Williams Ruth M, Winkfein Robert J, Ginger Rebecca S, Green Martin R, Schnetkamp Paul P, Wheeler Grant N
School of Biological Sciences, University of East Anglia, Norwich, United Kingdom.
Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada.
PLoS One. 2017 Jul 10;12(7):e0180465. doi: 10.1371/journal.pone.0180465. eCollection 2017.
NCKX5 is an ion exchanger expressed mostly in pigment cells; however, the functional role for this protein in melanogenesis is not clear. A variant allele of SLC24A5, the gene encoding NCKX5, has been shown to correlate with lighter skin pigmentation in humans, indicating a key role for SLC24A5 in determining human skin colour. SLC24A5 expression has been found to be elevated in melanoma. Knockdown analyses have shown SLC24A5 to be important for pigmentation, but to date the function of this ion exchanger in melanogenesis has not been fully established. Our data suggest NCKX5 may have an alternative activity that is key to its role in the regulation of pigmentation. Here Xenopus laevis is employed as an in vivo model system to further investigate the function of NCKX5 in pigmentation. SLC24A5 is expressed in the melanophores as they differentiate from the neural crest and develop in the RPE of the eye. Morpholino knockdown and rescue experiments were designed to elucidate key residues and regions of the NCKX5 protein. Unilateral morpholino injection at the 2 cell stage resulted in a reduction of pigmentation in the eye and epidermis of one lateral side of the tadpole. Xenopus and human SLC24A5 can rescue the morpholino effects. Further rescue experiments including the use of ion exchange inactive SLC24A5 constructs raise the possibility that full ion exchanger function of NCKX5 may not be required for rescue of pigmentation.
NCKX5是一种主要在色素细胞中表达的离子交换器；然而，这种蛋白质在黑色素生成中的功能作用尚不清楚。编码NCKX5的基因SLC24A5的一个变异等位基因已被证明与人类较浅的皮肤色素沉着相关，这表明SLC24A5在决定人类肤色方面起着关键作用。已发现SLC24A5在黑色素瘤中表达升高。敲低分析表明SLC24A5对色素沉着很重要，但迄今为止，这种离子交换器在黑色素生成中的功能尚未完全明确。我们的数据表明，NCKX5可能具有一种替代活性，这是其在色素沉着调节中发挥作用的关键。在这里，非洲爪蟾被用作体内模型系统，以进一步研究NCKX5在色素沉着中的功能。SLC24A5在黑素细胞中表达，黑素细胞从神经嵴分化并在眼睛的视网膜色素上皮中发育。设计了吗啉代敲低和拯救实验，以阐明NCKX5蛋白的关键残基和区域。在二细胞期单侧注射吗啉代导致蝌蚪一侧眼睛和表皮的色素沉着减少。非洲爪蟾和人类的SLC24A5可以拯救吗啉代的作用。包括使用离子交换无活性的SLC24A5构建体在内的进一步拯救实验增加了一种可能性，即色素沉着的拯救可能不需要NCKX5的完全离子交换器功能。
