title: Release of calcium from endolysosomes increases calcium influx through N-type calcium channels: Evidence for acidic store-operated calcium entry in neurons.
abstract: Neurons possess an elaborate system of endolysosomes. Recently, endolysosomes were found to have readily releasable stores of intracellular calcium; however, relatively little is known about how such 'acidic calcium stores' affect calcium signaling in neurons. Here we demonstrated in primary cultured neurons that calcium released from acidic calcium stores triggered calcium influx across the plasma membrane, a phenomenon we have termed "acidic store-operated calcium entry (aSOCE)". aSOCE was functionally distinct from store-operated calcium release and calcium entry involving endoplasmic reticulum. aSOCE appeared to be governed by N-type calcium channels (NTCCs) because aSOCE was attenuated significantly by selectively blocking NTCCs or by siRNA knockdown of NTCCs. Furthermore, we demonstrated that NTCCs co-immunoprecipitated with the lysosome associated membrane protein 1 (LAMP1), and that aSOCE is accompanied by increased cell-surface expression levels of NTCC and LAMP1 proteins. Moreover, we demonstrated that siRNA knockdown of LAMP1 or Rab27a, both of which are key proteins involved in lysosome exocytosis, attenuated significantly aSOCE. Taken together our data suggest that aSOCE occurs in neurons, that aSOCE plays an important role in regulating the levels and actions of intraneuronal calcium, and that aSOCE is regulated at least in part by exocytotic insertion of N-type calcium channels into plasma membranes through LAMP1-dependent lysosome exocytosis.
authors.affiliation: Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND 58203, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Hui
authors.affiliation: Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND 58203, USA.
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Geiger
authors.affiliation: Department of Pharmacology, University of Oxford, Mansfield Rd., Oxford OX1 3QT, UK.
authors.forename: Duncan
authors.initials: D
authors.lastname: Bloor-Young
authors.affiliation: Department of Pharmacology, University of Oxford, Mansfield Rd., Oxford OX1 3QT, UK.
authors.forename: Grant C
authors.initials: GC
authors.lastname: Churchill
authors.affiliation: Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND 58203, USA. Electronic address: jonathan.geiger@med.und.edu.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Geiger
authors.affiliation: Department of Biomedical Sciences, University of North Dakota, School of Medicine and Health Sciences, Grand Forks, ND 58203, USA.
authors.forename: Xuesong
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology; D008247:Lysosomes / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D017207:Rats, Sprague-Dawley
chemical_list: D020864:Calcium Channels, N-Type; D002118:Calcium
keywords: Calcium; Endolysosomes; GPN; Lysosome exocytosis; N-type calcium channels; NAADP; Store-operated calcium entry