Kahle Kristopher T, Flores Bianca, Bharucha-Goebel Diana, Zhang Jinwei, Donkervoort Sandra, Hegde Madhuri, Hussain Gulnaz, Duran Daniel, Liang Bo, Sun Dandan, Bönnemann Carsten G, Delpire Eric
Departments of Neurosurgery and Pediatrics and Cellular and Molecular Physiology, Centers for Mendelian Genomics, Yale School of Medicine, New Haven, CT 06510, USA.
Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Sci Signal. 2016 Aug 2;9(439):ra77. doi: 10.1126/scisignal.aae0546.
Using exome sequencing, we identified a de novo mutation (c.2971A>G; T991A) in SLC12A6, the gene encoding the K(+)-Cl(-) cotransporter KCC3, in a patient with an early-onset, progressive, and severe peripheral neuropathy primarily affecting motor neurons. Normally, the WNK kinase-dependent phosphorylation of T(991) tonically inhibits KCC3; however, cell swelling triggers Thr(991) dephosphorylation to activate the transporter and restore cell volume. KCC3 T991A mutation in patient cells abolished Thr(991) phosphorylation, resulted in constitutive KCC3 activity, and compromised cell volume homeostasis. KCC3(T991A/T991A) mutant mice exhibited constitutive KCC3 activity and recapitulated aspects of the clinical, electrophysiological, and histopathological findings of the patient. These results suggest that the function of the peripheral nervous system depends on finely tuned, kinase-regulated KCC3 activity and implicate abnormal cell volume homeostasis as a previously unreported mechanism of axonal degeneration.
通过外显子组测序，我们在一名主要影响运动神经元的早发性、进行性和严重周围神经病变患者中，鉴定出SLC12A6基因（编码K⁺-Cl⁻协同转运蛋白KCC3）存在一个新生突变（c.2971A>G；T991A）。正常情况下，T991位点的WNK激酶依赖性磷酸化可对KCC3产生持续性抑制；然而，细胞肿胀会触发苏氨酸991去磷酸化，从而激活转运蛋白并恢复细胞体积。患者细胞中的KCC3 T991A突变消除了苏氨酸991的磷酸化，导致KCC3组成性活性，并破坏了细胞体积稳态。KCC3(T991A/T991A)突变小鼠表现出KCC3组成性活性，并重现了该患者临床、电生理和组织病理学发现的某些方面。这些结果表明，周围神经系统的功能取决于精确调节的、激酶调控的KCC3活性，并提示异常的细胞体积稳态是轴突退变的一种此前未报道的机制。
