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: Phosphorylation of FTY720 is catalysed by nuclear SK-2, and it is required for its immune-suppressor and anti-MS activities (Billich et al, 2003; Paugh et al, 2003). However, whether P-FTY720 generation plays a role in I2PP2A/SET binding or tumour suppression is unknown. Therefore, we first examined whether P-FTY720 is necessary for its I2PP2A/SET binding in A549 cells. To achieve this, purified I2PP2A/SET was incubated with B-FTY720 in the absence/presence of unlabeled C18-Pyr-Cer, FTY720 or P-FTY720 as competitors. Incubation with unlabeled C18-ceramide or FTY720, but not P-FTY720, competed significantly with B-FTY720-I2PP2A/SET binding (Fig 5A). These data suggest that P-FTY720 is not as efficient as FTY720 to bind I2PP2A/SET, supporting our molecular modelling (Fig 3B) and in vitro SPR studies (Fig 3E and F), which suggested that presence of a primary hydroxyl group in the FTY720 structure is important for I2PP2A/SET binding and that I2PP2A/SET has a lower affinity to P-FTY720 compared to C18-ceramide and FTY720, respectively.
Affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA.