Biology subjects

Manandhar, A.

Publications and source records attributed to Manandhar, A..

6 recordsLinked to original sources

bioRxiv2026

Development of Potent G Protein Pathway-Biased GPR183 Agonists

GPR183 is an oxysterol-sensing GPCR predominantly expressed in lymphoid organs and tissues. Activation of the receptor by oxysterol 7,25-OHC leads to Gi protein-mediated signaling as well as {beta}-arrestin2 recruitment. GPR183/oxysterol signaling modulates localization of lymphoid cells, consequently the receptor is associated with several inflammation-associated diseases and is an interesting potential drug target. Previously, we reported the discovery of moderately potent G protein-biased partial agonists for GPR183 from a virtual screening based on the scaffold of the antagonist NIBR189. Herein, we present the detailed structure-activity investigations and optimizations, which led to the identification of full agonists for GPR183 with complete bias for Gi protein signaling and low nanomolar potency, including 63 (TUG-2604) with potency and efficacy similar to 7,25-OHC. Notably, 63 was unable to induce migration of human dendritic cells but inhibited migration induced by 7,25-OHC. This compound will be valuable for further explorations of the signaling-specific function and drug target potential of GPR183.

pharmacology and toxicology↗

bioRxiv2026

The origin of mechanical advantage in angiosperms

O_LIMechanical interaction between guard cells and epidermal pavement cells enables large stomatal apertures and high productivity in angiosperms. We do not know when this response evolved, but over the last 169 years we have found that mechanical advantage has been tested in at least 230 species from 85 families. To date no data on this trait exists among angiosperms outside magnoliids, monocots and eudicots. C_LIO_LITo resolve the evolutionary origins of this critical stomatal response we tested for mechanical advantage across 14 additional species including the earliest diverging lineages of angiosperms. C_LIO_LIWe find that mechanical advantage, while variable in magnitude, is present in all angiosperm species that have been measured, including Amborella trichopoda sister to all angiosperms. C_LIO_LIThis response likely evolved once in flowering plants, in the common ancestor of this clade, remaining widespread across angiosperms today. We hypothesize that angiosperms could not have realized the full potential of physiological innovations in water transport without the evolution of this key trait that increased operational stomatal aperture. C_LI

plant biology↗

bioRxiv2024

The SH Protein of Mumps Virus is a Druggable Pentameric Viroporin

Viral infections are on the rise and drugs targeting viral proteins are needed. Viroporins constitute a growing group of virus-encoded transmembrane oligomeric proteins that allow passage of small molecules across the membrane. Despite sparsity in viroporin structures, recent work has revealed diversity in both the number of transmembrane helices and oligomeric states. Here we provide evidence that the small hydrophobic protein (SH) from mumps virus is a pentameric viroporin. From extensive biophysical data, a HADDOCK model of full-length SH shows its intracellular C-terminal region to form an extended structure crucial to stabilization of the pentamer. Heterologous expression of wild type SH and variants in Xenopus laevis oocytes reveals the viroporin as a chloride channel, facilitated by conserved hydroxyl-carrying residues lining the pore. The channel function of SH is inhibited by the small-molecule BIT225, highlighting the potential for antiviral targeting through SH.

biophysics↗

bioRxiv2023

Passive stomatal closure under extreme drought in an angiosperm species

The phytohormone abscisic acid (ABA), synthesized as leaf turgor declines, plays a major role in closing stomata in species from this lineage, but recent reports of some angiosperms having a peaking-type ABA dynamic in which under extreme drought ABA levels decline to pre-stressed levels raises the possibility that passive stomatal closure by leaf water status alone can occur in species from this lineage. To test this hypothesis, we conducted instantaneous rehydration experiments in the peaking-type species Umbellularia californica through a long-term drought in which ABA levels declined to pre-stress levels yet stomata remain closed. We found that when ABA levels were lowest during extreme drought stomata of U. californica were passively closed by leaf water status alone, with stomata reopening rapidly to maximum rates of gas exchange on instantaneous rehydration. This contrasts with leaves early in drought in which ABA levels are highest, where we found stomata do not reopen on instantaneous rehydration. The transition from ABA driven stomatal closure to passively driven stomatal closure as drought progresses in this species occurs at very low water potentials facilitated by highly embolism resistant xylem. These results have important implications for understanding stomatal control during drought in angiosperms.

plant biology↗

bioRxiv2023

Application of DNA forensic to identify a problem leopard and its implications for human-leopard conflict mitigation

Attacks on humans by leopards Panthera pardus often escalate human-leopard conflict, influence extreme negative tolerance and encourage retaliatory killings. In the rural hilly region of Arghakhanchi district, mid-western Nepal, a leopard killed a child in November 2018. Government authorities captured a leopard a week later which was immediately killed by the villagers. We collected the predators salivary DNA from the victims bite wound and compared its DNA fingerprint profile with the killed leopards profile to resolve the case using 13 microsatellite markers for leopard individualization. Our genetic analysis confirmed that the leopard persecuted by the villagers was the same leopard that had killed the victim. We urge the government to devise dedicated policy and guidelines for human-leopard conflict management and mitigation in Nepal, and to incorporate protocols, including leopard individualization microsatellite panel we have standardized, that mandate correct identification of captured leopard before any interventions such as persecutions and translocations are attempted. We also recommend steering community programs to proactively safeguard children, people and livestock to avoid conflicts and to influence positive tolerance towards leopards. This will benefit leopard conservation and save human lives and livelihoods leading to a healthy coexistence.

genetics↗

bioRxiv2020

The two formyl peptide receptors differently regulate GPR84-mediated neutrophil NADPH-oxidase activity

Neutrophils express many G protein-coupled receptors (GPCRs) including the two formyl peptide receptors (FPR1 and FPR2) and the medium chain fatty acid receptor GPR84. The FPRs are known to define a hierarchy among neutrophil GPCRs, i.e., the GPCR-mediated response can be either suppressed or amplified by signals generated by FPRs. In this study, we investigated the position of GPR84 in the FPR-defined hierarchy regarding the activation of neutrophil NADPH-oxidase, an enzyme system designed to generate reactive oxygen species (ROS). When naive neutrophils are activated by GPR84 agonists a modest ROS release was induced. However, vast amounts of ROS production was induced by these GPR84 agonists in FPR2-desensitized neutrophils, and the response is inhibited not only by a GPR84 antagonist but also by an FPR2 specific antagonist. This suggests that the amplified GPR84 agonist response is achieved through a reactivation of the desensitized FPR2. In addition, the GPR84-mediated FPR2 reactivation was independent of {beta}-arrestin recruitment and sensitive to a protein phosphatase inhibitor. In contrast, the modest ROS production induced by GPR84 agonists was primarily suppressed in FPR1-desensitized neutrophils through hierarchical desensitization of GPR84 by FPR1 generated signals. In summary, our data show that FPRs control the NADPH-oxidase activity mediated through GPR84 in human neutrophils. While an amplified ROS generation is achieved by GPR84 agonists through reactivation of desensitized FPR2, FPR1 heterologously desensitizes GPR84 and by that suppresses the release of ROS induced by GPR84 agonists.

immunology↗