Ubiquitin-dependent lysosomal targeting of GABAA receptors regulates neuronal inhibition

doi:10.1073/pnas.0905502106

Ubiquitin-dependent lysosomal targeting of GABA_A receptors regulates neuronal inhibition

^aDepartment of Neuroscience, Physiology, and Pharmacology, University College London, Gower Street, London, WC1E 6BT, United Kingdom;
^bDepartment of Physiology and Biophysics, State University of New York, Buffalo, NY 14214;
^cDepartment of Internal Medicine, University of Cologne, 50937 Cologne, Germany; and
^dDepartment of Neuroscience, Tufts University School of Medicine, 136 Harrison Avenue Boston, MA 02111

Edited by Richard L. Huganir, Johns Hopkins University School of Medicine, Baltimore, MD, and approved August 31, 2009
↵¹J.T.K. and S.J.M. contributed equally to this work. (received for review May 19, 2009)

Abstract

The strength of synaptic inhibition depends partly on the number of GABA_A receptors (GABA_ARs) found at synaptic sites. The trafficking of GABA_ARs within the endocytic pathway is a key determinant of surface GABA_AR number and is altered in neuropathologies, such as cerebral ischemia. However, the molecular mechanisms and signaling pathways that regulate this trafficking are poorly understood. Here, we report the subunit specific lysosomal targeting of synaptic GABA_ARs. We demonstrate that the targeting of synaptic GABA_ARs into the degradation pathway is facilitated by ubiquitination of a motif within the intracellular domain of the γ2 subunit. Blockade of lysosomal activity or disruption of the trafficking of ubiquitinated cargo to lysosomes specifically increases the efficacy of synaptic inhibition without altering excitatory currents. Moreover, mutation of the ubiquitination site within the γ2 subunit retards the lysosomal targeting of GABA_ARs and is sufficient to block the loss of synaptic GABA_ARs after anoxic insult. Together, our results establish a previously unknown mechanism for influencing inhibitory transmission under normal and pathological conditions.

Footnotes

²To whom correspondence may be addressed. E-mail: j.kittler{at}ucl.ac.uk or stephen.moss{at}tufts.edu
Author contributions: I.L.A.-C., E.Y.Y., Z.Y., J.T.K., and S.J.M. designed research; I.L.A.-C., E.Y.Y., J.M., and G.M. performed research; I.L.A.-C., M.J.L., and R.S.S. contributed new reagents/analytic tools; I.L.A.-C., E.Y.Y., J.M., G.M., and Z.Y. analyzed data; and I.L.A.-C., T.G.S., J.T.K., and S.J.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0905502106/DCSupplemental.