Filamin, a synaptic organizer in Drosophila, determines glutamate receptor composition and membrane growth

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Abstract

Filamin is a scaffolding protein that functions in many cells as an actin-crosslinker. FLN90, an isoform of the Drosophila ortholog Filamin/cheerio that lacks the actin-binding domain, is here shown to govern the growth of postsynaptic membrane folds and the composition of glutamate receptor clusters at the larval neuromuscular junction. Genetic and biochemical analyses revealed that FLN90 is present surrounding synaptic boutons. FLN90 is required in the muscle for localization of the kinase dPak and, downstream of dPak, for localization of the GTPase Ral and the exocyst complex to this region. Consequently, Filamin is needed for growth of the subsynaptic reticulum. In addition, in the absence of filamin, type-A glutamate receptor subunits are lacking at the postsynapse, while type-B subunits cluster correctly. Receptor composition is dependent on dPak, but independent of the Ral pathway. Thus two major aspects of synapse formation, morphological plasticity and subtype-specific receptor clustering, require postsynaptic Filamin.

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GaYoung Lee

The F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, United States

Competing interests
The authors declare that no competing interests exist.
Thomas L Schwarz

The F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, United States

For correspondence
Thomas.Schwarz@childrens.harvard.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-7532-0250

Funding

National Institutes of Health (R01 NS041062)

Thomas L Schwarz

National Institutes of Health (NIH P30 HD018655)

Thomas L Schwarz

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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