title: RET activation by germline MEN2A and MEN2B mutations.
abstract: The RET proto-oncogene encodes a receptor tyrosine kinase (TK). It has been shown that distinct germline mutations in the RET proto-oncogene are associated with the dominantly inherited cancer syndromes multiple endocrine neoplasia type 2A and 2B (MEN 2A and MEN 2B) and familial medullary thyroid carcinoma (FMTC) as well as Hirschsprung disease (HSCR), a congenital disorder characterised by absent enteric innervation. In this study, we have transfected NIH3T3 and PC12 phaeochromocytoma cells with MEN2A (Cys634-> Arg) and MEN2B (Met918-> Thr) RET constructs. Both caused transformation of the NIH3T3 cells and differentiation of PC12 cells. The Ret (MEN2A) and Ret (MEN2B) proteins were constitutively phosphorylated on tyrosine, and their in vitro kinase activity was significantly higher than that of the wild type protein. The MTC cell line TT carries a CYs634-> Trp MEN2A mutation, and we have shown by immunoelectronmicroscopy that Ret is clustered on the cell surface in a manner reminiscent of ligand-induced aggregation of cell surface receptors. RET is activated, as RET/PTC oncogene, by somatic rearrangements which link the TK domain to a constitutive dimerization interface in papillary thyroid carcinomas. We have compared the biological and biochemical activity of the TK domains of the wild type and MEN 2B Ret in the context of the RET/PTC. The results show that the MEN 2B mutation significantly increases the TK domain enzymatic activity suggesting that dimerization may be still necessary for MEN 2B Ret to express its full activity.
authors.affiliation: Division of Experimental Oncology A, Istituto Nazionale Tumori, Milan, Italy.
authors.forename: M G
authors.initials: MG
authors.lastname: Borrello
authors.forename: D P
authors.initials: DP
authors.lastname: Smith
authors.forename: B
authors.initials: B
authors.lastname: Pasini
authors.forename: I
authors.initials: I
authors.lastname: Bongarzone
authors.forename: A
authors.initials: A
authors.lastname: Greco
authors.forename: M J
authors.initials: MJ
authors.lastname: Lorenzo
authors.forename: E
authors.initials: E
authors.lastname: Arighi
authors.forename: C
authors.initials: C
authors.lastname: Miranda
authors.forename: C
authors.initials: C
authors.lastname: Eng
authors.forename: L
authors.initials: L
authors.lastname: Alberti
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D029721:Drosophila Proteins; D018095:Germ-Line Mutation; D006627:Hirschsprung Disease / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009377:Multiple Endocrine Neoplasia / Q000235:genetics; D018813:Multiple Endocrine Neoplasia Type 2a / Q000235:genetics*; D018814:Multiple Endocrine Neoplasia Type 2b / Q000235:genetics*; D009838:Oligodeoxyribonucleotides; D010641:Phenotype; D010766:Phosphorylation; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D051096:Proto-Oncogene Proteins c-ret; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D029721:Drosophila Proteins; C000715470:MAS1 protein, human; D009838:Oligodeoxyribonucleotides; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila; C494999:Ret protein, mouse; C495001:Ret protein, rat