Mechanosensitivity of GIRK Channels Is Mediated by Protein Kinase C-dependent Channel-Phosphatidylinositol 4,5-Bisphosphate Interaction

Liyan Zhang, Jong Kook Lee, Scott A. John, Nobuyuki Uozumi, Itsuo Kodama

研究成果: Article査読

33 被引用数 (Scopus)

抄録

Gprotein-activated inwardly rectifying K+ channel (GIRK or Kir3) currents are inhibited by mechanical stretch of the cell membrane, but the underlying mechanisms are not understood. In Xenopus oocytes heterologously expressing GIRK channels, membrane stretch induced by 50% reduction of osmotic pressure caused a prompt reduction of GIRK1/4, GIRK1, and GIRK4 currents by 16.6-42.6%. Comparable GIRK current reduction was produced by protein kinase C (PKC) activation (phorbol 12-myristate 13-acetate). The mechanosensitivity of the GIRK4 current was abolished by pretreatment with PKC inhibitors (staurosporine or calphostin C). Neither hypo-osmotic challenge nor PKC activation affected IRK1 currents. GIRK4 chimera (GIRK4-IRK1-(Lys 207-Leu245)) and single point mutant (GIRK4(I229L)), in which the phosphatidylinositol 4,5-bisphosphate (PIP2) binding domain or residue was replaced by the corresponding region of IRK1 to strengthen the channel-PIP2 interaction, showed no mechanosensitivity and minimal PKC sensitivity. IRK1 gained mechanosensitivity and PKC sensitivity by reverse double point mutation of the PIP2 binding domain (L222I/R213Q). Overexpression of Gβγ, which is known to strengthen the channel-PIP2 interaction, attenuated the mechanosensitivity of GIRK4 channels. In oocytes expressing a pleckstrin homology domain of PLC-8 tagged with green fluorescent protein, hypo-osmotic challenge or PKC activation caused a translocation of the fluorescence signal from the cell membrane to the cytosol, reflecting PIP2 hydrolysis. The translocation was prevented by pretreatment with PKC inhibitors. Involvement of PKC activation in the mechanosensitivity of muscarinic K + channels was confirmed in native rabbit atrial myocytes. These results suggest that the mechanosensitivity of GIRK channels is mediated primarily by channel-PIP2 interaction, with PKC playing an important role in modulating the interaction probably through PIP2 hydrolysis.

本文言語English
ページ(範囲)7037-7047
ページ数11
ジャーナルJournal of Biological Chemistry
279
8
DOI
出版ステータスPublished - 2004 2 20
外部発表はい

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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