Advancing cell signaling interrogation using theoretical and experimental approaches in eukaryotic model systems
OA Version
Citation
Abstract
Understanding how cells use intracellular signaling to detect environmental changes and alter behaviors is essential for understanding a wide range of biological processes. The current gap of understanding resides in time-changing signals in individual cells (signaling dynamics) and cell-cell communication in multicellular contexts. Here, we used theoretical and experimental approaches to study cell signaling in two eukaryotic model systems, with a specific focus on processes that involve signaling dynamics and cell-cell communication. First, we focus on the starvation-induced population-level signaling oscillations in the social amoebae, Dictyostelium discoideum. By constructing a unifying theoretical framework, we were able to directly compare existing models and experimental data. From this systematic investigation, we identified that the key features in single-cell signaling networks that coordinate population-level oscillations are adaptive spiking and fold-change detection. We then applied experimental approaches to interrogate how temporal changes in a signaling molecule modulate cell behaviors ("signal decoding") and how environmental cues modulate the dynamics of a signaling molecule ("environment encoding") in mammalian fibroblast cells. First, we explored the impact of transient, direct activation of the cAMP pathway on cell migration using an optogenetic tool. We found that cell migration is inhibited by repetitive transient activation of the cAMP pathway, and the inhibitory effect depends on the extent of activation. By characterizing a series of single-cell behaviors, we found that transient activation of the cAMP pathway induces reversible cell contractile force relaxation and actin cytoskeleton reorganization, both of which can potentially mediate migration inhibition. Further, we confirmed that the induced actin cytoskeleton reorganization is mediated by calcium signaling. Next, we investigated cytosolic calcium dynamics in the presence of a common culture media supplement, serum. We found serum induces trains of calcium spikes and further identified a major serum component mediating this response as lysophosphatidic acid (LPA). Although features of calcium spiking display a great amount of variability among cells, the faction of spiking cells and spiking frequency generally encode the concentration of environmental LPA. Through a series of pharmaceutical inhibitor experiments, we identified major sources of calcium ions as well as other pathways that shape calcium spiking. This body of work demonstrates the different utilities of theoretical modeling and experiments in understanding cell signaling which provides an advanced understanding of biological processes that involve signaling dynamics or cell-cell communication.
Description
License
Attribution 4.0 International