title: The endoplasmic reticulum, not the pH gradient, drives calcium refilling of lysosomes.
abstract: Impaired homeostasis of lysosomal Ca(2+) causes lysosome dysfunction and lysosomal storage diseases (LSDs), but the mechanisms by which lysosomes acquire and refill Ca(2+) are not known. We developed a physiological assay to monitor lysosomal Ca(2+) store refilling using specific activators of lysosomal Ca(2+) channels to repeatedly induce lysosomal Ca(2+) release. In contrast to the prevailing view that lysosomal acidification drives Ca(2+) into the lysosome, inhibiting the V-ATPase H(+) pump did not prevent Ca(2+) refilling. Instead, pharmacological depletion or chelation of Endoplasmic Reticulum (ER) Ca(2+) prevented lysosomal Ca(2+) stores from refilling. More specifically, antagonists of ER IP3 receptors (IP3Rs) rapidly and completely blocked Ca(2+) refilling of lysosomes, but not in cells lacking IP3Rs. Furthermore, reducing ER Ca(2+) or blocking IP3Rs caused a dramatic LSD-like lysosome storage phenotype. By closely apposing each other, the ER may serve as a direct and primary source of Ca(2+)for the lysosome.
authors.affiliation: Neuroscience Program, University of Michigan, Ann Arbor, United States.
authors.forename: Abigail G
authors.initials: AG
authors.lastname: Garrity
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States.
authors.forename: Wuyang
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States.
authors.forename: Crystal Md
authors.initials: CM
authors.lastname: Collier
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States.
authors.forename: Sara A
authors.initials: SA
authors.lastname: Levey
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Gao
authors.affiliation: Neuroscience Program, University of Michigan, Ann Arbor, United States.|Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States.
authors.forename: Haoxing
authors.identifier: 0000-0003-3561-4654
authors.initials: H
authors.lastname: Xu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism*; D018892:Proton-Motive Force
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium
keywords: ER; calcium; cell biology; lysosome; mouse; neuroscience