Biology subjects

Eisenreichova, A.

Publications and source records attributed to Eisenreichova, A..

3 recordsLinked to original sources

bioRxiv2023

Fluorinated cGAMP analogs, which act as STING agonists and are not cleavable by poxins: structural basis of their function

The Stimulator of Interferon Genes (STING) plays a crucial role in the cGAS-STING pathway of innate immunity, detecting DNA in the cytoplasm and defending against certain cancers, viruses, and bacteria. We designed and synthesized fluorinated carbocyclic cGAMP analogs, MD1203 and MD1202D (MDs), to enhance their stability against nucleases and their affinity for STING. These compounds demonstrated exceptional activity against wild-type STING and all its allelic variations, including the hard-to-target REF isoform. Despite their distinct chemical modifications relative to the canonical CDNs, such as the substitution of guanine with hypoxanthine and the fluorination of the (pseudo)ribose ring, crystallographic analysis revealed a consistent binding mode with STING. Importantly, these compounds were resistant to cleavage by viral poxin nucleases. The crystallographic analysis of poxin/MD complexes unveiled their binding mode at the interface of poxin monomers, with dynamic adenine base orientations. Interestingly, MDs-bound poxin adopted an unliganded-like conformation, distinct from the conformation of cGAMP-bound poxin. Moreover, when MDs were in complex with poxin, they exhibited a different conformation than cGAMP when bound to poxin; in fact, it closely resembled the conformation observed when MDs were bound to STING. In conclusion, the development of MD1203 and MD1202D, showcases their potential as potent STING activators with remarkable stability against poxin-mediated degradation--a crucial characteristic for future development of antivirals.

molecular biology↗

bioRxiv2023

Coordination of transporter, cargo, and membrane properties during non-vesicular lipid transport.

Homeostasis of cellular membranes is maintained by fine-tuning their lipid composition. Yeast lipid transporter Osh6, belonging to the oxysterol-binding protein-related proteins family, was found to participate in the transport of phosphatidylserine (PS). PS synthesized in the endoplasmic reticulum is delivered to the plasma membrane, where it is exchanged for phosphatidylinositol-4 phosphate (PI4P). PI4P provides the driving force for the directed PS transport against its concentration gradient. In this study, we employed an in vitro approach to reconstitute the transport process into the minimalistic system of large unilamellar vesicles to reveal its fundamental biophysical determinants. Our study draws a comprehensive portrait of the interplay between the structure and dynamics of Osh6, the carried cargo lipid, and the physical properties of the involved membranes, with particular attention to their charge and fluidity. Specifically, we address the role of the cargo lipid, which, by occupying the transporter, imposes changes in its dynamics and, consequently, predisposes the cargo to disembark in the correct target membrane.

biophysics↗

bioRxiv2019

Defining the Subcellular Distribution and Metabolic Channeling of Phosphatidylinositol

Phosphatidylinositol (PtdIns) is an essential structural component of eukaryotic membranes that also serves as the common precursor for polyphosphoinositide (PPIn) lipids. Despite the recognized importance of PPIn species for signal transduction and membrane homeostasis, there is still a limited understanding of how the dynamic regulation of PtdIns synthesis and transport contributes to the turnover of PPIn pools. To address these shortcomings, we capitalized on the substrate selectivity of a bacterial enzyme, PtdIns-specific PLC, to establish a molecular toolbox for investigations of PtdIns distribution and availability within intact cells. In addition to its presence within the ER, our results reveal low steady-state levels of PtdIns within the plasma membrane (PM) and endosomes as well as a relative enrichment of PtdIns within the cytosolic leaflets of the Golgi complex, peroxisomes, and outer mitochondrial membranes. Kinetic studies also demonstrate the requirement for sustained PtdIns supply from the ER for the maintenance of monophosphorylated PPIn species within the PM, Golgi complex, and endosomal compartments.\n\nSummaryPemberton et al. characterize a molecular toolbox for the visualization and manipulation of phosphatidylinositol (PtdIns) within intact cells. Results using these approaches define the steady-state distribution of PtdIns across subcellular membrane compartments as well as provide new insights into the relationship between PtdIns availability and polyphosphoinositide turnover.

cell biology↗