Format

Send to

Choose Destination
J Neurosci. 2019 Mar 27;39(13):2416-2429. doi: 10.1523/JNEUROSCI.3068-18.2019. Epub 2019 Jan 28.

Endogenous Tagging Reveals Differential Regulation of Ca2+ Channels at Single Active Zones during Presynaptic Homeostatic Potentiation and Depression.

Author information

1
Department of Neuroscience.
2
Carney Institute for Brain Science, Brown University, Providence, Rhode Island 02912.
3
Department of Neurobiology, University of Southern California, Los Angeles, California 90089.
4
Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706.
5
Department of Biological Sciences and Wilkes Honors College, Florida Atlantic University, Jupiter, Florida 33458, and.
6
Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706.
7
Department of Neuroscience, oconnorgiles@brown.edu.

Abstract

Neurons communicate through Ca2+-dependent neurotransmitter release at presynaptic active zones (AZs). Neurotransmitter release properties play a key role in defining information flow in circuits and are tuned during multiple forms of plasticity. Despite their central role in determining neurotransmitter release properties, little is known about how Ca2+ channel levels are modulated to calibrate synaptic function. We used CRISPR to tag the Drosophila CaV2 Ca2+ channel Cacophony (Cac) and, in males in which all Cac channels are tagged, investigated the regulation of endogenous Ca2+ channels during homeostatic plasticity. We found that heterogeneously distributed Cac is highly predictive of neurotransmitter release probability at individual AZs and differentially regulated during opposing forms of presynaptic homeostatic plasticity. Specifically, AZ Cac levels are increased during chronic and acute presynaptic homeostatic potentiation (PHP), and live imaging during acute expression of PHP reveals proportional Ca2+ channel accumulation across heterogeneous AZs. In contrast, endogenous Cac levels do not change during presynaptic homeostatic depression (PHD), implying that the reported reduction in Ca2+ influx during PHD is achieved through functional adaptions to pre-existing Ca2+ channels. Thus, distinct mechanisms bidirectionally modulate presynaptic Ca2+ levels to maintain stable synaptic strength in response to diverse challenges, with Ca2+ channel abundance providing a rapidly tunable substrate for potentiating neurotransmitter release over both acute and chronic timescales.SIGNIFICANCE STATEMENT Presynaptic Ca2+ dynamics play an important role in establishing neurotransmitter release properties. Presynaptic Ca2+ influx is modulated during multiple forms of homeostatic plasticity at Drosophila neuromuscular junctions to stabilize synaptic communication. However, it remains unclear how this dynamic regulation is achieved. We used CRISPR gene editing to endogenously tag the sole Drosophila Ca2+ channel responsible for synchronized neurotransmitter release, and found that channel abundance is regulated during homeostatic potentiation, but not homeostatic depression. Through live imaging experiments during the adaptation to acute homeostatic challenge, we visualize the accumulation of endogenous Ca2+ channels at individual active zones within 10 min. We propose that differential regulation of Ca2+ channels confers broad capacity for tuning neurotransmitter release properties to maintain neural communication.

KEYWORDS:

Drosophila; calcium channels; gene editing; homeostatic plasticity; neurotransmitter release; synapse

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center