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Identification of functional nuclear export sequences in human sphingosine kinase 1
Yuichi Inagaki1, Pei-Yun Li, Atsushi Wada
1Department of Biomembrane and Biofunctional Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Biochemical and Biophysical Research Communications
|October 25, 2003
Summary
Human sphingosine kinase 1 (hSPHK1) is actively exported from the nucleus to the cytoplasm. This nuclear export, mediated by CRM1, is crucial for hSPHK1
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Sphingosine kinase (SPHK) phosphorylates sphingosine to sphingosine 1-phosphate (S1P).
- Human SPHK1 (hSPHK1) is predominantly localized in the cytoplasm.
- The precise subcellular localization and regulation of SPHK1 are not fully understood.
Purpose of the Study:
- To investigate the subcellular localization mechanisms of human sphingosine kinase 1 (hSPHK1).
- To identify signals and pathways regulating hSPHK1 localization.
- To determine if hSPHK1 undergoes active transport between cellular compartments.
Main Methods:
- Transient expression of wild-type and mutant hSPHK1 in Cos7 cells.
- Deletion and mutagenesis of potential nuclear export signals (NES).
- Treatment with leptomycin B, a CRM1 inhibitor, to assess nuclear export dependency.
Main Results:
- Two functional nuclear export signal (NES) sequences were identified in the middle region of hSPHK1.
- Cytoplasmic localization of hSPHK1 was found to be dependent on these NES sequences.
- Inhibition of CRM1 led to significant nuclear accumulation of hSPHK1, confirming nucleocytoplasmic shuttling.
Conclusions:
- hSPHK1 actively shuttles between the nucleus and cytoplasm.
- Nuclear export of hSPHK1 is mediated by a CRM1-dependent pathway.
- This study provides the first evidence of active nuclear export for SPHK1.