Filamin A Expression Negatively Regulates Sphingosine-1-Phosphate-Induced NF-κB Activation in Melanoma Cells by Inhibition of Akt Signaling

Abstract

d Sphingosine-1-phosphate (S1P) is a bioactive lipid mediator that regulates many processes in inflammation and cancer. S1P is a ligand for five G-protein-coupled receptors, S1PR1 to -5, and also has important intracellular actions. Previously, we showed that intracellular S1P is involved in tumor necrosis factor alpha (TNF)-induced NF-B activation in melanoma cell lines that express filamin A (FLNA). Here, we show that extracellular S1P activates NF-B only in melanoma cells that lack FLNA. In these cells, S1P, but not TNF, promotes IB kinase (IKK) and p65 phosphorylation, IB␣ degradation, p65 nuclear translocation, and NF-B reporter activity. NF-B activation induced by S1P was mediated via S1PR1 and S1PR2. Exogenous S1P enhanced the phosphorylation of protein kinase C␦ (PKC␦), and its downregulation reduced S1P-induced the phosphorylation of IKK and p65. In addition, silencing of Bcl10 also inhibited S1P-induced IKK phosphorylation. Surprisingly, S1P reduced Akt activation in melanoma cells that express FLNA, whereas in the absence of FLNA, high phosphorylation levels of Akt were maintained, enabling S1P-mediated NF-B signaling. In accord, inhibition of Akt suppressed S1P-mediated IKK and p65 phosphorylation and degradation of IB␣. Hence, these results support a negative role of FLNA in S1P-mediated NF-B activation in melanoma cells through modulation of Akt.

Rapid emergence and mechanisms of resistance by U87 glioblastoma cells to doxorubicin in an in vitro tumor microfluidic ecology

“…One possible explanation may have to do with the mutation of FLNA, the deficiency of which alters the transport of DOX via yet uncharacterized mechanisms (17). Interestingly, Campos et al (27) reported recently that FLNA negatively regulated NF-κB activation in melanoma cell by inhibition of Akt signaling, which may further link the loss-of-function mutation of FLNA to NF-κB activation.…”

Sphingosine-1 Phosphate: A New Modulator of Immune Plasticity in the Tumor Microenvironment

“…A very recent report showed that activation of S1PR2 in epithelial cells was crucial for elimination of neighboring cancer cells, a process known as epithelial defense against cancer (EDAC) ( 88 ). Of great interest, the process involved a gradual accumulation of Filamin A (FlnA), an actin-binding protein that we recently demonstrated to modulate S1P-induced NF-κB activation in melanoma cells ( 89 ).…”

“…Receptor-mediated activation involved S1PR1/3 in different cell types ( 115 , 148 – 153 ). Moreover, we have recently demonstrated that activation of NF-κB by extracellular S1P in melanoma cells involved both S1PR1 and S1PR2 and was inversely correlated with the expression of the actin-binding protein FlnA ( 89 ). Interestingly, FlnA physically interacts with SphK1 ( 16 ) and TNF receptor-associated factor 2 (TRAF2) ( 154 ).…”

Prion protein is required for tumor necrosis factor α (TNFα)-triggered nuclear factor κB (NF-κB) signaling and cytokine production

“…Binding of S1P to SIPR1 leads to activation of NF-κB ( 79 ). It has recently been reported that S1P only activates NF-κB in M2 cells but not in FLNa bearing A7 cells suggesting that FLNa is a negative regulator of NF-κB activation ( 80 ). In the same study, it was reported that although TNFα (10 ng/ml) induced robust IκBα degradation via the proteasomal pathway in A7 cells, it had no effect on M2 cells that do not express FLNa ( 80 ).…”