BK channels and a cGMP-dependent protein kinase (PKG) function through independent mechanisms to regulate the tolerance of synaptic transmission to acute oxidative stress at the Drosophila larval neuromuscular junction

Abstract

A cGMP-dependent protein kinase (PKG) has previously been shown to regulate synaptic transmission at the Drosophila neuromuscular junction (NMJ) during acute oxidative stress, potentially through modulation of downstream K⁺ channel kinetics; however, the specific K⁺ channels through which PKG functions remains unclear. In this study, we hypothesized that PKG may be acting on calcium-activated large-conductance Slo K⁺ channels, or BK channels. We found that genetic elimination and pharmacological inhibition of BK channel conductance increases synaptic transmission tolerance to acute H₂O₂-induced oxidative stress. Furthermore, we discovered that activation of PKG in BK channel loss-of-function (Slo⁴) mutants significantly decreases time to stimulus-induced synaptic failure, providing the first evidence of PKG and BK channels functioning independently to control synaptic transmission tolerance to acute oxidative stress.

Keywords:

• Drosophila melanogaster
• oxidative stress
• cGMP-dependent protein kinase
• neuromuscular junction
• BK channels
• iberiotoxin
• synaptic transmission

Acknowledgements

We would like to thank Dr. Gregory Macleod for providing fly stocks and critical feedback. We also thank Dr. William Ja, Dr. Colin Hughes, Stephanie Kelly, Karlis Justs, and anonymous reviewers for providing valuable insights.

This article is dedicated to Professor Harold Atwood, who spent a career building a body of knowledge on the integration of morphological and physiological processes that modulate neuromuscular junction synaptic transmission. He also created a vast field of study based on the numerous investigators he trained through the decades of his works. On a personal note, I strive to create a scientific and social environment like the one I experienced as a Ph.D. student. As most young people, I mistakenly assumed that having such an environment was an easy thing to implement; but I see now that skill and expertise is also required to create an environment that built, what most of us remember as, the Atwood Lab. I will continue to strive for this with my own laboratory.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was support by a CTP (Compound Transfer Program) grant from Pfizer (WI225058 to K.D.-S.).