Motor neuropathy-associated mutation impairs Seipin functions in neurotransmission

Authors

  • Shunhui Wei,

    1. Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore
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  • Stephanie Li-Ying Soh,

    1. Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore
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  • Julia Xia,

    1. Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore
    2. Child Health Institute of New Jersey, Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA
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  • Wei-Yi Ong,

    1. Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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  • Zhiping P. Pang,

    Corresponding author
    1. Child Health Institute of New Jersey, Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, USA
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  • Weiping Han

    Corresponding author
    1. Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, A*STAR, Singapore
    2. Institute of Molecular and Cell Biology, A*STAR, Singapore
    3. Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
    4. Cardiovascular and Metabolic Disorders Program, Duke-NUS Graduate Medical School, Singapore
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Abstract

Gain-of-toxic-function mutations in Seipin (Asparagine 88 to Serine (N88S) and Serine 90 to Leucine (S90L) mutations, both of which disrupt the N-glycosylation) cause autosomal dominant motor neuron diseases. However, the mechanism of how these missense mutations lead to motor neuropathy is unclear. Here, we analyze the impact of disruption of N-glycosylation of Seipin on synaptic transmission by over-expressing mutant Seipin in cultured cortical neurons via lentiviral infection. Immunostaining shows that over-expressed Seipin is partly colocalized with synaptic vesicle marker synaptophysin. Electrophysiological recordings reveal that the Seipin mutation significantly decreases the frequency, but not the amplitudes of miniature excitatory post-synaptic currents and miniature inhibitory post-synaptic currents. The amplitude of both evoked excitatory post-synaptic currents and inhibitory post-synaptic current is also compromised by mutant Seipin over-expression. The readily releasable pool and vesicular release probability of synaptic vesicles are both altered in neurons over-expressing Seipin-N88S, whereas neither γ-amino butyric acid (GABA) nor α-Amino-3-hydroxy-5-methyl-4- isoxazolepropionic acid (AMPA) induced whole cell currents are affected. Moreover, electron microscopy analysis reveals decreased number of morphologically docked synaptic vesicles in Seipin-N88S-expressing neurons. These data demonstrate that Seipin-N88S mutation impairs synaptic neurotransmission, possibly by regulating the priming and docking of synaptic vesicles at the synapse.

image

Motoneuropathy-associated endoplasmic reticulum (ER) protein Seipin-N88S mutation disrupts N-glycosylation and decreased the frequency of miniature excitatory and inhibitory post-synaptic currents (PSCs), and the amplitude of evoked excitatory and inhibitory PSCs. The readily releasable pool and synaptic vesicle (SV) release probability were reduced in neurons over-expressing Seipin-N88S, along with decreased number of docked vesicles. We propose that Seipin-N88S mutation impairs synaptic neurotransmission by regulating the docking of synaptic vesicles.

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