Src transduces erythropoietin-induced differentiation signals through phosphatidylinositol 3-kinase

Abstract

In this study, we examined the molecular mechanism of erythropoietin‐initiated signal transduction of erythroid differentiation through Src and phosphatidylinositol 3‐kinase (PI3‐kinase). Antisense oligonucleotides against src but not lyn inhibited the formation of erythropoietin‐dependent colonies derived from human bone marrow cells and erythropoietin‐induced differentiation of K562 human erythroleukaemia cells. Antisense p85α oligonucleotide or LY294002, a selective inhibitor of PI3‐kinase, independently inhibited the formation of erythropoietin‐dependent colonies. In K562 cells, Src associated with PI3‐kinase in response to erythropoietin. Antisense src RNA expression in K562 cells inhibited the erythropoietin‐induced activation of PI3‐kinase and its association with erythropoietin receptor. PP1, a selective inhibitor of the Src family, reduced erythropoietin‐induced tyrosine phosphorylation of erythropoietin receptor and its association with PI3‐kinase in F‐36P human erythroleukaemia cells. The coexpression experiments and in vitro kinase assay further demonstrated that Src directly tyrosine‐phosphorylated erythropoietin receptor, and associated with PI3‐kinase. In vitro binding experiments proved that glutathione S‐transferase–p85α N‐ or C‐terminal SH2 domains independently bound to erythropoietin receptor, which was tyrosine‐phosphorylated by Src. Taken together, Src transduces the erythropoietin‐induced erythroid differentiation signals by regulating PI3‐kinase activity.

Constitutive activation of PI3K is involved in the spontaneous proliferation of primary acute myeloid leukemia cells: direct evidence of PI3K activation

“…To address the involvement of PI3K in the proliferation of the leukemia cells from 40 patients with AML (M0, 2; M1, 5; M2, 11; M3, 3; M4, 8; M5, 7; M6, 3; M7, 1), we performed an in vitro PI3K and 3 H-thymidine incorporation assays as described previously, 5,6 after obtaining informed consent from the patients. PI3K was constitutively activated in 21 (52.5%) of 40 AML cases (Table 1 and Figure 1a).…”

“…The sequence of p85a AS-and S-ODNs used was 5 0 -GTACTGGTACCCCTCAGCACTCAT-3 0 and 5 0 -ATGAGTGCTGAGGGGTACCAGTAC-3 0 , respectively, as described previously. 5 …”

Inhibition of PI-3 kinase sensitizes human leukemic cells to histone deacetylase inhibitor-mediated apoptosis through p44/42 MAP kinase inactivation and abrogation of p21CIP1/WAF1 induction rather than AKT inhibition

“…In this context, PI-3 kinase inhibitors such as LY294002 and wortmannin have been shown to block retinoic acid-and PMA-mediated maturation in HL-60 cells (Lewandowski et al, 2002;Park et al, 2002), DMSO-and erythropoietin-induced differentiation in erythroleukemia cells (Cataldi et al, 2000;Kubota et al, 2001), and PDGF and CSF-1 receptormediated maturation in the IL-3-dependent hematopoietic cell line FDC-P1 (Kubota et al, 1998). The recent observation that administration of LY with SB, an agent known to induce colon cancer cell maturation (Gum et al, 1987), blocks Akt activation and increases lethality (Wang et al, 2002) is also consistent with this concept.…”

Lyn deficiency reduces GATA-1, EKLF and STAT5, and induces extramedullary stress erythropoiesis

“…While JAK2 is widely regarded as the primary kinase involved in Epo signaling (Witthuhn et al, 1993), members of the Src family of tyrosine kinases have also been implicated in intracellular signaling cascades (Tilbrook et al, 1997Chin et al, 1998;Kubota et al, 2001). Indeed, Src itself is activated by Epo , and is capable of promoting STAT5 phosphorylation .…”