Highly Localized intracellular Ca2+ signals promote optimal salivary gland fluid secretion

  1. Takahiro Takano
  2. Amanda Wahl
  3. Kai-Ting Huang
  4. Takanori Narita
  5. John Rugis
  6. James Sneyd
  7. David I Yule  Is a corresponding author
  1. University of Rochester School of Medicine and Dentistry, United States
  2. U. Rochester, United States
  3. Nihon University, Japan
  4. University of Auckland, New Zealand

Abstract

Salivary fluid secretion involves an intricate choreography of membrane transporters to result in the trans-epithelial movement of NaCl and water into the acinus lumen. Current models are largely based on experimental observations in enzymatically isolated cells where the Ca2+ signal invariably propagates globally and thus appears ideally suited to activate spatially separated Cl and K channels, present on the apical and basolateral plasma membrane, respectively. We monitored Ca2+ signals and salivary secretion in live mice expressing GCamp6F, following stimulation of the nerves innervating the submandibular gland. Consistent with in vitro studies, Ca2+ signals were initiated in the apical endoplasmic reticulum. In marked contrast to in vitro data, highly localized trains of Ca2+ transients that failed to fully propagate from the apical region were observed. Following stimuli optimum for secretion, large apical-basal gradients were elicited. A new mathematical model, incorporating these data was constructed to probe how salivary secretion can be optimally stimulated by apical Ca2+ signals.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 2,3,4,5,6,9,10,11

Article and author information

Author details

  1. Takahiro Takano

    Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Amanda Wahl

    Pharmacology and Physiology, U. Rochester, Rochester, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Kai-Ting Huang

    Pharmacology and Physiology, U. Rochester, Rochester, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Takanori Narita

    Nihon University, Fujisawa, Japan
    Competing interests
    The authors declare that no competing interests exist.
  5. John Rugis

    Mathematics, University of Auckland, Auckland, New Zealand
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8009-4152
  6. James Sneyd

    Mathematics, University of Auckland, Auckland, New Zealand
    Competing interests
    The authors declare that no competing interests exist.
  7. David I Yule

    Pharmacology and Physiology, U. Rochester, Rochester, United States
    For correspondence
    david_yule@urmc.rochester.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6743-0668

Funding

National Institute of Dental and Craniofacial Research (DE019245)

  • David I Yule

National Institute of Dental and Craniofacial Research (DE014756)

  • David I Yule

Marsden Fund

  • James Sneyd

National Institute of Dental and Craniofacial Research (F31 DE030670)

  • Amanda Wahl

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 University Committee on Animal Resources (UCAR-2001-214E)

Copyright

© 2021, Takano 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

  • 1,755
    views
  • 254
    downloads
  • 24
    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. Takahiro Takano
  2. Amanda Wahl
  3. Kai-Ting Huang
  4. Takanori Narita
  5. John Rugis
  6. James Sneyd
  7. David I Yule
(2021)
Highly Localized intracellular Ca2+ signals promote optimal salivary gland fluid secretion
eLife 10:e66170.
https://doi.org/10.7554/eLife.66170

Share this article

https://doi.org/10.7554/eLife.66170

Further reading

    1. Cell Biology
    Erli Jin, Jennifer K Briggs ... Matthew J Merrins
    Research Article

    Oscillations in insulin secretion, driven by islet Ca2+ waves, are crucial for glycemic control. Prior studies, performed with single-plane imaging, suggest that subpopulations of electrically coupled β-cells have privileged roles in leading and coordinating the propagation of Ca2+ waves. Here, we used three-dimensional (3D) light-sheet imaging to analyze the location and Ca2+ activity of single β-cells within the entire islet at >2 Hz. In contrast with single-plane studies, 3D network analysis indicates that the most highly synchronized β-cells are located at the islet center, and remain regionally but not cellularly stable between oscillations. This subpopulation, which includes ‘hub cells’, is insensitive to changes in fuel metabolism induced by glucokinase and pyruvate kinase activation. β-Cells that initiate the Ca2+ wave (leaders) are located at the islet periphery, and strikingly, change their identity over time via rotations in the wave axis. Glucokinase activation, which increased oscillation period, reinforced leader cells and stabilized the wave axis. Pyruvate kinase activation, despite increasing oscillation frequency, had no effect on leader cells, indicating the wave origin is patterned by fuel input. These findings emphasize the stochastic nature of the β-cell subpopulations that control Ca2+ oscillations and identify a role for glucokinase in spatially patterning ‘leader’ β-cells.

    1. Cell Biology
    Kelsey R Baron, Samantha Oviedo ... R Luke Wiseman
    Research Article

    Excessive mitochondrial fragmentation is associated with the pathologic mitochondrial dysfunction implicated in the pathogenesis of etiologically diverse diseases, including many neurodegenerative disorders. The integrated stress response (ISR) – comprising the four eIF2α kinases PERK, GCN2, PKR, and HRI – is a prominent stress-responsive signaling pathway that regulates mitochondrial morphology and function in response to diverse types of pathologic insult. This suggests that pharmacologic activation of the ISR represents a potential strategy to mitigate pathologic mitochondrial fragmentation associated with human disease. Here, we show that pharmacologic activation of the ISR kinases HRI or GCN2 promotes adaptive mitochondrial elongation and prevents mitochondrial fragmentation induced by the calcium ionophore ionomycin. Further, we show that pharmacologic activation of the ISR reduces mitochondrial fragmentation and restores basal mitochondrial morphology in patient fibroblasts expressing the pathogenic D414V variant of the pro-fusion mitochondrial GTPase MFN2 associated with neurological dysfunctions, including ataxia, optic atrophy, and sensorineural hearing loss. These results identify pharmacologic activation of ISR kinases as a potential strategy to prevent pathologic mitochondrial fragmentation induced by disease-relevant chemical and genetic insults, further motivating the pursuit of highly selective ISR kinase-activating compounds as a therapeutic strategy to mitigate mitochondrial dysfunction implicated in diverse human diseases.