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Fetal brain mTOR signaling activation in tuberous sclerosis complex.

ABSTRACT: Tuberous sclerosis complex (TSC) is characterized by developmental malformations of the cerebral cortex known as tubers, comprised of cells that exhibit enhanced mammalian target of rapamycin (mTOR) signaling. To date, there are no reports of mTORC1 and mTORC2 activation in fetal tubers or in neural progenitor cells lacking Tsc2. We demonstrate mTORC1 activation by immunohistochemical detection of substrates phospho-p70S6K1 (T389) and phospho-S6 (S235/236), and mTORC2 activation by substrates phospho-PKC? (S657), phospho-Akt (Ser473), and phospho-SGK1 (S422) in fetal tubers. Then, we show that Tsc2 shRNA knockdown (KD) in mouse neural progenitor cells (mNPCs) in vitro results in enhanced mTORC1 (phospho-S6, phospho-4E-BP1) and mTORC2 (phospho-Akt and phospho-NDRG1) signaling, as well as a doubling of cell size that is rescued by rapamycin, an mTORC1 inhibitor. Tsc2 KD in vivo in the fetal mouse brain by in utero electroporation causes disorganized cortical lamination and increased cell volume that is prevented with rapamycin. We demonstrate for the first time that mTORC1 and mTORC2 signaling is activated in fetal tubers and in mNPCs following Tsc2 KD. These results suggest that inhibition of mTOR pathway signaling during embryogenesis could prevent abnormal brain development in TSC.

SUBMITTER: Tsai V

PROVIDER: S-EPMC3888364 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Fetal brain mTOR signaling activation in tuberous sclerosis complex.

Tsai Victoria V Parker Whitney E WE Orlova Ksenia A KA Baybis Marianna M Chi Anthony W S AW Berg Benjamin D BD Birnbaum Jacqueline F JF Estevez Jacqueline J Okochi Kei K Sarnat Harvey B HB Flores-Sarnat Laura L Aronica Eleonora E Crino Peter B PB

Cerebral cortex (New York, N.Y. : 1991) 20121018 2

Tuberous sclerosis complex (TSC) is characterized by developmental malformations of the cerebral cortex known as tubers, comprised of cells that exhibit enhanced mammalian target of rapamycin (mTOR) signaling. To date, there are no reports of mTORC1 and mTORC2 activation in fetal tubers or in neural progenitor cells lacking Tsc2. We demonstrate mTORC1 activation by immunohistochemical detection of substrates phospho-p70S6K1 (T389) and phospho-S6 (S235/236), and mTORC2 activation by substrates ph ...[more]

PMID: 23081885

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Project description:Tuberous Sclerosis Complex (TSC) is a multisystem genetic disorder characterized by the development of benign tumors in various organs, including the brain, and is often accompanied by epilepsy, neurodevelopmental comorbidities including intellectual disability and autism. A key hallmark of TSC is the hyperactivation of the mechanistic target of rapamycin (mTOR) signaling pathway, which induces alterations in cortical development and metabolic processes in astrocytes, among other cellular functions. These changes could modulate seizure susceptibility, contributing to the progression of epilepsy and its associated comorbidities. Epilepsy is characterized by dysregulation of calcium (Ca2+) channels and intracellular Ca2+ dynamics. These factors contribute to hyperexcitability, disrupted synaptogenesis, and altered synchronization of neuronal networks, all of which contribute to seizure activity. This study investigates the intricate interplay between altered Ca2+ dynamics, mTOR pathway dysregulation, and cellular metabolism in astrocytes. The transcriptional profile of TSC patients revealed significant alterations in pathways associated with cellular respiration, ER and mitochondria, and Ca2+ regulation. TSC astrocytes exhibited lack of responsiveness to various stimuli, compromised oxygen consumption rate and reserve respiratory capacity underscoring their reduced capacity to react to environmental changes or cellular stress. Furthermore, our study revealed significant reduction of store operated calcium entry (SOCE) along with strong decrease of basal mitochondrial Ca2+ concentration and Ca2+ influx in TSC astrocytes. In addition, we observed alteration in mitochondrial membrane potential, characterized by increased depolarization in TSC astrocytes. Lastly, we provide initial evidence of structural abnormalities in mitochondria within TSC patient-derived astrocytes, suggesting a potential link between disrupted Ca2+ signaling and mitochondrial dysfunction. Our findings underscore the complexity of the relationship between Ca2+ signaling, mitochondria dynamics, apoptosis, and mTOR hyperactivation. Further exploration is required to shed light on the pathophysiology of TSC and on TSC associated neuropsychiatric disorders offering further potential avenues for therapeutic development.

Dataset Information

Fetal brain mTOR signaling activation in tuberous sclerosis complex.

Publications

Fetal brain mTOR signaling activation in tuberous sclerosis complex.

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