title: Activation of galanin receptor 2 stimulates large conductance Ca(2+)-dependent K(+) (BK) channels through the IP3 pathway in human embryonic kidney (HEK293) cells.
abstract: The large conductance Ca(2+)-activated K(+) (BK) channels are widely distributed in the brain, and act as intracellular calcium sensors in neurons. They play an important feedback role in controlling Ca(2+) flux and Ca(2+)-dependent processes, including neurotransmitter release and cellular excitability. In this study, the effects of the neuropeptide galanin on BK channels were examined by determining the whole-cell currents and single-channel activities in human embryonic kidney (HEK293) cells co-expressing GalR2 and the BK alpha subunit. Galanin enhanced the currents of BK channels, in a concentration-dependent and PTX-independent manner, with an ED50 value of 71.8±16.9 nM. This activation was mediated by GalR2, since its agonist AR-M1896 mimicked the effect of galanin, and since galanin did not facilitate BK currents in cells co-expressing cDNAs of BK and GalR1 or GalR3. The galanin-induced BK current persisted after replacement with Ca(2+)-free solution, suggesting that extracellular Ca(2+) is not essential. Chelating intracellular Ca(2+) by either the slow Ca(2+) buffer EGTA or the fast Ca(2+) buffer BAPTA abolished galanin-mediated activation of BK channels, indicating the important role of intracellular Ca(2+). The role of Ca(2+) efflux from the sarcoplasmic reticulum/endoplasmic reticulum (SR/ER) was confirmed by application of thapsigargin, an irreversible inhibitor that depletes Ca(2+) from SR/ER. Moreover, the inositol-1,4,5-triphosphate receptor (IP3R) was identified as the mediator responsible for increased intracellular Ca(2+) activating BK channels. Taken together, activation of GalR2 leads to elevation of intracellular Ca(2+) is due to Ca(2+) efflux from ER through IP3R sequentially opening BK channels.
authors.affiliation: Beijing Key Laboratory of Neural Regeneration and Repair, Department of Neurobiology, Beijing Laboratory of Brain Disorders (MOST), Beijing 100069, China; Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
authors.forename: Na Clara
authors.initials: NC
authors.lastname: Pan
authors.affiliation: Beijing Key Laboratory of Neural Regeneration and Repair, Department of Neurobiology, Beijing Laboratory of Brain Disorders (MOST), Beijing 100069, China; Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
authors.forename: Yun-Fei
authors.initials: YF
authors.lastname: Bai
authors.affiliation: Beijing Key Laboratory of Neural Regeneration and Repair, Department of Neurobiology, Beijing Laboratory of Brain Disorders (MOST), Beijing 100069, China; Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
authors.forename: Yutao
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Neuroscience, Karolinska Institutet, S-17177 Stockholm, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Hökfelt
authors.affiliation: Beijing Key Laboratory of Neural Regeneration and Repair, Department of Neurobiology, Beijing Laboratory of Brain Disorders (MOST), Beijing 100069, China; Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China; Department of Neuroscience, Karolinska Institutet, S-17177 Stockholm, Sweden. Electronic address: zhiqingx@ccmu.edu.cn.
authors.forename: Zhi-Qing David
authors.initials: ZQ
authors.lastname: Xu
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D004721:Endoplasmic Reticulum / Q000378:metabolism; D019004:Galanin / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D044092:Receptor, Galanin, Type 2 / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; C494841:KCNMA1 protein, human; C465449:Kcnma1 protein, mouse; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D044092:Receptor, Galanin, Type 2; D015544:Inositol 1,4,5-Trisphosphate; D019004:Galanin
keywords: Endoplasmic reticulum; Neuropeptide; Patch clamp