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

J Biol Chem. 2002 Jan 18;277(3):1974-80. doi: 10.1074/jbc.M107984200. Epub 2001 Nov 16.


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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Astrocytes / enzymology
  • Astrocytes / metabolism
  • Brain / enzymology
  • Brain / metabolism*
  • Cells, Cultured
  • Down-Regulation
  • Isoenzymes / metabolism*
  • Potassium Channels / physiology*
  • Potassium Channels, Inwardly Rectifying*
  • Protein Kinase C / metabolism*
  • Protein Kinase C-delta
  • Rats
  • Rats, Wistar
  • Signal Transduction / physiology
  • Transforming Growth Factor beta / physiology*
  • Type C Phospholipases / metabolism*


  • Isoenzymes
  • Kcnj4 protein, rat
  • Potassium Channels
  • Potassium Channels, Inwardly Rectifying
  • Transforming Growth Factor beta
  • Prkcd protein, rat
  • Protein Kinase C
  • Protein Kinase C-delta
  • Type C Phospholipases