About

Joshua Levitz, Ph.D., is a Professor of Biochemistry and Biophysics at Weill Cornell Medicine. His laboratory employs a variety of optical techniques to enhance understanding of synaptic signaling molecules, with a particular focus on neurotransmitter-gated G protein-coupled receptors (GPCRs). The research aims to probe GPCRs at the molecular, synaptic, and circuit levels to develop a more coherent and mechanistic understanding of their roles in physiology and neuropsychiatric disease.

Research topics

• Biology
• Genetics
• Cell biology
• Computational biology
• Neuroscience
• Chemistry
• Biophysics
• Biochemistry

Selected publications

• Mechanism-guided identification of antidepressant G protein-coupled receptor drug targets

  Cell · 2026-04-01 · 1 citations

  article
  PublisherDOI

• Structures of partially occupied hetero-tetramers provide insight into kainate receptor activation and desensitization

  Nature Communications · 2026-04-24

  articleOpen accessSenior authorCorresponding

  Kainate receptors (KARs) are critical mediators and modulators of synaptic transmission which undergo rapid activation and desensitization upon binding of the neurotransmitter glutamate. Under various physiological and pharmacological conditions agonist binding likely occurs to only a subset of subunits within these tetrameric receptors, motivating an analysis of the functional and conformational effects of partial versus complete ligand occupancy. Here we report cryo-EM structures of the GluK2/GluK5 hetero-tetramer under partially-occupied conditions using 5-iodowillardiine and AMPA as GluK5-selective agonists. High-resolution pre-active state structures containing closed/open ligand binding domain (LBD) dimers with intact interfaces reveal gating-associated interface reshaping, inter-dimer motions, and pore-linker repositioning in response to asymmetric agonist binding. Interfacial LBD mutations to a central cluster formed by the GluK5 subunits and to an inter-dimer interface between GluK2 and GluK5 subunits, highlight the roles of interactions between LBD dimers in controlling receptor function, including the distinct slow deactivation of GluK5-containing receptors. Finally, the absence or presence of intact, partially, and fully ruptured LBD interfaces under different ligand conditions allows us to propose a revised model of stepwise ionotropic glutamate receptor activation and desensitization.

  PublisherOA PDFDOI

• A general one-step protocol to generate impermeable fluorescent HaloTag substrates for in situ live cell application and super-resolution imaging

  Nature Communications · 2026-01-12 · 2 citations

  articleOpen access

  Visualization of proteins can be achieved by genetically grafting HaloTag Protein (HTP) into the protein of interest followed by incubation with a dye-linked HaloTag Ligand (HTL). This approach allows for use of fluorophores optimized for specific optical techniques or of cell-impermeable dyes to selectively label cell surface proteins. However, these two goals often conflict, as many high-performing dyes exhibit membrane permeability. Here we show that several dye-HTL reagents can be made cell-impermeable by inserting a charged sulfonate directly into the HTL, leaving the dye moiety unperturbed, using a one-step protocol. We validate such compounds, termed dye-SHTL (dye shuttle), in living cells, and demonstrate exclusive membrane staining. In transduced primary hippocampal neurons, we label a neuromodulatory receptor with dyes optimized for stimulated emission by depletion super-resolution microscopy, allowing accuracy in distinguishing surface versus internal receptors of the presynaptic terminal. This approach offers broad utility for surface-specific protein labelling.

  PublisherOA PDFDOI

• MRAP2 potentiates GPCR signaling by conserved mechanisms that are disrupted by obesity-associated genetic variants

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-09-28 · 1 citations

  preprintOpen access

  Accessory proteins such as members of the melanocortin-2 receptor accessory protein family (MRAP) have been described to interact with and regulate the signaling of diverse G protein-coupled receptors (GPCRs), however, surprisingly little is known about the mechanisms by which they mediate these effects. MRAP2 modifies signaling of three distinct GPCRs, melanocortin receptor 4 (MC4R), MC3R and the ghrelin receptor (GHSR), which each play essential roles in appetite regulation. Human mutations in MRAP2 cause obesity with hyperglycaemia and hypertension, suggesting that its regulation of GPCRs is critical for maintaining metabolic homeostasis. However, the nature of MRAP2/GPCR complexes and whether there are shared mechanisms for complex assembly, critical structural regions or consistent effects on receptor signaling and trafficking remains unknown. Here we showed all three GPCRs preferentially interact with MRAP2 as 1:1 complexes and that MRAP2 binding disrupts GPCR homodimerization. MRAP2 interacts with the same receptor transmembrane regions to promote GPCR signaling, and the accessory protein impairs β-arrestin-2 recruitment to prolong signaling and delay internalization. Deletion of the cytoplasmic region of MRAP2 impairs GPCR signaling by modulating receptor constitutive activity. Genetic variants in MRAP2 associated with overweight or obesity modulate the constitutive activity of all three GPCRs. Thus, MRAP2 regulates GPCR function using shared molecular mechanisms and these studies provide further evidence of the importance of GHSR constitutive activity.

  PublisherOA PDFDOI

• Developing HaloTag and SNAP‐Tag Chemical Inducers of Dimerization to Probe Receptor Oligomerization and Downstream Signaling

  Angewandte Chemie International Edition · 2025-06-30 · 6 citations

  articleOpen access

  Controlling protein-protein interactions is critical for dissecting signaling pathways, especially those initiated by ligand-receptor interactions, which alter receptor oligomerization and drive downstream signaling cascades. Traditional methods for driving protein-protein complexes use antibodies that face limitations in terms of stoichiometry, geometric rigidity, and antibody specificity. Chemical inducers of dimerization (CIDs) for fusion proteins such as HaloTag (Halo) and SNAP-Tags (SNAP) offer precise and covalent control of protein proximities, overcoming limitations of antibody-dependent methods. In this study, we expand the toolkit of Halo and SNAP CIDs with (1) benzylguanine (BG) and HaloTag ligand (HTL) crosslinkers featuring varying polyethylene glycol linker lengths and update this kit with (2) a FRET-based dimerizing sensor to induce and verify protein proximity. Here we establish our CIDs on extracellularly Halo- and SNAP-tagged TGFβ, BMP, neurotrophic factor, and metabotropic glutamate receptors, thereby elucidating the signaling potential of ligand-independent dimerization in a heteromeric fashion.

  PublisherOA PDFDOI

• Projection-targeted photopharmacology reveals distinct anxiolytic roles for presynaptic mGluR2 in prefrontal- and insula-amygdala synapses

  Neuron · 2025-01-28 · 9 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• Entwicklung von chemischen Initiatoren der Dimerisierung von HaloTag und SNAP‐Tag zur Untersuchung von Signaltransduktion induziert durch Rezeptor‐Oligomerisierung

  Angewandte Chemie · 2025-06-30

  articleOpen access

  Zusammenfassung Protein‐Protein‐Interaktionen gezielt kontrollieren zu können ist essenziell für die Analyse von Signalwegen, insbesondere solcher, die durch das Binden von Liganden eine Oligomerisierung von Rezeptoren herbeiführen und somit nachgeschaltete Signalwege aktivieren. Traditionelle Methoden, die zur Bildung von Protein‐Protein‐Komplexen verwendet werden, nutzen häufig Antikörper, welche durch ihre Stöchiometrie, geometrische Starrheit und Antikörperspezifität nur limitiert einsetzbar sind. Chemische Initiatoren von Dimerisierung (CIDs) für Fusionsproteine wie HaloTag (Halo) und SNAP‐Tag (SNAP) erlauben eine hochselektive und kovalente Bildung von Protein‐Protein‐Proximitäten und überkommen dabei die Limitationen von Antikörpern. In dieser Studie erweitern wir das Ensemble der Halo‐ und SNAP‐CIDs um (1) Benzylguanin (BG) und Halo‐Tag‐Liganden (HTL) CIDs mit unterschiedlichen Polyethylenglykol‐Linker‐Längen und (2) um einen FRET‐basierten Dimerisierungssensor, welcher erlaubt Proteinnähe zu induzieren und diese gleichzeitig auszulesen. Wir etablieren unsere CIDs im Folgenden an extrazellulär Halo‐ und SNAP‐getaggten TGFβ‐, BMP‐, neurotrophen Faktor‐ und metabotropen Glutamatrezeptoren und untersuchen damit das Signalpotenzial von Liganden unabhängiger heteromerer Dimerisierung.

  PublisherDOI

• A Photochromic Controller for Reversible Regulation of Peripheral Opioid Analgesia

  Journal of Pain · 2025-04-01

  articleSenior author
  PublisherDOI

• The accessory protein MRAP2 directly interacts with melanocortin-3 receptor to enhance signaling

  Science Signaling · 2025-12-16 · 3 citations

  articleOpen access

  The central melanocortin system links nutrition to energy expenditure. Melanocortin-4 receptor (MC4R) controls appetite and food intake, and its signaling is potentiated by melanocortin-2 receptor accessory protein 2 (MRAP2). Human mutations in MC4R and MRAP2 are associated with obesity. Here, we sought to determine whether MRAP2 affected the activity of MC3R, which is structurally similar to MC4R and which regulates sexual maturation, linear growth rate, and lean mass accumulation. Single-molecule pull-down assays showed that MC3R and MRAP2 interacted in HEK293 cells. Analysis of fluorescence photobleaching steps showed that MC3R and MRAP2 readily formed heterodimers, most commonly with a 1:1 stoichiometry. Mining of previously published human single-nucleus and spatial transcriptomic data showed coexpression of MRAP2 and MC3R in hypothalamic neurons that function in energy homeostasis and appetite control. In HEK293 cells, MRAP2 enhanced cAMP signaling downstream of MC3R, impaired β-arrestin recruitment to MC3R, and reduced MC3R internalization. The ability of MRAP2 to promote MC3R signaling was suppressed by alanine mutagenesis of five MRAP2 and two MC3R transmembrane residues identified by structural homology models as important for the interaction. We showed that variants of MRAP2 found in individuals who are overweight or obese did not enhance MC3R-driven signaling. Thus, these studies implicate MRAP2 as an important regulator of MC3R function and provide further evidence for the crucial role of MRAP2 in energy homeostasis.

  PublisherOA PDFDOI

• Structural Diversity and Dynamics of Metabotropic Glutamate Receptor/Beta-Arrestin Coupling

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-02-05 · 3 citations

  preprintOpen accessSenior authorCorresponding

  Beta-arrestins (β-arrs) are cytosolic proteins which mediate G protein-coupled receptor (GPCR) desensitization, endocytosis, and signaling. Despite the widespread physiological roles of β-arr coupling, the molecular basis of GPCR/β-arr interaction has been studied primarily in monomeric family A GPCRs. Here we take an integrative biophysical and structural approach to uncover molecular diversity in β-arr coupling to the neuromodulatory metabotropic glutamate receptors (mGluRs), prototypical, dimeric family C GPCRs. We find, using a new single molecule pulldown assay, that mGluRs couple to β-arrs with a 2:1 or 2:2 stoichiometry via a combination of "tail" and "core" interactions. Using single molecule FRET analysis, we also find that β-arr1 stabilizes active conformations of mGluR8. Cryo-EM structures of mGluR8 alone or with either G proteins or β-arr1 reveal transducer-specific mGluR8 active states and, in combination with molecular dynamics simulations, define the positioning of mGluR8-bound β-arr1, supporting a steric mechanism of mGluR desensitization involving interactions with both subunits and the lipid bilayer. Finally, combinatorial mutagenesis enables the identification of a landscape of homo- and hetero-dimeric mGluR/β-arr complexes, including mGluR/β-arr1/β-arr2 megacomplexes, providing a framework for family C GPCR/β-arr coupling and expanding the known range of GPCR/transducer coupling modes.

  PublisherOA PDFDOI

Recent grants

• Molecular Mechanisms of Synaptic G Protein-Coupled Receptors

  NIH · $1.7M · 2017–2022

• Molecular Mechanisms of Synaptic G Protein-Coupled Receptors

  NIH · $409k · 2017–2022

• Photopharmacological interrogation of presynaptic neuromodulation of cortico-amygdalar circuits

  NIH · $2.4M · 2022–2027

• Molecular and Synaptic Mechanisms of Neurotrophin-glutamate Crosstalk

  NIH · $2.2M · 2022–2027

• Genetically-Targeted Photo-Pharmacology for Native Opioid Receptors

  NIH · $1.4M · 2020–2023

Frequent coauthors

• Johannes Broichhagen

  Leibniz-Forschungsinstitut für Molekulare Pharmakologie

  83 shared

• Joon Lee

  Cornell University

  69 shared

• Vanessa A. Gutzeit

  Weill Cornell Medicine

  62 shared

• Alberto J. Gonzalez-Hernandez

  Cornell University

  51 shared

• Ehud Y. Isacoff

  50 shared

• Conor Liston

  45 shared

• Hermany Munguba

  39 shared

• Melanie Kristt

  Cornell University

  37 shared

Labs

• Levitz LabPI