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Transforming growth factor beta1 rescues serum deprivation-induced apoptosis via the mitogen-activated protein kinase
B Y Chin1, I Petrache, A M Choi
1Toxicological Sciences, Environmental Health Sciences, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
Abstract:
Cell death and cell survival are central components of normal development and pathologic states. Transforming growth factor beta1 (TGF-beta1) is a pleiotropic cytokine that regulates both cell growth and cell death. To better understand the molecular mechanisms that control cell death or survival, we investigated the role of TGF-beta1 in the apoptotic process by dominant-negative inhibition of both TGF-beta1 and mitogen-activated protein kinase (MAPK) signaling pathways. Murine macrophages (RAW 264.7) undergo apoptosis following serum deprivation, as determined by DNA laddering assay. However, apoptosis is prevented in serum-deprived macrophages by the presence of exogenous TGF-beta1. Using stably transfected RAW 264.7 cells with the kinase-deleted dominant-negative mutant of TbetaR-II (TbetaR-IIM) cDNA, we demonstrate that this protective effect by TGF-beta1 is completely abrogated. To determine the downstream signaling pathways, we examined TGF-beta1 effects on the MAPK pathway. We show that TGF-beta1 induces the extracellular signal-regulated kinase (ERK) activity in a time-dependent manner up to 4 h after stimulation. Furthermore, TGF-beta1 does not rescue serum deprivation-induced apoptosis in RAW 264.7 cells transfected with a dominant-negative mutant MAPK (ERK2) cDNA or in wild type RAW 264.7 cells in the presence of the MAPK kinase (MEK1) inhibitor. Taken together, our data demonstrate for the first time that TGF-beta1 is an inhibitor of apoptosis in cultured macrophages and may serve as a cell survival factor via TbetaR-II-mediated signaling and downstream intracellular MAPK signaling pathway.
Insights
Transforming growth factor beta1 (TGF-beta1) prevents apoptosis in macrophages, acting as a cell survival factor. This protective effect is mediated through TGF-beta receptor II (TbetaR-II) and downstream mitogen-activated protein kinase (MAPK) signaling pathways.
Area of Science:
- Cellular biology
- Immunology
- Molecular signaling
Background:
- Cell death and survival are critical in development and disease.
- Transforming growth factor beta1 (TGF-beta1) is a cytokine influencing cell growth and death.
- Understanding TGF-beta1's role in apoptosis is key to elucidating cell fate mechanisms.
Purpose of the Study:
- To investigate the role of TGF-beta1 in regulating apoptosis in macrophages.
- To identify the specific signaling pathways involved in TGF-beta1's effect on cell survival.
Main Methods:
- Utilized murine macrophages (RAW 264.7) subjected to serum deprivation.
- Employed dominant-negative inhibition of TGF-beta1 receptor II (TbetaR-II) and mitogen-activated protein kinase (MAPK) pathways.
- Assessed apoptosis using DNA laddering assays and measured extracellular signal-regulated kinase (ERK) activity.
Main Results:
- TGF-beta1 inhibited apoptosis in serum-deprived macrophages.
- This protective effect was abolished by dominant-negative TbetaR-II.
- TGF-beta1 induced ERK activity, and inhibiting MAPK signaling blocked its anti-apoptotic function.
Conclusions:
- TGF-beta1 acts as an inhibitor of apoptosis in cultured macrophages.
- Cell survival mediated by TGF-beta1 involves TbetaR-II and downstream MAPK signaling.
- These findings highlight TGF-beta1's role as a crucial cell survival factor in macrophages.