克洛素

克洛素（Klotho，或譯可羅素）是一種由人類KL基因編碼而成的酵素。 該基因屬於第一型跨膜蛋白，且具有β-葡萄糖醛酸苷酶（英语：beta-glucuronidase）活性。慢性腎衰竭患者體內的可羅素製造會減少，這也可能是造成慢性腎衰後一連串併發症的原因（如動脈硬化、骨質疏鬆、以及皮膚鬆弛等等）。該編碼基因的突變也與老化、骨質流失有關。過度表現可羅素的小鼠，壽命會較野生型小鼠長。 克洛素為一種跨膜蛋白，會調控生物體對於胰島素的敏感性，且可能也與老化有關。本蛋白最早由黑尾誠等人於1997年發現，該蛋白命名自希腊神话命運三女神中的克洛托（Klotho）。 克洛素具有β-葡萄糖醛酸苷酶（英语：beta-glucuronidase）活性，可以水解β-葡萄糖醛酸（英语：glucuronide），與人類老化有關。血漿中的循環克洛素會隨年紀逐漸減少。β-克洛素會與FGF受體行程協同受體（英语：co-receptor），可與FGF19、FGF20、FGF23等成纤维细胞生长因子（FGF）結合進行作用。 克洛素缺乏的小鼠會出現類似人類早衰的症狀，並加速动脉血管硬化的進程，同時也會損傷血管新生和內皮調控血管擴張的能力。推論克洛素可能可以透過內皮源性一氧化氮釋放來保護心血管系統。 過度表現克洛素的小鼠，平均壽命會較一般小數多出19%至31%。克洛速基因的某些變異還與長壽和增進認知功能相關。 克洛素的作用機轉迄今未明，目前已知可以透過提升TRPV5（英语：TRPV5）和降低TRPC6（英语：TRPC6）的表達調控細胞的鈣平衡。此外，克洛素也會增加內向整流離子通道ROMK（英语：ROMK）的表達。克洛素缺乏的小鼠會會增加維他命D的製造。 GRCh38: Ensembl release 89: ENSG00000133116 - Ensembl, May 2017 GRCm38: Ensembl release 89: ENSMUSG00000058488 - Ensembl, May 2017 Human PubMed Reference:. National Center for Biotechnology Information, U.S. National Library of Medicine.  Mouse PubMed Reference:. 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Kidney International. Sep 2008, 74 (6): 702–4. PMID 18756295. doi:10.1038/ki.2008.382.  Entrez Gene entry for Klotho GenAge entry for Klotho （页面存档备份，存于互联网档案馆） 克洛素引用了美国国家医学图书馆提供的資料，这些資料属于公共领域。 分子与细胞生物学主題