Michal Hershfinkel

ZnT1 is the main transporter mediating Zn²⁺ efflux from the cytoplasm to the extracellular space. Paradoxically, due to relatively low Zn²⁺ affinity of ZnT1, physiological levels of cytoplasmic free Zn²⁺ are seemingly insufficient to support ZnT1 function. However, physiological modulation of NMDA receptor responses by synaptically released Zn²⁺ requires a Zn²⁺ rise in the postsynaptic neurons, accompanied by ZnT1 activity. We hypothesized that Zn²⁺ import from the extracellular space could generate intracellular Zn²⁺ microdomains in the vicinity of ZnT1 to enable its activity, thus forming a localized "Zn²⁺-cycle." To identify the functional machinery that may drive this process, we investigated the expression and function of ZIP proteins that import Zn²⁺ into the neuronal cytoplasm. We focused on the dorsal cochlear nucleus (DCN) and hippocampus, regions where synaptic Zn²⁺ modulates postsynaptic NMDA responses and synaptic plasticity. We demonstrate that ZIP3 is expressed on DCN cartwheel cells and required for postsynaptic Zn²⁺ influx. Importantly, ZIP3 physically interacts with ZnT1, suggesting that it is an integral component of the synaptic Zn²⁺-cycle machinery. In the hippocampus, ZIP1, but not ZIP3, mediates Zn²⁺ import into postsynaptic CA3 cells and we find that ZIP1 interacts with ZnT1 in this brain region. Importantly, Zn²⁺ efflux rates are enhanced in SH-SY5Y cells co-expressing ZnT1 and either ZIP3 or ZIP1, compared to rates in cells expressing ZnT1 alone. Our findings indicate that ZnT1-dependent Zn²⁺ efflux is facilitated by ZIP-ZnT1 complexes, which potentially induce local intracellular Zn²⁺ microdomains supporting a Zn²⁺-cycle capable of modulating synaptic signaling.

The Concise Guide to Pharmacology 2025/26 marks the seventh edition in this series of biennial publications in the British Journal of Pharmacology. Presented in landscape format, the guide provides a comparative overview of the pharmacology of drug target families. The concise nature of the Concise Guide refers to the style of presentation, being clear, accessible, and well‐structured, rather than the scope of the content, which spans approximately 500 pages. The Concise Guide summarises the key pharmacological properties of around 1900 human drug targets, and nearly 7000 interactions, involving around 4400 ligands. While the content is a substantially condensed version of the more detailed information and links available at the www.guidetopharmacology.org website, the printed guide serves as a permanent, citable, point‐in‐time record, that remains stable despite ongoing updates to the online database. The full contents of this publication can be found at https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bph.70235 . The Concise Guides provide expert‐curated recommendations of ‘Gold Standard’ selective pharmacological tools, available either commercially or as donations, which enable the identification of individual drug targets or families of drug targets. While the Concise Guide offers a more streamlined overview, more comprehensive information, including detailed pharmacological profiles and links to multiple online databases, is available through the Guide to Pharmacology website. The 2025/26 edition of the Concise Guide is based on material current as of mid‐2025, and supersedes all previous editions, including the 2023/24 Guide, and earlier Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), and as such provides official IUPHAR classification and nomenclature for human drug targets, where applicable. Transporters are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors and enzymes. Each section includes nomenclature guidance, concise summaries, information of the best available pharmacological tools, key references, and suggestions for further reading.

ZnT1 is the main transporter mediating Zn²⁺ efflux from the cytoplasm to the extracellular space. Paradoxically, due to relatively low Zn ²⁺ affinity of ZnT1, physiological levels of cytoplasmic free Zn ²⁺ are seemingly insufficient to support ZnT1 function. However, physiological modulation of NMDA receptor responses by synaptically released Zn ²⁺ required ZnT1 activity, accompanied by a Zn ²⁺ rise in the postsynaptic neurons. We hypothesized that Zn ²⁺ import from the extracellular space could generate intracellular Zn ²⁺ microdomains in the vicinity of ZnT1 to enable its activity, thus forming a localized “Zn ²⁺ -cycle”. To identify the functional machinery that may drive this process, we investigated the expression and function of ZIP proteins that import Zn ²⁺ into the neuronal cytoplasm. We focused on the dorsal cochlear nucleus (DCN) and hippocampus, regions where synaptic Zn ²⁺ modulates postsynaptic NMDA responses and synaptic plasticity. We demonstrate that ZIP3 is expressed on DCN cartwheel cells and required for postsynaptic Zn ²⁺ influx. Importantly, ZIP3 physically interacts with ZnT1, suggesting that it is an integral component of the synaptic Zn ²⁺ -cycle machinery. In the hippocampus, ZIP1, but not ZIP3, mediates Zn ²⁺ import into postsynaptic CA3 cells and we find that ZIP1 interacts with ZnT1 in this brain region. Importantly, Zn ²⁺ efflux rates are enhanced in SH-SY5Y cells co-expressing ZnT1 and either ZIP3 or ZIP1, compared to rates in cells expressing ZnT1 alone. Our findings indicate that a Zn ²⁺ -cycle, mediated by ZIP-ZnT1 complexes, establishes local intracellular Zn ²⁺ microdomains that facilitate ZnT1-dependent Zn ²⁺ efflux, which, in turn, modulates synaptic signaling.

Along with the SLC30 family, SLC39 family members regulate zinc movement in cells. SLC39 metal ion transporters accumulate zinc into the cytosol. Membrane topology modelling suggests the presence of eight TM regions with both termini extracellular or in the lumen of intracellular organelles. The mechanism for zinc transport for many members is unknown but appears to involve co-transport of bicarbonate ions [3, 5].

Mood disorders, particularly depression and anxiety, are associated with zinc dyshomeostasis and aberrant GABAergic signaling. Activation of ZnR/GPR39 by synaptic zinc in the hippocampus triggers phosphorylation of extracellular regulated kinase (ERK1/2), which regulates the K+/Cl− cotransporter (KCC2) and thereby GABAergic inhibitory neurotransmission and seizure activity. Therefore, we studied whether impaired ZnR/GPR39 signaling is linked to anxiety-related behavior in male or female mice. Using the acoustic startle response, elevated plus maze, and open field test, we found increased anxiety-related behavior in ZnR/GPR39 knockout (KO) mice. Despite a well-established sex difference, where females are typically more prone to anxiety, both male and female ZnR/GPR39 KO mice exhibited increased anxiety-related behavior compared to wildtype (WT) mice. Additionally, ZnR/GPR39 KO mice displayed impaired motor coordination in the pole and rotarod tests but did not show reduced muscle strength, as indicated by a grip test. Finally, we found intrinsic alterations in the expression level of KCC2, a major Cl− transporter regulating GABAergic signaling, in the amygdala of naïve ZnR/GPR39 KO mice compared to controls. Our findings indicate that loss of ZnR/GPR39 enhances anxiety-related behavior in both male and female mice. Moreover, ZnR/GPR39 KO mice exhibit impaired motor coordination, which may be associated with increased anxiety. Finally, we demonstrate that loss of ZnR/GPR39 modulates the expression of KCC2 in the amygdala. Thus, we propose that ZnR/GPR39 can serve as a target for regulating GABAergic signaling in anxiety treatment.

Hepatic Ca ²⁺ signaling is emerging as a key factor in mediating gluconeogenesis. However, the identity of the hepatic mitochondrial Ca ²⁺ transporter is controversial and the role of mitochondria in controlling hormonal Ca ²⁺ signaling and linking them to metabolic activity is poorly understood. We first interrogated the role of the mitochondrial Na ⁺ /Ca ²⁺ exchanger NCLX by triggering cytosolic Ca ²⁺ purinergic signaling in primary hepatocytes, and Ca ²⁺ responses in isolated mitochondria from WT, global NCLX KO, and conditional hepatic NCLX KO mice models. We monitored a higher rate of Na ⁺ -dependent mitochondrial Ca ²⁺ efflux in NCLX-expressing hepatocytes, indicating that it constitutes the major Ca ²⁺ efflux pathway. We then asked if NCLX is controlling the hormone-dependent mitochondrial Ca ²⁺ oscillations by employing physiological concentrations of glucagon and vasopressin. Consistent with previous studies, hormone applications triggered mitochondrial Ca ²⁺ oscillations in WT hepatocytes. In NCLX KO hepatocytes the cytosolic oscillations persisted, however, the mitochondrial Ca ²⁺ oscillations were suppressed. To further understand the metabolic role of NCLX in the hepatic system, we examined gluconeogenic function in vivo and ex vitro by monitoring hepatic glucose production. We found that blood glucose dropped faster in the conditional KO mice and their hepatic glucagon-dependent glucose production was reduced, indicating that gluconeogenesis was impaired in hepatic conditional NCLX KO mice. Taken together, our results indicate that NCLX is the primary Ca ²⁺ extruder in hepatocytes and is required for mediating the hormone-dependent mitochondrial Ca ²⁺ oscillations and gluconeogenesis. Significance: Hepatic Ca ²⁺ signaling is crucial for gluconeogenesis, but the mitochondrial control of this process is not resolved. This study identifies the mitochondrial transporter, NCLX, as a critical link between hormonal-dependent mitochondrial Ca ²⁺ oscillations and gluconeogenesis. We first show that NCLX is the major hepatic mitochondrial efflux pathway. We then demonstrate that NCLX is required for glucagon-dependent mitochondrial Ca ²⁺ oscillations and the acceleration of mitochondrial oxidative function. Using a conditional hepatic NCLX-null mouse model, we show that NCLX is required for maintaining hepatic glucose production during fasting and in response to glucagon stimulation. Overall, the study identifies NCLX as the integrator of hepatic mitochondrial Ca ²⁺ signaling, required for gluconeogenesis.

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and over 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (https://www.guidetopharmacology.org/), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point‐in‐time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.16182. Transporters are one of the six major pharmacological targets into which the Guide is divided, with the others being: G protein‐coupled receptors, ion channels, nuclear hormone receptors, catalytic receptors and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid‐2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Zinc is essential for many physiological functions, with a major role in digestive system, skin health, and learning and memory. On the cellular level, zinc is involved in cell proliferation and cell death. A selective zinc sensing receptor, ZnR/GPR39 is a Gq‐coupled receptor that acts via the inositol trisphosphate pathway to release intracellular Ca²⁺. The ZnR/GPR39 serves as a mediator between extracellular changes in Zn²⁺ concentration and cellular Ca²⁺ signalling. This signalling pathway regulates ion transporters activity and thereby controls the formation of transepithelial gradients or neuronal membrane potential, which play a fundamental role in the physiological function of these tissues. This review focuses on the role of Ca²⁺ signalling, and specifically ZnR/GPR39, with respect to the regulation of the Na⁺/H⁺ exchanger, NHE1, and of the K⁺/Cl⁻ cotransporters, KCC1‐3, and also describes the physiological implications of this regulation. image