Abstract

Heterogeneity of glucose-stimulated insulin secretion (GSIS) in pancreatic islets is physiologically important but poorly understood. Here, we utilize mouse islets to determine how microtubules affect secretion toward the vascular extracellular matrix at single cell and subcellular levels. Our data indicate that microtubule stability in the β-cell population is heterogenous, and that GSIS is suppressed in cells with highly stable microtubules. Consistently, microtubule hyper-stabilization prevents, and microtubule depolymerization promotes capacity of single β-cell for GSIS. Analysis of spatiotemporal patterns of secretion events shows that microtubule depolymerization activates otherwise dormant β-cells via initiation of secretion clusters (hot spots). Microtubule depolymerization also enhances secretion from individual cells, introducing both additional clusters and scattered events. Interestingly, without microtubules, the timing of clustered secretion is dysregulated, extending the first phase of GSIS and causing oversecretion. In contrast, glucose-induced Ca2+ influx was not affected by microtubule depolymerization yet required for secretion under these conditions, indicating that microtubule-dependent regulation of secretion hot spots acts in parallel with Ca2+ signaling. Our findings uncover a novel microtubule function in tuning insulin secretion hot spots, which leads to accurately measured and timed response to glucose stimuli and promotes functional β-cell heterogeneity.

Data availability

All numerical data generated during this study are included in the manuscript and supporting files. Source data files have been provided for all figures. Code is provided for computational data.

Article and author information

Author details

  1. Kathryn P Trogden

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-3288-3859
  2. Justin S Lee

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Kai M Bracey

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Kung-Hsien Ho

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Hudson McKinney

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Xiaodong Zhu

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Goker Arpag

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6893-2678
  8. Thomas G Folland

    Department of Mechanical Engineering, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  9. Anna B Osipovich

    Cell and Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  10. Mark A Magnuson

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8824-6499
  11. Marija Zanic

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-5127-5819
  12. Guoqiang Gu

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  13. William R Holmes

    Cell and Developmental Biology, Vanderbilt University, Nashville, United States
    Competing interests
    The authors declare that no competing interests exist.
  14. Irina Kaverina

    Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University, Nashville, United States
    For correspondence
    irina.kaverina@vanderbilt.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-4002-8599

Funding

National Institutes of Health (T32 DK07061)

  • Kathryn P Trogden

National Institutes of Health (1F32DK117529)

  • Kathryn P Trogden

National Institutes of Health (R35-GM127098)

  • Irina Kaverina

National Institutes of Health (R01-DK65949)

  • Guoqiang Gu

National Institutes of Health (DMS1562078)

  • William R Holmes

National Institutes of Health (R01-DK106228)

  • Guoqiang Gu
  • William R Holmes
  • Irina Kaverina

National Institutes of Health (R35-GM119552)

  • Marija Zanic

National Institutes of Health (F31 DK122650)

  • Kai M Bracey

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

Ethics

Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (protocol M1500060-00) of Vanderbilt University.

Copyright

© 2021, Trogden 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.

Metrics

  • 2,485
    views
  • 350
    downloads
  • 16
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Kathryn P Trogden
  2. Justin S Lee
  3. Kai M Bracey
  4. Kung-Hsien Ho
  5. Hudson McKinney
  6. Xiaodong Zhu
  7. Goker Arpag
  8. Thomas G Folland
  9. Anna B Osipovich
  10. Mark A Magnuson
  11. Marija Zanic
  12. Guoqiang Gu
  13. William R Holmes
  14. Irina Kaverina
(2021)
Microtubules regulate pancreatic β cell heterogeneity via spatiotemporal control of insulin secretion hot spots
eLife 10:e59912.
https://doi.org/10.7554/eLife.59912

Share this article

https://doi.org/10.7554/eLife.59912

Further reading

    1. Cell Biology
    Marjan Slak Rupnik
    Insight

    Functional subpopulations of β-cells emerge to control pulsative insulin secretion in the pancreatic islets of mice through calcium oscillations.

    1. Cell Biology
    Giuliana Giamundo, Daniela Intartaglia ... Ivan Conte
    Research Article

    Endosomes have emerged as major signaling hubs where different internalized ligand–receptor complexes are integrated and the outcome of signaling pathways are organized to regulate the strength and specificity of signal transduction events. Ezrin, a major membrane–actin linker that assembles and coordinates macromolecular signaling complexes at membranes, has emerged recently as an important regulator of lysosomal function. Here, we report that endosomal-localized EGFR/Ezrin complex interacts with and triggers the inhibition of the Tuberous Sclerosis Complex (TSC complex) in response to EGF stimuli. This is regulated through activation of the AKT signaling pathway. Loss of Ezrin was not sufficient to repress TSC complex by EGF and culminated in translocation of TSC complex to lysosomes triggering suppression of mTORC1 signaling. Overexpression of constitutively active EZRINT567D is sufficient to relocalize TSC complex to the endosomes and reactivate mTORC1. Our findings identify EZRIN as a critical regulator of autophagy via TSC complex in response to EGF stimuli and establish the central role of early endosomal signaling in the regulation of mTORC1. Consistently, Medaka fish deficient for Ezrin exhibit defective endo-lysosomal pathway, attributable to the compromised EGFR/AKT signaling, ultimately leading to retinal degeneration. Our data identify a pivotal mechanism of endo-lysosomal signaling involving Ezrin and its associated EGFR/TSC complex, which are essential for retinal function.