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HPC-1 is associated with synaptotagmin and omega-conotoxin receptor

A Yoshida1, C Oho, A Omori

  • 1Mitsubishi Kasei Institute of Life Sciences, Tokyo, Japan.

The Journal of Biological Chemistry
|December 15, 1992
PubMed

Insights

Researchers identified a brain membrane protein (p35) that interacts with the omega-conotoxin receptor, a calcium channel. This protein, also known as HPC-1, forms a complex with synaptotagmin, suggesting a role in neurotransmitter release.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Cell Biology

Background:

  • The omega-conotoxin (omega-CgTX) receptor is a putative N-type calcium channel crucial for neuronal function.
  • Synaptotagmin is a known synaptic vesicle protein involved in neurotransmitter release.
  • The function and interactions of specific membrane proteins in the brain are not fully elucidated.

Purpose of the Study:

  • To characterize a 35,000 Da membrane protein (p35) expressed in the brain and adrenal medulla.
  • To investigate the relationship between p35, the omega-CgTX receptor, and synaptotagmin.
  • To determine the role of p35 in neurotransmitter release mechanisms.

Main Methods:

  • Production of monoclonal antibodies against p35.
  • Immunoprecipitation assays using anti-p35 and anti-synaptotagmin antibodies with solubilized rat brain proteins.
  • Isolation and sequencing of p35 cDNA from a rat brain library.
  • Bioinformatic analysis of the p35 primary structure.

Main Results:

  • Monoclonal antibodies against p35 immunoprecipitated 50% of the omega-CgTX receptor from rat brain.
  • p35 and synaptotagmin were found to co-immunoprecipitate with the omega-CgTX receptor, forming a ternary complex.
  • The primary structure of p35 was identical to HPC-1, possessing a transmembrane segment and heptad motifs suggestive of protein-protein interactions.

Conclusions:

  • p35, identified as HPC-1, is a component associated with the omega-CgTX-sensitive N-type calcium channel.
  • A subpopulation of the omega-CgTX receptor exists in a complex with p35 and synaptotagmin.
  • HPC-1 likely plays a role in neurotransmitter release by interacting with the N-type calcium channel and synaptotagmin.

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