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A novel dominant hyperekplexia mutation Y705C alters trafficking and biochemical properties of the presynaptic glycine transporter GlyT2

Gimenez, C., Perez-Siles, G., Martinez-Villarreal, J., Arribas-Gonzalez, E., Jimenez, E., Nunez, E., de Juan-Sanz, J., Fernandez-Sanchez, E., Garcia-Tardon, N., Ibanez, I., Romanelli, V., Nevado, J., James, V. M., Topf, M., Chung, S.-K., Thomas, Rhys Huw, Desviat, L. R., Aragon, C., Zafra, F., Rees, M. I., Lapunzina, P., Harvey, R. J. and Lopez-Corcuera, B. 2012. A novel dominant hyperekplexia mutation Y705C alters trafficking and biochemical properties of the presynaptic glycine transporter GlyT2. Journal of Biological Chemistry 287 (34) , pp. 28986-29002. 10.1074/jbc.M111.319244

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Hyperekplexia or startle disease is characterized by an exaggerated startle response, evoked by tactile or auditory stimuli, producing hypertonia and apnea episodes. Although rare, this orphan disorder can have serious consequences, including sudden infant death. Dominant and recessive mutations in the human glycine receptor (GlyR) α1 gene (GLRA1) are the major cause of this disorder. However, recessive mutations in the presynaptic Na+/Cl−-dependent glycine transporter GlyT2 gene (SLC6A5) are rapidly emerging as a second major cause of startle disease. In this study, systematic DNA sequencing of SLC6A5 revealed a new dominant GlyT2 mutation: pY705C (c.2114A→G) in transmembrane domain 11, in eight individuals from Spain and the United Kingdom. Curiously, individuals harboring this mutation show significant variation in clinical presentation. In addition to classical hyperekplexia symptoms, some individuals had abnormal respiration, facial dysmorphism, delayed motor development, or intellectual disability. We functionally characterized this mutation using molecular modeling, electrophysiology, [3H]glycine transport, cell surface expression, and cysteine labeling assays. We found that the introduced cysteine interacts with the cysteine pair Cys-311–Cys-320 in the second external loop of GlyT2. This interaction impairs transporter maturation through the secretory pathway, reduces surface expression, and inhibits transport function. Additionally, Y705C presents altered H+ and Zn2+ dependence of glycine transport that may affect the function of glycinergic neurotransmission in vivo.

Item Type: Article
Status: Published
Schools: Medicine
MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Subjects: R Medicine > R Medicine (General)
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Uncontrolled Keywords: Neurotransmitter Transport; pH Regulation; Trafficking; Transport; Zinc; GlyT2; Disulfide Bond; Glycine; Hyperekplexia
Publisher: American Society for Biochemistry and Molecular Biology
ISSN: 0021-9258
Last Modified: 04 Jun 2017 08:58

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