slesinger lab
laboratory of membrane excitability & disease
My long-term objective is to discover new drugs for treating addiction to drugs of abuse and alcohol. Currently, there are few FDA approved drugs for treating these diseases and more are greatly needed. Many of the neurotransmitters in the drug-reward pathway exert their effects by activating G protein-coupled receptors, which, in turn, communicate with specific G proteins and affect down-stream signaling pathways. One of the down-stream targets is the G protein-gated inwardly rectifying potassium (GIRK) channel, which we study in my laboratory. By controlling the membrane excitability of neurons, GIRK channels provide a fundamental source of neuromodulatory inhibition in the brain. My laboratory has been addressing fundamental questions concerning the function of GIRK channels in the brain, taking a broad approach of combining structural biology, biochemistry, electrophysiology and behavior. We have contributed significant work on the mechanism underlying G protein-regulation and gating of GIRK channels, provided evidence for the assembly of GIRK channels in macromolecular signaling complexes, and identified novel proteins that regulate GIRK channels. More recently, we have elucidated the subcellular mechanisms underlying the neuroplastic changes in GIRK channel signaling with drugs of abuse and alcohol.

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.


Watching thoughts – and addiction – form in the brain — Aug 22, 2016

More than a hundred years ago, Ivan Pavlov conducted what would become one of the most famous and influential psychology studies —he conditioned dogs to salivate at the ringing of a bell. Now, scientists are able to see in real time what happens in the brains of live animals during this classic experiment with a new technique. Ultimately, the approach could lead to a greater understanding of how we learn, and develop and break addictions. View.

— American Chemical Soicety