Activation of cAMP-guanine exchange factor confers PKA-independent protection from hepatocyte apoptosis

2004 ◽  
Vol 287 (2) ◽  
pp. G334-G343 ◽  
Author(s):  
Kimberly A. Cullen ◽  
John McCool ◽  
M. Sawkat Anwer ◽  
Cynthia R. L. Webster
Keyword(s):  
Bile Acid ◽  
Protective Effect ◽  
Signaling Pathway ◽  
Fas Ligand ◽  
Kinase Inhibitor ◽  
Pi3 Kinase ◽  
Akt Phosphorylation ◽  
Tnf Α ◽  
Induced Apoptosis

cAMP has previously been shown to promote cell survival in a variety of cell types, but the downstream signaling pathway(s) of this antiapoptotic effect is unclear. Thus the role of cAMP signaling through PKA and cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs) in cAMP's antiapoptotic action was investigated in the present study. cAMP's protective effect against bile acid-, Fas ligand-, and TNF-α-induced apoptosis in rat hepatocytes was largely unaffected by the selective PKA inhibitor, Rp-8-(4-chlorophenylthio)-cAMP (Rp-cAMP). In contrast, a novel cAMP analog, 8-(4-chlorophenylthio)-2′- O-methyl (CPT-2-Me)-cAMP, which activated cAMP-GEFs in hepatocytes without activating PKA, protected hepatocytes against apoptosis induced by bile acids, Fas ligand, and TNF-α. The role of cAMP-GEF and PKA on activation of Akt, a kinase implicated in cAMP survival signaling, was investigated. Inhibition of PKA with RP-cAMP had no effect on cAMP-mediated Akt phosphorylation, whereas CPT-2-Me-cAMP, which did not activate PKA, induced phosphatidylinositol 3-kinase (PI3-kinase)-dependent activation of Akt. Pretreatment of hepatocytes with the PI3-kinase inhibitor, Ly-294002, prevented CPT-2-Me-cAMP's protective effect against bile acid and Fas ligand, but not TNF-α-mediated apoptosis. Glucagon, CPT-cAMP, and CPT-2-Me-cAMP all activated Rap 1, a downstream effector of cAMP-GEF. These results suggest that a PKA-independent cAMP/cAMP-GEF/Rap pathway exists in hepatocytes and that activation of cAMP-GEFs promotes Akt phosphorylation and hepatocyte survival. Thus a cAMP/cAMP-GEF/Rap/PI3-kinase/Akt signaling pathway may confer protection against bile acid- and Fas-induced apoptosis in hepatocytes.

scholarly journals cAMP-GEF cytoprotection by Src tyrosine kinase activation of phosphoinositide-3-kinase p110 β/α in rat hepatocytes

2009 ◽  
Vol 296 (4) ◽  
pp. G764-G774 ◽  
Author(s):  
Anna Gates ◽  
Simon Hohenester ◽  
M. Sawkat Anwer ◽  
Cynthia R. L. Webster
Keyword(s):  
Bile Acid ◽  
Signaling Pathway ◽  
Rat Hepatocytes ◽  
Cytoprotective Effect ◽  
Src Tyrosine Kinase ◽  
Akt Phosphorylation ◽  
Egfr Inhibition ◽  
Phosphoinositide 3 Kinase ◽  
Induced Apoptosis ◽  
Α Subunits

Cyclic AMP protects against hepatocyte apoptosis by a protein kinase A-independent cAMP-GEF/phosphoinositide-3-kinase (PI3K)/Akt signaling pathway. However, the signaling pathway coupling cAMP-GEF with PI3K is unknown. The aim of this study was to investigate the role of Src tyrosine kinases (Src-TYK) and PI3K-p110 isoforms in this pathway. Studies were done in rat hepatocytes using the hydrophobic bile acid glycochenodeoxycholic acid (GCDC) to induce apoptosis. cAMP-binding guanine nucleotide exchange factors (cAMP-GEFs) were selectively activated by using 4-(4-chloro-phenylthio)-2′- O-methyladenosine-3′-5′-cyclic monophosphate (CPT-2-Me-cAMP), which sequentially phosphorylated Src-TYK (within 1 min) followed by Akt (within 5 min). The Src inhibitors PP2 and SU6656 inhibited basal and CPT-2-Me-cAMP-mediated Src and Akt phosphorylation. These inhibitors had no effect on CPT-2-Me-cAMP-mediated activation of Rap GTPases. CPT-2-Me-cAMP induced transient Src dependent autophosphorylation of the epidermal growth factor receptor (EGFR). Inhibition of the EGFR with AG 1478 partially inhibited the ability of CPT-2-Me to phosphorylate Akt. Whereas PP2 completely abolished the protective effect of CPT-2-Me-cAMP in GCDC induced apoptosis, AG 1478 partially inhibited the cytoprotective effect. CPT-2-Me-cAMP treatment resulted in Src-dependent activation of the p110 β and α subunits of PI3K, but only the latter was sensitive to inhibition with AG 1478. In conclusion, activation of cAMP-GEFs results in phosphorylation of Src-TYK and Akt and activation of the p110 β/α subunits of PI3K. Maximal cAMP-GEF-mediated Akt phosphorylation as well as protection from bile acid-induced apoptosis requires activation of Src-TYK and the EGFR. These studies support the existence of two pathways: cAMP-GEF/Rap/Src/PI3Kβ/Akt and cAMP-GEF/Rap/Src/EGFR/PI3Kα/Akt, both of which are necessary for maximal cytoprotective effect of cAMP-GEFs in hepatocytes.

GAS-6 Rescues Endothelial Cells from Apoptosis through FOXO1 Inactivation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3686-3686
Author(s):  
Jorge Ganopolsky ◽  
Brian Varnum ◽  
Mark Blostein
Keyword(s):  
Endothelial Cells ◽  
Kinase Inhibitor ◽  
Pi3 Kinase ◽  
Serum Starvation ◽  
Specific Gene ◽  
Dependent Manner ◽  
Akt Phosphorylation ◽  
Mediate Cell ◽  
Induced Apoptosis ◽  
First Time

Abstract Growth Arrest Specific gene product 6 (GAS-6), a γ-carboxylated protein expressed in quiescent fibroblasts and endothelial cells, exerts an anti-apoptotic function by binding to the receptor tyrosine kinase Axl. Recently, our laboratory has demonstrated that gas6-Axl interactions activate PI3-kinase with subsequent Akt phosphorylation during gas6-mediated protection from apoptosis. The current study explores further the mechanism by which this survival mechanism is achieved. FOXO1 is a member of the Forkhead family of transcription factors that plays a role in the expression of pro-apoptototic genes. Phosphorylation of FOXO1 at Thr24, Ser256 and Ser319 results in phospho-FOXO1 translocation from the nucleus to the cytoplasm, with consequent suppression of FOXO1 transcriptional activity and inhibition of apoptosis. In the present study we show, for the first time, that the treatment of serum-starved endothelial cells with 100 ng/ml of GAS-6 induces FOXO1 phosphorylation in a time dependent manner. Phosphorylated FOXO1 is translocated from the nucleus to the cytoplasm as evidenced by Western blot analysis of both nuclear and cytoplasmic extracts. Using fluorescence microscopy, FOXO1 is found predominantly in the nucleus during apoptosis induced by serum starvation. Upon gas6 stimulation, phosphorylated FOXO1 is translocated to the cytoplasm (see Figure 1). It is suggested that anti-apoptotic genes are then released from suppression and are thereby able to mediate cell survival. Both FOXO1 phosphorylation and translocation are suppressed by Wortmannin, a PI3-kinase inhibitor demonstrating that FOXO1 phosphorylation is PI3-kinase dependent. These results provide mechanistic insight of how gas6 rescues endothelial cells from serum-starvation-induced apoptosis. Foxo1 distribution Foxo1 distribution

scholarly journals The Role of Fas-FasL Signaling Pathway in Induction of Apoptosis in Patients with Sulfur Mustard-Induced Chronic Bronchiolitis

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Gila Pirzad ◽  
Mahvash Jafari ◽  
Sasan Tavana ◽  
Homayoon Sadrayee ◽  
Saeid Ghavami ◽  
...  
Keyword(s):  
Lung Injury ◽  
Signaling Pathway ◽  
Caspase 3 ◽  
Fas Ligand ◽  
Sulfur Mustard ◽  
Control Group ◽  
Induced Apoptosis ◽  
Apoptosis And Necrosis ◽  
And Control

Sulfur mustard (SM) is an alkylating agent that induces apoptosis and necrosis in cells. Fas-Fas ligand (FasL) interaction could induce apoptosis as well. In this study, it was hypothesized that apoptosis might play an important role in the pathogenesis of SM-induced lung injury via Fas-FasL signaling pathway. In a case-control study, Fas and FasL levels, caspase-3 activity and percent of apoptotic cells were measured in bronchoalveolar lavage (BAL) fluid of patients 20 years after exposure to sulfur mustard and compared with the control group. Results show that Fas and FasL levels were significantly higher in BAL fluid cells in patients group compared with the control (P=.001). No significant differences were observed between mild and moderate-severe groups. BAL fluid cells caspase-3 activity was not significantly different among the mild, moderate-severe, and control groups. The data suggest that Fas-FasL-induced apoptosis was impaired in BAL fluid cells of SM-exposed patients which might be one of the initiators of pathogenesis in SM-induced lung injury in these patients.

scholarly journals Ubiquitination of RIPK1 suppresses programmed cell death by regulating RIPK1 kinase activation during embryogenesis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xixi Zhang ◽  
Haiwei Zhang ◽  
Chengxian Xu ◽  
Xiaoming Li ◽  
Ming Li ◽  
...  
Keyword(s):  
Cell Fate ◽  
Kinase Activity ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Kinase Activation ◽  
Tnf Α ◽  
Induced Apoptosis ◽  
Activity Dependent

Abstract The ubiquitination status of RIPK1 is considered to be critical for cell fate determination. However, the in vivo role for RIPK1 ubiquitination remains undefined. Here we show that mice expressing RIPK1K376R which is defective in RIPK1 ubiquitination die during embryogenesis. This lethality is fully rescued by concomitant deletion of Fadd and Ripk3 or Mlkl. Mechanistically, cells expressing RIPK1K376R are more susceptible to TNF-α induced apoptosis and necroptosis with more complex II formation and increased RIPK1 activation, which is consistent with the observation that Ripk1K376R/K376R lethality is effectively prevented by treatment of RIPK1 kinase inhibitor and is rescued by deletion of Tnfr1. However, Tnfr1−/−Ripk1K376R/K376R mice display systemic inflammation and die within 2 weeks. Significantly, this lethal inflammation is rescued by deletion of Ripk3. Taken together, these findings reveal a critical role of Lys376-mediated ubiquitination of RIPK1 in suppressing RIPK1 kinase activity–dependent lethal pathways during embryogenesis and RIPK3-dependent inflammation postnatally.

scholarly journals Role of endogenous TNF-α in cardiomyocyte apoptosis induced by bacteria lipoprotein and the protective effect of IL-10

2015 ◽  
Vol 13 (2) ◽  
pp. 117-125 ◽  
Author(s):  
Zhicai Li ◽  
Jing Zhou ◽  
Dongmei Zhu ◽  
Qian Zhang ◽  
Min Huang ◽  
...  
Keyword(s):  
Protective Effect ◽  
Cardiomyocyte Apoptosis ◽  
Tnf Α

Role of testosterone in regulating induction of TNF-α in rat spleen via ERK signaling pathway

Steroids ◽  
2016 ◽  
Vol 111 ◽  
pp. 148-154 ◽  
Author(s):  
Chien-Wei Chen ◽  
Cai-Yun Jian ◽  
Po-Han Lin ◽  
Chih-Chieh Chen ◽  
Fu-Kong Lieu ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Erk Signaling ◽  
Tnf Α

Role of PI3-kinase–dependent Bad phosphorylation and altered transcription in cytokine-mediated neutrophil survival

Blood ◽  
2002 ◽  
Vol 100 (7) ◽  
pp. 2607-2616 ◽  
Author(s):  
Andrew S. Cowburn ◽  
Karen A. Cadwallader ◽  
Benjamin J. Reed ◽  
Neda Farahi ◽  
Edwin R. Chilvers
Keyword(s):  
Kinase Inhibitor ◽  
Apoptotic Cell ◽  
Pi3 Kinase ◽  
Human Neutrophils ◽  
Marginal Effect ◽  
Mrna Levels ◽  
Gm Csf ◽  
Tnf Α ◽  
Neutrophil Survival ◽  
Survival Effect

Phosphoinositide 3-kinase (PI3-kinase)–dependent phosphorylation of the proapoptotic Bcl-2 family member Bad has been proposed as an important regulator of apoptotic cell death. To understand the importance of this pathway in nontransformed hematopoietic cells, we have examined the effect of survival cytokines on PI3-kinase activity and Bad expression and phosphorylation status in human neutrophils. Granulocyte macrophage–colony-stimulating factor (GM-CSF) and tumor necrosis factor-α (TNF-α) both reduced the rate of apoptosis in neutrophils cultured in vitro for 20 hours. Coincubation with the PI3-kinase inhibitor LY294002, which in parallel experiments abolished GM-CSF–primed, fMLP-stimulated superoxide anion production and GM-CSF–stimulated PtdIns(3,4,5)P3accumulation, inhibited the GM-CSF and TNF-α survival effect. In contrast, the MAP kinase kinase (MEK1/2) inhibitor PD98059 and the protein kinase A inhibitor H-89 had only a marginal effect on GM-CSF–mediated neutrophil survival. GM-CSF substantially increased Bad phosphorylation at Ser112 and Ser136 and increased the cytosolic accumulation of Bad. GM-CSF also regulated Bad at a transcription level with a marked decrease in mRNA levels at 4 hours. TNF-α caused a biphasic effect on the rate of morphologic apoptosis, which corresponded to an early increase, and a late inhibition, of Bad mRNA levels. LY294002 inhibited GM-CSF– and TNF-α–mediated changes in Bad phosphorylation and mRNA levels. These data suggest that the survival effect of GM-CSF and TNF-α in neutrophils is caused by a PI3-kinase–dependent phosphorylation and cytosolic translocation of Bad, together with an inhibition of Bad mRNA levels. This has important implications for the regulation of neutrophil apoptosis in vivo.

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