Intracellular calcium signals regulate growth of hepatic stellate cells via specific effects on cell cycle progression.
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.
Soliman
Elwy M
EM
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.
Rodrigues
Michele Angela
MA
Gomes
Dawidson Assis
DA
Sheung
Nina
N
Yu
Jin
J
Amaya
Maria Jimina
MJ
Nathanson
Michael H
MH
Dranoff
Jonathan A
JA
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
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