RET signaling-induced SPHK1 gene expression plays a role in both GDNF-induced differentiation and MEN2-type oncogenesis.

Abstract

RET, the receptor of glial cell line-derived neurotrophic factor (GDNF) family ligands, is important for the development of kidney and peripheral neurons. GDNF promotes survival and differentiation of neurons. Mutation of RET leads to the constitutive signal activation causing papillary thyroid carcinoma and multiple endocrine neoplasia type 2 (MEN2). In this study, we report that GDNF/RET signaling up-regulates sphingosine kinase (SPHK) enzyme activity, SPHK1 protein and SPHK1 message in TGW human neuroblastoma cells. Silencing of SPHK1 using siRNA inhibited GDNF-induced neurite formation, GAP43 expression, and cell growth, suggesting the important role of SPHK1 in GDNF signal transduction. Furthermore, NIH3T3 cells transfected with MEN2A type mutated RET but not c-RET demonstrated the up-regulation of SPHK activity, SPHK1 protein and SPHK1 message compared with NIH3T3 cells. The cell growth and anchorage-independent colony formation of MEN2A-NIH3T3 was inhibited with siRNA of SPHK1, while no effect of scramble siRNA was observed. These results suggest the oncogenic role of SPHK1 in MEN2A type tumor. Promoter analysis showed that activator protein 2 and specificity protein 1 binding motif of the 5' promoter region of SPHK1 gene is important for its induction by GDNF. Furthermore, we demonstrated that ERK1/2 and PI3 kinase are involved in GDNF-induced SPHK1 transcription by using specific inhibitors.

• Authors: Masashi Murakami, Masatoshi Ichihara, Sayaka Sobue, Ryosuke Kikuchi, Hiromi Ito, Ami Kimura, Takashi Iwasaki, Akira Takagi, Tetsuhito Kojima, Masahide Takahashi, Motoshi Suzuki, Yoshiko Banno, Yoshinori Nozawa, Takashi Murate
• Journal: Journal of neurochemistry (J Neurochem) Vol. 102 Issue 5 Pg. 1585-1594 (Sep 2007) ISSN: 0022-3042 [Print] England
• PMID: 17555548 (Publication Type: Journal Article)

Chemical References

• Glial Cell Line-Derived Neurotrophic Factor
• Phosphotransferases (Alcohol Group Acceptor)
• sphingosine kinase
• Proto-Oncogene Proteins c-ret
• Ret protein, mouse

Topics

• Animals
• Cell Differentiation (drug effects, physiology)
• Cell Line
• Cell Proliferation (drug effects)
• Electrophoretic Mobility Shift Assay (methods)
• Glial Cell Line-Derived Neurotrophic Factor (pharmacology)
• Humans
• Mice
• Multiple Endocrine Neoplasia Type 2a
• Mutation (physiology)
• Neuroblastoma (enzymology)
• Phosphotransferases (Alcohol Group Acceptor) (genetics, metabolism)
• Proto-Oncogene Proteins c-ret (physiology)
• Signal Transduction (drug effects, physiology)
• Time Factors
• Transfection (methods)
• Up-Regulation (drug effects, physiology)