mcl-1 Is an Immediate-Early Gene Activated by the Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) Signaling Pathway and Is One Component of the GM-CSF Viability Response

Abstract

mcl-1, a bcl-2 family member, was originally identified as an early gene induced during differentiation of ML-1 myeloid leukemia cells. In the present study, we demonstrate that Mcl-1 is tightly regulated by the granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling pathway. Upon deprivation of survival factor from TF-1 myeloid progenitor cells, Mcl-1 levels quickly dropped prior to visible detection of apoptosis of these cells. Upon restimulation of these deprived cells with GM-CSF, the mcl-1 mRNA was immediately induced and its protein product was accordingly resynthesized. Analysis with Ba/F3 cells expressing various truncation mutants of the GM-CSF receptor revealed that the membrane distal region between amino acids 573 and 755 of the receptor ␤ chain was required for mcl-1 induction. Transient-transfection assays with luciferase reporter genes driven by various regions of the mcl-1 promoter demonstrated that the upstream sequence between ؊197 and ؊69 is responsible for cytokine activation of the mcl-1 gene. Overexpression of mcl-1 delayed but did not completely prevent apoptosis of cells triggered by cytokine withdrawal. Its down regulation by antisense constructs overcame, at least partially, the survival activity of GM-CSF and induced the apoptosis of TF-1 cells. Taken together, these results suggest that mcl-1 is an immediate-early gene activated by the cytokine receptor signaling pathway and is one component of the GM-CSF viability response.

Epidermal growth factor (EGF) suppresses staurosporine-induced apoptosis by inducing mcl-1 via the mitogen-activated protein kinase pathway

“…We found that overexpression of Mcl-1 protected CE81T/VGH cells from staurosporine-induced apoptosis and transfection of a Mcl-1 antisense plasmid substantially increased the percentage of apoptotic cells (Figure 7). Our data support the fact that Mcl-1 is an inducible, antiapoptotic protein, as previously described in myeloid cells induced by TPA and GM-CSF (Kozopas et al, 1993;Chao et al, 1998), and in EBV immortalized B cells induced by IL-6 (Altmeyer et al, 1997). While the induction of Mcl-1 by TPA was mediated through the MAP kinase pathway in myeloblastic leukemia cells (Townsend et al, 1998), the IL-3 activation of mcl-1 gene expression was mediated via PI3-K-Akt-dependent andindependent pathways in murine pro-B Ba/F3 cells (Wang et al, 1999).…”

“…Plasmid pCMV-b is a mammalian expression vector which expresses bacterial bgalactosidase. The human Mcl-1 expression vector, pcDNA3-HA-h-mcl-1 (Chao et al, 1998) was kindly provided by Dr Hsin-Fang Yang-Yen (Academia Sinica, Taipei, Taiwan, ROC). The Mcl-1 antisense plasmid pcDNA3-h-mcl-1AS was constructed by excising pcDNA3-HA-h-mcl-1 with HindIII and XbaI, ®lling the protruding end of the fragments by T4 polymerase, and ligating the 1.1-kb human mcl-1 cDNA with the vector.…”

Over-expression of interleukin-6 enhances cell survival and transformed cell growth in human malignant cholangiocytes

“…However, Mcl-1 can act as a survival factor in hematopoeitic cells in cell culture as well as in transgenic mice (47). Furthermore, Mcl-1 may play an essential role in cytokine mediated survival of hematopoeitic cells and function as an early response gene when stimulated with granulocyte/ macrophage colony stimulating factor, (48)(49)(50). Our findings are consistent with these observations and suggest that Mcl-1 can act as an IL-6 early response gene in mediating survival signaling in malignant cholangiocytes.…”

Immunohistochemical Detection of Bcl-2 in Kaposi's Sarcoma Lesions Varies According to Histopathologic Stage, Whereas Expression of Bcl-x and Mcl-1 Differs According to Human Immunodeficiency Virus Serologic Status of Patients

“…Mcl-1 expression is induced by several cytokines, such as ␥IFN (38), granulocyte-macrophage colonystimulating factor (39), and IL6 (40), in several cell models. The intracellular distribution of Mcl-1 is essentially mitochondrial (41), being physiologically expressed in many types of long-lived cells (13) and frequently overexpressed in neoplasms.…”