Spatially compartmentalized phase regulation of a Ca2+-cAMP-PKA oscillatory circuit.

Brian Tenner,Donya Ohadi,Brian Ross,Eric Greenwald,Sohum Mehta,Christopher H Bohrer,Jin Zhang,Michael Getz,Jie Xiao,Padmini Rangamani

doi:10.7554/elife.55013

Brian Tenner, Donya Ohadi + Show 8 more

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https://doi.org/10.7554/elife.55013

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Abstract

Signaling networks are spatiotemporally organized to sense diverse inputs, process information, and carry out specific cellular tasks. In β cells, Ca2+, cyclic adenosine monophosphate (cAMP), and Protein Kinase A (PKA) exist in an oscillatory circuit characterized by a high degree of feedback. Here, we describe a mode of regulation within this circuit involving a spatial dependence of the relative phase between cAMP, PKA, and Ca2+. We show that in mouse MIN6 β cells, nanodomain clustering of Ca2+-sensitive adenylyl cyclases (ACs) drives oscillations of local cAMP levels to be precisely in-phase with Ca2+ oscillations, whereas Ca2+-sensitive phosphodiesterases maintain out-of-phase oscillations outside of the nanodomain. Disruption of this precise phase relationship perturbs Ca2+ oscillations, suggesting the relative phase within an oscillatory circuit can encode specific functional information. This work unveils a novel mechanism of cAMP compartmentation utilized for localized tuning of an oscillatory circuit and has broad implications for the spatiotemporal regulation of signaling networks.

Highlights

Cyclic adenosine monophosphate and Ca2+ act as essential second messengers in almost every cell type and regulate many functional pathways within a cell, such as hormonal signal transduction, metabolism, and secretion (Clapham, 2007; Sassone-Corsi, 2012)
In order to study the spatiotemporal relationship between key players of the Ca2+-Cyclic adenosine monophosphate (cAMP)-protein kinase (PKA) circuit, we chose to focus our attention on an important class of molecular scaffolds, A-kinase anchoring proteins (AKAPs), which are responsible for recruiting PKA to specific substrates at distinct subcellular locations
Due to the extensive and multivalent nature of AKAP79/ 150 and a report describing the functional impairment of glucose-stimulated insulin secretion (GSIS) in pancreatic b cells upon its knock-out (Hinke et al, 2012), we hypothesized that the AKAP79/150 scaffold might play an important role in the spatiotemporal regulation of the Ca2+-cAMP-PKA oscillatory circuit

Summary

Introduction

Cyclic adenosine monophosphate (cAMP) and Ca2+ act as essential second messengers in almost every cell type and regulate many functional pathways within a cell, such as hormonal signal transduction, metabolism, and secretion (Clapham, 2007; Sassone-Corsi, 2012). In some cell types, including neurons, cardiomyocytes, and pancreatic b cells, these messengers’ concentrations oscillate intracellularly (Dupont et al, 2011; Dyachok et al, 2006), and the oscillations encode critical signaling information (e.g. signal strength, duration, and target diversity) into parameters such as frequency and amplitude (Berridge et al, 1998; De Pittaet al., 2008; Parekh, 2011) This phenomenon is perhaps best exemplified in b cells, where oscillations of Ca2+ drive pulsatile insulin secretion (Rorsman and Ashcroft, 2018) and oscillating cAMP levels (Nesher et al, 2002; Tengholm, 2012). By combining dynamic live-cell imaging, super-resolution microscopy, and computational modeling, we further found that fine-scale, compartment-specific perturbations of this precise phase regulation impact Ca2+ oscillations in b cells These findings suggest that the relative phase in oscillatory signaling circuits, like the amplitude and frequency, represents yet another mode of informational encoding and processing, which is subjected to spatiotemporal regulation within the cell

Results

Discussion

Materials and methods

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