Biology subjects

Nguyen, A. M.

Publications and source records attributed to Nguyen, A. M..

5 recordsLinked to original sources

bioRxiv2026

DIFFERENTIAL ACTIVATION OF G-PROTEIN SUBTYPES BY DOPAMINE D1 RECEPTOR ALLOSTERIC MODULATION

Allosteric modulation of G protein-coupled receptors (GPCR) is a rapidly advancing area of drug discovery with considerable therapeutic potential. In this study, we used various bioluminescence resonance energy transfer (BRET) assay configurations to investigate the differential activity of LY3154207, a dopamine D1 receptor (D1R)- positive allosteric modulator (PAM), in potentiating D1R-mediated signaling pathways. Our data showed that LY3154207 demonstrated clear bias toward {beta}-arrestin recruitment over G-protein engagement. Among the G-protein subtypes, LY3154207 preferentially potentiated Gs signaling induced by DA. Interestingly, when tested for its effect on the Gs-selective D1R agonist DHX and the Golf-selective agonist TAV, LY3154207 further enhanced the selectivity of these compounds, suggesting a probe-dependent effect. We also studied the structural mechanism underlying this subtype selectivity and found that W123 and R130 in the intracellular loop 2 (ICL2) of D1R were crucial for the activity of LY3154207. Furthermore, the N domain of the G-protein appeared to make minor contributions to this G-protein subtype selectivity of LY3154207. Lastly, our data demonstrated that LY3154207 induced cAMP production in the absence of the orthosteric ligand, indicating that this compound is an ago-PAM.

pharmacology and toxicology↗

bioRxiv2024

Decreased CREB phosphorylation impairs embryonic retinal neurogenesis in the Oa1-/- mouse model of Ocular albinism

Mutations in the human Ocular albinism type-1 gene OA1 are associated with abnormal retinal pigment epithelium (RPE) melanogenesis and poor binocular vision resulting from misrouting of ipsilateral retinal ganglion cell (iRGC) axons to the brain. We studied the latter using wild-type (WT) and Oa1-/- mouse eyes. At embryonic stages, the WT RPE-specific Oa1 protein signals through cAMP/Epac1-Erk2-CREB. Following CREB phosphorylation, a pCREB gradient extends from the RPE to the differentiating retinal amacrine and RGCs. In contrast to WT, the Oa1-/- RPE and ventral ciliary-margin-zone, a niche for iRGCs, express less pCREB while their retinas have a disrupted pCREB gradient, indicating Oa1s involvement in pCREB maintenance. Oa1-/- retinas also show hyperproliferation, enlarged nuclei, reduced differentiation, and fewer newborn amacrine and RGCs than WT retinas. Our results demonstrate that Oa1s absence leads to reduced binocular vision through a hyperproliferation-associated block in differentiation that impairs neurogenesis. This may affect iRGC axons routing to the brain.

developmental biology↗

bioRxiv2023

Characterization of Gαs and Gαolf activation by catechol and non-catechol dopamine D1 receptor agonists

The dopamine D1 receptor (D1R) couples to Gs and Golf and plays a crucial role in regulating voluntary movement and other cognitive functions, making it a potential therapeutic target for several neurological and neuropsychiatric disorders, such as Parkinsons disease and schizophrenia. In the central nervous system, Gs is widely expressed in the cortex and Golf is predominantly found in the striatum. We used two different configurations of bioluminescence resonance energy transfer (BRET) assays and a fluorescence-based cyclic AMP (cAMP) production functional assay to test a series of tetracyclic catechol (dihydrexidine, methyl-dihydrexidine, doxanthrine) and non-catechol (tavapadon, PF-8294, PF-6142) D1R agonists for their activity at these G proteins. We discovered that these tetracyclic catechol compounds, PF-8294 and PF-6142 exerted full agonism when D1R coupled to Gs but partial agonism when D1R coupled to Golf. In contrast, tavapadon acted as a full agonist at Golf and a partial agonist at Gs. The effects of these compounds on the cortical and nigral electrophysiological events agree with their selectivity profiles. This suggests the possibility of achieving region-specific pharmacology and opens new directions for developing D1R drugs to treat relevant neurological and neuropsychiatric disorders.

pharmacology and toxicology↗

bioRxiv2022

Oral mTOR Inhibition Limits And Reduces Actinic Keratosis And Cutaneous Squamous Cell Carcinoma In A UVB-Induced Mouse Model

Actinic keratosis (AK) is a skin disease that is characterized by clinical and subclinical cutaneous lesions in sun-exposed areas. It is a considerable burden due to its high occurrence in middle-aged and older populations, as well as its propensity to progress to invasive cutaneous squamous cell carcinoma. The mammalian target of rapamycin (mTOR) pathway is critical in carcinogenesis and tumor development, and it has been shown to be over-activated during skin tumorigenesis, particularly upon ultraviolet (UV) radiation exposure, the key risk factor for AK. However, the ability of mTOR inhibitors to treat AK is not well documented. Herein, we evaluated the effect of oral mTOR inhibitors in vitro and in vivo and found that mTOR inhibitors lower keratinocyte cell proliferation in vitro and both clear and prevent AK and cutaneous squamous cell carcinoma (cSCC) in a UV-B induced SKH1 hairless mouse model of disease. mTOR inhibition reduced the number and size of skin lesions and the frequency of cSCC, resulting in a considerable reduction in disease severity. mTOR inhibition prevented lesion occurrence in areas of field cancerization, without affecting epidermal thickness, keratinocyte proliferation in vivo, or the presence of p53+ cells. Our findings indicate that, when appropriately dosed, oral mTOR inhibitors provide a safe home-based systemic treatment alternative with significant benefits to patients over current topical treatment options.

pharmacology and toxicology↗

bioRxiv2020

A Multi-Phenotype System to Discover Therapies for Age-Related Dysregulation of the Immune Response to Viral Infections

Age-related immune dysregulation contributes to increased susceptibility to infection and disease in older adults. We combined high-throughput laboratory automation with machine learning to build a multi-phenotype aging profile that models the dysfunctional immune response to viral infection in older adults. From a single well, our multi-phenotype aging profile can capture changes in cell composition, physical cell-to-cell interaction, organelle structure, cytokines, and other hidden complexities contributing to age-related dysfunction. This system allows for rapid identification of new potential compounds to rejuvenate older adults immune response. We used our technology to screen thousands of compounds for their ability to make old immune cells respond to viral infection like young immune cells. We observed beneficial effects of multiple compounds, of which two of the most promising were disulfiram and triptonide. Our findings indicate that disulfiram could be considered as a treatment for severe coronavirus disease 2019 and other inflammatory infections.

immunology↗