title: Impaired Relaxation of Airway Smooth Muscle in Mice Lacking the Actin-Binding Protein Gelsolin.
abstract: Diverse classes of ligands have recently been discovered that relax airway smooth muscle (ASM) despite a transient increase in intracellular calcium concentrations ([Ca2+]i). However, the cellular mechanisms are not well understood. Gelsolin is a calcium-activated actin-severing and -capping protein found in many cell types, including ASM cells. Gelsolin also binds to phosphatidylinositol 4,5-bisphosphate, making this substrate less available for phospholipase Cβ-mediated hydrolysis to inositol triphosphate and diacylglycerol. We hypothesized that gelsolin plays a critical role in ASM relaxation and mechanistically accounts for relaxation by ligands that transiently increase [Ca2+]i. Isolated tracheal rings from gelsolin knockout (KO) mice showed impaired relaxation to both a β-agonist and chloroquine, a bitter taste receptor agonist, which relaxes ASM, despite inducing transiently increased [Ca2+]i. A single inhalation of methacholine increased lung resistance to a similar extent in wild-type and gelsolin KO mice, but the subsequent spontaneous relaxation was less in gelsolin KO mice. In ASM cells derived from gelsolin KO mice, serotonin-induced Gq-coupled activation increased both [Ca2+]iand inositol triphosphate synthesis to a greater extent compared to cells from wild-type mice, possibly due to the absence of gelsolin binding to phosphatidylinositol 4,5-bisphosphate. Single-cell analysis showed higher filamentous:globular actin ratio at baseline and slower cytoskeletal remodeling dynamics in gelsolin KO cells. Gelsolin KO ASM cells also showed an attenuated decrease in cell stiffness to chloroquine and flufenamic acid. These findings suggest that gelsolin plays a critical role in ASM relaxation and that activation of gelsolin may contribute to relaxation induced by ligands that relax ASM despite a transient increase in [Ca2+]i.
authors.affiliation: 1 Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, New York.
authors.forename: Maya
authors.initials: M
authors.lastname: Mikami
authors.affiliation: 1 Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, New York.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: 1 Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, New York.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Danielsson
authors.affiliation: 2 Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Tiarra
authors.initials: T
authors.lastname: Joell
authors.affiliation: 2 Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Hwan Mee
authors.initials: HM
authors.lastname: Yong
authors.affiliation: 1 Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, New York.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Townsend
authors.affiliation: 3 Department of Biology and Biochemistry, University of Houston, Baylor College of Medicine, Houston, Texas; and.
authors.forename: Seema
authors.initials: S
authors.lastname: Khurana
authors.affiliation: 2 Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.|4 Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland.
authors.forename: Steven S
authors.initials: SS
authors.lastname: An
authors.affiliation: 1 Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, New York.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Emala
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D002469:Cell Separation; D002738:Chloroquine / Q000494:pharmacology; D017097:Electric Impedance; D018260:Gelsolin / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000199:Actins; D018260:Gelsolin; D007295:Inositol Phosphates; D043562:Receptors, G-Protein-Coupled; D002738:Chloroquine
keywords: actin cytoskeleton; bitter taste receptor agonist; cell stiffness; flexiVent; smooth muscle relaxation