Sphingosine analogue drug FTY720 targets I2PP2A/SET and mediates lung tumour suppression via activation of PP2A-RIPK1-dependent necroptosis.
Bottom Line: Mechanistically, targeting I2PP2A/SET by FTY720 mediated PP2A/RIPK1-dependent programmed necrosis (necroptosis), but not by apoptosis.The RIPK1 inhibitor necrostatin and knockdown or genetic loss of RIPK1 prevented growth inhibition by FTY720.Expression of WT- or death-domain-deleted (DDD)-RIPK1, but not the kinase-domain-deleted (KDD)-RIPK1, restored FTY720-mediated necroptosis in RIPK1(-/-) MEFs.
Affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA.Show MeSH
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Mentions: To validate I2PP2A/SET as a target of FTY720 for its tumour suppressor roles, we determined the effects of FTY720 on cell death and/or tumour suppression in response to shRNA-mediated knockdown of I2PP2A and its reconstitution in A549/sh-I2PP2A/SET versus A549/sh-I2PP2A/SET-WT-I2PP2A/SET cells in situ and in vivo. Treatment with FTY720 or knockdown of I2PP2A/SET alone significantly induced cell death compared to their respective controls (Fig 7A). Importantly, knockdown of I2PP2A/SET prevented FTY720-induced cell death (Fig 7A). Reconstitution of WT-I2PP2A/SET expression in A549/sh-I2PP2A/SET cells restored FTY720-mediated cell death (Fig 7A). These data were consistent with the effects of I2PP2A/SET knockdown and expression of WT-I2PP2A/SET on PP2A activation in the absence/presence of FTY720 in these cells (Fig 6B). Expression of Y122C-I2PP2A/SET-GFP and ER-I2PP2A/SET-GFP restored FTY720-mediated cell death when endogenous I2PP2A/SET was down-regulated compared to controls in A549/sh-I2PP2A/SET cells (Fig 7B). However, expression of K209D-I2PP2A/SET had no significant effect on cell death in response to FTY720 in A549/sh-I2PP2A/SET cells (Fig 7B). I2PP2A/SET-GFP expression in A549/sh-I2PP2A/SET cells was confirmed by Western blotting (Supporting Information Fig S10B).
Affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA.