Cyclic‐AMP inhibits cell growth and negatively interacts with platelet membrane glycoprotein expression on the Dami human megakaryoblastic cell line

Abstract

Intracellular signaling processes by which hematopoietic growth factors regulate megakaryocytopoiesis remain incompletely understood. Cyclic AMP (cAMP) has been shown to be implicated in the regulation of growth and differentiation in various normal and malignant cell types. Since a few studies have suggested the possible involvement of the cAMP pathway as one of the intracellular mechanisms whereby megakaryocytopoiesis may be regulated, we investigated the functional effects of cAMP on the human megakaryoblastic Dami cell line. We observed that exposure of Dami cells to cAMP analogs or to agents elevating intracellular cAMP levels yielded dose-dependent cell growth inhibition. Cell cycle progression analysis of cells predominantly synchronized at the G1/S boundary by prior treatment with hydroxyurea revealed that cAMP transiently accumulated cells in the G2/M phase, then slowing down cell cycle. On the other hand, immunofluorescence and Northern blot analysis of megakaryocytic differentiation marker expression showed that probes we have used significantly inhibited GPIb expression. Moreover, although these agents used alone did not affect GPIIb/IIIa expression, they markedly reversed phorbol ester-induced GPIIb/IIIa expression increase. These inhibitory cAMP actions on glycoprotein expression were not the result of cell cycle perturbation since we observed that GPIb and GPIIb/IIIa expression were not cell cycle dependent. All these data may then be consistent with a potential negative regulatory role of the cAMP intracellular signaling pathway during megakaryocytopoiesis.

Hematopoietic stem cell differentiation affects expression and function of MRP4 (ABCC4), a transport protein for signaling molecules and drugs

“…The high abundance of MRP4 in human platelets and in vitro evidence for its involvement in transport of transmitter molecules including ADP23 indicates an important role of this protein in platelets. Furthermore, cyclic nucleotides, substrates of MRP4 and MRP5,20 have been shown to modulate differentiation of megakaryoblastic and leukemia cells 27–30. Regulation of these proteins during hematopoietic differentiation has not been studied.…”

“…In addition, MRP proteins have been shown to be directly involved in hematopoietic differentiation. Dendritic cells required MRP1 transporter activity for optimal differentiation26 and intracellular levels of cyclic nucleotides, substrates of MRP4 and MRP5, modulated differentiation of monocytes as well as megakaryoblastic and leukemia cells 27–30…”

Coupling of Epidermal Growth Factor (EGF) with the Antiproliferative Activity of cAMP Induces Neuronal Differentiation

“…Cessation of proliferation appears to be a prerequisite for neuronal differentiation in NGF-treated PC12 cells and does not occur when cells are treated with EGF alone. EGF is a known mitogen for PC12 cells (22), whereas cAMP is antimitogenic, inhibits DNA synthesis, and accumulates cells in G 2 /M phase (23)(24)(25)(26).…”

Cyclic AMP Signaling Inhibits Megakaryocytic Differentiation by Targeting Transcription Factor 3 (E2A) Cyclin-dependent Kinase Inhibitor 1A (CDKN1A) Transcriptional Axis

“…Augmentation of intracellular cAMP levels by a variety of pharmacologic agents has been shown to impair megakaryocytic differentiation in cell lines and in primary progenitors (1,2). Of clinical relevance, the phosphodiesterase inhibitor anagrelide serves as a first line therapy to lower platelet counts in patients with myeloproliferative disorders such as essential thrombocythemia (3)(4)(5).…”