Biology subjects

Meka, D. P.

Publications and source records attributed to Meka, D. P..

6 recordsLinked to original sources

bioRxiv2023

Actin Y53 Phosphorylation Regulates Somatic F-actin Radial Translocation to Promote Neuronal Polarization

How neurons accomplish the growth of an axon, and several dendrites sequentially is a cellular process not well understood. Here, we show that preferential somatic F-actin delivery to neurites inhibits neurite growth during axon formation. Thus, the neurite receiving less somatic F-actin is growing as an axon. During dendrites outgrowth, radial somatic F-actin translocation into all neurites is drastically diminished suggesting that cellular growth is restricted by the somatic F-actin flow into the growing neurites. Mechanistically, we report that radial somatic F-actin translocation is mediated via the Myosin II motor. Pharmacological inhibition of these molecular motors promotes neurite elongation and precludes F-actin translocation into neurites. Moreover, we show that actin phosphorylation at Y53, which promotes F-actin instability, is enriched selectively in some neurite shafts to exclude/minimize translocation of somatic F-actin only into those neurites. Therefore, enrichment of actin pY53 in the neurite shaft correlates with the longer neurite during axon formation. Accordingly, the Kinesin-1 motor domain, which accumulates transiently in neurites of stage 2 neurons and only in the emerging axon of stage 3 neurons, localizes preferentially in the neurite with the increased actin pY53 signal in the neurite shaft. Finally, we demonstrate that microtubule acetylation promotes actin phosphorylation, and these cytoskeleton modifications coexist in the longest neurite that grows as an axon. Collectively, our data support a model in which somatic F-actin translocation into undifferentiated neurites impedes growth counteracted by actin pY53, consequently, supporting neuronal polarization during axon formation.

cell biology↗

bioRxiv2022

TAOK2β represses translation via phosphorylation of eEF2 and ameliorates exaggerated protein synthesis in a mouse model of 16p11.2 microdeletion-driven autism

Microdeletions in the 16p11.2 region of the human genome are frequently associated with autism spectrum disorders (ASDs), but how these genomic rearrangements cause ASD remains unclear. Here, we reveal that TAOK2{beta}, a protein isoform encoded by the human TAOK2 gene located in the 16p11.2 locus, regulates mRNA translation. To identify key functional interaction partners of TAOK2{beta}, we performed proteomic screening from Neuro-2a (N2a) cells, mouse cortices, and cultured neurons. This revealed translation factors as a major class of enriched interacting proteins. Consistently, TAOK2{beta} is present in mouse cortical polyribosomes and cortices from Taok2 knockout mice show increased ribosome density on mRNAs and enhanced protein synthesis. Several lines of evidence support an effect of TAOK2{beta} on translation elongation via phosphorylation of eukaryotic elongation factor (eEF2). TAOK2 can directly phosphorylate eEF2 on Threonine 56 and this phosphorylation is reduced in cortices from Taok2 knockout mice. TAOK2{beta} WT overexpression increased eEF2 phosphorylation levels and reduced protein synthesis, whereas a kinase-dead allele of TAOK2{beta} showed opposite effects. Finally, we show that cortices from the mouse model of the human 16p11.2 microdeletion have increased polysome/monosome (P/M) ratios and protein synthesis, phenocopying Taok2 loss of function. Importantly, defective translation phenotypes observed in the mouse 16p11.2 microdeletion model of ASD could be normalized either by reintroducing Taok2 in vivo or by delivering TAOK2{beta} to cortical neurons derived from 16p11.2 microdeletion mice. Our results uncover a critical role of TAOK2{beta} as a regulator of protein synthesis and support the idea that translational control is a common endpoint of ASD-associated signaling pathways.

neuroscience↗

bioRxiv2022

Neuron-specific protein network mapping of autism risk genes identifies shared biological mechanisms and disease relevant pathologies

Manuscript summaryThere are hundreds of risk genes associated with autism spectrum disorder (ASD), but signaling networks at the protein level remain unexplored. We use neuron-specific proximity-labeling proteomics (BioID) to identify protein-protein interaction (PPI) networks for 41 ASD-risk genes. Neuron-specific PPI networks, including synaptic transmission proteins, are disrupted by de novo missense variants. The PPI network map reveals convergent pathways, including mitochondrial/metabolic processes, Wnt signaling, and MAPK signaling. CRISPR knockout reveal an association between mitochondrial activity and ASD-risk genes. The PPI network shows an enrichment of 112 additional ASD-risk genes and differentially expressed genes from post-mortem ASD patients. Clustering of risk genes based on PPI networks identifies gene groups corresponding to clinical behavior score severity. Our data reveal that cell type-specific PPI networks can identify individual and convergent ASD signaling networks, provide a method to assess patient variants, and reveal biological insight into disease mechanisms and sub-cohorts of ASD.

neuroscience↗

bioRxiv2020

Centrosome-dependent microtubule organization sets the conditions for axon formation

Microtubule remodeling is critical during axon development when the more stable microtubules populate the axon. It is not completely understood, however, how this local cytoskeleton remodeling is coordinated. The centrosome, the main microtubule-organizing center (MTOC), has been suggested to be crucial for axon specification 1-5. Conversely, it was proposed that axon elongation is independent of centrosomal functions 6. Here we report that microtubule dynamics in early neurons follow a radial organization which establishes the conditions for the axon formation. Using high-resolution microscopy of early developing neurons, we demonstrate that few somatic acetylated microtubules are restricted near the centrosome. At later stages, however, acetylated microtubules spread out in the soma and concentrate in the growing axon. Furthermore, live-imaging of the microtubule plus-end binding protein EB3 in early differentiating neurons shows that growing microtubules have increased length and growth speed near the MTOC, suggesting local differences that might favor axon selection. Importantly, due to the lack of somatic stable/acetylated microtubules in early developing neurons, disruption of the F-actin cytoskeleton does not induce multiple axons, as it does at later stages of differentiation. Finally, we demonstrate that overexpression of the centrosomal protein 120 (Cep120), known for promoting microtubule acetylation and stabilization, induces multiple axons, while its downregulation decreases the content of proteins regulating microtubule dynamics and stability, hence hampering axon formation. Collectively, our data show that early centrosome-dependent microtubule organization contributes to axon formation.

cell biology↗

bioRxiv2019

Parkin deficiency perturbs striatal circuit dynamics

Loss-of-function mutations in the parkin-encoding PARK2 gene cause young-onset, autosomal recessive Parkinsons disease (PD). Here, we investigated how parkin mutations affect cortico-basal ganglia circuit dynamics and cell-type-specific functional connectivity by recording simultaneously from motor cortex, striatum and globus pallidus (GP) in anesthetized parkin-mutant mice.\n\nWhile ongoing activity of presumed striatal spiny projection neurons and their downstream counterparts in the GP was not different from controls, parkin deficiency had a differential impact on striatal interneurons: In parkin-mutant mice, tonically active neurons displayed elevated activity levels. Baseline firing of transgenic striatal fast spiking interneurons (FSI), on the contrary, was reduced and the correlational structure of the FSI microcircuitry was disrupted. The entire transgenic striatal microcircuit showed enhanced and phase-shifted phase coupling to slow (1-3Hz) cortical population oscillations. Unexpectedly, local field potentials recorded from striatum and GP of parkin-mutant mice robustly displayed amplified beta oscillations ([~]22Hz), phase-coupled to cortex. Moreover, parkin deficiency selectively increased spike-field coupling of FSIs to beta oscillations.\n\nOur findings suggest that loss of parkin function leads to amplifications of synchronized cortico-striatal oscillations and intrastriatal reconfiguration of interneuronal circuits. This presymptomatic disarrangement of dynamic functional connectivity may precede nigro-striatal neurodegeneration and predispose to imbalance of striatal outflow accompanying symptomatic PD.

neuroscience↗

bioRxiv2018

Radial F-actin Organization During Early Neuronal Development

The centrosome is thought to be the major neuronal microtubule-organizing center (MTOC) in early neuronal development, producing microtubules with a radial organization. In addition, albeit in vitro, recent work showed that isolated centrosomes could serve as an actin-organizing center (Farina et al., 2016), raising the possibility that neuronal development may, in addition, require a centrosome-based actin radial organization. Here we report, using super-resolution microscopy and live-cell imaging, F-actin organization around the centrosome with dynamic F-actin aster-like structures with F-actin fibers extending and retracting actively. Photoconversion/photoactivation experiments and molecular manipulations of F-actin stability reveal a robust flux of somatic F-actin towards the cell periphery. Finally, we show that somatic F-actin intermingles with centrosomal PCM-1 satellites. Knockdown of PCM-1 and disruption of centrosomal activity not only affect F-actin dynamics near the centrosome but also in distal growth cones. Collectively the data show a radial F-actin organization during early neuronal development, which might be a cellular mechanism for providing peripheral regions with a fast and continuous source of actin polymers; hence sustaining initial neuronal development.

neuroscience↗