Biology subjects

Mohamed, M. S.

Publications and source records attributed to Mohamed, M. S..

4 recordsLinked to original sources

bioRxiv2023

Opto4E-BP, an optogenetic tool for inducible, reversible, and cell type-specific inhibition of translation initiation

The protein kinase mechanistic target of rapamycin complex 1 (mTORC1) is one of the primary triggers for initiating cap-dependent translation. Amongst its functions, mTORC1 phosphorylates eIF4E-binding proteins (4E-BPs), which prevents them from binding to eIF4E and thereby enables translation initiation. mTORC1 signaling is required for multiple forms of protein synthesis-dependent synaptic plasticity and various forms of long-term memory (LTM), including associative threat memory. However, the approaches used thus far to target mTORC1 and its effectors, such as pharmacological inhibitors or genetic knockouts, lack fine spatial and temporal control. The development of a conditional and inducible eIF4E knockdown mouse line partially solved the issue of spatial control, but still lacked optimal temporal control to study memory consolidation. Here, we have designed a novel optogenetic tool (Opto4E-BP) for cell type-specific, light-dependent regulation of eIF4E in the brain. We show that light-activation of Opto4E-BP decreases protein synthesis in HEK cells and primary mouse neurons. In situ, light-activation of Opto4E-BP in excitatory neurons decreased protein synthesis in acute amygdala slices. Finally, light activation of Opto4E-BP in principal excitatory neurons in the lateral amygdala (LA) of mice after training blocked the consolidation of LTM. The development of this novel optogenetic tool to modulate eIF4E-dependent translation with spatiotemporal precision will permit future studies to unravel the complex relationship between protein synthesis and the consolidation of LTM.

neuroscience↗

bioRxiv2023

The Integrated Stress Response effector GADD34 is repurposed by neurons to promote stimulus-induced translation

Neuronal protein synthesis is required for long-lasting plasticity and long-term memory consolidation. Dephosphorylation of eukaryotic initiation factor 2 is one of the key translational control events that is required to increase de novo protein synthesis that underlies long-lasting plasticity and memory consolidation. Here, we interrogate the molecular pathways of translational control that are triggered by stimulation of neurons with brain-derived neurotrophic factor (BDNF), which results in eIF2 dephosphorylation and de novo protein synthesis. Primary rodent neurons exposed to BDNF displayed elevated translation, but not transcription, of GADD34, which facilitates eIF2 dephosphorylation and subsequent de novo protein synthesis. Furthermore, GADD34 requires G-actin generated by cofilin to dephosphorylate eIF2 and enhance protein synthesis. Finally, GADD34 is required for the BDNF-induced translation of synaptic plasticity-related proteins. Overall, we provide evidence that neurons repurpose GADD34, an effector of the Integrated Stress Response, as an orchestrator of rapid increases in eIF2-dependent translation in response to plasticity-inducing stimuli.

neuroscience↗

bioRxiv2023

Autism- and epilepsy-associated EEF1A2 mutations lead to translational dysfunction and altered acting bundling

Protein synthesis is a fundamental cellular process in neurons that is essential for synaptic plasticity and memory consolidation. Here, we describe our investigations of a neuron- and muscle-specific translation factor, eukaryotic Elongation Factor 1a2 (eEF1A2), which when mutated in patients results in autism, epilepsy, and intellectual disability. We characterize three most common EEF1A2 patient mutations, G70S, E122K, and D252H, and demonstrate that all three mutations decrease de novo protein synthesis and elongation rates in HEK293 cells. In mouse cortical neurons, the EEF1A2 mutations not only decrease de novo protein synthesis, but also alter neuronal morphology, regardless of endogenous levels of eEF1A2, indicating that the mutations act via a toxic gain of function. We also show that eEF1A2 mutant proteins display increased tRNA binding and decreased actin bundling activity, suggesting that these mutations disrupt neuronal function by decreasing tRNA availability and altering the actin cytoskeleton. More broadly, our findings are consistent with the idea that eEF1A2 acts as a bridge between translation and the actin skeleton, which is essential for proper neuron development and function. Significance StatementEukaryotic Elongation Factor 1A2 (eEF1A2) is a muscle- and neuron-specific translation factor responsible for bringing charge tRNAs to the elongating ribosome. Why neurons express this unique translation factor is unclear; however, it is known that mutations in EEF1A2 cause severe drug-resistant epilepsy, autism and neurodevelopmental delay. Here, we characterize the impact of three common disease-causing mutations in EEF1A2 and demonstrate that they cause decreased protein synthesis via reduced translation elongation, increased tRNA binding, decreased actin bundling activity, as well as altered neuronal morphology. We posit that eEF1A2 serves as a bridge between translation and the actin cytoskeleton, linking these two processes that are essential for neuronal function and plasticity.

neuroscience↗

bioRxiv2020

Contamination of Currency Notes with Kanamycin Resistant Shigella flexneri

Shigella flexneri is the main causative agent of shigellosis commonly distributed in developing countries with high morbidity and mortality rates. This study aimed to examine the presence of Shigella species in Sudanese currency notes using both traditional and molecular techniques. One hundred thirty five currency notes were collected and their contaminants were isolated and identified conventionally and genetically using 16S rRNA gene amplification and sequencing. Eight isolates were identified as Shigella species in different notes, and 3 of them were resistant to penicillin, kanamycin and nitrofurantoin. One S. flexneri isolate has insertion mutation of guanine nucleotide at position 730 of lifes essential gene 16S rRNA which known evolutionarily to be stable gene. Banknotes are highly circulating items and therefore, appropriate measures such as regular replacement of the dirty notes with new papers are necessary to protect peoples from being infected with drug resistant pathogens.

microbiology↗