Munoz MB and Slesinger PA. (2014) Sorting Nexin 27 regulation of G protein-gated inwardly rectifying potassium channels attenuates in vivo cocaine response. Neuron 82(3):659-69.
Bodhinathan K and Slesinger PA. (2013) Molecular mechanism underlying ethanol activation of G-protein-gated inwardly rectifying potassium channels. Proc Natl Acad Sci USA. 110(45):18309-14. PMCID: PMC3831446
Muller A, Joseph V, Slesinger PA and Kleinfeld D (2014) Cell-based reporters reveal in vivo dynamics of dopamine and norepinephrine release in murine cortex. Nature Methods 11, 1245–1252 (2014) doi:10.1038/nmeth.3151 PMCID: PMC4245316
Munoz MB, Padgett CL, Rifkin R, Terunuma M, Wickman K, Contet C, Moss SJ, Slesinger PA. A Role for the GIRK3 Subunit in Methamphetamine-Induced Attenuation of GABAB Receptor-Activated GIRK Currents in VTA Dopamine Neurons.. J Neurosci. 2016 Mar 16;36(11):3106-14. doi: 10.1523/JNEUROSCI.1327-15.2016.
Paul A. Slesinger, PhD
Areas of Research
I. Molecular studies of GIRK channels in Alcoholism
The alcoholic beverages that we consume contain the alcohol ethanol. Ethanol produces a wide range of pharmacological effects on the nervous system, ranging from anxiolytic to intoxication. For some, however, alcohol consumptions leads to alcohol dependence, or alcohol use disorders. Ethanol produces complex effects on the body, primarily through its interactions with the central nervous system. The molecular mechanism by which ethanol alters neuronal circuits in the brain and causes alcohol use disorders is poorly understood. A major challenge in the field is determining how ethanol, which has a chemical structure of only two carbons and an hydroxyl, elicits alcohol-mediated behaviors and leads to abuse and dependence.
Ethanol directly alters the function of a number of different brain proteins, including GIRK channels. We are currently investigating the structural mechanism underlying alcohol-dependent activation of GIRK channels and the role of these channels in alcohol-related behaviors. We are taking an innovative approach of using structural biology to guide screening and selection of novel therapeutics, and validating drug effects with ex vivo and in vivo systems. Defining the physical features of the GIRK alcohol pocket for ethanol will reveal how binding of ethanol to a channel leads to changes in channel activity and affects brain function.
II. Role for GIRK channels in addiction
Psychostimulants, e.g., methamphetamine and cocaine, are highly addictive, accessible and abused by >1 million people. Recent work from our laboratory has established that drug exposure reduces slow inhibition, mediated by GABAB receptors that couple to GIRK channels. For example, five daily injections of a psychostimulant reduces the size of the GABAB receptor-activated GIRK current in ventral tegmental area (VTA) dopamine (DA) neurons of the reward pathway. These changes alter the excitability of DA neurons and contribute to circuit level changes in DA signaling involved in addiction.
Recently, we have described two different pathways for drug-dependent plasticity in the VTA. In GABA neurons, psychostimulant-dependent depression of GABAB-GIRK currents involves de-phosphorylation of the GABAB R2 receptor via the protein phosphatase PP2a. In DA neurons, psychostimulant-dependent depression of GABAB-GIRK currents involves the GIRK3 subunit and an endosomal trafficking protein SNX27. We are currently examining the role of GIRK channels and associated proteins in the psychostimulant-dependent modulation of slow inhibition and its impact in mouse models of addiction. To develop new therapeutics for treating addiction, it is essential to dissect out the components of drug-dependent plasticity in the brain and discover novel protein targets in the reward pathway.
III. Real-time optical measurements of neurotransmitter release in vivo
In collaboration with Professor Kleinfeld at UCSD, we have developed an innovative neurotechnique for optically measuring release of neurotransmitters in cell-specific and circuit-specific processes in the brain. Our technique is based on a new technology of cell-based neurotransmitter fluorescent engineered reporters, referred to as CNiFERs. A CNiFER is a clonal HEK293 cell that is engineered to express a specific G-protein coupled receptor and couples to a FRET-based Ca2+ indicator. Release of transmitter stimulates the native GPCR and induces an increase in FRET in the CNiFER. CNiFERs can detect nanoMolar concentrations of transmitter, have a temporal resolution of seconds, and a spatial resolution of < 100 μm. CNiFERs are implanted in the brain, where they produce minimal inflammation, and can be monitored over one week or more for in vivo longitudinal studies. We have created CNiFERs for detecting acetylcholine (M1-CNiFER), dopamine (D2-CNiFER) and norepinephrine (α1a-CNiFER) and have measured volume transmission of DA, norepinephrine, and acetylcholine in vivo during learning.
We are currently constructing CNiFERs for detecting neuropeptides in vivo. Neuropeptides are genetically encoded molecules that are widely expressed in the brain. Neuropeptides diffuse over long distances and signal through G protein coupled neuropeptide receptors. It is currently not possible to monitor release of peptides in real time. Neuropeptide CNiFERs should make it possible to measure in peptide release in real-time in awake animals as they perform complex behaviors, significantly advancing studies on the function of neuropeptides in regulating neural circuits in the brain.