Characterization of a novel stimulus-induced glial calcium wave in Drosophila larval peripheral segmental nerves and its role in PKG-modulated thermoprotection

Abstract

Insects, as poikilotherms, have adaptations to deal with wide ranges in temperature fluctuation. Allelic variations in the foraging gene that encodes a cGMP dependent protein kinase, were discovered to have effects on behavior in Drosophila by Dr. Marla Sokolowski in 1980. This single gene has many pleiotropic effects and influences feeding behavior, metabolic storage, learning and memory and has been shown to affect stress tolerance. PKG regulation affects motoneuronal thermotolerance in Drosophila larvae as well as adults. While the focus of thermotolerance studies has been on the modulation of neuronal function, other cell types have been overlooked. Because glia are vital to neuronal function and survival, we wanted to determine if glia play a role in thermotolerance as well. In our investigation, we discovered a novel calcium wave at the larval NMJ and set out to characterize the wave’s dynamics and the potential mechanism underlying the wave prior to determining what effect, if any, PKG modulation has on the thermotolerance of glia cells. Using pharmacology, we determined that calcium buffering mechanisms of the mitochondria and endoplasmic reticulum play a role in the propagation of our novel glial calcium wave. By coupling pharmacology with genetic manipulation using RNA interference (RNAi), we found that PKG modulation in glia alters thermoprotection of function as well as glial calcium wave dynamics.

Keywords:

• foraging
• PKG
• glia
• calcium
• mitochondria
• endoplasmic reticulum
• thermotolerance
• Drosophila melanogaster
• NMJ
• RNAi
• 3rd instar larvae
• peripheral nervous system

Acknowledgements

We would like to thank Dr. Marla Sokolowski for her innovative work in the field of behavioral genetics after her pioneering discovery of the foraging gene. Marla’s exploration of the interaction of foraging and Protein Kinase G with the environment, as well as the molecular basis of behavior, have inspired our research over the past decade. Her groundbreaking research has motivated several laboratories, including our own, to characterize the molecular underpinnings of neuroprotection and physiological changes resulting from foraging and PKG pathway variation. We would also like to thank Dr. Gregory Macleod and Dr. Adam Rossano for their early efforts in helping duplicate our glial Ca²⁺ wave findings in the Drosophila larval NMJ. Fly lines were supplied by Dr. Marla Sokolowski and Dr. Greg Macleod.

Disclosure statement

No potential conflict of interest was reported by the author(s).