Abstract
During chemotaxis, neutrophils use cell surface G Protein Coupled Receptors to detect chemoattractant gradients. The downstream signaling system is wired with multiple feedback loops that amplify weak inputs and promote spatial separation of cell front and rear activities. Positive feedback could promote rapid signal spreading, yet information from the receptors is transmitted with high spatial fidelity, enabling detection of small differences in chemoattractant concentration across the cell. How the signal transduction network achieves signal amplification while preserving spatial information remains unclear. The GTPase Cdc42 is a cell-front polarity coordinator that is predictive of cell turning, suggesting an important role in spatial processing. Here we directly measure information flow from receptors to Cdc42 by pairing zebrafish parapinopsina, an optogenetic G Protein Coupled Receptor with reversible ON/OFF control, with a spectrally compatible red/far red Cdc42 Fluorescence Resonance Energy Transfer biosensor. Using this toolkit, we show that positive and negative signals downstream of G proteins shape a rapid, dose-dependent Cdc42 response. Furthermore, F-actin and Cdc42 itself provide two distinct negative signals that limit the duration and spatial spread of Cdc42 activation, maintaining output signals local to the originating receptors.
Highlights
IntroductionNeutrophils use cell surface G Protein Coupled Receptors to detect chemoattractant gradients
During chemotaxis, neutrophils use cell surface G Protein Coupled Receptors to detect chemoattractant gradients
Prior studies indicate that receptors are uniformly distributed on the plasma membrane[9,10], and in Dictyostelium discoideum amoeba chemotaxis, G protein activity largely mirrors receptor binding[4], suggesting that spatial processing occurs downstream
Summary
Neutrophils use cell surface G Protein Coupled Receptors to detect chemoattractant gradients. We directly measure information flow from receptors to Cdc[42] by pairing zebrafish parapinopsina, an optogenetic G Protein Coupled Receptor with reversible ON/OFF control, with a spectrally compatible red/far red Cdc[42] Fluorescence Resonance Energy Transfer biosensor. Using this toolkit, we show that positive and negative signals downstream of G proteins shape a rapid, dose-dependent Cdc[42] response. Signal processing in chemotaxis balances two potentially competing challenges It must amplify signals using positive feedback to polarize cells with asymmetric protein activities, but it must retain information about receptor status locally. The negative signaling mechanisms helping to maintain spatial information remain unclear
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