June Liu, PhD.

Associate Professor
Cell Biology and Anatomy
Neuroscience Center of Excellence

1901 Perdido Street
New Orleans LA 70112
Phone: (504) 568-2258
Fax: (504) 568-4392

sliu@lsuhsc.edu

Degrees

PhD Biophysics
University of Rochester

MD
Beijing Medical University

Research Interests

The Liu lab is interested in synaptic transmission in the central nervous system. In particular we study how emotional stress and fear memories regulate excitatory and inhibitory synaptic transmission in the cerebellum. This is a brain region that is important for learning/memory and is involved in emotion. We use behavioral, electrophysiological, fluorescent imaging, and cellular/molecular techniques. Our experiments are performed using brain slices and primary neuronal cultures.  

Emotional stress regulates glutamate receptor gene expression. Changes in emotional state are known to alter neuronal excitability and can modify learning and memory formation. In a recent study we have shown that a single exposure to a fear-inducing stimulus induces a long-lasting increase in the transcription of the GluR2 subunit of the AMPA-type glutamate receptor in cerebellar inhibitory interneurons (Liu et al, 2010). This reduces the AMPA receptor Ca2+ permeability and alters synaptic efficacy.

We are currently investigating how a stress hormone, noradrenaline, promotes the expression of the GluR2 gene in inhibitory interneurons and how enhanced GluR2 transcription in inhibitory interneurons changes the activity of cerebellar circuits. We detect changes in GluR2 mRNA levels using real time single cell RT-PCR, identify AMPA receptor subunit composition at individual synapses using electrophysiological techniques and monitor morphological changes using confocal microscopy. 

Fear memories and synaptic plasticity. We are also interested in how fear memories modulate GABA release from cerebellar inhibitory interneurons. We have found that an excitatory transmitter, glutamate, enhances the release of GABA (Liu and Lachamp, 2006; Lachamp et al, 2009). We are investigating (1) how a fear-stimulus alters synaptic transmission, (2) what are the underlying molecular mechanism(s); (3) how synaptic plasticity alters the activity of cerebellar neuronal circuits.

Selected Publications

Dubois, C, Ramamoorthy, P, Whim, MD and Liu, S.J. (2012) Activation of neuropeptide Y5 receptors induces a long-lasting suppression of GABA release from cerebellar stellate cells. J. Neurophysiol. In press.

Liu S. J., Savtchouk, I. (2012) Ca-permeable AMPA receptors switch allegiances: mechanisms and consequences. J. Physiol. 590:13-20

Liu, Y, Savtchouk, I, Acharjee, S and Liu, S.J. (2011) Action potential duration regulates GluR2 expression in cerebellar stellate cells. J Neurophysiol. 106:144-153

Savtchouk, I. and Liu, S. J. (2011) Remodeling of synaptic AMPA receptor subtype alters the probability and pattern of action potential firing. J. Neurosci. 31:501-511.

Liu, Y, Formisano, L, Takayasu, Y, Savtchouk I, Szabó G, Zukin, R.S. and Liu S. J. A single exposure to a fear-inducing stimulus induces GluR2 gene transcription and a switch in synaptic AMPA receptor phenotype in cerebellar stellate cells. Nature Neurosci. 13:223-231.

Lachamp, P. M., Liu, Y and Liu, S.J. (2009) Glutamatergic modulation of cerebellar interneuron activity is mediated by an enhancement of GABA release and requires PKA/RIM1-signaling. J. Neurosci. 29:381-92.

Liu, S. J., Lachamp P, Liu Y, Savtchouk I and Sun L. (2008) Long-term synaptic  plasticity in cerebellar stellate cells. The Cerebellum. 7:559-62.

Sun, L. and Liu, S. J. (2007) Activation of extrasynaptic NMDA receptors induces a PKC-dependent switch in AMPA receptor subtypes in mouse cerebellar stellate cells. J. Physiol. 583:537-553.

Liu, S. J. (2007) Biphasic Modulation of GABA Release from stellate cells by glutamatergic receptor subtypes. J. Neurophysiol. 98:550-556.

Liu S.J. and Zukin RS (2007) Ca2+-permeable AMPA receptors in synaptic plasticity and neuronal death. Trends in Neurosci. 30:126-34.

Liu S. J. and Lachamp P (2006) The activation of excitatory glutamate receptors evokes a long-lasting increase in the release of GABA from cerebellar stellate cells. J Neurosci. 26:9332-9

Liu S. J. and Cull-Candy S (2005) Subunit interaction with PICK and GRIP controls Ca2+-permeability of  AMPARs at cerebellar synapses. Nature Neurosci. 8:768-775.

Liu S. Q. and Kaczmarek LK. (2004) Aminoglycosides block the Kv3.1 potassium channel and reduce the ability of inferior colliculus neurons to fire at high frequencies. J Neurobiol. 62:439-452

Liu, S. J. and S. G. Cull-Candy. (2002) Activity-dependent change in AMPA receptor properties in cerebellar stellate cells. J. Neurosci. 22: 3881-9.

Liu, S. J. and S. G. Cull-Candy (2000) Synaptic activity at calcium-permeable AMPA receptors induces a switch in receptor subtype. Nature  405: 454-458.

Book chapter:
Liu S, J. Stellate cells: synaptic processing and plasticity. In Handbook of Cerebellum and Cerebellar Disorder. In press.