentary disorders.

Methods: We identified the small-molecule Ro31-8220 from CREB/CRTC activity screening and examined its melanogenic activity in cultured mouse and human melanocytes as well as in human skin. Molecular mechanisms were deciphered by immunoblotting, RT-PCR, promoter assays, tyrosinase activity assays, immunofluorescent examination of CRTC3 subcellular localization, and shRNA-based knockdown.

Results: Ro31-8220 suppressed basal and cAMP-stimulated melanin production in melanocytes and human melanocyte co-culture as well as UVR-stimulated melanin accumulation in human skin through downregulation of MITF and tyrosinase expression. Mechanistically, down regulation of MITF expression by Ro31-8220 was due to inhibition of transcriptional activity of CREB, which was resulted from phosphorylation-dependent blockade of nuclear translocation of CRTC3 via JNK activation. The selective JNK activator anisomycin also inhibited melanin production through phosphoinhibition of CRTC3, while JNK inhibition enhanced melanogenesis by stimulating CRTC3 dephosphorylation and nuclear migration.

Conclusions: Melanogenesis can be enhanced or suppressed via pharmacological modulation of a previously unidentified JNK-CRTC/CREB-MITF signaling axis. As Ro31-8220 potently inhibits UVR-stimulated melanin accumulation in human skin, suggesting that small-molecule JNK-CRTC signaling modulators may provide therapeutic benefit for pigmentation disorders.

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Most cited references 31

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Specificity and mechanism of action of some commonly used protein kinase inhibitors.

S. P. Davies, H. Reddy, M Caivano … (2000)

The specificities of 28 commercially available compounds reported to be relatively selective inhibitors of particular serine/threonine-specific protein kinases have been examined against a large panel of protein kinases. The compounds KT 5720, Rottlerin and quercetin were found to inhibit many protein kinases, sometimes much more potently than their presumed targets, and conclusions drawn from their use in cell-based experiments are likely to be erroneous. Ro 318220 and related bisindoylmaleimides, as well as H89, HA1077 and Y 27632, were more selective inhibitors, but still inhibited two or more protein kinases with similar potency. LY 294002 was found to inhibit casein kinase-2 with similar potency to phosphoinositide (phosphatidylinositol) 3-kinase. The compounds with the most impressive selectivity profiles were KN62, PD 98059, U0126, PD 184352, rapamycin, wortmannin, SB 203580 and SB 202190. U0126 and PD 184352, like PD 98059, were found to block the mitogen-activated protein kinase (MAPK) cascade in cell-based assays by preventing the activation of MAPK kinase (MKK1), and not by inhibiting MKK1 activity directly. Apart from rapamycin and PD 184352, even the most selective inhibitors affected at least one additional protein kinase. Our results demonstrate that the specificities of protein kinase inhibitors cannot be assessed simply by studying their effect on kinases that are closely related in primary structure. We propose guidelines for the use of protein kinase inhibitors in cell-based assays.

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Photochemistry. Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure.

Sanjay Premi, Silvia Wallisch, Camila Mano … (2015)

Mutations in sunlight-induced melanoma arise from cyclobutane pyrimidine dimers (CPDs), DNA photoproducts that are typically created picoseconds after an ultraviolet (UV) photon is absorbed at thymine or cytosine. We found that in melanocytes, CPDs are generated for >3 hours after exposure to UVA, a major component of the radiation in sunlight and in tanning beds. These "dark CPDs" constitute the majority of CPDs and include the cytosine-containing CPDs that initiate UV-signature C→T mutations. Dark CPDs arise when UV-induced reactive oxygen and nitrogen species combine to excite an electron in fragments of the pigment melanin. This creates a quantum triplet state that has the energy of a UV photon but induces CPDs by energy transfer to DNA in a radiation-independent manner. Melanin may thus be carcinogenic as well as protective against cancer. These findings also validate the long-standing suggestion that chemically generated excited electronic states are relevant to mammalian biology.

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A Fasting Inducible Switch Modulates Gluconeogenesis Via Activator-Coactivator Exchange

Guan-Yi Liu, Renaud Dentin, Danica Chen … (2008)

During early fasting, increases in skeletal muscle proteolysis liberate free amino acids for hepatic gluconeogenesis in response to pancreatic glucagon. Hepatic glucose output diminishes during the late protein-sparing phase of fasting, when ketone body production by the liver supplies compensatory fuel for glucose-dependent tissues 1–4. Glucagon stimulates the gluconeogenic program by triggering the dephosphorylation and nuclear translocation of the CREB regulated transcription coactivator 2 (CRTC2; also known as TORC2), while parallel decreases in insulin signaling augment gluconeogenic gene expression through the de-phosphorylation and nuclear shuttling of Forkhead Box O1 (FOXO1) 5–7. Here we show that a fasting-inducible switch, consisting of the histone acetyl-transferase (HAT) P300 and the nutrient-sensing deacetylase Sirtuin 1 (SIRT1), maintains energy balance through the sequential induction of CRTC2 and FOXO1. Following glucagon induction, CRTC2 stimulated gluconeogenic gene expression through an association with P300, which we show here is also activated by de-phosphorylation at Ser89 during fasting. In turn, P300 increased hepatic CRTC2 activity by acetylating it at Lys628, a site that also targets CRTC2 for degradation following its ubiquitination by the E3 ligase Constitutive Photomorphogenic Protein (COP1) 8. Glucagon effects were attenuated during late fasting, when CRTC2 was down-regulated due to SIRT1-mediated deacetylation and when FOXO1 supported expression of the gluconeogenic program. Disrupting SIRT1 activity, by liver-specific knockout of the SIRT1 gene or by administration of SIRT1 antagonist, increased CRTC2 activity and glucose output, while exposure to SIRT1 agonists reduced them. In view of the reciprocal activation of FOXO1 and its coactivator peroxisome proliferator activated receptor gamma coactivator 1 alpha (PGC-1α) by SIRT1 activators 9–12, our results illustrate how the exchange of two gluconeogenic regulators during fasting maintains energy balance.

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Author and article information

Journal

Journal ID (nlm-ta): Theranostics

Journal ID (iso-abbrev): Theranostics

Journal ID (publisher-id): thno

Title: Theranostics

Publisher: Ivyspring International Publisher (Sydney )

ISSN (Electronic): 1838-7640

Publication date Collection: 2020

Publication date (Electronic): 4 March 2020

Volume: 10

Issue: 9

Pages: 4017-4029

Affiliations

[1 ]Department of Biomedical Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea.

[2 ]Bio-Medical Institute of Technology (BMIT), University of Ulsan College of Medicine, Seoul 05505, Korea.

[3 ]Department of Dermatology, University of Ulsan College of Medicine, Seoul 05505 Korea.

[4 ]Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.

Author notes

✉ Corresponding authors: Sung Eun Chang, MD, Ph.D., Department of Dermatology, University of Ulsan , College of Medicine, Asan Medical Center, Olympic-ro 43-gil 88, Songpa-Gu, Seoul 05505, Republic of Korea; Phone: +82-2-3010-3467; Email: csenumd@ 123456gmail.com or Youngsup Song, Ph.D., Department of Biomedical Sciences, University of Ulsan, College of Medicine, Asan Medical Center, Olympic-ro 43-gil 88, Songpa-Gu, Seoul 05505, Republic of Korea; Phone: +82-2-3010-2089; Email: ysong@ 123456amc.seoul.kr

Competing Interests: The authors have declared that no competing interest exists.

Article

Publisher ID: thnov10p4017

DOI: 10.7150/thno.41502

PMC ID: 7086364

PubMed ID: 32226536

SO-VID: b76bb466-c41b-457e-810e-b0a7c24cb43b

License:

This is an open access article distributed under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions.

JNK suppresses melanogenesis by interfering with CREB-regulated transcription coactivator 3-dependent MITF expression

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Most cited references 31

Specificity and mechanism of action of some commonly used protein kinase inhibitors.

Photochemistry. Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure.

A Fasting Inducible Switch Modulates Gluconeogenesis Via Activator-Coactivator Exchange

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