Characterization of Beta-leptinotarsin-h and the Effects of Calcium Flux Antagonists on its Activity

Abstract

Beta-Leptinotarsin-h, purifed from the hemolymph of the beetle Leptinotarsa haldemani, is a potent neuroactive protein that stimulates Ca2+ influx and neurotransmitter release. Our goals were to further characterize beta-leptinotarsin-h and to test the hypthesis that it stimulates Ca2+ influx through presynaptic Ca2+ channels. Analysis of partial amino acid sequences revealed that beta-leptinotarsin-h is a unique protein with significant similarity to only one other protein, the juvenile hormone esterase of Leptinotarsa decemlineata, commonly known as the Colorado potato beetle. We examined the effect of beta-leptinotarsin-h on neurotransmitter release, Ca2+ current, Ca2+ uptake, and Ca2+ levels in several cell lines and neuronal systems. We found that its preferred site of action appears to be mammalian presynaptic nerve terminals. We tested antagonists of Ca2+ flux for their effects on beta-leptinotarsin-h-stimulated Ca2+ uptake in rat brain synaptosomes. We found that the nonselective Ca2+ channel blockers flunarizine, Ni2+, ruthenium red, high-concentration thapsigargin, and SKF 96365 inhibited beta-leptinotarsin-h's activity, but that non of the selective blockers of voltage-operated Ca2+ channels (w-agatoxin, IVA, w-conotoxin GVIA, w-conotoxin MVIIC, nicardipine, SNX 482) that we tested was inhibitory. Selective inhibitors of ligand-operated, store-operated, and transduction-operated channels were also not inhibitory. beta-leptinotarsin-h did not stimulate Na+ uptake, ruling out Na+ channels and nonselective cation channels as targets. We conclude that beta-leptinotarsin-h stimulated Ca2+ channels, which channel is yet to be determined.

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Document Details

Document Type
Technical Report
Publication Date
Apr 07, 2005
Accession Number
ADA434670

Entities

People

  • Harry B. Hines
  • Richard D. Crosland
  • Richard W. Fitch

Organizations

  • United States Army Medical Research Institute of Infectious Diseases

Tags

Communities of Interest

  • Biomedical

DTIC Thesaurus Topics

  • Amino Acids
  • Animal Structures
  • Cell Line
  • Cell Membrane
  • Cells
  • Cellular Structures
  • Chemical Synthesis
  • Chemistry
  • Diseases And Disorders
  • Inhibitors
  • Liquid Chromatography
  • Measurement
  • Organic Chemistry
  • Peripheral Nervous System
  • Rodents
  • Sequence Analysis
  • Spiders

Fields of Study

  • Biology

Readers

  • Cellular and Molecular Pathways of Apoptosis.
  • Neuroscience