The p42/p44 MAP Kinase Pathway Prevents Apoptosis Induced by Anchorage and Serum Removal

Abstract

Anchorage removal like growth factor removal induces apoptosis. In the present study we have characterized signaling pathways that can prevent this cell death using a highly growth factor- and anchorage-dependent line of lung fibroblasts (CCL39). After anchorage removal from exponentially growing cells, annexin V-FITC labeling can be detected after 8 h. Apoptosis was confirmed by analysis of sub-G1 DNA content and Western blotting of the caspase substrate poly (ADP-ribose) polymerase. Growth factor withdrawal accelerates and potentiates suspension-induced cell death. Activation of Raf-1 kinase in suspension cultures of CCL39 or Madin-Darby canine kidney cells stably expressing an estrogen-inducible activated-Raf-1 construct (DeltaRaf-1:ER) suppresses apoptosis induced by growth factor and/or anchorage removal. This protective effect appears to be mediated by the Raf, mitogen- or extracellular signal-regulated kinase kinase (MEK), and mitogen-activated protein kinase module because it is sensitive to pharmacological inhibition of MEK-1 and it can be mimicked by expression of constitutively active MEK-1 in CCL39 cells. Finally, apoptosis induced by disruption of the actin cytoskeleton with the Rho-directed toxin B (Clostridium difficile) is prevented by activation of the DeltaRaf-1:ER chimeric construct. These findings highlight the ability of p42/p44 mitogen-activated protein kinase to generate survival signals that counteract cell death induced by loss of matrix contact, cytoskeletal integrity, and extracellular mitogenic factors.

Anoikis: an emerging hallmark in health and diseases

“…both extracellular signal-regulated kinase (ERK) and phosphoinositide-3-kinase (PI3K)/Akt-mediated phosphorylation of Bim, thus avoiding Bim proteasomal degradation and determining its accumulation [18,19]. In addition, loss of ECM contact, leading to disruption of Bim sequestration by dynein cytoskeleton complexes, strongly increases Bim cytoplasmic accumulation and increases Bad availability [17].…”

The Transcriptional Response to Raf Activation Is Almost Completely Dependent on Mitogen-activated Protein Kinase Kinase Activity and Shows a Major Autocrine Component

“…Once activated, Raf phosphorylates and activates its major substrates, the dual specificity kinases mitogen-activated protein kinase kinase (MEK)1 and MEK2, which go on to phosphorylate and activate the mitogen-activated protein (MAP) kinases ERK1 and ERK2 (Kolch, 2000). Raf acting through MEK and ERK has been found to play a critical role in the control of cell cycle progression (Marshall, 1999), can induce protection against various apoptotic stimuli (Bonni et al, 1999;Erhardt et al, 1999;Kazama and Yonehara, 2000;Le Gall et al, 2000), and has numerous other effects on cell behavior.…”

Suppression of hypoxic cell death by APIP-induced sustained activation of AKT and ERK1/2

“…Also, activation of ERK pathway inhibits cell death induced by serum deprivation or matrix detachment, and can suppress caspase-3 activation even though cytochrome c is released from the mitochondria (Le Gall et al, 2000;Rytomaa et al, 2000). Anti-apoptotic functions of ERK pathway are associated with the inhibition of caspase-9 through direct phosphorylation (Allan et al, 2003).…”