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Ubeysinghe, S.

Publications and source records attributed to Ubeysinghe, S..

4 recordsLinked to original sources

AGS3-based optogenetic GDI induces GPCR-independent Gβγ signaling and macrophage migration

G protein-coupled receptors (GPCRs) are efficient Guanine nucleotide exchange factors (GEFs) and exchange GDP to GTP on the G subunit of G protein heterotrimers in response to various extracellular stimuli, including neurotransmitters and light. GPCRs primarily broadcast signals through activated G proteins, GGTP, and free G{beta}{gamma} and are major disease drivers. Evidence shows that the ambient low threshold signaling required for cells is likely supplemented by signaling regulators such as non-GPCR GEFs and Guanine nucleotide Dissociation Inhibitors (GDIs). Activators of G protein Signaling 3 (AGS3) are recognized as a GDI involved in multiple health and disease-related processes. Nevertheless, understanding of AGS3 is limited, and no significant information is available on its structure-function relationship or signaling regulation in living cells. Here, we employed in silico structure-guided engineering of a novel optogenetic GDI, based on the AGS3s G protein regulatory (GPR) motif, to understand its GDI activity and induce standalone G{beta}{gamma} signaling in living cells on optical command. Our results demonstrate that plasma membrane recruitment of OptoGDI efficiently releases G{beta}{gamma}, and its subcellular targeting generated localized PIP3 and triggered macrophage migration. Therefore, we propose OptoGDI as a powerful tool for optically dissecting GDI-mediated signaling pathways and triggering GPCR-independent G{beta}{gamma} signaling in cells and in vivo.

molecular biology↗

Optical Control of Cell-Surface and Endomembrane-Exclusive β-Adrenergic Receptor Signaling

Beta-adrenergic receptors ({beta}ARs) are G protein-coupled receptors (GPCRs) that mediate catecholamine-induced stress responses, such as heart rate increase and bronchodilation. In addition to signals from the cell surface, {beta}ARs also broadcast non-canonical signaling activities from the cell interior membranes (endomembranes). Dysregulation of these receptor pathways underlies severe pathological conditions. Excessive {beta}AR stimulation is linked to cardiac hypertrophy, leading to heart failure, while impaired stimulation causes compromised fight or flight stress responses and homeostasis. In addition to plasma membrane {beta}AR, emerging evidence indicates potential pathological implications of deeper endomembrane {beta}ARs, such as inducing cardiomyocyte hypertrophy and apoptosis, underlying heart failure. However, the lack of approaches to control their signaling in subcellular compartments exclusively has impeded linking endomembrane {beta}AR signaling with pathology. Informed by the {beta}1AR-catecholamine interactions, we engineered an efficiently photo-labile, protected hydroxy {beta}1AR pro-ligand (OptoIso) to trigger {beta}AR signaling at the cell surface, as well as exclusive endomembrane regions upon blue light stimulation. Not only does OptoIso undergo blue light deprotection in seconds, but it also efficiently enters cells and allows examination of G protein heterotrimer activation exclusively at endomembranes. In addition to its application in the optical interrogation of {beta}ARs in unmodified cells, given its ability to control deep organelle {beta}AR signaling, OptoIso will be a valuable experimental tool.

biochemistry↗

Spatiotemporal optical control of Gαq-PLCβ interactions

Cells experience time-varying and spatially heterogeneous chemokine signals in vivo, activating cell surface proteins, including G protein-coupled receptors (GPCRs). The Gq pathway activation by GPCRs is a major signaling axis with a broad physiological and pathological significance. Compared to other G members, GqGTP activates many crucial effectors, including PLC{beta} (Phospholipase C{beta}) and Rho GEFs (Rho guanine nucleotide exchange factors). PLC{beta} regulates many key processes, such as hematopoiesis, synaptogenesis, and cell cycle, and is therefore implicated in terminal - debilitating diseases, including cancer, epilepsy, Huntingtons Disease, and Alzheimers Disease. However, due to a lack of genetic and pharmacological tools, examining how the dynamic regulation of PLC{beta} signaling controls cellular physiology has been difficult. Since activated PLC{beta} induces several abrupt cellular changes, including cell morphology, examining how the other pathways downstream of Gq-GPCRs contribute to the overall signaling has also been difficult. Here we show the engineering, validation, and application of a highly selective and efficient optogenetic inhibitor (Opto-dHTH) to completely disrupt GqGTP-PLC{beta} interactions reversibly in user-defined cellular-subcellular regions on optical command. Using this newly gained PLC{beta} signaling control, our data indicate that the molecular competition between RhoGEFs and PLC{beta} for GqGTP determines the potency of Gq-GPCR-governed directional cell migration.

molecular biology↗

Molecular regulation of GPCR-G-protein-governed PIP3 generation and its adaptation

Phosphatidylinositol (3,4,5) trisphosphate (PIP3) is a plasma membrane-bound signaling phospholipid involved in many cellular signaling pathways that control crucial cellular processes and behaviors, including cytoskeleton remodeling, metabolism, chemotaxis, and apoptosis. Therefore, defective PIP3 signaling is implicated in various disease driving processes, including cancer metastasis, diabetes, obesity, and cardiovascular diseases. Upon activation by G protein-coupled receptors (GPCRs) or receptor tyrosine kinases (RTKs), phosphoinositide-3-kinases (PI3Ks) phosphorylate phosphatidylinositol (4,5) bisphosphate (PIP2), generating PIP3. Interestingly, though the mechanisms are unclear, PIP3 produced upon GPCR activation attenuates within minutes, indicating a tight temporal regulation. Our data show the subcellular redistributions of G proteins govern this PIP3 attenuation in the presence of sustained receptor stimulation, and thus meet the definition of signaling adaptation. Interestingly the observed adaptation of PIP3 was G{gamma} subtype-dependent. Considering distinct cell-tissue-specific G{gamma} expression profiles, our findings not only demonstrate how the GPCR-induced PIP3 response is adapted but also show how diversely this adaptation process is regulated by the dominant G{gamma}s of a cell.

cell biology↗