Biology subjects

Elsabbagh, S.

Publications and source records attributed to Elsabbagh, S..

3 recordsLinked to original sources

bioRxiv2024

A new class of receptors: Lipids regulate mammalian Gsalpha-stimulated adenylyl cyclase activities via their membrane anchors

The biosynthesis of cAMP by mammalian membrane-bound adenylyl cyclases (mACs) is predominantly regulated by G-protein-coupled-receptors (GPCRs). Up to now the two hexahelical transmembrane domains of mACs were considered to fix the enzyme to membranes. Here we show that the transmembrane domains serve in addition as signal receptors and transmitters of lipid signals that control Gs-stimulated mAC activities. We identify aliphatic fatty acids and anandamide as receptor ligands of mAC isoforms 1 to 7 and 9. The ligands enhance (mAC isoforms 2, 3, 7, and 9) or attenuate (isoforms 1, 4, 5, and 6) Gs-stimulated mAC activities in vitro and in vivo. Substitution of the stimulatory membrane receptor of mAC3 by the inhibitory receptor of mAC5 results in a ligand inhibited mAC5-mAC3 chimera. Thus, we discovered a new class of membrane receptors in which two signaling modalities are at a crossing, direct tonic lipid and indirect phasic GPCR-Gs signaling regulating the biosynthesis of cAMP.

biochemistry↗

bioRxiv2023

Multiepitope-based vaccine design against DiiA in Streptococcus pneumoniae, An immunoinformatics approach.

Streptococcus pneumoniae (SPN) infection has resulted in significant morbidity and mortality worldwide in children and adults. It is responsible for colonizing the human nasopharynx and can also cause diseases, including otitis media, pneumonia, bacteraemia, and meningitis. SPN is exhibiting resistance to multiple antibiotics and current vaccines have a number of limitations including poor immunogenicity and limited effectiveness against all pneumococcal serotypes. Here, we explain the design of a novel multi-epitope vaccine using Dimorphic invasion-involved protein A (DiiA) as a target protein. For designing the vaccine, the sequence of DiiA was obtained and various bioinformatics tools were employed to predict multiple CTL, HTL, B lymphocyte epitopes of DiiA. After evaluating antigenicity, allergenicity, toxicity, and immunogenicity, the most promising epitopes were chosen for constructing the vaccine, followed by an analysis of their physicochemical and immunological characteristics.The prediction, refinement, and validation of the 3D structure of the vaccine were carried out. Molecular docking, molecular dynamic simulation, and immune simulation were executed to examine the binding affinities and biological interactions at the atomic level between the vaccine and Toll-like receptor (TLR4). Vaccine translation, codon optimization were performed and expression efficiency was assessed through an in-silico cloning experiment performed to transfer into pET28a(+) plasmid vector.The obtained results proved that the vaccine maintained structural stability and possessed the capability to stimulate an efficient immune response against S. pneumoniae infection. The constructed vaccine has the potential for subsequent wet lab experimentation, leading to the development of an innovative vaccine.

bioinformatics↗

bioRxiv2022

Distinct glycerophospholipids potentiate Gsα-activated adenylyl cyclase activity

Nine mammalian adenylyl cyclases (AC) are pseudoheterodimers with two hexahelical membrane domains which are isoform-specifically conserved. Previously we proposed that these membrane domains are orphan receptors (10.7554/eLife.13098; 10.1016/j.cellsig.2020.109538). Lipids extracted from fetal bovine serum at pH 1 inhibited several mAC activities. Guided by a lipidomic analysis we tested glycerophospholipids as potential ligands. Contrary to expectations we surprisingly discovered that 1-stearoyl-2-docosahexaenoyl-phosphatidic acid (SDPA) potentiated Gs-activated activity of human AC isoform 3 seven-fold. The specificity of fatty acyl esters at glycerol positions 1 and 2 was rather stringent. 1-Stearoyl-2-docosahexaenoyl-phosphatidylserine and 1-stearoyl-2-docosahexaenoyl-phosphatidylethanolamine significantly potentiated several Gs-activated mAC isoforms to different extents. SDPA appears not interact with forskolin activation of AC isoform 3. SDPA enhanced Gs-activated AC activities in membranes from mouse brain cortex. The action of SDPA was reversible. Unexpectedly, SDPA did not affect cAMP generation in HEK293 cells stimulated by isoproterenol, PGE2 and adenosine, virtually excluding a role as an extracellular ligand and, instead, suggesting an intracellular role. In summary, we discovered a new dimension of intracellular AC regulation by chemically defined glycerophospholipids.

biochemistry↗