RESUMO
Neuropeptides are important for regulating numerous neural functions and behaviors. Release of neuropeptides requires long-lasting, high levels of cytosolic Ca2+ However, the molecular regulation of neuropeptide release remains to be clarified. Recently, Stac3 was identified as a key regulator of L-type Ca2+ channels (CaChs) and excitation-contraction coupling in vertebrate skeletal muscles. There is a small family of stac genes in vertebrates with other members expressed by subsets of neurons in the central nervous system. The function of neural Stac proteins, however, is poorly understood. Drosophila melanogaster contain a single stac gene, Dstac, which is expressed by muscles and a subset of neurons, including neuropeptide-expressing motor neurons. Here, genetic manipulations, coupled with immunolabeling, Ca2+ imaging, electrophysiology, and behavioral analysis, revealed that Dstac regulates L-type CaChs (Dmca1D) in Drosophila motor neurons and this, in turn, controls the release of neuropeptides.
Assuntos
Canais de Cálcio/metabolismo , Proteínas de Drosophila/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Neurônios Motores/metabolismo , Junção Neuromuscular/metabolismo , Neuropeptídeos/metabolismo , Animais , Animais Geneticamente Modificados , Técnicas de Observação do Comportamento , Comportamento Animal , Drosophila melanogaster , Feminino , Microscopia Intravital , Larva , Masculino , Modelos Animais , Neurônios Motores/citologia , Músculo Esquelético/citologia , Músculo Esquelético/metabolismo , Junção Neuromuscular/citologia , Imagem Óptica , Técnicas de Patch-Clamp , Terminações Pré-Sinápticas/metabolismoRESUMO
Many neurons influence their targets through co-release of neuropeptides and small-molecule transmitters. Neuropeptides are packaged into dense-core vesicles (DCVs) in the soma and then transported to synapses, while small-molecule transmitters such as monoamines are packaged by vesicular transporters that function at synapses. These separate packaging mechanisms point to activity, by inducing co-release as the sole scaler of co-transmission. Based on screening in Drosophila for increased presynaptic neuropeptides, the receptor protein tyrosine phosphatase (Rptp) Ptp4E was found to post-transcriptionally regulate neuropeptide content in single DCVs at octopamine synapses. This occurs without changing neuropeptide release efficiency, transport and DCV size measured by both stimulated emission depletion super-resolution and transmission electron microscopy. Ptp4E also controls the presynaptic abundance and activity of the vesicular monoamine transporter (VMAT), which packages monoamine transmitters for synaptic release. Thus, rather than rely on altering electrical activity, the Rptp regulates packaging underlying monoamine-neuropeptide co-transmission by controlling vesicular membrane transporter and luminal neuropeptide content.This article has an associated First Person interview with the first author of the paper.