We report herein the first total synthesis of (+)-pierisketone B, a bioactive diterpene that possesses a unique tetracyclic 7/5/6/5 carbocyclic framework that is punctuated with numerous stereocenters, two of which are quaternary and five of which are contiguous. The synthesis features an unusual Pauson Khand cyclization to generate the bridged tricyclic core. Creation of the requisite cis-fused hydrindanone moiety was achieved by hydroxyl directed hydrogenation of an allylic alcohol, and the A-ring of the natural product was formed by a Mukaiyama aldol reaction followed by a cyclization involving addition of a vinyl anion to a proximal ketone group. The resulting tetracyclic intermediate was then elaborated in six steps to complete the first total synthesis of (+)-pierisketone B in a longest linear sequence of 20 steps from (-)-linalool.

Age-related macular degeneration (AMD) is a common eye disease that significantly affects daily activities and impedes the quality of life in aging adults, yet effective treatments to halt or reverse disease progression are currently lacking. Ongoing research aims at understanding the complex mechanisms underlying AMD pathophysiology involving retinal pigment epithelium (RPE) dysfunction, drusen formation, inflammation, neovascularization, and RPE/photoreceptor degeneration. Sigma 2 receptor/transmembrane protein 97 (σ2R/TMEM97) is a multifunctional protein implicated in cellular processes including cholesterol homeostasis, lysosome-dependent autophagy, calcium homeostasis, and integrated stress response (ISR). Recent genome-wide association studies (GWASs) have identified σ2R/TMEM97 as a novel genetic risk factor strongly associated with AMD development. In this review, we summarize recent research progress on σ2R/TMEM97 in age-related neurodegenerative diseases, highlighting its implication as a molecular target in AMD via regulating oxidative stress, inflammation, lipid uptake, drusen formation, and epithelial–mesenchymal transition (EMT). We also discuss the potential of modulating σ2R/TMEM97 function with novel small-molecule drugs as a promising treatment for dry AMD and the unresolved questions in understanding the mechanistic basis of their actions.

Supplemental air filtration can reduce indoor exposure to hazardous aerosols without requiring modifications to building heating, ventilation, and air conditioning (HVAC) systems. Portable air cleaners were widely used during the COVID-19 pandemic, but they can have drawbacks including noise, space obstruction, and electrical cord safety considerations. Built-in air filtration units are an alternative to provide supplemental air filtration. We conducted a case study of a HEPA air filtration unit installed in the ceiling of a conference room using radial laminar flow or square cone ceiling air supply diffusers. A respiratory aerosol simulator exhaled aerosol particles (0.3 to 10 mu m), and the particle concentrations were measured in the personal breathing zones of three breathing simulators representing a speaker and two meeting participants. For the speaker, using one square cone supply diffuser reduced inhalation exposure by 49 % to 81 % while using two square supply diffusers reduced exposure by 68 % to 93 %. For the participants, the exposures were reduced by 23 % to 64 % with one square supply diffuser and 58 % to 86 % with two square supply diffusers. Results when using the radial supply air diffusers were more variable and more dependent on the simulator layouts. Combining the use of cloth face masks on all simulators with the ceiling unit reduced the speaker's exposure by 87 % to 99 % and the participants' exposures by 84 % to 97 %. In most cases the ceiling air filtration unit provided protection against simulated respiratory aerosol particles comparable to that seen previously with portable air cleaners.

[This corrects the article DOI: 10.1021/acsptsci.5c00157.].

Posterior segment-related diseases are among the leading causes of irreversible blindness and loss of vision globally. These diseases are extremely difficult to treat due to the drug delivery barriers posed by the eye, among other challenges. One delivery method that bypasses many of these obstacles, albeit not without risk, is ocular injections, and long-acting formulations such as implants can improve patient compliance by allowing for longer intervals between injections. Here, we report our development of a preclinical in situ-forming implant dosage form that provides sustained release of a novel compound, DKR-1677, with a target in the retina. An in situ-forming implant based on polylactic co glycolic acid (PLGA) was chosen in this preclinical stage because it is readily translatable to a preformed implant product. The formulations were tested in vitro, in rat and rabbit animal models for drug release and pharmacokinetics. A two-step in vitro dissolution method with implant formation in a biorelevant gel followed by incubation in release media showed a 30-day three-phase release profile with an initial burst release of 36.04 ± 4.23 %, a plateau, and a controlled release up to 93.75 ± 4.68 % at day 30, typical of PLGA-based implant formulations. Immediate and controlled-release formulations were tested in rat and rabbit animal models and confirmed that DKR-1677 is taken up by the retina after intravitreal administration. Furthermore, the in situ-forming implant was found to prolong drug presence in the retina to 30 days following a single administration, confirming that a PLGA-based implant is a viable approach for this drug candidate.

The sigma 2 receptor (σ2R), which was recently identified as the transmembrane protein 97 (TMEM97), is increasingly attracting interest as a possible therapeutic target for indications in neuroscience. Toward identifying novel modulators of σ2R/TMEM97, we prepared a collection of benzoxazocine, benzomorphan, and methanobenzazepine ligands related to the known bioactive norbenzomorphans DKR-1677, FEM-1689, and EES-1686 and determined their Ki values for σ2R/TMEM97 and the sigma 1 receptor (σ1R). The σ2R/TMEM97 binding affinities and selectivities relative to σ1R of these new benzoxazocine, benzomorphan, and methanobenzazepine analogs are lower, often significantly lower, than their respective norbenzomorphan counterparts, suggesting the spatial orientation of pharmacophoric substituents is critical for binding to the two proteins. The benzoxazocine, benzomorphan, and methanobenzazepine congeners of DKR-1677 and FEM-1689 tend to be weakly selective for σ2R/TMEM97 versus σ1R, whereas EES-1686 derivatives exhibit the greatest selectivity, suggesting the size and/or nature of the substituent on the nitrogen atom of the scaffold may be important for selectivity. Computational docking studies were performed for the 1S,5R-and 1R,5S-enantiomers of DKR-1677, FEM-1689, and EES-1686 and their benzoxazocine, benzomorphan, and methanobenzazepine counterparts. These computations predict that the protonated amino group of each ligand forms a highly conserved salt bridge and a H-bonding interaction with Asp29 as well as a cation-π interaction with Tyr150 of σ2R/TMEM97. These electrostatic interactions are major driving forces for binding to σ2R/TMEM97 and are similar, though not identical, for each ligand. Other interactions within the well-defined binding pocket also tend to be comparable, but there are some major differences in how the hydrophobic aryl groups of various ligands interact with the protein surface external to the binding pocket. Overall, these studies show that the orientations of aryl and N-substituents on the norbenzomorphan and related scaffolds are important determinants of binding affinity of σ2R/TMEM97 ligands, and small changes can have significant effects upon binding profiles.

The Sigma-2 receptor (σ2/TMEM97), recently identified as Tmem97, is a transmembrane protein that is located in the endoplasmic reticulum (ER) and the plasma membrane. While the literature has highlighted ligands targeting Tmem97 for anti-neuropathic effects, its involvement in inflammatory pain-like responses remains understudied compared to neuropathic pain. Here, we aim to characterize Tmem97-associated inflammatory pain-like behaviors using global Tmem97 knockout (KO) and conditional Tmem97 knockout mice (cKO). Results indicate that Tmem97 KO mice exhibit a prolonged hypersensitivity to mechanical stimulation, but not to thermal stimulation, in a complete freud’s adjuvant (CFA)-induced inflammatory pain model (male and female, age 2-3 months). Similarly, Tmem97 floxed mice, crossed with Nav1.8-cre, show prolonged mechanical hypersensitivity but not thermal sensitivity (male and female, age 2-3 months). Three days post-CFA injection, a decrease in Tmem97 RNA expression in the dorsal root ganglion (DRG) is observed, which gradually returned to baseline in tandem with the resolution of inflammatory pain-like responses of wildtype mice. Loss of Tmem97, whether germline or specific to nociceptors, contributes to increased hypersensitivity in a sensory modality-dependent manner. The study’s outcomes provide critical insight into the peripheral role of σ2/TMEM97 in inflammatory pain modulation, suggesting that Tmem97 may be a promising therapeutic target for inflammation-associated pain. Future research aims to unravel the specific mechanisms, including Tmem97-associated cellular calcium response and/or signaling pathway, that may govern inflammatory pain-like responses. Funded by National Institutes of Health (F31NS129269).

Previous studies have shown that ligands that bind to sigma-2 receptor/TMEM97 (s 2 R/TMEM97), a transmembrane protein, have anxiolytic/antidepressant-like properties and relieve neuropathic painlike effects in rodents. Despite medical interest in s 2 R/TMEM97, little affective and pain behavioral characterization has been done using transgenic mice, which limits the development of s 2 R/TMEM97 as a viable therapeutic target. Using wild-type (WT) and global Tmem97 knock-out (KO) mice, we sought to identify the contribution of Tmem97 in modulating affective and pain-like behaviors using a battery of affective and pain assays, including open field, light/dark preference, elevated plus maze, forced swim test, tail suspension test, and the mechanical sensitivity tests. Our results demonstrate that female Tmem97 KO mice show less anxiety-like and depressive-like behaviors in light/dark preference and tail suspension tests but not in an open field, elevated plus maze, and forced swim tests at baseline. We next performed spared nerve injury in WT and Tmem97 KO mice to assess the role of Tmem97 in neuropathic paininduced anxiety and depression. WT mice, but not Tmem97 KO mice, developed a prolonged neuropathic pain-induced depressive-like phenotype when tested 10 weeks after nerve injury in females. Our results show that Tmem97 plays a role in modulating anxiety-like and depressive-like behaviors in naive animals with a significant change in the presence of nerve injury in female mice. Overall, these data demonstrate that Tmem97 could be a target to alleviate affective comorbidities of pain disorders.

The Sigma 2 receptor (σ 2 R) was described pharmacologically more than three decades ago, but its molecular identity remained obscure until recently when it was identified as transmembrane protein 97 (TMEM97). We and others have shown that σ 2 R/TMEM97 ligands alleviate mechanical hypersensitivity in mouse neuropathic pain models with a time course wherein maximal anti-nociceptive effect is approximately 24 hours following dosing. We sought to understand this unique anti-neuropathic pain effect by addressing two key questions: do these σ 2 R/TMEM97 compounds act selectively via the receptor, and what is their downstream mechanism on nociceptive neurons? Using male and female conventional knockout (KO) mice for Tmem97, we find that a new σ 2 R/TMEM97 binding compound, FEM-1689, requires the presence of the gene to produce anti-nociception in the spared nerve injury model in mice. Using primary mouse dorsal root ganglion (DRG) neurons, we demonstrate that FEM-1689 inhibits the integrated stress response (ISR) and promotes neurite outgrowth via a σ 2 R/TMEM97-specific action. We extend the clinical translational value of these findings by showing that FEM-1689 reduces ISR and p-eIF2α levels in human sensory neurons and that it alleviates the pathogenic engagement of ISR by methylglyoxal. We also demonstrate that σ 2 R/TMEM97 is expressed in human nociceptors and satellite glial cells. These results validate σ 2 R/TMEM97 as a promising target for further development for the treatment of neuropathic pain. Significance Statement Neuropathic pain is a major medical problem that is poorly treated with existing therapeutics. Our findings demonstrate that targeting σ 2 R/TMEM97 with a newly described modulator reduces pain hypersensitivity in a mouse model with exquisite selectivity. We also identify integrated stress response (ISR) inhibition as a potential mechanism of action that links the receptor to cellular signaling events that have preclinical and clinical validation for pain relief. Our work suggests that σ 2 R/TMEM97 can be selectively engaged by specific small molecules to produce ISR inhibition in a subset of cells that are critical for neuropathic pain. σ 2 R/TMEM97-targeted therapeutics thus have the potential to offer effective pain relief without engagement of opioid receptors.

Improving ventilation has been one of several COVID-19 prevention strategies implemented by kindergarten through grade 12 (K-12) schools to stay open for safe in-person learning. Because transmission of SARS-CoV-2 occurs through inhalation of infectious viral particles, it is important to reduce the concentration of and exposure time to infectious aerosols (1-3). CDC examined reported ventilation improvement strategies among U.S. K-12 public school districts using telephone survey data collected during August-December 2022. Maintaining continuous airflow through school buildings during active hours was the most frequently reported strategy by school districts (50.7%); 33.9% of school districts reported replacement or upgrade of heating, ventilation, and air conditioning (HVAC) systems; 28.0% reported installation or use of in-room air cleaners with high-efficiency particulate air (HEPA) filters; and 8.2% reported installation of ultraviolet (UV) germicidal irradiation (UVGI) devices, which use UV light to kill airborne pathogens, including bacteria and viruses. School districts in National Center for Education Statistics (NCES) city locales, the West U.S. Census Bureau region, and those designated by U.S. Census Bureau Small Area Income Poverty Estimates (SAIPE) as high-poverty districts reported the highest percentages of HVAC system upgrades and HEPA-filtered in-room air cleaner use, although 28%-60% of all responses were unknown or missing. Federal funding remains available to school districts to support ventilation improvements. Public health departments can encourage K-12 school officials to use available funding to improve ventilation and help reduce transmission of respiratory diseases in K-12 settings.

The sigma 2 receptor (σ 2 R) was described pharmacologically more than three decades ago, but its molecular identity remained obscure until recently when it was identified as transmembrane protein 97 (TMEM97). We and others have shown that σ 2 R/TMEM97 ligands alleviate mechanical hypersensitivity in mouse neuropathic pain models with a time course wherein maximal antinociceptive effect is approximately 24 h following dosing. We sought to understand this unique antineuropathic pain effect by addressing two key questions: do these σ 2 R/TMEM97 compounds act selectively via the receptor, and what is their downstream mechanism on nociceptive neurons? Using male and female conventional knockout mice for Tmem97, we find that a σ 2 R/TMEM97 binding compound, FEM-1689, requires the presence of the gene to produce antinociception in the spared nerve injury model in mice. Using primary mouse dorsal root ganglion neurons, we demonstrate that FEM-1689 inhibits the integrated stress response (ISR) and promotes neurite outgrowth via a σ 2 R/TMEM97-specific action. We extend the clinical translational value of these findings by showing that FEM-1689 reduces ISR and p-eIF2α levels in human sensory neurons and that it alleviates the pathogenic engagement of ISR by methylglyoxal. We also demonstrate that σ 2 R/TMEM97 is expressed in human nociceptors and satellite glial cells. These results validate σ 2 R/TMEM97 as a promising target for further development for the treatment of neuropathic pain.

The Sigma 2 receptor ( σ 2 R) was described pharmacologically more than three decades ago, but its molecular identity remained obscure until recently when it was identified as transmembrane protein 97 (TMEM97). We and others have shown that σ 2 R/TMEM97 ligands produce analgesia in mouse neuropathic pain models with a time course wherein analgesic onset is 24 hours following dosing. We sought to understand this unique anti-neuropathic pain effect by addressing two key questions: do these σ 2 R/TMEM97 compounds act selectively via the receptor, and what is their downstream mechanism on nociceptive neurons. Using male and female conventional knockout (KO) mice for Tmem97, we find that a novel σ 2 R/TMEM97 binding compound, FEM-1689, requires the presence of the gene to produce analgesia in the spared nerve injury model in mice. Using primary mouse dorsal root ganglion (DRG) neurons, we demonstrate that FEM-1689 inhibits the integrated stress response and promotes neurite outgrowth via a σ 2 R/TMEM97-specific action. We extend the clinical translational value of these findings by showing that FEM-1689 reduces ISR and p-eIF2 α levels in human sensory neurons and that it alleviates the pathogenic engagement of ISR by methylglyoxal. We also demonstrate that σ 2 R/TMEM97 is expressed in human nociceptors and satellite glial cells. These results validate σ 2 R/TMEM97 as a promising target for further development for the treatment of neuropathic pain.

The sigma 2 receptor (ci2R), which is identical to transmembrane protein 97 (TMEM97), is attracting increasing interest as a possible therapeutic target for various indications in neuroscience. In continuation of a program to identify novel compounds that bind with high affinity and selectivity to ci2R/TMEM97, we performed structure -affinity-relationship (SAfiR) studies of several sets of ci2R/TMEM97 ligands having a B-norbenzomorphan ring core. Binding data for ci2R/TMEM97 and ci1R of several enantiomeric pairs of piperazine-substituted norben-zomorphans show the (1S,5R)-enantiomers have affinities (Ki = 9-75 nM) for ci2R/TMEM97 that are 2-3-fold higher than their enantiomorphic (1R,5S)-analogs; however, there is no clear trend for selectivity for ci2R/ TMEM97 vs ci1R. A series of N -alkyl piperazino (1S,5R)-norbenzomorphans was then evaluated, and with the exception of compounds having N -alkyl groups substituted with oxygen or amino groups at C (2) of an ethylene chain, Ki values for ci2R/TMEM97 are less than 25 nM, and several compounds have good selectivities (ca 7-16 -fold) for ci2R/TMEM97 vs ci1R. Mono-substituted carbobenzyloxy analogs have Ki values for ci2R/TMEM97 comparable to the unsubstituted parent (Ki = ca 7-27 nM), but replacing the N-acyloxy group with N-acyl or N- arylsulfonyl groups provides analogs having lower affinity and selectivity. Some congeners with bioisosteric replacements of the piperazine group on the (1S,5R)-norbenzomorphan core have high affinity (Ki= <30 nM) for ci2R/TMEM97, but selectivities are modest. Computational docking studies for racemic pairs of piperazino norbenzomorphans show that individual (1S,5R)-and (1R,5S)-enantiomers adopt distinct poses upon binding to & sigma;2R/TMEM97, whereas ligands belongingto the same enantiomeric series adopt closely similar binding poses. The protonated amino group in each of the enantiomorphic ligands engages in highly conserved salt bridges with Asp29 and cation-ic interactions with Tyr150 that are the primary determinants of binding affinity. There is no correlation between any of the computational parameter outputs and Ki values, but this is unsurprising given the small energetic differences involved. Modeling also suggest sthat some compounds can extend deeper into ci2R/ TMEM97 binding pocket forming salt bridges with Glu73.

Many respiratory diseases, including COVID-19, can be spread by aerosols expelled by infected people when they cough, talk, sing, or exhale. Exposure to these aerosols indoors can be reduced by portable air filtration units (air cleaners). Homemade or Do-It-Yourself (DIY) air filtration units are a popular alternative to commercially produced devices, but performance data is limited. Our study used a speaker-audience model to examine the efficacy of two popular types of DIY air filtration units, the Corsi-Rosenthal cube and a modified Ford air filtration unit, in reducing exposure to simulated respiratory aerosols within a mock classroom. Experiments were conducted using four breathing simulators at different locations in the room, one acting as the respiratory aerosol source and three as recipients. Optical particle spectrometers monitored simulated respiratory aerosol particles (0.3-3 mu m) as they dispersed throughout the room. Using two DIY cubes (in the front and back of the room) increased the air change rate as much as 12.4 over room ventilation, depending on filter thickness and fan airflow. Using multiple linear regression, each unit increase of air change reduced exposure by 10%. Increasing the number of filters, filter thickness, and fan airflow significantly enhanced the air change rate, which resulted in exposure reductions of up to 73%. Our results show DIY air filtration units can be an effective means of reducing aerosol exposure. However, they also show performance of DIY units can vary considerably depending upon their design, construction, and positioning, and users should be mindful of these limitations.

To the Editors — We read with concern the letter by Hurlburt et al 1 proposing revisions to the recommended room air clearance times for infectious aerosols in healthcare facilities. We believe that the calculations performed to justify the changes are based on flawed assumptions and an erroneous calculation. Experimental data on the survival of airborne SARS-CoV-2 virus and the dynamics of room ventilation do not support their conclusions. Hurlburt et al based their proposed changes on data describing the effects of humidity on the viability of airborne influenza viruses, and on reports that influenza decays more rapidly at mid-range humidities. They then assumed that these decay rates apply to SARS-CoV-2 as well. In fact, this is not the case. Schuit et al 2 studied the decay in viability of airborne SARS-CoV-2 for relative humidities of 20% to 70% at 20°C and found that SARS-CoV-2 was relatively stable in air in the absence of sunlight (k infect = 0.008 per minute) and that humidity did not significantly affect the decay rate. Other researchers have also reported either no effect or a small effect of humidity on the decay rate of airborne SARS-CoV-2. 3,4 Using data for influenza rather than SARS-CoV-2, Hurlburt et al assumed that a relative humidity of 40% to 60% would reduce the viability of SARS-CoV-2 by 30% to 50%. Unfortunately, these researchers miscalculated the effect that this would have on air clearance times. They simply multiplied the equation for the clearance time by their assumed reduction in viability, which has the mathematical effect of assuming that the reduction in viability occurs instantaneously. In fact, experimental for SARS-CoV-2 and other that in

Exposure to elevated levels of diacetyl in flavoring and microwave popcorn production has been associated with respiratory impairment among workers including from a severe lung disease known as obliterative bronchiolitis. Laboratory studies demonstrate damage to the respiratory tract in rodents exposed to either diacetyl or the related alpha-diketone 2,3-pentanedione. Respiratory tract damage includes the development of obliterative bronchiolitis-like changes in the lungs of rats repeatedly inhaling either diacetyl or 2,3-pentanedione. In one flavored coffee processing facility, current workers who spent time in higher diacetyl and 2,3-pentanedione areas had lower lung function values, while five former flavoring room workers were diagnosed with obliterative bronchiolitis. In that and other coffee roasting and packaging facilities, grinding roasted coffee beans has been identified as contributing to elevated levels of diacetyl and 2,3-pentanedione. To reduce worker exposures, employers can take various actions to control exposures according to the hierarchy of controls. Because elimination or substitution is not applicable to coffee production facilities not using flavorings, use of engineering controls to control exposures at their source is especially important. This work demonstrates the use of temporary ventilated enclosures around grinding equipment in a single coffee roasting and packaging facility to mitigate diacetyl and 2,3-pentanedione emissions from grinding equipment to the main production space. Concentrations of diacetyl and 2,3-pentanedione were measured in various locations throughout the main production space as well as inside and outside of ventilated enclosures to evaluate the effect of the enclosures on exposures. Diacetyl and 2,3-pentanedione concentrations outside one grinder enclosure decreased by 95 and 92%, respectively, despite ground coffee production increasing by 12%, after the enclosure was installed. Outside a second enclosure, diacetyl and 2,3-pentanedione concentrations both decreased 84%, greater than the 33% decrease in ground coffee production after installation. Temporary ventilated enclosures used as engineering control measures in this study effectively reduced emissions of diacetyl and 2,3-pentanedione at the source in this facility. These findings motivated management to explore options with a grinding equipment manufacturer to permanently ventilate their grinders to reduce emissions of diacetyl and 2,3-pentanedione.

Fused filament fabrication three-dimensional (FFF 3-D) printing is thought to be environmentally sustainable; however, significant amounts of waste can be generated from this technology. One way to improve its sustainability is via distributed recycling of plastics in homes, schools, and libraries to create feedstock filament for printing. Risks from exposures incurred during recycling and reuse of plastics has not been incorporated into life cycle assessments. This study characterized contaminant releases from virgin (unextruded) and recycled plastics from filament production through FFF 3-D printing. Waste polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) plastics were recycled to create filament; virgin PLA, ABS, high and low density polyethylenes, high impact polystyrene, and polypropylene pellets were also extruded into filament. The release of particles and chemicals into school classrooms was evaluated using standard industrial hygiene methodologies. All tasks released particles that contained hazardous metals (e.g., manganese) and with size capable of depositing in the gas exchange region of the lung, i.e., granulation of waste PLA and ABS (667 to 714 nm) and filament making (608 to 711 nm) and FFF 3-D printing (616 to 731 nm) with waste and virgin plastics. All tasks released vapors, including respiratory irritants and potential carcinogens (benzene and formaldehyde), mucus membrane irritants (acetone, xylenes, ethylbenzene, and methyl methacrylate), and asthmagens (styrene, multiple carbonyl compounds). These data are useful for incorporating risks of exposure to hazardous contaminants in future life cycle evaluations to demonstrate the sustainability and circular economy potential of FFF 3-D printing in distributed spaces.

We report the design, synthesis and evaluation of two novel photocages, NCARB and isoNCARB, belonging to the o-nitrobenzyl chemotype and based on the carbazole ring system. The synthesis of each of these isomeric caging molecules was achieved in five steps and in 29 % overall yield, and their photochemical properties were evaluated using benzoic acid as a model for caging. In the event, upon irradiation at 400 nm for 60 min, 82 % and 42 % of benzoic acid was freed from the NCARB and isoNCARB photocages, respectively, whereas only 22 % was released from the nitrodibenzofuran (NDBF) cage. Moreover, the photochemical decaging efficiencies, ϵΦ, of the benzoates photocaged with NCARB and isoNCARB are about 150- and 20-fold better, respectively, at 400 nm than the corresponding caged benzoate derived from NDBF. The water solubility of molecules caged with nitrocarbazole analogs was improved by N-alkylation of NCARB, the better of the two new photocages, with an aminodicarboxylate group. This modified cage, NCARB-DA, was exploited in the design of a caged fluoroquinolone antibiotic, the efficacy of which was illustrated in a bacterial growth inhibition assay, and a phenol-caged tyrosine derivative.

Initially associated with cancer diagnosis and therapy, the sigma 2 receptor (σ2R) has recently been implicated in several disorders of the central nervous system (CNS). It remained a poorly characterized target until we identified it as the transmembrane protein 97 (TMEM97). As part of a program to identify novel compounds that bind with high affinity and selectivity to σ2R/TMEM97 relative to the sigma 1 receptor (σ1R) and other CNS proteins, we employed a scaffold simplification strategy to design novel sets of piperazine-substituted aminotetralins based on analogous norbenzomorphans that we previously developed. JVW-1601 was identified as a reference aminotetralin analog that had high affinity (Ki = 5.5 nM) and selectivity (36-fold) for σ2R/TMEM97 versus σ1R. An expanded investigation of structure-activity relationships (SAR) in several structural regions of this compound was conducted, and among the ligands thus prepared, many had Ki values < 20 nM for σ2R/TMEM97 and selectivities of >20-fold versus σ1R. Structural features that enhance σ2R/TMEM97 affinity and selectivity were identified, leading to an optimized compound having a high σ2R/TMEM97 affinity (Ki of 4.5 nM) and 366-fold selectivity relative to σ1R. Significantly, during the course of this work we discovered JVW-1625, which enabled the isolation and identification of σ2R as TMEM97 and resolved a question that had eluded researchers for decades. Computational docking studies for selected aminotetralins suggest they adopt similar poses upon binding to σ2R/TMEM97, engaging in highly conserved salt bridges with Asp29 and cation-π interactions with Tyr150. Collectively, these studies show that aminotetralins are useful tool compounds for studying the mechanism and function of σ2R/TMEM97.

The sigma 2 receptor (σ 2 R) was recently identified as an endoplasmic reticulum (ER) membrane protein known as transmembrane protein 97 (TMEM97). Studies have shown that σ 2 R/TMEM97 binding compounds are neuroprotective, suggesting a role of σ 2 R/TMEM97 in neurodegenerative processes. To understand the function of σ 2 R/TMEM97 in neurodegeneration pathways, we characterized ischemia-induced retinal ganglion cell (RGC) degeneration in TMEM97 −/− mice and found that RGCs in TMEM97 −/− mice are resistant to degeneration. In addition, intravitreal injection of a selective σ 2 R/TMEM97 ligand DKR-1677 significantly protects RGCs from ischemia-induced degeneration in wildtype mice. Our results provide conclusive evidence that σ 2 R/TMEM97 plays a role to facilitate RGC death following ischemic injury and that inhibiting the function of σ 2 R/TMEM97 is neuroprotective. This work is a breakthrough toward elucidating the biology and function of σ 2 R/TMEM97 in RGCs and likely in other σ 2 R/TMEM97 expressing neurons. Moreover, these findings support future studies to develop new neuroprotective approaches for RGC degenerative diseases by inhibiting σ 2 R/TMEM97.