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Characterization of G Protein-coupled Receptors by a Fluorescence-based Calcium Mobilization Assay
11:49

Characterization of G Protein-coupled Receptors by a Fluorescence-based Calcium Mobilization Assay

Published on: July 28, 2014

G-protein modulation of alpha 1A (P/Q) type calcium channel expressed in GH3 cells

S Zong1, M Yassin, T Tanabe

  • 1Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536-0812, USA.

Biochemical and Biophysical Research Communications
|October 4, 1995
PubMed

Insights

G-protein modulation of alpha 1A channels in GH3 cells was investigated. Carbachol application revealed both pertussis toxin-sensitive and insensitive pathways affecting channel activity.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Pharmacology

Background:

  • G-protein coupled receptors (GPCRs) modulate ion channel function through complex signaling pathways.
  • Alpha 1A voltage-gated calcium channels (VGCCs) play critical roles in neuronal excitability and neurotransmitter release.
  • GH3 cell lines provide a model system for studying cellular signaling and ion channel behavior.

Purpose of the Study:

  • To investigate the modulation of stably expressed alpha 1A calcium channels in GH3 cells by G-proteins.
  • To elucidate the involvement of membrane-delimited pathways in G-protein mediated channel regulation.
  • To characterize the distinct mechanisms underlying pertussis toxin (PTX)-sensitive and PTX-insensitive G-protein modulation of alpha 1A channels.

Main Methods:

  • Establishment of GH3 cell lines stably expressing alpha 1A calcium channels.
  • Electrophysiological recordings (e.g., patch-clamp) to measure calcium currents.
  • Application of carbachol to activate G-protein signaling pathways.
  • Treatment with pertussis toxin (PTX) to differentiate between G-protein signaling pathways.
  • Voltage-clamp protocols to assess channel kinetics and voltage-dependence.

Main Results:

  • Wild-type GH3 cells exhibited omega-conotoxin MVIIC (MVIIC)-sensitive Ca2+ currents, distinct from alpha 1A channels due to G-protein modulation.
  • Carbachol application to alpha 1A-expressing GH3 cells resulted in slowed activation and reduced current amplitude.
  • These carbachol-induced effects were voltage-dependent and sensitive to pertussis toxin (PTX).
  • Alpha 1A channels were also modulated via a PTX-insensitive pathway, exhibiting similar modulatory effects.
  • The findings suggest distinct mechanisms govern PTX-sensitive and PTX-insensitive G-protein modulation pathways.

Conclusions:

  • G-protein modulation of alpha 1A calcium channels in GH3 cells occurs through both PTX-sensitive and PTX-insensitive pathways.
  • These distinct pathways likely involve different G-protein subtypes and downstream signaling elements.
  • The study highlights the complexity of ion channel regulation by G-proteins, with implications for understanding neuronal function and drug development.

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