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J Mol Cell Biol. 2015 Apr;7(2):168-79. doi: 10.1093/jmcb/mjv011. Epub 2015 Feb 20.

Function coupling of otoferlin with GAD65 acts to modulate GABAergic activity.

Author information

1
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada.
2
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada Present address: Department of Anesthesiology & Perioperative Care, University of California Irvine, Irvine, CA, USA.
3
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada jia@queensu.ca.

Abstract

Otoferlin, an integral membrane protein implicated in a late stage of exocytosis, has been reported to play a critical role in hearing although the underlying mechanisms remain elusive. However, its widespread tissue distribution infers a more ubiquitous role in synaptic vesicle trafficking. Glutamate, an excitatory neurotransmitter, is converted to its inhibitory counterpart, γ-aminobutyric acid (GABA), by L-glutamic acid decarboxylase (GAD), which exists in soluble (GAD67) and membrane-bound (GAD65) forms. For the first time, we have revealed a close association between otoferlin and GAD65 in both HEK293 and neuronal cells, including SH-SY5Y neuroblastoma and primary rat hippocampus cells, showing a direct interaction between GAD65 and otoferlin's C2 domains. In primary rat hippocampus cells, otoferlin and GAD65 co-localized in a punctate pattern within the cell body, as well as in the axon along the path of vesicular traffic. Significantly, GABA is virtually abolished in otoferlin-knockdown neuronal cells whereas otoferlin overexpression markedly increases endogenous GABA. GABA attenuation in otoferlin-knockdown primary cells is correlated with diminished L-type calcium current. This previously unknown and close correlation demonstrates that otoferlin, through GAD65, modulates GABAergic activity. The discovery of otoferlin-GAD65 functional coupling provides a new avenue for understanding the molecular mechanism by which otoferlin functions in neurological pathways.

KEYWORDS:

GABA; GAD65; exocytosis; neurotransmitter; otoferlin

PMID:
25701657
DOI:
10.1093/jmcb/mjv011
[Indexed for MEDLINE]

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