Kainic Acid Induces mTORC1-Dependent Expression of Elmo1 in Hippocampal Neurons

Abstract

Epileptogenesis is a process triggered by initial environmental or genetic factors that result in epilepsy and may continue during disease progression. Important parts of this process include changes in transcriptome and the pathological rewiring of neuronal circuits that involves changes in neuronal morphology. Mammalian/mechanistic target of rapamycin (mTOR) is upregulated by proconvulsive drugs, e.g., kainic acid, and is needed for progression of epileptogenesis, but molecular aspects of its contribution are not fully understood. Since mTOR can modulate transcription, we tested if rapamycin, an mTOR complex 1 inhibitor, affects kainic acid-evoked transcriptome changes. Using microarray technology, we showed that rapamycin inhibits the kainic acid-induced expression of multiple functionally heterogeneous genes. We further focused on engulfment and cell motility 1 (Elmo1), which is a modulator of actin dynamics and therefore could contribute to pathological rewiring of neuronal circuits during epileptogenesis. We showed that prolonged overexpression of Elmo1 in cultured hippocampal neurons increased axonal growth, decreased dendritic spine density, and affected their shape. In conclusion, data presented herein show that increased mTORC1 activity in response to kainic acid has no global effect on gene expression. Instead, our findings suggest that mTORC1 inhibition may affect development of epilepsy, by modulating expression of specific subset of genes, including Elmo1, and point to a potential role for Elmo1 in morphological changes that accompany epileptogenesis.Electronic supplementary materialThe online version of this article (doi:10.1007/s12035-016-9821-6) contains supplementary material, which is available to authorized users.

ESCRT Proteins Control the Dendritic Morphology of Developing and Mature Hippocampal Neurons

“…However, the way in which ESCRT-III or potentially other ESCRTs affect the maturation of dendritic spines is not yet known. The knockdown of some proteins can affect specifically mushroom spines without detrimental effects on dendritic arbors (e.g., Elmo-1 [32]).…”

GSK3β Controls mTOR and Prosurvival Signaling in Neurons

“…We evaluated whether constitutively active GSK3β limits KA-induced apoptosis. We used KA-treated hippocampal organotypic cultures in vitro, a convenient experimental system that reliably recapitulates in vivo neuropathology and provides high reproducibility in molecular analyses [ 25 ]. Organotypic hippocampal slices were obtained from newborn wildtype and GSK3β S9A mice and cultured for 10–14 days before being treated with KA for 24 h. The slices were stained by TUNEL to identify dying cells.…”

“…Hippocampal slice cultures were prepared from 5-day-old mice according to a previously described method [ 25 ]. The maintenance medium was changed every 3–4 days.…”

“…The TUNEL assay was performed using the In Situ Cell Death Detection Kit, TMR red (Roche Applied Science, Mannheim, Germany), as described previously [ 25 ]. TUNEL staining was performed on two independent slice cultures.…”

Morphometric reconstructions atlas shows insult-driven plasticity in cortical VIP/ChAT interneurons

“…Gene ontology analysis of the DE transcripts reflected involvment of all major neuronal compartments, especialy ones related to synapse and neurite projections (Figure 5b) and of biological pathways related to synapse and neuron development and transcription factor networks. Intriguingly, the top two overexpressed genes, Arpp21 and Sema5b, and the top under-expressed gene, Elmo1, were very recently found to play substantial roles in the branching of dendrites and axons, as well as in synapse stability and microtubule organization [45][46][47] (Figure 5d). In particular, over-expressed Arpp21 increases dendrite complexity and proximal branching 47 .…”