Crosstalk between the Smad and the Mitogen-Activated Protein Kinase Pathways is Essential for Erythroid Differentiation of Erythroleukemia Cells Induced by TGF-β, Activin, Hydroxyurea and Butyrate

Abstract

The role of crosstalk between the Smad and the MAPK signaling pathways in activin-, transforming growth factor-β (TGF-β)-, hydroxyurea (HU) - and butyrate-dependent erythroid differentiation of K562 leukemic cells was studied. Treatment with all four inducers caused transient phosphorylation of Smad2/3 and MAPK proteins including ERK, p38 and JNK. Use of specific inhibitors of p38, ERK and JNK MAPK proteins, and TGF-β type I receptor indicated that differentiation induced by each of these agents involves activation of Smad2/3 and p38 MAPK, and inhibition of ERK MAPK. Also, treatment of cells with an inhibitor of protein serine/threonine phosphatase, okadaic acid (OA), induced phosphorylation of Smad2/3, and p38 MAPK, coincident with its induction of erythroid differentiation. Specific inhibition of TGF-β type I receptor kinase activity not only abolished TGF-β/activin effects but also prevented Smad2/3 activation and erythroid differentiation induced by OA, HU and butyrate. The TGF-β type I receptor kinase inhibitor blocked OA-induced differentiation but not p38 MAPK phosphorylation demonstrating that signals from both pathways are needed. As previously observed, addition of ERK1/2 MAPK inhibitors upregulated Smad2/3 phosphorylation and enhanced differentiation, but these effects were dependent on signals from the TGF-β type I receptor. These data indicate that activation of both Smad2/3 and p38 MAPK signaling pathways is a prerequisite to induce erythroid differentiation of erythroleukemia cells by activin, TGF-β, HU, OA and butyrate.

Activated Phosphatidylinositol 3-Kinase/Akt Inhibits the Transition of Endothelial Progenitor Cells to Mesenchymal Cells by Regulating the Forkhead Box Subgroup O-3a Signaling

“…Suppression of Erk1/2 phosphorylation upregulates Smad2/3 phosphorylation and enhances cellular differentiation [32]. These results and those of our study suggest a potential role of Erk1/2 in the activation of PI3K/Akt and suppression of Smad3-dependent signaling in the EndMT of EPCs.…”

miR-150 inhibits terminal erythroid proliferation and differentiation

“…Here, we found that aberrantly expressed miR-150 suppressed the two major signaling pathways involved in erythroblast proliferation and survival, ErbB-MAPK-p38 and ErbB-PI3K-AKT. Activation of the p38 MAPK pathway has been reported to be a prerequisite for inducing erythroid differentiation of K562 cells [ 74 – 75 ]. TfR1 engagement increased cell sensitivity to EPO to induce erythropoiesis via activating PI3K-AKT pathways [ 76 ].…”

Melatonin promotes self-renewal of nestin-positive pancreatic stem cells through activation of the MT2/ERK/SMAD/nestin axis

“…Previous studies have indicated that the TGF-b1 pathway acts through SMADdependent (canonical) and SMAD-independent (non-canonical) pathways [37,38]. Smad2 and Smad3, the principal receptor-activated proteins involved in the TGF-b pathway, are activated directly by TGF-b type I receptor kinase, then translocated to the nucleus complexed with a common co-SMAD, Smad4, to regulate the transcription of target genes [39,40]. Many signaling pathways interact with the TGF-b1 pathway.…”

“…The mitogen-activated protein kinase (MAPK) cascade, composed mainly of ERK, p38 MAPK and c-Jun N-terminal kinases (JNKs), has been shown to represent a major signaling pathway for TGF-b-dependent SMAD activation [41,42]. In crosstalk between the SMAD and MAPK pathways, TGFb-dependent or -independent induction of activated ERK can occur [40]. We tested crosstalk between the TGF-b/SMAD and ERK pathways in melatonin-induced cell proliferation in our research by transfecting siERK1, siERK2, siS2, siS3 and siS4 into pancreatic progenitor cells treated with melatonin.…”