title: Suppression of melanin production by expression of HSP70.
abstract: Skin hyperpigmentation disorders due to abnormal melanin production induced by ultraviolet (UV) irradiation are both a clinical and cosmetic problem. UV irradiation stimulates melanin production in melanocytes by increasing intracellular cAMP. Expression of heat shock proteins (HSPs), especially HSP70, is induced by various stressors, including UV irradiation, to provide cellular resistance to such stressors. In this study we examined the effect of expression of HSP70 on melanin production both in vitro and in vivo. 3-Isobutyl-1-methylxanthine (IBMX), a cAMP-elevating agent, stimulated melanin production in cultured mouse melanoma cells, and this stimulation was suppressed in cells overexpressing HSP70. IBMX-dependent transcriptional activation of the tyrosinase gene was also suppressed in HSP70-overexpressing cells. Expression of microphthalmia-associated transcription factor (MITF), which positively regulates transcription of the tyrosinase gene, was up-regulated by IBMX; however, this up-regulation was not suppressed in HSP70-overexpressing cells. On the other hand, immunoprecipitation and immunostaining analyses revealed a physical interaction between and co-localization of MITF and HSP70, respectively. Furthermore, the transcription of tyrosinase gene in nuclear extract was inhibited by HSP70. In vivo, UV irradiation of wild-type mice increased the amount of melanin in the basal layer of the epidermis, and this increase was suppressed in transgenic mice expressing HSP70. This study provides the first evidence of an inhibitory effect of HSP70 on melanin production both in vitro and in vivo. This effect seems to be mediated by modulation of MITF activity through a direct interaction between HSP70 and MITF.
authors.affiliation: Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hoshino
authors.forename: Minoru
authors.initials: M
authors.lastname: Matsuda
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Masaya
authors.initials: M
authors.lastname: Takehara
authors.forename: Masayo
authors.initials: M
authors.lastname: Fukuya
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Mineda
authors.forename: Daisuke
authors.initials: D
authors.lastname: Maji
authors.forename: Hironobu
authors.initials: H
authors.lastname: Ihn
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Adachi
authors.forename: Gen
authors.initials: G
authors.lastname: Sobue
authors.forename: Yoko
authors.initials: Y
authors.lastname: Funasaka
authors.forename: Tohru
authors.initials: T
authors.lastname: Mizushima
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D017495:Hyperpigmentation / Q000235:genetics / Q000378:metabolism; D008543:Melanins / Q000096:biosynthesis*; D008545:Melanoma / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000096:biosynthesis / Q000235:genetics; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D018840:HSP70 Heat-Shock Proteins; D008543:Melanins; D051739:Microphthalmia-Associated Transcription Factor; C497235:Mitf protein, mouse; D010726:Phosphodiesterase Inhibitors; D000242:Cyclic AMP; D014442:Monophenol Monooxygenase; D015056:1-Methyl-3-isobutylxanthine