Shank promotes action potential repolarization by recruiting BK channels to calcium microdomains
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Evaluation Summary:
The authors use C. elegans to explore the relationship between shank (an Autism-associated gene orthologue), CaV1 (Ca) channels, and BK (slo) calcium-dependent K channels in controlling muscle excitability. The data annotate a novel activity of Shank as an organizer of ion channel domains with potential relevance to human disease.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)
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Abstract
Mutations altering the scaffolding protein Shank are linked to several psychiatric disorders, and to synaptic and behavioral defects in mice. Among its many binding partners, Shank directly binds CaV1 voltage activated calcium channels. Here, we show that the Caenorhabditis elegans SHN-1/Shank promotes CaV1 coupling to calcium activated potassium channels. Mutations inactivating SHN-1, and those preventing SHN-1 binding to EGL-19/CaV1 all increase action potential durations in body muscles. Action potential repolarization is mediated by two classes of potassium channels: SHK-1/KCNA and SLO-1 and SLO-2 BK channels. BK channels are calcium-dependent, and their activation requires tight coupling to EGL-19/CaV1 channels. SHN-1’s effects on AP duration are mediated by changes in BK channels. In shn-1 mutants, SLO-2 currents and channel clustering are significantly decreased in both body muscles and neurons. Finally, increased and decreased shn-1 gene copy number produce similar changes in AP width and SLO-2 current. Collectively, these results suggest that an important function of Shank is to promote microdomain coupling of BK with CaV1.
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Evaluation Summary:
The authors use C. elegans to explore the relationship between shank (an Autism-associated gene orthologue), CaV1 (Ca) channels, and BK (slo) calcium-dependent K channels in controlling muscle excitability. The data annotate a novel activity of Shank as an organizer of ion channel domains with potential relevance to human disease.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)
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Reviewer #1 (Public Review):
Technically, the paper from the Kaplan rests on solid ground. An array of mutations and transgenic lines are used in the study the Shank gene, and are nicely documented. The electrophysiological assessment of ionic currents in C. elegans muscle is clear and well documented. Finally, the light-level protein localization analyses are clear and well documented. The authors cleanly define a set of phenotypes caused by mutations in the Shank gene, influencing muscle action potentials in C elegans.
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Reviewer #2 (Public Review):
The authors use C. elegans to explore the relationship between shank, CaV1 (Ca) channels, and BK (slo) calcium-dependent K channels in controlling muscle excitability. They use a range of genetic approaches to mutate or knock out one or more of these players and assess the impact on muscle action potential generation and slo currents. Their data show that shank controls AP width and plateau potential generation (pp) through Slo channels, and this effect is cell-autonomous in muscle. They go on to suggest this effect is mediated through CaV1-slo coupling, by using previously characterized mutant that reduce this binding. Because these mutations may affect binding with other partners, these experiments do not unequivocally implicate direct binding between these three players; however, use of fast and slow Ca …
Reviewer #2 (Public Review):
The authors use C. elegans to explore the relationship between shank, CaV1 (Ca) channels, and BK (slo) calcium-dependent K channels in controlling muscle excitability. They use a range of genetic approaches to mutate or knock out one or more of these players and assess the impact on muscle action potential generation and slo currents. Their data show that shank controls AP width and plateau potential generation (pp) through Slo channels, and this effect is cell-autonomous in muscle. They go on to suggest this effect is mediated through CaV1-slo coupling, by using previously characterized mutant that reduce this binding. Because these mutations may affect binding with other partners, these experiments do not unequivocally implicate direct binding between these three players; however, use of fast and slow Ca buffers also suggests that shank keeps CaV1 and slo in close association, presumably allowing Ca influx through CaV1 channels to effectively activate slo channels. Finally, they show that overexpression of shank has a similar impact on excitability as reduction; this is somewhat puzzling and not further explored mechanistically, but is interesting given gene dosage effects of shanks in humans.
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Reviewer #3 (Public Review):
Gao et al. present a nice set of data, using electrophysiology and molecular genetics, to address the function of C. elegans Shank (shn-1) in shaping muscle action potentials. Using genome-edited Cre-dependent deletion and expression of SHN-1, they show that removal of shn-1 specifically in body muscle widens the duration of action potentials and increases prolonged depolarization events known as plateau potentials (PP). They provide new evidence that SHN-1 couples the activity of the calcium channel EGL-19 to that of the BK potassium channels SLO-1/2. They additionally reveal that action potentials are sensitive to SHN-1 dosage. The experiments are generally conducted rigorously, and conclusions are stated appropriately. The findings offer insights into how human Shank misexpression might contribute to …
Reviewer #3 (Public Review):
Gao et al. present a nice set of data, using electrophysiology and molecular genetics, to address the function of C. elegans Shank (shn-1) in shaping muscle action potentials. Using genome-edited Cre-dependent deletion and expression of SHN-1, they show that removal of shn-1 specifically in body muscle widens the duration of action potentials and increases prolonged depolarization events known as plateau potentials (PP). They provide new evidence that SHN-1 couples the activity of the calcium channel EGL-19 to that of the BK potassium channels SLO-1/2. They additionally reveal that action potentials are sensitive to SHN-1 dosage. The experiments are generally conducted rigorously, and conclusions are stated appropriately. The findings offer insights into how human Shank misexpression might contribute to neurological disorder.
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