Biology subjects

Amemiya, Y.

Publications and source records attributed to Amemiya, Y..

2 recordsLinked to original sources

bioRxiv2024

Calmodulin enhances mTORC1 signaling by preventing TSC2-Rheb binding

The mechanistic target of rapamycin complex 1 (mTORC1) functions as a master regulator of cell growth and proliferation. We previously demonstrated that intracellular calcium ion (Ca2+) concentration modulates the mTORC1 pathway via binding of the Ca2+ sensor protein calmodulin (CaM) to tuberous sclerosis complex 2 (TSC2), a critical negative regulator of mTORC1. However, the precise molecular mechanism by which Ca2+/CaM modulates mTORC1 activity remains unclear. Here, we performed a binding assay based on nano-luciferase reconstitution, a method for detecting weak interactions between TSC2 and its target, Ras homolog enriched in brain (Rheb), an activator of mTORC1. CaM inhibited the binding of TSC2 to Rheb in a Ca2+-dependent manner. Live-cell imaging analysis indicated increased interaction between the CaM-binding region of TSC2 and CaM in response to elevated intracellular Ca2+ levels. Furthermore, treatment with carbachol, an acetylcholine analog, elevated intracellular Ca2+ levels, and activated mTORC1. Notably, carbachol-induced activation of mTORC1 was inhibited by CaM inhibitors, corroborating the role of Ca2+/CaM in promoting the mTORC1 pathway. Consistent with the effect of Ca2+/CaM on the TSC2-Rheb interaction, increased intracellular Ca2+ concentration promoted the dissociation of TSC2 from lysosomes without affecting Akt-dependent phosphorylation of TSC2, suggesting that the regulatory mechanism of TSC2 by Ca2+/CaM is distinct from the previously established action mechanism of TSC2. Collectively, our findings offer mechanistic insights into TSC2-Rheb regulation mediated by Ca2+/CaM, which links Ca2+ signaling to mTORC1 activation.

biochemistry↗

bioRxiv2024

NEUROG2 regulates a human-specific neurodevelopmental gene regulatory program

Unique hallmarks of human neocortical development include slower rates of neurogenesis and the establishment of an extracellular matrix-rich, outer-subventricular zone that supports basal neural progenitor cell expansion. How gene regulatory networks have evolved to support these human-specific neurodevelopmental features is poorly understood. Mining single cell data from cerebral organoids and human fetal cortices, we found that NEUROG2 expression is enriched in basal neural progenitor cells. To identify and purify NEUROG2-expressing cells and trace their short-term lineage, we engineered two NEUROG2-mCherry knock-in human embryonic stem cell lines to produce cerebral organoids. Transcriptomic profiling of mCherry-high organoid cells revealed elevated expression of PPP1R17, associated with a fast-evolving human-accelerated regulatory region, oligodendrocyte precursor cell and extracellular matrix-associated gene transcripts. Conversely, only neurogenic gene transcripts were enriched in mCherry-high cortical cells from Neurog2:mCherry knock-in mice. Finally, we show that Neurog2 is sufficient to induce Ppp1r17, which slows human neural progenitor cell division, and Col13a1, an extracellular matrix gene, in P19 cells. NEUROG2 thus regulates a human neurodevelopmental gene regulatory program implicated in supporting a pro-proliferative basal progenitor cell niche and tempering the neurogenic pace. SUMMARY STATEMENTTranscriptomic analyses of NEUROG2-mCherry knock-in human embryonic stem cell-derived cerebral organoids reveal a link between NEUROG2 and extracellular matrix remodeling during human cortical development.

developmental biology↗