An ERK-Dependent Feedback Mechanism Prevents Hematopoietic Stem Cell Exhaustion

Publication date: Available online 24 May 2018
Source:Cell Stem Cell
Author(s): Christian Baumgartner, Stefanie Toifl, Matthias Farlik, Florian Halbritter, Ruth Scheicher, Irmgard Fischer, Veronika Sexl, Christoph Bock, Manuela Baccarini
Hematopoietic stem cells (HSCs) sustain hematopoiesis throughout life. HSCs exit dormancy to restore hemostasis in response to stressful events, such as acute blood loss, and must return to a quiescent state to prevent their exhaustion and resulting bone marrow failure. HSC activation is driven in part through the phosphatidylinositol 3-kinase (PI3K)/AKT/mTORC1 signaling pathway, but less is known about the cell-intrinsic pathways that control HSC dormancy. Here, we delineate an ERK-dependent, rate-limiting feedback mechanism that controls HSC fitness and their re-entry into quiescence. We show that the MEK/ERK and PI3K pathways are synchronously activated in HSCs during emergency hematopoiesis and that feedback phosphorylation of MEK1 by activated ERK counterbalances AKT/mTORC1 activation. Genetic or chemical ablation of this feedback loop tilts the balance between HSC dormancy and activation, increasing differentiated cell output and accelerating HSC exhaustion. These results suggest that MEK inhibitors developed for cancer therapy may find additional utility in controlling HSC activation.

Graphical abstract

Teaser

Baccarini and colleagues identify a cell-intrinsic feedback mechanism limiting the strength of MEK/ERK and AKT/mTORC1 signals during the activation of hematopoietic stem cells. The mechanism hinges on the negative feedback phosphorylation of MEK1 by activated ERK and is required to prevent HSC exhaustion.


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