title: Intracellular calcium signals regulate growth of hepatic stellate cells via specific effects on cell cycle progression.
abstract: Hepatic stellate cells (HSC) are important mediators of liver fibrosis. Hormones linked to downstream intracellular Ca(2+) signals upregulate HSC proliferation, but the mechanisms by which this occurs are unknown. Nuclear and cytosolic Ca(2+) signals may have distinct effects on cell proliferation, so we expressed plasmid and adenoviral constructs containing the Ca(2+) chelator parvalbumin (PV) linked to either a nuclear localization sequence (NLS) or a nuclear export sequence (NES) to block Ca(2+) signals in distinct compartments within LX-2 immortalized human HSC and primary rat HSC. PV-NLS and PV-NES constructs each targeted to the appropriate intracellular compartment and blocked Ca(2+) signals only within that compartment. PV-NLS and PV-NES constructs inhibited HSC growth. Furthermore, blockade of nuclear or cytosolic Ca(2+) signals arrested growth at the G2/mitosis (G2/M) cell-cycle interface and prevented the onset of mitosis. Blockade of nuclear or cytosolic Ca(2+) signals downregulated phosphorylation of the G2/M checkpoint phosphatase Cdc25C. Inhibition of calmodulin kinase II (CaMK II) had identical effects on LX-2 growth and Cdc25C phosphorylation. We propose that nuclear and cytosolic Ca(2+) are critical signals that regulate HSC growth at the G2/M checkpoint via CaMK II-mediated regulation of Cdc25C phosphorylation. These data provide a new logical target for pharmacological therapy directed against progression of liver fibrosis.
authors.affiliation: Yale University School of Medicine, Department of Internal Medicine, Section of Digestive Diseases and Yale Liver Center, 333 Cedar St. LMP 1080, New Haven, CT 06515, USA.
authors.forename: Elwy M
authors.initials: EM
authors.lastname: Soliman
authors.forename: Michele Angela
authors.initials: MA
authors.lastname: Rodrigues
authors.forename: Dawidson Assis
authors.initials: DA
authors.lastname: Gomes
authors.forename: Nina
authors.initials: N
authors.lastname: Sheung
authors.forename: Jin
authors.initials: J
authors.lastname: Yu
authors.forename: Maria Jimina
authors.initials: MJ
authors.lastname: Amaya
authors.forename: Michael H
authors.initials: MH
authors.lastname: Nathanson
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Dranoff
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors; D002451:Cell Compartmentation / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D049109:Cell Proliferation / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016195:G2 Phase / Q000187:drug effects; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D010320:Parvalbumins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport; D051381:Rats; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D002614:Chelating Agents; D004791:Enzyme Inhibitors; D010320:Parvalbumins; D004533:Egtazic Acid; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D020687:cdc25 Phosphatases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid