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Choy, R.

Publications and source records attributed to Choy, R..

2 recordsLinked to original sources

A Bioluminescent Assay for Quantification of Cellular Glycogen Levels

Glycogen is a large polymer of glucose that functions as an important means of storing energy and maintaining glucose homeostasis. Glycogen synthesis and degradation pathways are highly regulated and their dysregulation can contribute to disease. Glycogen storage diseases are a set of disorders that arise from improper glycogen metabolism. Glycogen storage disease II, known as Pompe disease, is caused by a genetic mutation that leads to increased glycogen storage in cells and tissues, resulting in progressive muscle atrophy and respiratory decline for patients. One approach for treating Pompe disease is to reduce glycogen levels by interfering with the glycogen synthesis pathway through glycogen synthase inhibitors. To facilitate the study of glycogen synthase inhibitors in biological samples, such as cultured cells, a high-throughput approach for measuring cellular glycogen was developed. A bioluminescent glycogen detection assay was automated and used to measure glycogen content in cells grown in 384-well plates. The assay successfully quantified reduced glycogen stores in cells treated with a series of glycogen synthase 1 inhibitors, verifying inhibitor activity in biological systems and validating the utility of the assay for glycogen metabolism studies. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=90 SRC="FIGDIR/small/595028v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@1ae263borg.highwire.dtl.DTLVardef@50124eorg.highwire.dtl.DTLVardef@e1ca53org.highwire.dtl.DTLVardef@1aa41dc_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

Connexin-36-expressing Gap Junctions in VTA GABA Neurons Sustain Opiate Dependence

Drug dependence is characterized by a switch in motivation wherein a positively reinforcing substance becomes negatively reinforcing. Ventral tegmental area (VTA) GABA neurons form a point of divergence between two double dissociable pathways responsible for these respective motivational states. Here we show that this switch from drug-naive to opiate-dependent and withdrawn (ODW) motivation is contingent upon the gap junction-forming protein, connexin-36 (Cx36), in VTA GABA neurons. Intra-VTA infusions of the Cx36 blocker, mefloquine, in ODW rats resulted in a reversion to a drug-naive motivational state and a loss of opiate withdrawal aversions. Consistent with these data, conditional knockout mice lacking Cx36 in GABA neurons (GAD65-Cre;Cx36fl(CFP)/fl(CFP)) were perpetually drug-naive and never experienced opiate withdrawal aversions. Further, viral-mediated rescue of Cx36 in VTA GABA neurons was sufficient to restore their susceptibility to ODW motivation. Our findings reveal a functional role for VTA gap junctions that has eluded prevailing circuit models of addiction. SignificanceThe motivation to seek drugs can vary depending on prior exposure. For instance, recreational and habitual drug use can stem from a desire to experience the pleasurable or relieving properties of the substance, respectively. Here we identify a subpopulation of midbrain neurons that dictate opiate-seeking motivation via expression of the gap junction protein, connexin-36. We show that connexin-36 expression increases upon opiate dependence and withdrawal. We then demonstrate that this is not merely a correlation, as pharmacological or genetic manipulations that interfere with connexin-36 function prevent the development of opiate dependence in rats and mice. Our results identify gap junctions as a critical node in the pathogenesis of opiate addiction, and a potential new target for substance use disorder pharmacotherapies.

neuroscience↗