Identification of functional nuclear export sequences in human sphingosine kinase 1.
Sphingosine kinase (SPHK) is an enzyme that phosphorylates sphingosine to form sphingosine 1-phosphate (S1P). Human SPHK1 (hSPHK1) was localized predominantly in the cytoplasm when transiently expressed in Cos7 cells. In this study, we have found two functional nuclear export signal (NES) sequences in the middle region of hSPHK1. Deletion and mutagenesis studies revealed that the cytoplasmic localization of SPHK1 depends on its nuclear export, directed by the NES. Furthermore, upon treatment with leptomycin B, a specific inhibitor of the nuclear export receptor CRM1, a marked nuclear accumulation of hSPHK1 was observed, indicating that hSPHK1 shuttles between the cytoplasm and the nucleus. Our results provide the first evidence of the active nuclear export of SPHK1 and suggest it is mediated by a CRM1-dependent pathway.
Department of Biomembrane and Biofunctional Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Yuichi
Y
Inagaki
Pei-Yun
PY
Li
Atsushi
A
Wada
Susumu
S
Mitsutake
Yasuyuki
Y
Igarashi
D021581:Active Transport, Cell Nucleus / Q000235:genetics; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics* / Q000648:ultrastructure; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D006801:Humans; D008969:Molecular Sequence Data; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020539:Sequence Analysis, Protein / Q000379:methods*; D013329:Structure-Activity Relationship; D014018:Tissue Distribution; D000099157:Sphingosine Kinase
D017853:Phosphotransferases (Alcohol Group Acceptor); D000099157:Sphingosine Kinase