Olauson Hannes, Mencke Rik, Hillebrands Jan-Luuk, Larsson Tobias E
Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.
Division of Pathology, Department of Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Bone. 2017 Jul;100:19-35. doi: 10.1016/j.bone.2017.03.043. Epub 2017 Mar 18.
αKlotho (Klotho), a type I transmembrane protein and a coreceptor for Fibroblast Growth Factor-23, was initially thought to be expressed only in a limited number of tissues, most importantly the kidney, parathyroid gland and choroid plexus. Emerging data may suggest a more ubiquitous Klotho expression pattern which has prompted reevaluation of the restricted Klotho paradigm. Herein we systematically review the evidence for Klotho expression in various tissues and cell types in humans and other mammals, and discuss potential reasons behind existing conflicting data. Based on current literature and tissue expression atlases, we propose a classification of tissues into high, intermediate and low/absent Klotho expression. The functional relevance of Klotho in organs with low expression levels remain uncertain and there is currently limited data on a role for membrane-bound Klotho outside the kidney. Finally, we review the evidence for the tissue source of soluble Klotho, and conclude that the kidney is likely to be the principal source of circulating Klotho in physiology.
α-klotho（Klotho）是一种I型跨膜蛋白，也是成纤维细胞生长因子-23的共受体，最初被认为仅在有限数量的组织中表达，最重要的是肾脏、甲状旁腺和脉络丛。新出现的数据可能表明Klotho的表达模式更为普遍，这促使人们重新评估Klotho表达受限的模式。在此，我们系统地回顾了人类和其他哺乳动物各种组织和细胞类型中Klotho表达的证据，并讨论了现有相互矛盾数据背后的潜在原因。基于当前的文献和组织表达图谱，我们提出将组织分为高、中、低/无Klotho表达三类。Klotho在低表达水平器官中的功能相关性仍不确定，目前关于肾脏以外膜结合型Klotho作用的数据有限。最后，我们回顾了可溶性Klotho组织来源的证据，并得出结论，在生理状态下，肾脏可能是循环中Klotho的主要来源。
