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1673 Lyn Kinase Activity Is Required for Akt Mediated Erythroleukemia Cell Differentiation

Program: Oral and Poster Abstracts
Session: 101. Red Cells and Erythropoiesis, Structure and Function, Metabolism, and Survival, Excluding Iron: Poster II
Hematology Disease Topics & Pathways:
red blood cells, Biological Processes, Cell Lineage, erythropoiesis, hematopoiesis, pathways, signal transduction
Sunday, December 6, 2020, 7:00 AM-3:30 PM

Janice H. C. Plani-LAM, PhD1*, Mhairi Maxwell2*, Neli Slavova-Azmanova3*, Nicole Kucera1*, Alison Louw, PhD1*, Jiulia Satiaputra1*, Susan Wu1*, Edward Bastow1*, Cindy Le1*, Cathy Quilici4*, Margaret L Hibbs5* and Evan Ingley, PhD, BSc1,6

1Harry Perkins Institute of Medical Research, Nedlands, Australia
2Monash University, Melbourne, Australia
3The University of Western Australia, Crawley, AUS
4Leukocyte Signalling Laboratory, Monash University, Melbourne, Australia
5Leukocyte Signaling Laboratory, Monash University, Melbourne, Australia
6College of Health, Science, Engineering and Education, Murdoch University, Murdoch, Australia

Erythroleukemia (M6 subtype of Acute Myeloid Leukaemia) is uncommon but has a poor prognosis, with reports of successful differentiation therapy using erythropoietin (Epo). Signaling through the Epo-receptor, which involves JAK2 and Lyn tyrosine kinases, controls red blood cell progenitor development. We have highlighted the importance of Lyn for regulating downstream Akt, and feed-back inhibitory signaling of the Epo-receptor through analysis of Lyn-/-, Lynup/up (hyperactive Lyn) and Cbp-/- (Csk-binding protein, a negative regulator of Lyn) erythroid cells. However, the importance of maintaining Lyn activity as opposed to Lyn protein for erythroid cell development and signaling, has not been delineated. To address this, we generated LynKD/KD mice (expressing a kinase dead K275M mutant Lyn), and analysed their erythroid compartment and signaling in immortalized erythroid progenitors. We show that LynKD/KD mice display splenic extramedullary erythropoiesis and have evidence of elevate bone marrow erythropoiesis, similar to Lyn-/- mice but with a less severe phenotype. Immortalized erythroid progenitors from LynKD/KD mice show impaired Epo-induced differentiation and a greater dependence on Epo for viability, but unaltered proliferation, compared to wild-type cells. Epo-induced signaling of LynKD/KD cells showed enhanced pJAK2/pSTAT5, reduced pAkt/pGAB2, and substantially reduced ALAS-e levels, compared to wild-type cells. Importantly, elevating Akt signaling in LynKD/KD cells by addition of phosphatase inhibitors (okadaic acid or Calyculin A), or via expression of active Akt, restored their differentiation capacity (and ALAS-e levels) and reduced their dependence on Epo for viability. We have unveiled that Lyn kinase activity, and not just its expression, is required for correct signaling of Akt to GATA-1 to maintain ALAS-e expression in erythroid cells, enabling hemoglobin production and viability during differentiation.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH