Biology subjects

Serpe, M.

Publications and source records attributed to Serpe, M..

6 recordsLinked to original sources

bioRxiv2025

Multilayer control of KaiR1D-autoreceptor function by the auxiliary protein Neto

Kainate-type glutamate receptors and their dedicated auxiliary protein Neto function at both pre- and postsynaptic sites to regulate the activity of synaptic networks. However, attributing specific synaptic functions to Neto and/or kainate receptors is challenging. Here we focus on Drosophila KaiR1D receptors, which modulate synaptic transmission at neuromuscular junction, and elucidate the role of Neto in the regulation of autoreceptor activities and neurotransmitter release. We show that Neto- limits the presynaptic accumulation and function of KaiR1D autoreceptors in vivo. Using outside-out patch recordings, we demonstrate that Neto- modulates the KaiR1D gating properties, slowing desensitization and attenuating the block by intracellular polyamines and extracellular toxins. Neto- also promotes the axonal distribution of KaiR1D, but this function is not critical for the KaiR1D-dependent regulation of synaptic transmission. Instead, Neto- increases the charge transfer and likely the KaiR1D-mediated influx of Ca2+ in the presynaptic compartment leading to increased neurotransmitter release. Our data demonstrate that Neto- provides multiple layers of modulation to KaiR1D autoreceptors to ensure proper neurotransmitter release. These findings broaden our view on how auxiliary subunits shape channel gating and subcellular distribution, suggesting that coordinated regulation of receptor function and localization represents an ancestral strategy to safeguard synaptic stability.

neuroscience↗

bioRxiv2024

Neto proteins differentially modulate the gating properties of Drosophila NMJ glutamate receptors

The formation of functional synapses requires co-assembly of ion channels with their accessory proteins which controls where, when, and how neurotransmitter receptors function. The auxiliary protein Neto modulates the function of kainate-type glutamate receptors in vertebrates as well as at the Drosophila neuromuscular junction (NMJ), a glutamatergic synapse widely used for genetic studies on synapse development. We previously reported that Neto is essential for the synaptic recruitment and function of glutamate receptors. Here, using outside-out patch-clamp recordings and fast ligand application, we examine for the first time the biophysical properties of recombinant Drosophila NMJ receptors expressed in HEK293T cells and compare them with native receptor complexes of genetically controlled composition. The two Neto isoforms, Neto- and Neto-{beta}, differentially modulate the gating properties of NMJ receptors. Surprisingly, we found that deactivation is extremely fast and that the decay of synaptic currents resembles the rate of iGluR desensitization. The functional analyses of recombinant iGluRs that we report here should greatly facilitate the interpretation of compound in vivo phenotypes of mutant animals.

neuroscience↗

bioRxiv2019

Selective disruption of synaptic BMP signaling by a Smad mutation adjacent to the highly conserved H2 helix

Bone morphogenetic proteins (BMPs) shape normal development and function via canonical and non-canonical signaling pathways. When activating the canonical pathway, BMPs initiate signaling by binding to transmembrane receptors that phosphorylate pathway effectors, the Smad proteins, inducing their translocation into the nucleus and thus regulation of target genes. Phosphorylated Smads also accumulate at cellular junctions, but this non-canonical signaling modality remains less defined. We have recently reported that phosphorylated Smad (pMad in Drosophila) accumulates at synaptic junctions in complexes with genetically distinct composition and regulation. Here we examined a wide collection of Drosophila Mad alleles and searched for molecular features relevant to pMad accumulation at synaptic junctions. We found that strong Mad alleles generally disrupt both synaptic and nuclear pMad accumulation, whereas moderate Mad alleles have a wider range of phenotypes and could selectively impact different BMP signaling modalities. Interestingly, synaptic pMad appeared more sensitive to net reduction in Mad levels than nuclear pMad. Importantly, a previously uncharacterized allele, Mad8, showed markedly reduced synaptic pMad levels but only moderately diminished nuclear pMad signals. The postsynaptic composition and electrophysiological properties of Mad8 NMJs were similarly altered. Using biochemical approaches, we examined how single point mutations such as S359L, present in Mad8, could influence the Mad-receptor interface and we identified a key molecular determinant, the H2 helix. Our study highlights the biological relevance of the Smad-dependent, non-canonical BMP signaling and uncovers a highly conserved structural feature of Smads, critical for normal development and function.

genetics↗

bioRxiv2019

A presynaptic spectrin network controls active zone assembly and neurotransmitter release

We have previously reported that Drosophila Tenectin (Tnc) recruits PS2/{beta}PS integrin to ensure structural and functional integrity at larval NMJs (Wang et al., 2018). In muscles, Tnc/integrin engages the spectrin network to regulate the size and architecture of synaptic boutons. In neurons, Tnc/integrin controls neurotransmitter release. Here we show that presynaptic Tnc/integrin modulates the synaptic accumulation of key active zone components, including the Ca2+ channel Cac and the active zone scaffold Brp. Presynaptic -Spectrin appears to be both required and sufficient for the recruitment of Cac and Brp. We visualized the endogenous -Spectrin and found that Tnc controls spectrin recruitment at synaptic terminals. Thus, Tnc/integrin anchors the presynaptic spectrin network and ensures the proper assembly and function of the active zones. Since pre- and postsynaptic Tnc/integrin limit each other, we hypothesize that this pathway links dynamic changes within the synaptic cleft to changes in synaptic structure and function.

neuroscience↗

bioRxiv2019

Neto-α controls synapse organization and homeostasis at the Drosophila neuromuscular junction

Glutamate receptor auxiliary proteins control receptor distribution and function, ultimately controlling synapse assembly, maturation and plasticity. At the Drosophila neuromuscular junction (NMJ), a synapse with both pre- and post-synaptic kainate-type glutamate receptors (KARs), we show that the auxiliary protein Neto evolved functionally distinct isoforms to modulate synapse development and homeostasis. Using genetics, cell biology and electrophysiology we demonstrate that Neto- functions on both sides of the NMJ. In muscle, Neto- limits the size of the postsynaptic receptors field. In motor neurons, Neto- controls neurotransmitter release in a KAR-dependent manner. Furthermore, Neto- is both required and sufficient for the presynaptic increase in neurotransmitter release in response to reduced postsynaptic sensitivity. This KAR-independent function of Neto- is involved in activity-induced cytomatrix remodeling. We propose that Drosophila ensured NMJ functionality by acquiring two Neto isoforms with differential expression patterns and activities.

neuroscience↗

bioRxiv2019

IRBIT Directs Differentiation of Intestinal Stem Cell Progeny to Maintain Tissue Homeostasis

The maintenance of the intestinal epithelium is ensured by the controlled proliferation of intestinal stem cells (ISCs) and differentiation of their progeny into various cell types, including enterocytes (ECs) that both mediate nutrient absorption and provide a barrier against pathogens. The signals that regulate transition of proliferative ISCs into differentiated ECs are not fully understood. IRBIT is an evolutionarily conserved protein that regulates ribonucleotide reductase (RNR), an enzyme critical for the generation of DNA precursors. Here, we show that IRBIT expression in ISC progeny within the Drosophila midgut epithelium cells is essential for their differentiation via suppression of RNR activity. Disruption of this IRBIT-RNR regulatory circuit causes a rapid, premature loss of intestinal tissue integrity as flies age. This age-related dysplasia can be reversed by suppression of RNR activity in ISC progeny. Collectively, our findings demonstrate an unexpected and novel role of the IRBIT-RNR pathway in gut homeostasis.

developmental biology↗