Jaime Santo-Domingo

• Biology, PhD
• Researcher at University of Valladolid

Mitochondria play a central role in pancreatic b-cell nutrient sensing by coupling their metabolism to plasma membrane excitability and insulin granule exocytosis. Whether non-nutrient secretagogues stimulate mitochondria as part of the molecular mechanism to promote insulin secretion is not known.Here,we showthat PKC signaling, which is employed b...

The chemical nature and functional significance of mitochondrial flashes associated with fluctuations in mitochondrial membrane potential is unclear. Using a ratiometric pH probe insensitive to superoxide, we show that flashes reflect matrix alkalinization transients of ∼0.4 pH units that persist in cells permeabilized in ion-free solutions and can...

The ability of mitochondria to capture Ca2+ ions has important functional implications for cells, because mitochondria shape cellular Ca2+ signals by acting as a Ca2+ buffer and respond to Ca2+ elevations either by increasing the cell energy supply or by triggering the cell death program of apoptosis. A mitochondrial Ca2+ channel known as the unipo...

The thiourea derivative KB-R7943, originally developed as inhibitor of the plasma membrane Na(+)/Ca(2+) exchanger, has been shown to protect against myocardial ischemia-reperfusion injury. We have studied here its effects on mitochondrial Ca(2+) fluxes. [Ca(2+)] in cytosol, mitochondria and endoplasmic reticulum (ER), and mitochondrial membrane pot...

We have previously shown that the compound CGP37157, a mitochondrial Na⁺/Ca²⁺ exchanger inhibitor, increases lifespan and improves muscle and mitochondrial structure during aging in wild-type C. elegans nematodes. We used here a rotenone model of Parkinson’s disease in C. elegans to test the ability of CGP37157 to rescue the alterations induced by...

Regulation of mitochondrial redox balance is emerging as a key event for cell signaling in both physiological and pathological conditions. However, the link between the mitochondrial redox state and the modulation of these conditions remains poorly defined. Here, we discovered that activation of the evolutionary conserved mitochondrial calcium unip...

Introduction: The high prevalence of neurodegenerative diseases in our population and the lack of effective treatments encourage the search for new therapeutic targets for these pathologies. We have recently described that submaximal inhibition of the Sarco-Endoplasmic Reticulum Ca²⁺ ATPase (SERCA), the main responsible for ER calcium storage, is a...

Glucose sensing in pancreatic beta-cells depends on oxidative phosphorylation and mitochondria-derived signals that promote insulin secretion. Using mass spectrometry-based phosphoproteomics to search for down-stream effectors of glucose dependent signal transduction in INS-1E insulinoma cells, we identified the outer mitochondrial membrane protein...

The molecular mechanisms that mediate and regulate calcium (Ca2+) fluxes through the membranes of intracellular organelles play a key role in the generation and shaping of the local and global cytosolic Ca2+ signals triggering the process of regulated exocytosis in chromaffin cells. Beyond that role, intraorganellar Ca2+ homeostasis also regulates...

Background and aims: Insulin-degrading enzyme (IDE) is a ubiquitous metalloprotease that degrades insulin and glucagon among other substrates. By decades, its main function has been attributed to hepatic insulin clearance, a process that regulates availability of insulin levels. Recent studies indicate a more important role of this protein in insul...

Barrier integrity is central to the maintenance of healthy immunological homeostasis. Impaired skin barrier function is linked with enhanced allergen sensitization and the development of diseases such as atopic dermatitis (AD), which can precede the development of other allergic disorders, for example, food allergies and asthma. Epidemiological evi...

Mitochondrial dysfunction induces a strong adaptive retrograde signaling response; however, many of the down-stream effectors of this response remain to be discovered. Here, we studied the shared transcriptional responses to three different mitochondrial respiratory chain inhibitors in human primary skin fibroblasts using QuantSeq 3’-RNA-sequencing...

Alzheimer’s disease (AD) is the most frequent cause of dementia. After decades of research, we know the importance of the accumulation of protein aggregates such as β-amyloid peptide and phosphorylated tau. We also know that mutations in certain proteins generate early-onset Alzheimer’s disease (EOAD), and many other genes modulate the disease in i...

Aims/hypothesis: In islets from individuals with type 2 diabetes and in islets exposed to chronic elevated glucose, mitochondrial energy metabolism is impaired. Here, we studied early metabolic changes and mitochondrial adaptations in human beta cells during chronic glucose stress. Methods: Respiration and cytosolic ATP changes were measured in...

Pancreatic beta‐cells are central regulators of glucose homeostasis. By tightly coupling nutrient sensing and granule exocytosis, beta‐cells adjust the secretion of insulin to the circulating blood glucose levels. Failure of beta‐cells to augment insulin secretion in insulin‐resistant individuals leads progressively to impaired glucose tolerance, T...

Pancreatic β-cells secrete insulin to lower blood glucose, following a meal. Maintenance of β-cell function is essential to preventing type 2 diabetes. In pancreatic β-cells, mitochondrial matrix calcium is an activating signal for insulin secretion. Recently, the molecular identity of the mitochondrial calcium uniporter (MCU), the transporter that...

Mitochondria carry out many essential functions in metabolism. A central task is the oxidation of nutrients and the generation of ATP by oxidative phosphorylation. Mitochondrial metabolism needs to be tightly regulated for the cell to respond to changes in ATP demand and nutrient supply. Here we review how protein lysine acetylation contributes to...

Background and Purpose Quinic acid (QA) is an abundant natural compound from plant sources which may improve metabolic health. However, little attention has been paid to its effects on pancreatic beta‐cell functions, which contribute to the control of metabolic health by lowering blood glucose. Strategies targeting beta‐cell signal transduction are...

Background: Glucose is the main secretagogue of pancreatic beta-cells. Uptake and metabolism of the nutrient stimulates the beta-cell to release the blood glucose lowering hormone insulin. This metabolic activation is associated with a pronounced increase in mitochondrial respiration. Glucose stimulation also initiates a number of signal transducti...

In pancreatic β‐cells, mitochondria generate signals that promote insulin granule exocytosis. Here we study how lysine acetylation of mitochondrial proteins mechanistically affects metabolism‐secretion coupling in insulin‐secreting cells. Using mass spectrometry‐based proteomics, we identified lysine acetylation sites in rat insulinoma cell line cl...

The 5' AMP-activated protein kinase (AMPK) is a nutrient-sensitive kinase that plays a key role in the control of cellular energy metabolism. We have explored here the relationship between AMPK and Ca²⁺ signaling by looking at the effect of an AMPK activator (A769662) and an AMPK inhibitor (dorsomorphin) on histamine-induced Ca²⁺-release from the e...

Changes in mitochondrial and cytosolic pH alter the chemical gradient across the inner mitochondrial membrane. The proton chemical gradient contributes to mitochondrial ATP synthesis as well as the uptake and release of metabolites and ions from the organelle. Here mitochondrial pH and ΔpH were studied for the first time in human pancreatic β-cells...

Scientific Reports 7 : Article number: 45961 10.1038/srep45961 ; published online: 12 April 2017 ; updated: 09 May 2017 This Article contains a typographical error in the Methods section under subheading ‘Data Availability.

Chloramphenicol and several other antibiotics targeting bacterial ribosomes inhibit mitochondrial protein translation. Inhibition of mitochondrial protein synthesis leads to mitonuclear protein imbalance and reduced respiratory rates as confirmed here in HeLa and PC12 cells. Unexpectedly, respiration in INS-1E insulinoma cells and primary human isl...

A robust and reproducible method for culturing monolayers of adherent and well-spread primary islet cells on glass coverslips is required for detailed imaging studies by super-resolution and live-cell microscopy. Guided by an observation that dispersed islet cells spread and adhere well on glass surfaces in neuronal co-culture and form a monolayer...

Pancreatic beta-cells sense glucose promoting insulin secretion. Glucose sensing requires the sequential stimulation of glycolysis, mitochondrial metabolism and Ca2+ entry. To elucidate how mitochondrial activation in beta-cells contributes to insulin secretion, we have compared the effects of glucose and the mitochondrial substrate methylsuccinate...

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Mitochondrial flashes mediated by optic atrophy 1 (OPA1) fusion protein are bioenergetic responses to stochastic drops in mitochondrial membrane potential (Δψm) whose origin is unclear. Using structurally distinct genetically encoded pH-sensitive probes, we confirm that flashes are matrix alkalinization transients, thereby establishing the pH natur...

Medium-chain triglycerides have been used as part of a ketogenic diet effective in reducing epileptic episodes. The health benefits of the derived medium-chain fatty acids (MCFAs) are thought to result from the stimulation of liver ketogenesis providing fuel for the brain. We tested whether MCFAs have direct effects on energy metabolism in induced...

Metabolism-secretion coupling describes the molecular mechanism linking nutrient sensing to insulin secretion in pancreatic beta-cells. This process requires the activation of mitochondria, leading to ATP production and coupling factors, which amplify secretion. Several mitochondrial derived coupling factors were proposed but the mechanisms linking...

Mitochondria sense, shape and integrate signals, and thus function as central players in cellular signal transduction. Ca(2+) waves and redox reactions are two such intracellular signals modulated by mitochondria. Mitochondrial Ca(2+) transport is of utmost physio-pathological relevance with a strong impact on metabolism and cell fate. Despite its...

Mitochondria capture and subsequently release Ca2+ ions, thereby sensing and shaping cellular Ca2+ signals. The Ca2+ uniporter MCU mediates Ca2+ uptake, while NCLX (mitochondrial Na/Ca exchanger) and Letm1 (Leucine zipper-EF-hand-containing transmembrane protein 1) were proposed to exchange Ca2+ against Na+ or H+ respectively. Here we study the rol...

Background: Whether mitochondrial Ca 2 extrusion is mediated by NCLX (mitochondrial sodium/calcium exchanger) or LETM1 (leucine zipper-EF-hand-containing transmembrane protein 1) and controls matrix redox state is unknown. Results: NCLX, but not LETM1, increases Ca 2 extrusion, limits NAD(P)H production, and promotes matrix oxidation. Conclusion: N...

The pH within the mitochondrial matrix (pHmito) is an important bioenergetic parameter well studied in isolated mitochondria but poorly characterized in intact cells, and all in situ studies available report spatially averaged measurements of pHmito. We used a new pH-sensitive GFP-based fluorescent probe targeted to the mitochondrial matrix, mito-S...

Securin and separase play a key role in sister chromatid separation during anaphase. However, a growing body of evidence suggests that in addition to regulating chromosome segregation, securin and separase display functions implicated in membrane traffic in Caenorhabditis elegans and Drosophila. Here we show that in mammalian cells both securin and...

Mitochondria extrude protons across their inner membrane to generate the mitochondrial membrane potential (ΔΨ(m)) and pH gradient (ΔpH(m)) that both power ATP synthesis. Mitochondrial uptake and efflux of many ions and metabolites are driven exclusively by ΔpH(m), whose in situ regulation is poorly characterized. Here, we report the first dynamic m...

Secretory vesicles have low pH and have been classically identified as those labelled by a series of acidic fluorescent dyes such as acridine orange or neutral red, which accumulate into the vesicles according to the pH gradient. More recently, several fusion proteins containing enhanced green fluorescent protein (EGFP) and targeted to the secretor...

We have investigated the dynamics of the free [Ca(2+)] inside the secretory granules of neurosecretory PC12 and INS1 cells using a low-Ca(2+)-affinity aequorin chimera fused to synaptobrevin-2. The steady-state secretory granule [Ca(2+)] ([Ca(2+)](SG)] was around 20-40 μM in both cell types, about half the values previously found in chromaffin cell...

Hypoxia activates chemoreceptor cells of the carotid body (CB) promoting an increase in their normoxic release of neurotransmitters. Catecholamine (CA) release rate parallels the intensity of hypoxia. Coupling of hypoxia to CA release requires cell depolarization, produced by inhibition of O(2)-regulated K(+) channels, and Ca(2+) entering the cells...

The secretory granules constitute one of the less well-known compartments in terms of Ca2+ dynamics. They contain large amounts of total Ca2+, but the free intragranular [Ca2+] ([Ca2+]SG), the mechanisms for Ca2+ uptake and release from the granules and their physiological significance regarding exocytosis are still matters of debate. We used in th...

The recent availability of activators of the mitochondrial Ca(2+) uniporter allows direct testing of the influence of mitochondrial Ca(2+) uptake on the overall Ca(2+) homeostasis of the cell. We show here that activation of mitochondrial Ca(2+) uptake by 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT) or kaempferol stimulates histami...

There is increasing evidence that mitochondria play an important role in the control of cytosolic Ca2+ signaling. We show here that the main mitochondrial Ca2+-exit pathway, the mitochondrial Na+/Ca2+ exchanger, controls the pattern of cytosolic Ca2+ oscillations in non-excitable cells. In HeLa cells, the inhibitor of the mitochondrial Na+/Ca2+ exc...

Ca ²⁺ uptake by mitochondria is a key element in the control of cellular Ca ²⁺ homeostasis and Ca ²⁺ ‐dependent phenomena. It has been known for many years that this Ca ²⁺ uptake is mediated by the mitochondrial Ca ²⁺ uniporter, a specific Ca ²⁺ channel of the inner mitochondrial membrane. We have shown previously that this channel is strongly acti...

We have used an aequorin chimera targeted to the membrane of the secretory granules to monitor the free [Ca(2+)] inside them in neurosecretory PC12 cells. More than 95% of the probe was located in a compartment with an homogeneous [Ca(2+)] around 40 microM. Cell stimulation with either ATP, caffeine or high-K(+) depolarization increased cytosolic [...

During cell activation, mitochondria play an important role in Ca2+ homoeostasis due to the presence of a fast and specific Ca2+ channel in its inner membrane, the mitochondrial Ca2+ uniporter. This channel allows mitochondria to buffer local cytosolic [Ca2+] changes and controls the intramitochondrial Ca2+ levels, thus modulating a variety of phen...