Despite the high incidence of neuropathic and inflammatory pain worldwide, effective drugs with few side effects are currently unavailable for the treatment of chronic pain. Recently, researchers have proposed that inhibitors of purinergic chemical transmission, which plays a key role in the pathological pain response, may allow for targeted treatment of pathological neuropathic and inflammatory pain. However, such therapeutic analgesic agents have yet to be developed. In the present study, we demonstrated that clodronate, a first-generation bisphosphonate with comparatively fewer side effects than traditional treatments, significantly attenuates neuropathic and inflammatory pain unrelated to bone abnormalities via inhibition of vesicular nucleotide transporter (VNUT), a key molecule for the initiation of purinergic chemical transmission. In vitro analyses indicated that clodronate inhibits VNUT at a half-maximal inhibitory concentration of 15.6 nM without affecting other vesicular neurotransmitter transporters, acting as an allosteric modulator through competition with Cl⁻. A low concentration of clodronate impaired vesicular ATP release from neurons, microglia, and immune cells. In vivo analyses revealed that clodronate is more effective than other therapeutic agents in attenuating neuropathic and inflammatory pain, as well as the accompanying inflammation, in wild-type but not VNUT^−/− mice, without affecting basal nociception. These findings indicate that clodronate may represent a unique treatment strategy for chronic neuropathic and inflammatory pain via inhibition of vesicular ATP release. Significance Although the incidence of chronic pain is estimated at 20–25% worldwide, optimal drug treatment regimens with few side effects have yet to be developed. In this study, we demonstrated that clodronate is a potent and selective inhibitor of vesicular ATP release that attenuates neuropathic and inflammatory pain unrelated to bone abnormalities. Clodronate was more effective and associated with comparatively fewer side effects than existing drugs. Thus, the nonopioid agent clodronate may represent a unique treatment strategy for chronic pain via inhibition of vesicular ATP release, suggesting that clodronate may be effective in the treatment of several diseases involving purinergic chemical transmission, including inflammatory diseases, diabetes, and neurological disorders. Our study identifies a transporter-targeted analgesic drug.

Mulitidrug and toxic compound extrusion (MATE) family transporters export xenobiotics to maintain cellular homeostasis. The human MATE transporters mediate the excretion of xenobiotics and cationic clinical drugs, whereas some plant MATE transporters are responsible for aluminum tolerance and secondary metabolite transport. Here we report the crystal structure of the eukaryotic MATE transporter from Arabidopsis thaliana, at 2.6 Å resolution. The structure reveals that its carboxy-terminal lobe (C-lobe) contains an extensive hydrogen-bonding network with well-conserved acidic residues, and their importance is demonstrated by the structure-based mutational analysis. The structural and functional analyses suggest that the transport mechanism involves the structural change of transmembrane helix 7, induced by the formation of a hydrogen-bonding network upon the protonation of the conserved acidic residue in the C-lobe. Our findings provide insights into the transport mechanism of eukaryotic MATE transporters, which is important for the improvement of the pharmacokinetics of the clinical drugs.

Silicon (Si) is the most abundant mineral element in the earth’s crust. Some plants actively accumulate Si as amorphous silica (phytoliths), which can protect plants from stresses. Here, we report a gene (SIET4) that is required for the proper accumulation and cell-specific deposition of Si in rice and show that it is essential for normal growth. SIET4 is constitutively expressed in leaves and encodes a Si transporter. SlET4 polarly localizes at the distal side of epidermal cells and cells surrounding the bulliform cells (motor cells) of the leaf blade, where Si is deposited. Knockout of SIET4 leads to the death of rice in the presence but not absence of Si. Further analysis shows that SIET4 knockout induces abnormal Si deposition in mesophyll cells and the induction of hundreds of genes related to various stress responses. These results indicate that SIET4 is required for the proper export of Si from leaf cells to the leaf surface and for the healthy growth of rice on land.

Multidrug resistance (MDR) poses a major challenge to medicine. A principle cause of MDR is through active efflux by MDR transporters situated in the bacterial membrane. Here we present the crystal structure of the major facilitator superfamily (MFS) drug/H⁺ antiporter MdfA from Escherichia coli in an outward open conformation. Comparison with the inward facing (drug binding) state shows that, in addition to the expected change in relative orientations of the N- and C-terminal lobes of the antiporter, the conformation of TM5 is kinked and twisted. In vitro reconstitution experiments demonstrate the importance of selected residues for transport and molecular dynamics simulations are used to gain insights into antiporter switching. With the availability of structures of alternative conformational states, we anticipate that MdfA will serve as a model system for understanding drug efflux in MFS MDR antiporters.

During Drosophila aversive olfactory conditioning, aversive shock information needs to be transmitted to the mushroom bodies (MBs) to associate with odor information. We report that aversive information is transmitted by ensheathing glia (EG) that surround the MBs. Shock induces vesicular exocytosis of glutamate from EG. Blocking exocytosis impairs aversive learning, whereas activation of EG can replace aversive stimuli during conditioning. Glutamate released from EG binds to N -methyl- d -aspartate receptors in the MBs, but because of Mg ²⁺ block, Ca ²⁺ influx occurs only when flies are simultaneously exposed to an odor. Vesicular exocytosis from EG also induces shock-associated dopamine release, which plays a role in preventing formation of inappropriate associations. These results demonstrate that vesicular glutamate released from EG transmits negative valence information required for associative learning.