title: Tumor necrosis factor alpha and ceramide depolarise the resting membrane potential of thyroid FRTL-5 cells via a protein kinase Czeta-dependent regulation of K+ channels.
abstract: Tumor necrosis factor alpha (TNFalpha) alters the electrophysiological properties of many cell types. In thyroid cells however, the effects have not yet been elucidated. Here, we report the effect of TNFalpha and its second messenger ceramide on the resting membrane potential (RMP) of thyroid FRTL-5 cells. In patch-clamp experiments, we showed that TNFalpha and ceramide depolarise the RMP by inhibiting an acid-sensitive inwardly rectifying potassium current. This depolarisation depended on the activation of protein kinase Czeta (PKCzeta), because it can be blocked by calphostin C, a PKC-inhibitory peptide and a specific inhibitor peptide for PKCzeta. The activation of PKCzeta was confirmed by Western blotting, in which a stimulation with TNFalpha led to the translocation of PKCzeta to the particulate fraction. We conclude that TNFalpha and ceramide depolarise the RMP of thyroid FRTL-5 cells by attenuating a Ba(2+)- and acid-sensitive potassium conductance via activation of PKCzeta.
authors.affiliation: Department of Biology, Abo Akademi University, BioCity, Artillerigatan 6, 20520, Turku, Finland.
authors.forename: Cia
authors.initials: C
authors.lastname: Ramström
authors.forename: Hugh
authors.initials: H
authors.lastname: Chapman
authors.forename: Elina
authors.initials: E
authors.lastname: Ekokoski
authors.forename: Raimo K
authors.initials: RK
authors.lastname: Tuominen
authors.forename: Michael
authors.initials: M
authors.lastname: Pasternack
authors.forename: Kid
authors.initials: K
authors.lastname: Törnquist
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D049109:Cell Proliferation; D002518:Ceramides / Q000737:chemistry / Q000494:pharmacology*; D004594:Electrophysiology; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008564:Membrane Potentials / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000737:chemistry; D015221:Potassium Channels / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D000099221:Protein Kinase C zeta
chemical_list: D001464:Barium; D002518:Ceramides; D007477:Ions; D010455:Peptides; D015221:Potassium Channels; D011493:Protein Kinase C; D014409:Tumor Necrosis Factor-alpha; D000099221:Protein Kinase C zeta