recording-gap-junction-current-from-xenopus-oocytes

Recording Gap Junction Current from <em>Xenopus</em> Oocytes

Heterologous expression of connexins and innexins in Xenopus oocytes is a powerful approach for studying the biophysical properties of gap junctions ...

University of Connecticut School of Medicine

Rectifying electrical synapses (RESs) exist across animal species, but their rectification mechanism is largely unknown. We investigated why RESs between AVA premotor interneurons and A-type cholinergic motoneurons (A-MNs) in  escape circuit conduct junctional currents ( ) only in the antidromic direction. These RESs consist of UNC-7 innexin in AVA and UNC-9 innexin in A-MNs. UNC-7 has multiple isoforms differing in the length and sequence of the amino terminus. In a heterologous expression system, only one UNC-7 isoform, UNC-7b, can form heterotypic gap junctions (GJs) with UNC-9 that strongly favor   in the UNC-9 to UNC-7 direction. Knockout of  alone almost eliminated the  , whereas AVA-specific expression of UNC-7b substantially rescued the coupling defect of  mutant. Neutralizing charged residues in UNC-7b amino terminus abolished the rectification property of UNC-7b/UNC-9 GJs. Our results suggest that the rectification property results from electrostatic interactions between charged residues in UNC-7b amino terminus.

Molecular basis of junctional current rectification at an electrical synapse.

Melatonin (Mel) promotes sleep through G protein-coupled receptors. However, the downstream molecular target(s) is unknown. We identified the  BK channel SLO-1 as a molecular target of the Mel receptor PCDR-1-. Knockout of , , or  (a gene required for Mel synthesis) causes substantially increased neurotransmitter release and shortened sleep duration, and these effects are nonadditive in double knockouts. Exogenous Mel inhibits neurotransmitter release and promotes sleep in wild-type (WT) but not  and  mutants. In a heterologous expression system, Mel activates the human BK channel (hSlo1) in a membrane-delimited manner in the presence of the Mel receptor MT but not MT A peptide acting to release free Gβγ also activates hSlo1 in a MT-dependent and membrane-delimited manner, whereas a Gβλ inhibitor abolishes the stimulating effect of Mel. Our results suggest that Mel promotes sleep by activating the BK channel through a specific Mel receptor and Gβλ.

Article	Year
Molecular basis of junctional current rectification at an electrical synapse. Science advances\| PubMed ID: 32923588	2020
Melatonin promotes sleep by activating the BK channel in . Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 32958651	2020

Yuan Shui

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