Activation of protein kinase Calpha couples cell volume to membrane Cl- permeability in HTC hepatoma and Mz-ChA-1 cholangiocarcinoma cells.
Physiological increases in liver cell volume lead to an adaptive response that includes opening of membrane Cl- channels, which is critical for volume recovery. The purpose of these studies was to assess the potential role for protein kinase C (PKC) as a signal involved in cell volume homeostasis. Studies were performed in HTC rat hepatoma and Mz-ChA-1 human cholangiocarcinoma cells, which were used as model hepatocytes and cholangiocytes, respectively. In each cell type, cell volume increases were followed by: 1) translocation of PKC from cytosolic to particulate (membrane) fractions; 2) a 10- to 40-fold increase in whole-cell membrane Cl- current density; and 3) partial recovery of cell volume. In HTC cells, the volume-dependent Cl- current response (-46 +/- 5 pA/pF) was inhibited by down-regulation of PKC (100 nmol/L phorbol 12-myristate 13-acetate for 18 hours [PMA]; -1.97 +/- 1.5 pA/pF), chelation of cytosolic Ca2+ (2 mmol/L EGTA; -5.3 +/- 4.0 pA/pF), depletion of cytosolic adenosine triphosphate (ATP) (3 U/mL apyrase; -12.58 +/- 1. 45 pA/pF), and by the putative PKC inhibitor, chelerythrine (25 micromol/L; -7 +/- 3 pA/pF). In addition, PKC inhibition by chelerythrine and calphostin C (500 nmol/L) prevented cell volume recovery from swelling. Similar results were obtained in Mz-ChA-1 biliary cells. These findings indicate that swelling-induced activation of PKC represents an important signal coupling cell volume to membrane Cl- permeability in both hepatic and biliary cell models.
Roman
R M
RM
University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Bodily
K O
KO
Wang
Y
Y
Raymond
J R
JR
Fitz
J G
JG
D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D001650:Bile Duct Neoplasms / Q000378:metabolism / Q000503:physiopathology*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000503:physiopathology*; D020134:Catalytic Domain; D002463:Cell Membrane Permeability / Q000502:physiology*; D018118:Chloride Channels / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D018281:Cholangiocarcinoma / Q000378:metabolism / Q000503:physiopathology*; D003470:Culture Media; D004789:Enzyme Activation; D006801:Humans; D007038:Hypotonic Solutions; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008113:Liver Neoplasms / Q000378:metabolism / Q000503:physiopathology*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism / Q000503:physiopathology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051381:Rats; D014407:Tumor Cells, Cultured
D000470:Alkaloids; D053119:Benzophenanthridines; D018118:Chloride Channels; D002712:Chlorides; D003470:Culture Media; D007038:Hypotonic Solutions; D007527:Isoenzymes; D010617:Phenanthridines; C016299:chelerythrine; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha