Transforming growth factor-beta 1 regulates Kir2.3 inward rectifier K+ channels via phospholipase C and protein kinase C-delta in reactive astrocytes from adult rat brain.
The multifunctional cytokine, transforming growth factor beta(1) (TGF-beta(1)), exerts complex effects on astrocytes with early signaling events being less well characterized than transcriptional mechanisms. We examined the effect of TGF-beta(1) on the 14-pS Kir2.3 inward rectifier K(+) channel in rat primary cultured reactive astrocytes. Immunofluorescence study showed that cells co-expressed TGF-beta(1) receptors 1 and 2, Kir2.3, and glial fibrillary acidic protein (GFAP). Patch clamp study showed that TGF-beta(1) (0.1-100 ng/ml) caused a rapid (<5 min) depolarization because of dose-dependent down-regulation of Kir2.3 channels, which was mimicked by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (10-500 nm) and which was inhibited by the PKC inhibitor calphostin C (100 nm), by PKC desensitization produced by 3 h of exposure to phorbol 12-myristate 13-acetate (100 nm), and by the PKC-delta isoform-specific inhibitor rottlerin (50 microm). Immunoblot analysis and confocal imaging showed that TGF-beta(1) caused PKC-delta translocation to membrane, and co-immunoprecipitation experiments showed that TGF-beta(1) enhanced association between Kir2.3 and PKC-delta. Additional electrophysiological experiments showed that Kir2.3 channel down-regulation was blocked by the phospholipase C inhibitors, neomycin (100 microm) and D609 (200 microm). Given the commonality of signaling involving PLC-PKC-delta, we speculate that TGF-beta(1)-evoked depolarization may be an early signaling event related to gene transcription in astrocytes.
Perillan
Pablo R
PR
Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Chen
Mingkui
M
Potts
Eric A
EA
Simard
J Marc
JM
D000818:Animals; D001253:Astrocytes / Q000201:enzymology / Q000378:metabolism; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D002478:Cells, Cultured; D015536:Down-Regulation; D007527:Isoenzymes / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism*
D007527:Isoenzymes; C490968:Kcnj4 protein, rat; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D016212:Transforming Growth Factor beta; C497260:Prkcd protein, rat; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D010738:Type C Phospholipases