Cellular Physiology and Biochemistry | |
A Novel Mode of Action of the Putative Sphingosine Kinase Inhibitor 2-(p-hydroxyanilino)-4-(p-chlorophenyl) Thiazole (SKI II): Induction of Lysosomal Sphingosine Kinase 1 Degradation | |
关键词: SKI II; Sphingosine kinase 1; Protein degradation; Lysosome; Chloroquine; Cathepsin B; | |
DOI : 10.1159/000315110 | |
学科分类:分子生物学,细胞生物学和基因 | |
来源: S Karger AG | |
【 摘 要 】
Background Sphingosine kinase 1 (SK1) is a key enzyme in the generation of sphingosine 1-phosphate (S1P) which critically regulates a variety of important cell responses such as proliferation and migration. Therefore, inhibition of SK-1 has been suggested to be an attractive approach to treat tumor growth and metastasis formation. Results We show here that the previously developed putative SK-1 inhibitor 2-(p-hydroxyanilino)-4-(p-chlorophenyl) thiazole (SKI II) displays an additional facet of action complementary to the known inhibition of enzymatic SK-1 activity. In various human cell lines including glomerular podocytes and mesangial cells, the human endothelial cell line EA.hy 926, and the lung cancer cell line NCI H358, SKI II reduced TGFΒ- and TPA-stimulated cellular SK-1 activity by downregulating SK-1 protein expression without affecting SK-1 mRNA expression. By using cycloheximide to block the de novo protein synthesis, the protein expression of SK-1 under untreated conditions was stable over 24h. Under SKI II treatment, the half-live drastically decreased to approximately 0.8h. Mechanistically, this degradation occurred through a lysosomal pathway and involved cathepsin B since the general lysosomal inhibitor chloroquine and the specific cathepsin B inhibitor CA-074ME were able to reverse the effect of SKI II. Surprisingly, in vitro SK-1 activity assays revealed only a very weak direct inhibitory effect of SKI II on SK-1 overexpressed HEK293 cell lysates. Conclusion These data show for the first time that the previously developed SK inhibitor SKI II hardly inhibits SK-1 directly but rather acts by triggering the lysosomal degradation of SK-1 in various cell types. This finding discloses a new mode of action of SKI II and strongly suggests that additional direct targets of SKI II may exist other than SK-1.
【 授权许可】
CC BY-NC-ND
【 预 览 】
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