cAMP-Binding Site of PKA as a Molecular Target of Bisabolangelone against Melanocyte-Specific Hyperpigmented Disorder

Abstract

Microphthalmia-associated transcription factor (MITF) is inducible in response to cAMP and has a pivotal role in the melanocyte-specific expression of tyrosinase for skin pigmentation. Here we suggest that the cAMP-binding site of protein kinase A (PKA) is a target in the inhibition of the melanogenic process in melanocytes, as evidenced from the molecular mechanism of small molecules such as bisabolangelone (BISA) and Rp-adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMPS). BISA is a sesquiterpene constituent of Angelica koreana, a plant of the Umbelliferae family, whose roots are used as an alternative medicine. BISA competitively inhibited cAMP binding to the regulatory subunit of PKA and fitted into the cAMP-binding site on the crystal structure of PKA under the most energetically favorable simulation. In α-melanocyte-stimulating hormone (α-MSH)-activated melanocytes, BISA and Rp-cAMPS nullified cAMP-dependent PKA activation, dissociating catalytic subunits from an inactive holoenzyme complex. They resultantly inhibited cellular phosphorylation of the cAMP-responsive element-binding protein (CREB) or another transcription factor SOX9, thus downregulating the expression of MITF or the tyrosinase gene with decreased melanin production. Taken together, this study defined the antimelanogenic mechanism of BISA or Rp-cAMPS with a notable implication of the cAMP-binding site of PKA as a putative target ameliorating melanocyte-specific hyperpigmented disorder.

cAMP‐dependent activation of protein kinase A as a therapeutic target of skin hyperpigmentation by diphenylmethylene hydrazinecarbothioamide

“…These doses were based on the relative activity of QNT 3‐80 and arbutin in vitro ; the IC 50 value for QNT 3‐80 was more than 50‐fold less than that of arbutin (Supporting Information http://onlinelibrary.wiley.com/doi/10.1111/bph.13134/suppinfo), and concurrently irradiated with UVB (350 mJ·cm −2 per exposure). The dose of UVB was used in our previous work (Roh et al ., 2013; 2014) in order to induce facultative pigmentation without erythema or oedema in the dorsal skin of guinea pigs. Topical treatment with QNT 3‐80 on the UVB‐irradiated dorsal skin of guinea pigs decreased visual pigmentation in the absence of skin corrosion and increased the skin‐whitening index (L), as did arbutin (Supporting Information http://onlinelibrary.wiley.com/doi/10.1111/bph.13134/suppinfo).…”

“…The PKA‐directed cAMP antagonist Rp‐cAMPS decreased melanin production in α‐MSH‐ or db‐cAMP‐stimulated B16 cells, as did QNT 3‐80. Similarly, bisabolangelone (BISA) and 4‐hydroxy‐3‐methoxycinnamaldehyde (4H3MC) have been identified as inhibitors of cAMP‐induced dissociation and activation of inactive PKA holoenzyme in melanocytes and their topical application ameliorated UVB‐induced skin pigmentation in guinea pigs (Roh et al ., 2013; 2014). Therefore, QNT 3‐80 mimicked Rp‐cAMPS, BISA or 4H3MC in terms of its antimelanogenic mechanism.…”

“…Total RNAs were subjected to RT‐PCR with an RNA PCR kit (Bioneer, Daejeon, Korea), determining mRNA levels of MITF or tyrosinase gene with the internal control β‐actin. Nucleotide sequences of the PCR primers were previously described (Roh et al ., ). In brief, total RNAs were reversely transcribed at 42°C for 1 h and then subjected to 25–30 cycles of PCR consisting of 30 s denaturation at 94°C, 60 s annealing at 50–55°C and 90 s extension at 72°C.…”

Stimulating effect of modified Goa-Gi-Um herbal remedy on melanogenesis in B16F10 melanoma cells

“…이것은 궁극적으로 HR+OBE이 CREB을 활성화시킴으로 멜라노마 세포에서 멜라닌 합성을 증가시킨다는 것을 알 수 있었다. 멜라닌 합성은 tyrosinase, TRP-1과 TRP-2에 의해서 조 절된다는 것은 알려졌다 [15][16][17][18] . 이 중에서도 tyrosinase의 발 현과 활성에 의해서 멜라닌 합성이 주로 조절되므로 tyrosinase의 발현의 증가나 활성이 촉진되면 멜라닌 합성이 증가할 수 있다.…”

“…이러한 tyrosinase의 활성과 발현은 α -MSH에 의해서 향상되는데 이 과정에 세포내 cAMP 기전을 활성화시킴으로 일어난다. α-MSH는 멜라닌 생성세포의 MCR에 결합하여 cAMP의 발생을 증가시키고 이것이 CREB 의 인산화를 촉진하여 전사인자인 MITF의 발현을 증가시켜 tyrosinase의 mRNA 발현을 증가시키고, tyrosinase 활성을 향상시킨다는 보고가 많이 있다 16,17) . 특히, MITF는 tyrosinase 발현을 조절하는 중요 전사인자이다.…”