Binding and sequestration of poison frog alkaloids by a plasma globulin

  1. Aurora Alvarez-Buylla  Is a corresponding author
  2. Marie-Therese Fischer
  3. Maria Dolores Moya Garzon
  4. Alexandra E Rangel
  5. Elicio E Tapia
  6. Julia T Tanzo
  7. H Tom Soh
  8. Luis A Coloma
  9. Jonathan Z Long
  10. Lauren A O'Connell  Is a corresponding author
  1. Stanford University, United States
  2. Leibniz Institute for the Analysis of Biodiversity Change, Germany
  3. Centro Jambatu de Investigación y Conservación de Anfibios, Ecuador

Abstract

Alkaloids are important bioactive molecules throughout the natural world, and in many animals they serve as a source of chemical defense against predation. Dendrobatid poison frogs bioaccumulate alkaloids from their diet to make themselves toxic or unpalatable to predators. Despite the proposed roles of plasma proteins as mediators of alkaloid trafficking and bioavailability, the responsible proteins have not been identified. We use chemical approaches to show that a ~50 kDa plasma protein is the principal alkaloid binding molecule in blood of poison frogs. Proteomic and biochemical studies establish this plasma protein to be a liver-derived alkaloid-binding globulin (ABG) that is a member of the serine-protease inhibitor (serpin) family. In addition to alkaloid binding activity, ABG sequesters and regulates the bioavailability of “free” plasma alkaloids in vitro. Unexpectedly, ABG is not related to saxiphilin, albumin, or other known vitamin carriers, but instead exhibits sequence and structural homology to mammalian hormone carriers and amphibian biliverdin binding proteins. Alkaloid-binding globulin (ABG) represents a new small molecule binding functionality in serpin proteins, a novel mechanism of plasma alkaloid transport in poison frogs, and more broadly points towards serpins acting as tunable scaffolds for small molecule binding and transport across different organisms.

Data availability

All raw data, analysis scripts, and intermediate data analysis are available either as Source Data zip files for each figure, or through public repositories. Uncropped gel images, analysis and plotting code, raw and normalized MST data, normalized RNAseq data, and other intermediate analysis files used to make figures are available as "Source Data" zip files included with the submission. All raw proteomics and mass spectrometry data are available on DataDryad: https://doi.org/10.5061/dryad.mkkwh7143. The official ABG sequences can be found through GenBank with the following accessions: O. sylvatica (OQ032869), D. tinctorius (OQ032870), and E. tricolor (OQ032871). The O. sylvatica genome, field collected sample information, raw and trimmed sequencing reads are available through the NCBI BioProject PRJNA909817. The A. femoralis genome and raw sequencing data is available through NCBI BioProject PRJNA913987. Annotated versions of the A. femoralis and O. sylvatica genomes, as well as E. tricolor, D. tinctorius, and M. aurantiaca transcriptomes are available on DataDryad: https://doi.org/10.5061/dryad.mkkwh7143.

The following data sets were generated

Article and author information

Author details

  1. Aurora Alvarez-Buylla

    Department of Biology, Stanford University, Stanford, United States
    For correspondence
    auroraab@stanford.edu
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6256-0300
  2. Marie-Therese Fischer

    Department of Biology, Stanford University, Stanford, United States
    Competing interests
    No competing interests declared.
  3. Maria Dolores Moya Garzon

    Department of Pathology, Stanford University, Stanford, United States
    Competing interests
    No competing interests declared.
  4. Alexandra E Rangel

    Department of Radiology, Stanford University, Stanford, United States
    Competing interests
    No competing interests declared.
  5. Elicio E Tapia

    Center for Taxonomy and Morphology, Leibniz Institute for the Analysis of Biodiversity Change, Hamburg, Germany
    Competing interests
    No competing interests declared.
  6. Julia T Tanzo

    Department of Pathology, Stanford University, Stanford, United States
    Competing interests
    No competing interests declared.
  7. H Tom Soh

    Department of Radiology, Stanford University, Stanford, United States
    Competing interests
    No competing interests declared.
  8. Luis A Coloma

    Centro Jambatu de Investigación y Conservación de Anfibios, San Rafael, Ecuador
    Competing interests
    No competing interests declared.
  9. Jonathan Z Long

    Department of Pathology, Stanford University, Stanford, United States
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2631-7463
  10. Lauren A O'Connell

    Department of Biology, Stanford University, Stanford, United States
    For correspondence
    loconnel@stanford.edu
    Competing interests
    Lauren A O'Connell, Reviewing editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2706-4077

Funding

National Science Foundation (IOS-1822025)

  • Lauren A O'Connell

New York Stem Cell Foundation

  • Lauren A O'Connell

National Science Foundation Graduate Research Fellowship Program (DGE-1656518)

  • Aurora Alvarez-Buylla

Howard Hughes Medical Institute (GT13330)

  • Aurora Alvarez-Buylla

Fundacion Alfonso Martin Escudero

  • Maria Dolores Moya Garzon

Wu Tsai Human Performance Alliance

  • Maria Dolores Moya Garzon

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: All animal procedures were approved by the Institutional Animal Care and Use Committee at Stanford (protocol #34153). Topical benzocaine was used for anesthesia prior to the euthanasia of all animals. Laboratory-bred animals were purchased from Understory Enterprises (Ontario, Canada) or Josh's Frogs (Michigan, USA) depending on the species. Animals were either euthanized for plasma collection upon arrival, or housed in 183 inch glass terraria, and fed a diet of non-toxic Drosophila melanogaster until euthanasia. Plasma and tissues from a total of 62 animals were used for this study, consisting of 32 lab-bred animals and 30 field-collected animals that are described below. Sample size of field-collected animals was determined based on variability seen in previous studies, and for laboratory experiments based on experimental needs in terms of volume of plasma.

Copyright

© 2023, Alvarez-Buylla et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Aurora Alvarez-Buylla
  2. Marie-Therese Fischer
  3. Maria Dolores Moya Garzon
  4. Alexandra E Rangel
  5. Elicio E Tapia
  6. Julia T Tanzo
  7. H Tom Soh
  8. Luis A Coloma
  9. Jonathan Z Long
  10. Lauren A O'Connell
(2023)
Binding and sequestration of poison frog alkaloids by a plasma globulin
eLife 12:e85096.
https://doi.org/10.7554/eLife.85096

Share this article

https://doi.org/10.7554/eLife.85096

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