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Red Cell Biology & its Disorders
Finely-tuned regulation of AMP-activated protein kinase is crucial for human
adult erythropoiesis
Ferrata Storti Foundation
Haematologica 2019 Volume 104(5):907-918
Meriem Ladli,1,2,3,4 Cyrielle Richard1,2,3,4, Lilia Cantero Aguilar,1,2,3,4 Sarah Ducamp,1,2,3,4 Sabrina Bondu,1,2,3,4 Pierre Sujobert,1,2,3 Jérôme Tamburini,1,2,3 Catherine Lacombe,1,2,3,4 Nabih Azar,5 Marc Foretz,1,2,3,4 Yael Zermati,1,2,3,4 Patrick Mayeux,1,2,3,4 Benoit Viollet1,2,3,4 and Frédérique Verdier1,2,3,4
1Institut Cochin, INSERM U1016; 2CNRS UMR 8104, Paris; 3Université Paris Descartes, Sorbonne Paris Cité; 4Labex GREX and 5Service d’Hémobiologie, Hôpital La Pitié Salpétrière, Paris, France
ABSTRACT
AMP-activated protein kinase (AMPK) is a heterotrimeric complex containing a, β, and γ subunits involved in maintaining integrity
-/-
and survival of murine red blood cells. Indeed, Ampk a1 , Ampk
β1-/- and Ampk γ1-/- mice develop hemolytic anemia and the plasma mem- brane of their red blood cells shows elasticity defects. The membrane composition evolves continuously along erythropoiesis and during red blood cell maturation; defects due to the absence of Ampk could be ini- tiated during erythropoiesis. We, therefore, studied the role of AMPK during human erythropoiesis. Our data show that AMPK activation had two distinct phases in primary erythroblasts. The phosphorylation of AMPK (Thr172) and its target acetyl CoA carboxylase (Ser79) was ele- vated in immature erythroblasts (glycophorin Alow), then decreased con- jointly with erythroid differentiation. In erythroblasts, knockdown of the a1 catalytic subunit by short hairpin RNA led to a decrease in cell proliferation and alterations in the expression of membrane proteins (band 3 and glycophorin A) associated with an increase in phosphoryla- tion of adducin (Ser726). AMPK activation in mature erythroblasts (gly- cophorin Ahigh), achieved through the use of direct activators (GSK621 and compound 991), induced cell cycle arrest in the S phase, the induc- tion of autophagy and caspase-dependent apoptosis, whereas no such effects were observed in similarly treated immature erythroblasts. Thus, our work suggests that AMPK activation during the final stages of ery- thropoiesis is deleterious. As the use of direct AMPK activators is being considered as a treatment in several pathologies (diabetes, acute myeloid leukemia), this observation is pivotal. Our data highlighted the impor- tance of the finely-tuned regulation of AMPK during human erythro- poiesis.
Introduction
Mammalian AMP-activated protein kinase (AMPK) is a highly conserved eukaryotic serine/threonine protein kinase and a heterotrimeric complex consist- ing of a single catalytic (a) and two regulatory (β and γ) subunits, encoded by dif- ferent genes (a1, a2, β1, β2, γ1, γ2, and γ3). In the case of energy depletion, a decrease in the cellular ATP-to-AMP ratio leads to allosteric AMPK activation by AMP but also by the phosphorylation of Thr172 within the activation loop seg- ment of the a subunit by an upstream AMPK kinase, liver kinase B1 (LKB1). Another ‘‘canonical’’ mechanism of activation involves the phosphorylation of Thr172 by calcium/calmodulin-dependent kinase kinase β (CaMKKβ) in response to a rise in intracellular Ca2+.1 Once activated, AMPK phosphorylates metabolic targets, leading to a decrease in ATP consumption and an increase in ATP produc- tion. In particular, AMPK inhibits fatty acid synthesis via phosphorylation and inactivation of acetyl-CoA-carboxylase (ACC) or induces autophagy via the phos- phorylation of Unc-51 like autophagy activating kinase 1 (ULK1).2 Thus, AMPK is
Correspondence:
FRÉDÉRIQUE VERDIER frederique.verdier@inserm.fr
Received: February 18, 2018. Accepted: October 3, 2018. Pre-published: October 11, 2018.
doi:10.3324/haematol.2018.191403
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/104/5/907
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haematologica | 2019; 104(5)
907
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