RAI(ShcC/N-Shc)-dependent recruitment of GAB 1 to RET oncoproteins potentiates PI 3-K signalling in thyroid tumors.
RAI, also named ShcC/N-Shc, one of the members of the Shc proteins family, is a substrate of the RET receptor tyrosine kinase. Here, we show that RAI forms a protein complex with both RET/MEN 2 A and RET/PTC oncoproteins. By co-immunoprecipitation, we found that RAI associates with the Grb 2-associated binder 1 (GAB 1) adapter. This association is constitutive, but, in the presence of RET oncoproteins, both RAI and GAB 1 are tyrosine-phosphorylated, and the stoichiometry of this interaction remarkably increases. Consequently, the p 85 regulatory subunit of phosphatidylinositol-3 kinase (PI-3 K) is recruited to the complex, and its downstream effector Akt is activated. We show that human thyroid cancer cell lines derived from papillary or medullary thyroid carcinoma (PTC or MTC) carrying, respectively, RET/PTC and RET/MEN 2 A oncoproteins express RAI proteins. We also show that human PTC samples express higher levels of RAI, when compared to normal thyroid tissue. In thyroid cells expressing RET/PTC 1, ectopic expression of RAI protects cells from apoptosis; on the other hand, the silencing of endogenous RAI by small inhibitory duplex RNAs in a PTC cell line that expresses endogenous RET/PTC 1, increases the rate of spontaneous apoptosis. These data suggest that RAI is a critical substrate for RET oncoproteins in thyroid carcinomas.
De Falco
Valentina
V
Instituto di Endocrinologia ed Oncologia Sperimentale del CNR 'G. Salvatore', c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare, Via S. Pansini 5, 80131 Naples, Italy.
Guarino
Valentina
V
Malorni
Luca
L
Cirafici
Anna Maria
AM
Troglio
Flavia
F
Erreni
Marco
M
Pelicci
Giuliana
G
Santoro
Massimo
M
Melillo
Rosa Marina
RM
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D017931:DNA Primers; D004789:Enzyme Activation; D006801:Humans; D009479:Neuropeptides / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071427:Src Homology 2 Domain-Containing, Transforming Protein 3; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology
D048868:Adaptor Proteins, Signal Transducing; D017931:DNA Primers; C098587:GAB1 protein, human; D009479:Neuropeptides; D010750:Phosphoproteins; C122029:SHC3 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071427:Src Homology 2 Domain-Containing, Transforming Protein 3; D019869:Phosphatidylinositol 3-Kinases; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human