School of Public Health, Guizhou Medical University, Guiyang, Guizhou, 550004, China.
Department of Immunology, Basic Medical School, Guizhou Medical University, Guiyang, Guizhou, 550004, China.
Br J Dermatol. 2021 Aug;185(2):391-404. doi: 10.1111/bjd.19797. Epub 2021 May 5.
Human skin, which is constantly exposed to solar ultraviolet radiation (UVR), has a unique ability to respond by increasing its pigmentation in a protective process driven by melanogenesis in human epidermal melanocytes (HEMs). However, the molecular mechanisms used by HEMs to detect and respond to UVR remain unclear.
To investigate the function and potential mechanism of opsin 5 (OPN5), a photoreceptor responsive to UVR wavelengths, in melanogenesis in HEMs.
Melanin content in HEMs was determined using the NaOH method, and activity of tyrosinase (TYR) (a key enzyme in melanin synthesis) was determined by the l-DOPA method. OPN5 expression in UVR-treated vs. untreated HEMs and explant tissues was detected by reverse-transcription quantitative polymerase chain reaction (RT-qPCR), Western blotting and immunofluorescence. Short interfering RNA-mediated OPN5 knockdown and a lentivirus OPN5 overexpression model were used to examine their respective effects on TYR, tyrosinase-related protein 1 (TRP1), TRP2 and microphthalmia-associated transcription factor (MITF) expression, under UVR. Changes in expression of TYR, TRP1 and TRP2 caused by changes in OPN5 expression level were detected by RT-qPCR and Western blot. Furthermore, changes in signalling pathway proteins were assayed.
We found that OPN5 is the key sensor in HEMs responsible for UVR-induced melanogenesis. OPN5-induced melanogenesis required Ca -dependent G protein-coupled receptor- and protein kinase C signal transduction, thus contributing to the UVR-induced MITF response to mediate downstream cellular effects, and providing evidence of OPN5 function in mammalian phototransduction. Remarkably, OPN5 activation was necessary for UVR-induced increase in cellular melanin and has an inherent function in melanocyte melanogenesis.
Our results provide insight into the molecular mechanisms of UVR sensing and phototransduction in melanocytes, and may reveal molecular targets for preventing pigmentation or pigment diseases.
人类皮肤不断受到太阳紫外线辐射（UVR）的照射，具有独特的能力，通过黑色素生成在保护过程中增加其色素沉着。然而，人类表皮黑素细胞（HEM）中用于检测和响应 UVR 的分子机制尚不清楚。
研究光受体 opsin 5（OPN5）在 HEM 中的黑色素生成中的功能和潜在机制，该光受体对 UVR 波长有反应。
采用 NaOH 法测定 HEM 中的黑色素含量，采用 l-DOPA 法测定酪氨酸酶（TYR）（黑色素合成的关键酶）的活性。通过逆转录定量聚合酶链反应（RT-qPCR）、Western blot 和免疫荧光检测 UVR 处理与未处理的 HEM 和外植体组织中 OPN5 的表达。采用短发夹 RNA 介导的 OPN5 敲低和慢病毒 OPN5 过表达模型，观察 UVR 下 OPN5 各自对 TYR、酪氨酸酶相关蛋白 1（TRP1）、TRP2 和小眼畸形相关转录因子（MITF）表达的影响。通过 RT-qPCR 和 Western blot 检测 OPN5 表达水平变化对 TYR、TRP1 和 TRP2 表达的影响。此外，还检测了信号通路蛋白的变化。
我们发现 OPN5 是 HEM 中负责 UVR 诱导的黑色素生成的关键传感器。OPN5 诱导的黑色素生成需要 Ca2+依赖性 G 蛋白偶联受体和蛋白激酶 C 信号转导，从而有助于 UVR 诱导的 MITF 反应来介导下游细胞效应，并为 OPN5 在哺乳动物光转导中的功能提供证据。值得注意的是，OPN5 的激活对于 UVR 诱导的细胞黑色素增加是必需的，并且在黑素细胞黑色素生成中具有固有功能。
我们的研究结果提供了 UVR 感应和光转导在黑素细胞中的分子机制的深入了解，并可能揭示预防色素沉着或色素疾病的分子靶标。
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