TPC2 polymorphisms associated with a hair pigmentation phenotype in humans result in gain of channel function by independent mechanisms
TPC2 polymorphisms associated with a hair pigmentation phenotype in humans result in gain of channel function by independent mechanisms
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DOI：
10.1073/pnas.1705739114
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发表时间：
2017-10-10
影响因子：
11.1
通讯作者：
Grimm, Christian
中科院分区：
文献类型：
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作者：
Chao, Yu-Kai;Schludi, Verena;Grimm, Christian
双孔通道（TPC）是内溶酶体阳离子通道。人类中存在两个成员：TPC1 和 TPC2。与普遍表达的 TPC 相关的功能作用包括 VEGF 诱导的新血管生成、LDL 胆固醇运输和降解、禁食条件下的身体耐力、自噬调节、精子顶体反应、癌细胞迁移以及埃博拉病毒或细菌毒素（例如霍乱毒素）等病原体的细胞内运输。在一项针对与人类色素沉着特征相关的变体的全基因组关联研究中，发现 TPC2 的两个编码变体 rs35264875（编码 M484L）和 rs3829241（编码 G734E）与头发颜色从棕色到金色的转变有关。最近的两项后续研究进一步证实了 TPC2 在色素沉着中的作用。然而，这些人类多态性变异体迄今为止尚未得到功能表征。内溶酶体膜片钳技术的发展使得直接研究分离的内溶酶体细胞器中的离子通道活性和特征成为可能。我们在这里应用这种技术来仔细检查多态性 TPC2 变体的通道特征，并与 WT 直接比较。我们发现这两种多态性都通过独立的机制导致通道功能的增益。接下来，我们对 100 多名金发和棕色/黑发个体进行了一项临床研究。我们进行了基因型/表型分析，随后从 WT 和多态性变异携带者中分离出成纤维细胞，进行内溶酶体膜片钳实验，以确认关键的体外发现。
Two-pore channels (TPCs) are endolysosomal cation channels. Two members exist in humans, TPC1 and TPC2. Functional roles associated with the ubiquitously expressed TPCs include VEGF-induced neoangiogenesis, LDL-cholesterol trafficking and degradation, physical endurance under fasting conditions, autophagy regulation, the acrosome reaction in sperm, cancer cell migration, and intracellular trafficking of pathogens such as Ebola virus or bacterial toxins (e.g., cholera toxin). In a genome-wide association study for variants associated with human pigmentation characteristics two coding variants of TPC2, rs35264875 (encoding M484L) and rs3829241 (encoding G734E), have been found to be associated with a shift from brown to blond hair color. In two recent follow-up studies a role for TPC2 in pigmentation has been further confirmed. However, these human polymorphic variants have not been functionally characterized until now. The development of endolysosomal patch-clamp techniques has made it possible to investigate directly ion channel activities and characteristics in isolated endolysosomal organelles. We applied this technique here to scrutinize channel characteristics of the polymorphic TPC2 variants in direct comparison with WT. We found that both polymorphisms lead to a gain of channel function by independent mechanisms. We next conducted a clinical study with more than 100 blond-and brown/black-haired individuals. We performed a genotype/phenotype analysis and subsequently isolated fibroblasts from WT and polymorphic variant carriers for endolysosomal patch-clamp experimentation to confirm key in vitro findings.