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

• Published in: Journal of neurochemistry Vol. 102; no. 5; pp. 1585 - 1594
• Main Authors: Murakami, Masashi, Ichihara, Masatoshi, Sobue, Sayaka, Kikuchi, Ryosuke, Ito, Hiromi, Kimura, Ami, Iwasaki, Takashi, Takagi, Akira, Kojima, Tetsuhito, Takahashi, Masahide, Suzuki, Motoshi, Banno, Yoshiko, Nozawa, Yoshinori, Murate, Takashi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.09.2007; Blackwell
• Subjects: Animals; Biochemistry; Biological and medical sciences; Cancer; Cell Differentiation - drug effects; Cell Differentiation - physiology; Cell Line; Cell Proliferation - drug effects; Cellular biology; cellular function; Electrophoretic Mobility Shift Assay - methods; Endocrinopathies; Enzymes; gene expression; General aspects. Associated endocrine diseases. Endocrine paraneoplasic syndromes; Glial Cell Line-Derived Neurotrophic Factor - pharmacology; glial cell line‐derived neurotrophic factor; Humans; Malignant tumors; Medical sciences; Mice; multiple endocrine neoplasia type 2; Multiple Endocrine Neoplasia Type 2a; Mutation; Mutation - physiology; Neuroblastoma - enzymology; Neurology; Phosphotransferases (Alcohol Group Acceptor) - genetics; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Proto-Oncogene Proteins c-ret - physiology; RET; Signal transduction; Signal Transduction - drug effects; Signal Transduction - physiology; SPHK1; Thyroid. Thyroid axis (diseases); Time Factors; Transfection - methods; Up-Regulation - drug effects; Up-Regulation - physiology; Endocrinopathy; RET; Papillary carcinoma; glial cell line- derived neurotrophic factor; Activation; Kidney; Thyroid carcinoma; Signal transduction; Multiple endocrine neoplasia; Development; Glial cell line derived neurotrophic factor; Biological receptor; Human; multiple endocrine neoplasia type 2; Nervous system diseases; cellular function; Enzyme; Transferases; SPHK1; Thyroid diseases; Sphinganine kinase; Malignant tumor; Gene expression; Survival; Genetic disease; Neuron; Urinary system; Mutation; Phosphatidylinositol 3-kinase; Autonomic neuropathy; Differentiation
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2007.04673.x

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.