Biology subjects

de Juan-Sanz, J.

Publications and source records attributed to de Juan-Sanz, J..

10 recordsLinked to original sources

bioRxiv2026

Genetic sex of enteric neurons enables ovarian relaxin togate maternal gut plasticity

Animals must align intestinal plasticity and feeding with reproductive state, yet the checkpoint that gates these adaptations is unknown. Here we show that an ovary-to-enteric-neuron axis gates the onset of maternal gut plasticity in Drosophila. Genetic sex establishes endocrine competence in a subset of enteric neurons via the sex determination pathway, enabling female-specific expression of the relaxin-family receptor Lgr3. After mating, steroid signalling increases Lgr3 receptor expression, priming these neurons for reproductive adaptation. Once oocytes mature fully, follicle cells secrete the relaxin-like hormone dILP8, which activates Lgr3 to trigger gut enlargement and increased feeding. Disrupting the sex determination pathway in enteric neurons, Lgr3, or ovarian dILP8 prevents gut enlargement and reduces feeding. Thus, genetic sex establishes competence, steroid signalling primes it, and ovarian relaxin triggers it, defining a maternal intestinal plasticity checkpoint that ensures gut adaptations initiate only once reproduction is underway and energy demands peak. Our findings delineate an ovary-to-enteric-neuron axis that couples reproductive state to maternal gut plasticity.

physiology↗

bioRxiv2025

An expanded palette of bright and photostable organellar Ca2+ sensors

The use of fluorescent sensors for functional imaging has revolutionized the study of organellar Ca2+ signaling. However, understanding the dynamic interplay between intracellular Ca2+ sinks and sources has been hindered by the lack of bright, photostable, and multiplexed measurements in different organelles, limiting our ability to define how Ca2+ shapes cell physiology across fields of biology. Here we introduce a new toolkit of chemigenetic organellar Ca2+ indicators whose color is tunable by reconstituting their fluorescence with different exogenous rhodamine dye-ligands, which significantly expand the capacity for multiplexing organellar Ca2+ measurements. These sensors, which we named ER-HaloCaMP and Mito-HaloCaMP, are optimized to report Ca2+ dynamics in the endoplasmic reticulum (ER) and mitochondria of mammalian cells and neurons, and show significantly improved brightness, photostability and responsiveness when compared to current best-in-class alternatives. Using either red or far-red dye-ligands, both ER-HaloCaMP and Mito-HaloCaMP enable visualizing ER and mitochondrial Ca2+ dynamics in neuronal axons, a subcellular location that only contains a few ER tubules and small mitochondria, structural limitations that have impaired measurements with previous red sensors. To show the expanded multiplexing capacities of our toolkit, we measured interorganellar Ca2+ fluxes simultaneously in three different subcellular compartments in live cells, revealing that the amplitude of ER Ca2+ release controls the efficacy of ER-mitochondria Ca2+ coupling in a cooperative manner. Organellar HaloCaMPs enable also measuring Ca2+ dynamics in intact brain tissue from flies and rodents, demonstrating their versatility across biological models. Our new toolkit provides an expanded palette of bright, photostable and responsive organellar Ca2+ sensors, which will facilitate future studies of intracellular Ca2+ signaling across fields of biology in health and disease.

cell biology↗

bioRxiv2024

Activity-driven trafficking of endogenous synaptic proteins through proximity labeling

To enable transmission of information in the brain, synaptic vesicles fuse to presynaptic membranes, liberating their content and exposing transiently a myriad of vesicular transmembrane proteins. However, versatile methods for quantifying the synaptic translocation of endogenous proteins during neuronal activity remain unavailable, as the fast dynamics of synaptic vesicle cycling difficult specific isolation trafficking proteins during such a transient surface exposure. Here we developed a novel approach using synaptic cleft proximity labeling to capture and quantify activity-driven trafficking of endogenous synaptic proteins at the synapse. We show that accelerating cleft biotinylation times to match the fast dynamics of vesicle exocytosis allows capturing endogenous proteins transiently exposed at the synaptic surface during neural activity, enabling for the first time the study of the translocation of nearly every endogenous synaptic protein. As proof-of-concept, we further applied this technology to obtain direct evidence of the surface translocation of non-canonical trafficking proteins, such as ATG9A and NPTX1, which had been proposed to traffic during activity but for which direct proof had not yet been shown. The technological advancement presented here will facilitate future studies dissecting the molecular identity of proteins exocytosed at the synapse during activity, helping to define the molecular machinery that sustains neurotransmission in the mammalian brain. Significance statementSynaptic trafficking is critical for neurons to communicate and sustain brain function. Pascual-Caro and de Juan-Sanz develop a pioneering method to enable the study of the activity-driven translocation of any endogenous synaptic protein. Coordinating neuronal activity and proximity labeling at synaptic clefts during just a few seconds, the authors visualize the trafficking of endogenous synaptic vesicle proteins and non-canonical trafficking proteins at the synapse. This work provides a technological framework to uncover the complex molecular choreography of translocation events occurring within firing synapses, enabling a deeper study of the molecular control of neuronal communication and circuit physiology in the brain.

neuroscience↗

bioRxiv2024

Mitochondrial Ca2+ efflux controls neuronal metabolism and long-term memory across species

While impairing neuronal metabolism limits brain performance, it remains poorly understood whether enhancing metabolism in neurons, in contrast, could boost brain function. We find that reducing the expression of the mitochondrial H+/Ca2+ exchanger Letm1 results in increased Ca2+ retention in the mitochondrial matrix of firing neurons, which overactivates neuronal metabolism in flies and rodents. We find that upscaled metabolic states in active neurons of central memory circuits of flies and mice enable storing long-term memories in training paradigms in which wild-type counterparts of both species fail to remember. Our findings unveil an evolutionarily conserved mechanism that controls mitochondrial metabolism in active neurons and prove its crucial role in governing higher brain functions, such as long-term memory formation. Highlights- Letm1 controls activity-driven mitochondrial Ca2+ efflux in neurons - Increased mitochondrial Ca2+ retention during activity overactivates neuronal metabolism - Activity-driven upscaling of neuronal metabolism facilitates long-term olfactory memory in flies and mice

neuroscience↗

bioRxiv2023

Developmental transcriptional control of mitochondrial homeostasis is required for activity-dependent synaptic connectivity

During neuronal circuit formation, local control of axonal organelles ensures proper synaptic connectivity. Whether this process is genetically encoded is unclear and if so, its developmental regulatory mechanisms remain to be identified. We hypothesized that developmental transcription factors regulate critical parameters of organelle homeostasis that contribute to circuit wiring. We combined cell type-specific transcriptomics with a genetic screen to discover such factors. We identified Telomeric Zinc finger-Associated Protein (TZAP) as a temporal developmental regulator of neuronal mitochondrial homeostasis genes, including Pink1. In Drosophila, loss of dTzap function during visual circuit development leads to loss of activity-dependent synaptic connectivity, that can be rescued by Pink1 expression. At the cellular level, loss of dTzap/TZAP leads to defects in mitochondrial morphology, attenuated calcium uptake and reduced synaptic vesicle release in fly and mammalian neurons. Our findings highlight developmental transcriptional regulation of mitochondrial homeostasis as a key factor in activity-dependent synaptic connectivity.

neuroscience↗

bioRxiv2022

Activity-driven synaptic translocation of LGI1 controls excitatory neurotransmission

The fine control of synaptic function requires robust trans-synaptic molecular interactions. However, it remains poorly understood how the landscape of trans-synaptic bridges dynamically remodels to reflect functional states of the synapse. Here we developed novel optical tools to visualize in firing synapses the molecular behavior of a particular secreted trans-synaptic protein, LGI1, and its presynaptic receptor, ADAM23, and discovered that neuronal activity acutely rearranges the abundance of these proteins at the synaptic cleft. Surprisingly, LGI1 in synapses was not secreted, as described elsewhere, but exo- and endocytosed through its interaction with ADAM23. Activity-driven translocation of LGI1 facilitated the formation of trans-synaptic connections proportionally to the history of activity of the synapse, adjusting excitatory transmission to synaptic firing rates. Thus, our findings reveal that LGI1 abundance at the synaptic cleft can be acutely remodeled and serves as a critical point of activity-dependent control of synaptic function. Highlights- Neuronal activity translocates LGI1 and ADAM23 to the presynaptic surface - LGI1 and ADAM23 are not located in synaptic vesicles - Stable cleft localization of LGI1 depends on the history of synaptic activity - LGI1 abundance at the synaptic cleft controls glutamate release

neuroscience↗

bioRxiv2020

The presynaptic glycine transporter GlyT2 is regulated by the Hedgehog pathway in vitro and in vivo

The identity of a glycinergic synapse is maintained presynaptically by the activity of a surface glycine transporter, GlyT2, which recaptures glycine back to presynaptic terminals to preserve vesicular glycine content. GlyT2 loss-of-function mutations cause Hyperekplexia, a rare neurological disease in which loss of glycinergic neurotransmission causes generalized stiffness and strong motor alterations. However, the molecular underpinnings controlling GlyT2 activity remain poorly understood. In this work, we identify the Hedgehog pathway as a robust controller of GlyT2 expression and transport activity. Modulating the activation state of the Hedgehog pathway in vitro in rodent primary spinal cord neurons or in vivo in zebrafish embryos induced a selective control in GlyT2 expression, regulating GlyT2 transport activity. Our results indicate that activation of Hedgehog reduces GlyT2 expression by decreasing its mRNA levels and increasing its ubiquitination and degradation. This work describes a new molecular link between the Hedgehog signaling pathway and presynaptic glycine availability.

neuroscience↗

bioRxiv2019

Molecular tuning of the axonal mitochondrial Ca2+ uniporter ensures metabolic flexability of neurotransmission

The brain is a vulnerable metabolic organ and must adapt to different fuel conditions to sustain function. Nerve terminals are a locus of this vulnerability but how they regulate ATP synthesis as fuel conditions vary is unknown. We show that synapses can switch from glycolytic to oxidative metabolism, but to do so, they rely on activity-driven presynaptic mitochondrial Ca2+ uptake to accelerate ATP production. We demonstrate that while in non-neuronal cells mitochondrial Ca2+ uptake requires elevated extramitochondrial Ca2+, axonal mitochondria readily take up Ca2+ in response to small changes in Ca2+. We identified the brain-specific protein MICU3 as a critical driver of this tuning of Ca2+ sensitivity. Ablation of MICU3 renders axonal mitochondria similar to non-neuronal mitochondria, prevents acceleration of local ATP synthesis, and impairs presynaptic function under oxidative conditions. Thus, presynaptic mitochondria rely on MICU3 to facilitate mitochondrial Ca2+ uptake during activity and achieve metabolic flexibility.\n\nO_LISynapses rely on activity-driven mitochondrial ATP synthesis with oxidative fuels\nC_LIO_LIMitochondrial Ca2+ uptake is required to stimulate ATP synthesis in axons\nC_LIO_LIThe mitochondria Ca2+ uptake threshold is lower in axons than in non-neuronal cells\nC_LIO_LIMICU3 controls the Ca2+ sensitivity of MCU in axonal mitochondria\nC_LI

neuroscience↗

bioRxiv2017

Ubiquitin ligase LNX1 is a major regulator of glycine recapture by the presynaptic transporter GlyT2

The neuronal glycine transporter GlyT2 is an essential regulator of glycinergic neurotransmission that recaptures glycine in presynaptic terminals to facilitate quantal transmitter packaging in synaptic vesicles. Alterations in GlyT2 expression or activity result in lower cytosolic glycine levels, emptying glycinergic synaptic vesicles and impairing neurotransmission. Lack of glycinergic neurotransmission caused by GlyT2 loss-of-function mutations results in Hyperekplexia, a rare neurological disease characterized by generalized stiffness and motor alterations that may result in sudden infant death. Although the importance of GlyT2 in pathology is known, how this transporter is regulated at the molecular level is poorly understood, limiting current therapeutic strategies. Guided by an unbiased screening, we discovered that the E3 ubiquitin ligase Ligand of Numb protein X1 (LNX1) modulates the ubiquitination status of GlyT2. LNX1 ubiquitinates a cytoplasmic C-terminal lysine cluster in GlyT2 (K751, K773, K787 and K791) through its N-terminal RING-finger domain, and this process regulates the expression levels and transport activity of GlyT2 in neurons. These experiments reveal for the first time the identity of an E3 ubiquitin-ligase acting on GlyT2 and identify a novel regulatory mechanism by which neurons regulate GlyT2 expression and activity.

neuroscience↗

bioRxiv2017

Actin enhances ER-mitochondrial calcium transfer and IMM constriction during mitochondrial division

Mitochondrial division requires division of both the inner and outer mitochondrial membranes (IMM and OMM, respectively). Interaction with endoplasmic reticulum (ER) promotes OMM division by recruitment of the dynamin Drp1, but effects on IMM division are not well characterized. We previously showed that actin polymerization through the ER-bound formin INF2 stimulates Drp1 recruitment in mammalian cells. Here, we show that INF2-mediated actin polymerization stimulates a second mitochondrial response independent of Drp1: a rise in mitochondrial matrix calcium through the mitochondrial calcium uniporter. ER stores supply the increased mitochondrial calcium, and the role of actin is to increase ER-mitochondria contact. Myosin IIA is also required for this mitochondrial calcium increase. Elevated mitochondrial calcium in turn activates IMM constriction in a Drp1-independent manner. IMM constriction requires electron transport chain activity. IMM division precedes OMM division. These results demonstrate that actin polymerization independently stimulates the dynamics of both membranes during mitochondrial division: IMM through increased matrix calcium, and OMM through Drp1 recruitment.

cell biology↗