title: Self-association of the transmembrane domain of RET underlies oncogenic activation by MEN2A mutations.
abstract: In patients with medullary thyroid carcinoma (MTC) and type 2A multiple endocrine neoplasia (MEN2A), mutations of cysteine residues in the extracellular juxtamembrane region of the RET receptor tyrosine kinase cause the formation of covalent receptor dimers linked by intermolecular disulfide bonds between unpaired cysteines, followed by oncogenic activation of the RET kinase. The close proximity to the plasma membrane of the affected cysteine residues prompted us to investigate the possible role of the transmembrane (TM) domain of RET (RET-TM) in receptor-receptor interactions underlying dimer formation. Strong self-association of the RET-TM was observed in a biological membrane. Mutagenesis studies indicated the involvement of the evolutionary conserved residues Ser-649 and Ser-653 in RET-TM oligomerization. Unexpectedly, RET-TM interactions were also abrogated in the A639G/A641R double mutant, first identified in a sporadic case of MTC. In agreement with this, no transforming activity could be detected in full-length RET carrying the A639G and A641R mutations, which remained fully responsive to glial cell-line-derived neurotrophic factor (GDNF) stimulation. When introduced in the context of C634R - a cysteine replacement that is prevalent in MEN2A cases - the A639G/A641R mutations significantly reduced dimer formation and transforming activity in this otherwise highly oncogenic RET variant. These data suggest that a strong propensity to self-association in the RET-TM underlies - and may be required for - dimer formation and oncogenic activation of juxtamembrane cysteine mutants of RET, and explains the close proximity to the plasma membrane of cysteine residues implicated in MEN2A and MTC syndromes.
authors.affiliation: Department of Neuroscience, Division of Molecular Neurobiology, Karolinska Institute, Stockholm, Sweden. sven.kjaer@cancer.org.uk
authors.forename: S
authors.initials: S
authors.lastname: Kjaer
authors.forename: K
authors.initials: K
authors.lastname: Kurokawa
authors.forename: M
authors.initials: M
authors.lastname: Perrinjaquet
authors.forename: C
authors.initials: C
authors.lastname: Abrescia
authors.forename: C F
authors.initials: CF
authors.lastname: Ibáñez
mesh_terms: D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster; D015870:Gene Expression / Q000187:drug effects; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D018813:Multiple Endocrine Neoplasia Type 2a / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D051096:Proto-Oncogene Proteins c-ret / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013964:Thyroid Neoplasms / Q000235:genetics
chemical_list: D004220:Disulfides; D029721:Drosophila Proteins; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; C416649:Ret protein, Drosophila; D003545:Cysteine; D000409:Alanine