Distinct roles of Rheb and Raptor in activating mTOR complex 1 for the self-renewal of hematopoietic stem cells

Hui Peng, Atsuo Kasada, Masaya Ueno, Takayuki Hoshii, Yuko Tadokoro, Naho Nomura, Chiaki Ito, Yusuke Takase, Ha Thi Vu, Masahiko Kobayashi, Bo Xiao, Paul F. Worley, Atsushi Hirao

Research output: Contribution to journalArticlepeer-review

Abstract

The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) senses a cell's energy status and environmental levels of nutrients and growth factors. In response, mTORC1 mediates signaling that controls protein translation and cellular metabolism. Although mTORC1 plays a critical role in hematopoiesis, it remains unclear which upstream stimuli regulate mTORC1 activity in the context of hematopoietic stem cells (HSC) maintenance in vivo. In this study, we investigated the function of Rheb, a critical regulator of mTORC1 activity controlled by the PI3K-AKT-TSC axis, both in HSC maintenance in mice at steady-state and in HSC-derived hematopoiesis post-transplantation. In contrast to the severe hematopoietic dysfunction caused by Raptor deletion, which completely inactivates mTORC1, Rheb deficiency in adult mice did not show remarkable hematopoietic failure. Lack of Rheb caused abnormalities in myeloid cells but did not have impact on hematopoietic regeneration in mice subjected to injury by irradiation. As previously reported, Rheb deficiency resulted in defective HSC-derived hematopoiesis post-transplantation. However, while Raptor is essential for HSC competitiveness in vivo, Rheb is dispensable for HSC maintenance under physiological conditions, indicating that the PI3K-AKT-TSC pathway does not contribute to mTORC1 activity for sustaining HSC self-renewal activity at steady-state. Thus, the various regulatory elements that impinge upstream of mTORC1 activation pathways are differentially required for HSC homeostasis in vivo.

Original languageEnglish (US)
Pages (from-to)1129-1135
Number of pages7
JournalBiochemical and Biophysical Research Communications
Volume495
Issue number1
DOIs
StatePublished - Jan 1 2018

Keywords

  • Hematopoietic stem cell
  • Raptor
  • Rheb
  • mTOR

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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