Biology subjects

Jhaveri, V.

Publications and source records attributed to Jhaveri, V..

3 recordsLinked to original sources

bioRxiv2022

NMDAR mediated dynamic changes in m6A inversely correlates with neuronal translation

Epitranscriptome modifications are crucial in translation regulation and essential for maintaining cellular homeostasis. N6 methyladenosine (m6A) is one of the most abundant and well-conserved epitranscriptome modifications, which is known to play a pivotal role in diverse aspects of neuronal functions. However, the role of m6A modifications with respect to activity-mediated translation regulation and synaptic plasticity has not been studied. Here, we investigated the role of m6A modification in response to NMDAR stimulation. We have consistently observed that upon 5-minute NMDAR stimulation causes an increase in eEF2 phosphorylation. Correspondingly, NMDAR stimulation caused a significant increase in the m6A signal at 5 minutes time point, correlating with the global translation inhibition. The NMDAR induced increase in the m6A signal is accompanied by the redistribution of the m6A marked RNAs from translating to the non-translating pool of ribosomes. The increased m6A levels are well correlated with the reduced FTO levels observed on NMDAR stimulation. Additionally, we show that inhibition of FTO prevents NMDAR mediated changes in m6A levels. Overall, our results establish RNA-based molecular readout which corelates with the NMDAR-dependent translation regulation which helps in understanding changes in protein synthesis.

neuroscience↗

bioRxiv2021

Function of FMRP domains in regulating distinct roles of neuronal protein synthesis

The Fragile X Mental Retardation Protein (FMRP) is an RNA Binding Protein that regulates translation of mRNAs, essential for synaptic development and plasticity. FMRP interacts with a specific set of mRNAs and aids in their microtubule dependent transport and regulates their translation through its association with ribosomes. However, the biochemical role of individual domains of FMRP in forming neuronal granules and associating with microtubules and ribosomes is currently undefined. Here, we report that the C-terminus domain of FMRP is sufficient to bind to ribosomes as well as polysomes akin to the full-length protein. Furthermore, the C-terminus domain alone is essential and responsible for FMRP-mediated translation repression in neurons. However, FMRP-mediated puncta formation and microtubule association is favored by the synergistic combination of FMRP domains and not by individual domains. Interestingly, we show that the phosphorylation of hFMRP at Serine-500 is important in modulating the dynamics of translation by controlling ribosome/polysome association. This is a fundamental mechanism governing the size and number of FMRP puncta, which appear to contain actively translating ribosomes. Finally through the use of pathogenic mutations, we emphasize the hierarchy of the domains of FMRP in their contribution to translation regulation.

neuroscience↗

bioRxiv2020

APOE4 affects basal and NMDAR mediated protein synthesis in neurons by perturbing calcium homeostasis

Apolipoprotein E (APOE), one of the primary lipoproteins in the brain has three isoforms in humans - APOE2, APOE3, and APOE4. APOE4 is the most well-established risk factor increasing the pre-disposition for Alzheimers disease. The presence of the APOE4 allele alone is shown to cause synaptic defects in neurons and recent studies have identified multiple pathways directly influenced by APOE4. However, the mechanisms underlying APOE4 induced synaptic dysfunction remain elusive. Here, we report that the acute exposure of primary cortical neurons to APOE4 leads to a significant decrease in global protein synthesis. APOE4 treatment also abrogates the NMDA mediated translation response indicating an impairment of synaptic signaling. Importantly, we demonstrate that both APOE3 and APOE4 generate a distinct translation response which is closely linked to their respective calcium signature. Acute exposure to APOE3 causes a short burst of calcium through NMDARs in neurons leading to an initial decrease in protein synthesis which quickly recovers. Contrarily, APOE4 leads to a sustained increase in calcium levels by activating both NMDARs and L-VGCCs, thereby causing sustained translation inhibition through eEF2 phosphorylation, which in turn disrupts NMDAR response. Thus, we show that APOE4 affects basal and activity mediated protein synthesis response in neurons by affecting calcium homeostasis. We propose this as a possible mechanism to explain the synaptic dysfunction caused by APOE4. Highlights / SummaryO_LIAPOE3 treatment causes a short burst of calcium through NMDARs, leading to an acute increase in eEF2 phosphorylation which eventually recovers to basal levels. C_LIO_LIGlobal translation follows a similar temporal profile of initial inhibition followed by recovery in APOE3 treated neurons, thus unaffecting the NMDA mediated translation response. C_LIO_LIAPOE4 treatment activates both NMDARs and L-VGCCs leading to a marked elevation in calcium levels, thus causing sustained increase in eEF2 phosphorylation as well as global translation inhibition. C_LIO_LIHence, the NMDA mediated response is perturbed, potentially causing a stress-related phenotype in APOE4 treated neurons. C_LIO_LIThus, different calcium signatures and sources lead to distinct temporal profiles of translation. C_LI

neuroscience↗