Signaling diversity of PKA achieved via a Ca2+-cAMP-PKA oscillatory circuit

Abstract

Many protein kinases are key nodal signaling molecules that regulate a wide range of cellular functions. These functions may require complex spatiotemporal regulation of kinase activities. Here, we show that Protein Kinase A (PKA), Ca2+ and cAMP oscillate in sync in insulin-secreting MIN6 β cells, forming a highly integrated oscillatory circuit. We found that PKA activity was essential for this oscillatory circuit, and was capable of not only initiating the signaling oscillations but also modulating their frequency, thereby diversifying the spatiotemporal control of downstream signaling. Our findings suggest that exquisite temporal control of kinase activity, mediated via signaling circuits resulting from cross-regulation of signaling pathways, can encode diverse inputs into temporal parameters such as oscillation frequency, which in turn contributes to proper regulation of complex cellular functions in a context-dependent manner.

Calcium influx activates adenylyl cyclase 8 for sustained insulin secretion in rat pancreatic beta cells

“…R a t h e r t h a n g e n e r a t i n g pe r s i s t e n t m e m b r a n e depolarisation, as seen with KCl, glucose induces short trains of action potential spikes in beta cells [15,26]. Therefore, we used a perforated whole-cell voltage clamp, which keeps most of the intracellular metabolites intact during recording [3], to measure PKA activity evoked by a single depolarisation event.…”

“…Both Ca 2+ -activated and Ca 2+ -inhibited adenyl cyclase (ADCY) isoforms are expressed in insulinsecreting cells [13]. Ca 2+ -activated phosphodiesterase (PDE) has been proposed to mediate cAMP oscillations in clonal MIN6 cells [14,15]. Similarly, cAMP accumulation activates PKA, leading to phosphorylation of voltage-gated Ca 2+ channels (VGCCs) on the plasma membrane [16,17] and inositol 1,4,5-trisphosphate and ryanodine receptors on the endoplasmic membrane [18,19].…”

Fluorescence/Bioluminescence Resonance Energy Transfer Techniques to Study G-Protein-Coupled Receptor Activation and Signaling

“…However, only the advent of imaging technologies first by fluorescence (Tsien and Tsien, 1990) and later by FRET (Miyawaki, 2003) allowed the discovery of the full spectrum of spatiotemporal patterns in second-messenger concentrations. These studies revealed not only that concentrations in calcium as well as cAMP can show complex patterns of oscillations but that these may be interlinked by various intracellular mechanisms such as Ca 2ϩ -regulated phosphodiesterases and adenylyl cyclases (Zaccolo and Pozzan, 2003;Landa et al, 2005;Harbeck et al, 2006;Willoughby and Cooper, 2006;Kim et al, 2008;von Hayn et al, 2010;Ni et al, 2011;Werthmann et al, 2011). Oscillations have also been de- 326 scribed for the activity of protein kinase C (Violin et al, 2003).…”

Role of phosphodiesterases in the shaping of sub-plasma membrane cAMP oscillations and pulsatile insulin secretion

“…Moreover, the duration of a cAMP signal has been found to be crucial for the translocation of PKA catalytic subunits from the cytoplasm into the nucleus (Dyachok et al, 2006a;Dyachok et al, 2006b;Ni et al, 2011). cAMP oscillations could thereby provide a mechanism for spatially confining the activation of PKA-dependent effectors.…”