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Nitric oxide activates PKCalpha and inhibits Na+-K+-ATPase in opossum kidney cells

M Liang1, F G Knox

  • 1Departments of Medicine and Physiology and Biophysics, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.

The American Journal of Physiology
|December 22, 1999
PubMed

Insights

Nitric oxide (NO) inhibits kidney cell Na+-K+-ATPase activity by activating protein kinase C alpha (PKCα). This NO-induced PKCα activation, observed in opossum kidney (OK) cells, is linked to reduced enzyme function.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Physiology

Background:

  • Nitric oxide (NO) is a signaling molecule with diverse physiological roles.
  • Na+-K+-ATPase is a crucial ion pump in kidney proximal tubules, regulating ion transport and cell function.
  • Previous studies indicate NO affects Na+-K+-ATPase activity, but the underlying cellular mechanisms require elucidation.

Purpose of the Study:

  • To investigate the cellular mechanisms by which NO inhibits Na+-K+-ATPase activity in kidney proximal tubule cells.
  • To determine the role of protein kinase C (PKC) in mediating the effects of NO on Na+-K+-ATPase.

Main Methods:

  • Utilized opossum kidney (OK) cells and LLC-PK1 cells as model systems.
  • Administered sodium nitroprusside (SNP) as a NO donor and phorbol 12-myristate 13-acetate (PMA) as a PKC activator.
  • Employed PKC inhibitors (staurosporine, calphostin C) and a protein kinase G (PKG) inhibitor (KT-5823).
  • Performed immunoblotting to assess PKCalpha translocation.
  • Used phospholipase C (PLC) inhibitor (U-73122) and soluble guanylate cyclase (sGC) inhibitor (1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one).

Main Results:

  • SNP inhibited Na+-K+-ATPase in OK cells but not LLC-PK1 cells.
  • PMA also inhibited Na+-K+-ATPase in OK cells, suggesting a role for PKC.
  • PKC inhibitors abolished NO's inhibitory effect on Na+-K+-ATPase in OK cells.
  • NO donors induced PKCalpha translocation from cytosolic to particulate fractions in OK cells.
  • PLC inhibition attenuated NO-induced PKCalpha translocation and Na+-K+-ATPase inhibition.

Conclusions:

  • Nitric oxide activates protein kinase C alpha (PKCα) in opossum kidney (OK) cells.
  • This NO-induced PKCα activation is responsible for the inhibition of Na+-K+-ATPase activity in OK cells.
  • The mechanism involves phospholipase C (PLC) signaling pathway, but not protein kinase G (PKG).

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