Murata-Ohsawa Mai, Tohda Shuji, Sakano Seiji, Nara Nobuo
Department of Laboratory Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Int J Mol Med. 2004 Mar;13(3):419-23.
Notch signaling plays an important role in the regulation of self-renewal and differentiation of hematopoietic cells. Human monoblastic U937 cells undergo differentiation into macrophage-like cells, growth suppression, and apoptosis following stimulation with GM-CSF. We examined the effects of Notch activation induced by Notch ligands on GM-CSF-induced differentiation and apoptosis in U937 cells. Furthermore, the molecular mechanism of the effects was investigated. A recombinant Notch ligand, Delta-1 protein did not affect the growth of U937 cells by itself. GM-CSF-induced growth suppression and apoptosis of U937 cells were partially rescued by incubation with Delta-1. Delta-1 also reduced the GM-CSF-induced differentiation. Incubation with Delta-1 did not affect the expression of GM-CSF receptor. GM-CSF stimulation induced the phosphorylation of ERK1/2 and STAT5 and the cleavage of caspase-8, which were not affected by Delta-1 incubation, either. GM-CSF stimulation induced the cleavage of PARP, which is the key molecule for differentiation and apoptosis. We found that incubation with Delta-1 significantly suppressed the GM-CSF-induced cleavage of PARP. Taken together, we found that Notch activation induced by Delta-1 partially inhibited GM-CSF-induced differentiation, growth suppression, and apoptosis, along with reducing the GM-CSF-induced cleavage of PARP. These findings suggest one of the mechanisms by which Notch activation inhibits differentiation and apoptosis.
Notch信号通路在造血细胞的自我更新和分化调控中发挥着重要作用。人单核细胞白血病U937细胞在GM-CSF刺激后会分化为巨噬细胞样细胞、生长受抑制并发生凋亡。我们研究了Notch配体诱导的Notch激活对U937细胞中GM-CSF诱导的分化和凋亡的影响。此外，还探究了其作用的分子机制。重组Notch配体Delta-1蛋白本身并不影响U937细胞的生长。与Delta-1共同孵育可部分挽救GM-CSF诱导的U937细胞生长抑制和凋亡。Delta-1还降低了GM-CSF诱导的分化。与Delta-1共同孵育不影响GM-CSF受体的表达。GM-CSF刺激可诱导ERK1/2和STAT5的磷酸化以及caspase-8的裂解，而与Delta-1共同孵育对此也无影响。GM-CSF刺激可诱导PARP的裂解，PARP是分化和凋亡的关键分子。我们发现与Delta-1共同孵育可显著抑制GM-CSF诱导的PARP裂解。综上所述，我们发现Delta-1诱导的Notch激活可部分抑制GM-CSF诱导的分化、生长抑制和凋亡，并减少GM-CSF诱导的PARP裂解。这些发现提示了Notch激活抑制分化和凋亡的一种机制。
