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Related Experiment Videos

Receptors for calcium antagonists.

A Schwartz1, E McKenna, P L Vaghy

  • 1Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575.

The American Journal of Cardiology
|October 5, 1988
PubMed
Summary

Calcium antagonists bind to distinct alpha 1 and alpha 2 subunits of voltage-dependent calcium channels. These subunits have different structures, with only alpha 1 exhibiting ion channel characteristics.

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Area of Science:

  • Pharmacology
  • Molecular Biology
  • Biochemistry

Background:

  • Calcium antagonists, including nifedipine, verapamil, and diltiazem, are classified into three subclasses with distinct pharmacologic effects.
  • Previous research indicated that calcium antagonists bind to a 170 kDa polypeptide, identified as the alpha 2 subunit of voltage-dependent calcium channels.
  • This alpha 2 subunit exhibits a characteristic decrease in molecular weight from 170 to 140 kDa upon disulfide reduction.

Purpose of the Study:

  • To investigate the precise molecular targets of calcium antagonists within voltage-dependent calcium channels.
  • To differentiate between the alpha 1 and alpha 2 subunits of the calcium channel and their interaction with calcium antagonists.
  • To elucidate the structural and functional characteristics of the polypeptides involved in calcium channel modulation.

Main Methods:

  • Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was employed to determine the molecular weights of the polypeptides.
  • Disulfide reduction was used to assess changes in electrophoretic mobility.
  • Analysis of primary structures was performed to identify distinct polypeptide features.

Main Results:

  • Recent studies identified a previously unrecognized 165 kDa polypeptide, the alpha 1 subunit, to which calcium antagonists bind.
  • The alpha 1 subunit does not alter its electrophoretic mobility upon disulfide reduction, distinguishing it from the alpha 2 subunit.
  • Despite similar molecular weights potentially causing overlap on gels, primary structure analysis confirms the alpha 1 and alpha 2 subunits are distinct.
  • Only the alpha 1 subunit possesses the structural features characteristic of an ion channel.

Conclusions:

  • Calcium antagonists bind to both alpha 1 and alpha 2 subunits of voltage-dependent calcium channels.
  • The alpha 1 subunit is the primary component with ion channel properties.
  • The distinct structural characteristics of the alpha 1 and alpha 2 subunits explain the differential binding and effects of various calcium antagonists.

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