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Na,K-ATPase alpha 2 inhibition alters calcium responses in optic nerve astrocytes

April K Hartford1, Miranda L Messer, Amy E Moseley

  • 1Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, Louisville, Kentucky 40202, USA.

Glia
|January 20, 2004
PubMed

Insights

Selective inhibition of Na,K-ATPase alpha2 isoform enhances calcium signaling and capacitative calcium entry (CCE) in astrocytes. This suggests alpha2 Na,K-ATPase plays a key role in regulating cellular calcium responses.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Biochemistry

Background:

  • The Na,K-ATPase (sodium-potassium adenosine triphosphatase) is a crucial ion pump involved in maintaining cellular homeostasis.
  • Specific isoforms of Na,K-ATPase, such as alpha2, may play distinct roles in cellular signaling pathways, including calcium regulation.
  • Capacitative calcium entry (CCE) is a critical process for cellular calcium influx, regulated by various membrane proteins.

Purpose of the Study:

  • To investigate the effect of selective Na,K-ATPase alpha2 isoform inhibition on capacitative calcium entry (CCE) and ATP-elicited calcium responses in astrocytes.
  • To determine the role of the Na,K-ATPase alpha2 isoform in modulating intracellular calcium concentrations.

Main Methods:

  • Experiments utilized rat optic nerve astrocytes and immortalized astrocytes from Na,K-ATPase alpha2 knockout (KO) and wild-type (WT) mice.
  • Cytosolic calcium and sodium concentrations were measured using Fura-2 and SBFI fluorescent indicators, respectively.
  • The effects of 1 microM ouabain, a selective Na,K-ATPase alpha2 inhibitor in rats, were assessed on CCE and ATP-induced calcium release.

Main Results:

  • 1 microM ouabain significantly increased the magnitude of CCE and ATP-induced calcium responses in rat astrocytes.
  • Na,K-ATPase alpha2 KO astrocytes exhibited significantly higher CCE and ATP-induced calcium responses compared to WT astrocytes.
  • In KO astrocytes, CCE was insensitive to 1 microM ouabain, indicating a specific role for the alpha2 isoform.

Conclusions:

  • Selective inhibition or absence of the Na,K-ATPase alpha2 isoform enhances both capacitative calcium entry and calcium release from internal stores.
  • These findings suggest that the Na,K-ATPase alpha2 isoform plays a significant inhibitory role in regulating astrocytic calcium signaling.
  • Targeting the Na,K-ATPase alpha2 isoform may represent a novel strategy for modulating calcium signaling in the nervous system.

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