Rescue by 4-phenylbutyrate of several misfolded creatine transporter-1 variants linked to the creatine transporter deficiency syndrome

NEUROPHARMACOLOGY

卷:161

Article

El-Kasaby, Ali^1,2  Kasture, Ameya^1,2,3  Koban, Florian^1,2  Hotka, Matej⁴  Asjad, Hafiz M. M.^1,2,5  Kubista, Helmut⁴  Freissmuth, Michael^1,2  Sucic, Sonja^1,2 

[1] Med Univ Vienna, Inst Pharmacol, Vienna, Austria

[2] Med Univ Vienna, Gaston H Glock Res Labs Exploratory Drug Dev, Ctr Physiol & Pharmacol, Vienna, Austria

[3] Univ Vienna, Dept Neurobiol, Vienna, Austria

[4] Med Univ Vienna, Ctr Physiol & Pharmacol, Dept Neurophysiol & Neuropharmacol, Vienna, Austria

[5] Forman Christian Coll, Dept Pharm, Lahore, Pakistan

关键词: Creatine transporter-1;    Creatine deficiency syndrome;    Severe mental retardation;    Protein misfolding;    Pharmacochaperoning;    4-Phenylbutyrate;   

DOI  :  10.1016/j.neuropharm.2019.03.015

来源: Elsevier

【 摘 要 】

Diseases arising from misfolding of SLC6 transporters have been reported over recent years, e.g. folding-deficient mutants of the dopamine transporter and of the glycine transporter-2 cause infantile/juvenile Parkinsonism dystonia and hyperekplexia, respectively. Mutations in the coding sequence of the human creatine transporter-1 (hCRT-1/SLC6A8) gene result in a creatine transporter deficiency syndrome, which varies in its clinical manifestation from epilepsy, mental retardation, autism, development delay and motor dysfunction to gastrointestinal symptoms. Some of the mutations in hCRT-1 occur at residues, which are highly conserved across the SLC6 family. Here, we examined 16 clinically relevant hCRT-1 variants to verify the conjecture that they were misfolded and that this folding defect was amenable to correction. Confocal microscopy imaging revealed that the heterologously expressed YFP-tagged mutant CRTs were trapped in the endoplasmic reticulum (ER), colocalised with the ER-resident chaperone calnexin. In contrast, the wild type hCRT-1 reached the plasma membrane. Preincubation of transiently transfected HEK293 cells with the chemical chaperone 4-phenylbutyrate (4-PBA) restored ER export and surface expression of as well as substrate uptake by several folding-deficient CRT-1 mutants. A representative mutant (hCRT-1-P544L) was expressed in rat primary hippocampal neurons to verify pharmacochaperoning in a target cell: 4-PBA promoted the delivery of hCRT-1-P544L to the neurite extensions. These observations show that several folding-deficient hCRT-1 mutants can be rescued. This proof-ofprinciple justifies the search for additional pharmacochaperones to restore folding of 4PBA-unresponsive hCRT-1 mutants. Finally, 4-PBA is an approved drug in paediatric use: this provides a rationale for translating the current insights into clinical trials. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

【 授权许可】

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