Sphingosine kinases (SphKs) catalyze the conversion of the sphingosine to the promitogenic/migratory product, sphingosine-1-phosphate (S1P). SphK/S1P pathway has been linked to the progression of cancer and various other diseases including allergic inflammatory disease, cardiovascular diseases, rejection after transplantation, the central nervous system, and virus infections[1]. Gene-targeted mice null for the sphingosine kinase 1 isoform whose hearts are subjected to ischemia/reperfusion injury exhibit increased infarct size and respond poorly either to ischemic preconditioning or to ischemic postconditioning[2]. SphK2 is a nuclear protein that suppresses cell proliferation by inhibiting DNA synthesis, while also enhancing apoptosis in diverse cell types. Genetic inhibition of SphK2 did not significantly impact the severity or progression of inflammatory arthritis, while pharmacologic inhibition of SphK2 led to significantly more severe arthritis[3]. SphK2 is involved in regulating interleukin (IL)-12/interferon gamma (IFN-γ) and histone deacetylase-1/2 (HDAC-1/2) signalling and, potentially, retinoid-related orphan receptor gamma t (ROR-γt) stability linked with T helper (Th) 17 cell polarisation[4]. K145 inhibited the activity of SphK2 in a dose-dependent manner with an IC50 of 4.30 uM. The Lineweaver-Burk analysis revealed a Ki of 6.4±0.7 uM for SphK2 and indicated that K145 is a substrate competitive inhibitor (with sphingosine). K145 accumulates in U937 cells, suppresses the S1P level, and inhibits SphK2. K145 also exhibited inhibitory effects on the growth of U937 cells as well as apoptotic effects in U937 cells, and that these effects may be through the inhibition of downstream ERK and Akt signaling pathways[5].
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