Influence of PI-3K/Akt pathway on Wnt signalling in regulating myeloid progenitor cell proliferation. Evidence for a role of autocrine/paracrine Wnt regulation.
The regulation of myeloid progenitor cell (granulocyte-macrophage colony-forming units, CFU-GM) proliferation/differentiation by the Wnt and phosphatidylinositol-3 kinase (PI-3K) pathways was investigated using a colony-replating assay. The PI-3K pathway promoted differentiation of interleukin-3 (IL-3)-stimulated myelopoiesis via Akt, because inhibition of the PI-3K/Akt pathway with LY294002 or SH-5 increased proliferation. The involvement of canonical and non-canonical Wnt pathways was investigated using Wnt3a and Wnt5a respectively. Addition of the recombinant Wnts to IL-3 increased CFU-GM proliferation. Dkk-1, when combined with the Wnt proteins, abrogated the effects of Wnt3a but not Wnt5a. Surprisingly, the addition of Dkk-1 to LY294002 or SH-5 blocked their proliferative effects. We hypothesized that increased proliferation induced by PI-3K/Akt inhibitors was not mediated by downstream activation of the Wnt pathway but by induced endogenous production/release of Wnt proteins. The addition of SH-5 to IL-3 created an autocrine Wnt loop in CD34(+) cells, resulting in the phosphorylation of lipoprotein-receptor-related-protein 6. Furthermore, the addition of medium conditioned by CD34(+) cells cultured in IL-3 + SH-5 to IL-3 increased CFU-GM proliferation. This effect was abrogated by Dkk-1, suggesting that a Wnt in the conditioned medium increased proliferation. In summary, IL-3 via the PI-3K pathway promoted differentiation of myeloid progenitor cells through a decrease of endogenous Wnt production/release.
Nteliopoulos
Georgios
G
Department of Haematology, Faculty of Medicine, Imperial College London, London, UK. georgios.nteliopoulos04@imperial.ac.uk
Marley
Stephen B
SB
Gordon
Myrtle Y
MY
D018952:Antigens, CD34; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D055014:Granulocyte-Macrophage Progenitor Cells / Q000166:cytology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D007377:Interleukin-3 / Q000494:pharmacology*; D023461:Myeloid Progenitor Cells / Q000378:metabolism*; D038042:Myelopoiesis / Q000187:drug effects; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D051153:Wnt Proteins / Q000494:pharmacology; D000071818:Wnt-5a Protein; D060508:Wnt3 Protein; D060509:Wnt3A Protein
D018952:Antigens, CD34; C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D007377:Interleukin-3; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; C555510:WNT3A protein, human; C085389:WNT5A protein, human; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D060508:Wnt3 Protein; D060509:Wnt3A Protein