The v-Ki-Ras oncogene alters cAMP nuclear signaling by regulating the location and the expression of cAMP-dependent protein kinase IIbeta.
The v-Ki-Ras oncoprotein dedifferentiates thyroid cells and inhibits nuclear accumulation of the catalytic subunit of cAMP-dependent protein kinase. After activation of v-Ras or protein kinase C, the regulatory subunit of type II protein kinase A, RIIbeta, translocates from the membranes to the cytosol. RIIbeta mRNA and protein were eventually depleted. These effects were mimicked by expressing AKAP45, a truncated version of the RII anchor protein, AKAP75. Because AKAP45 lacks membrane targeting domains, it induces the translocation of PKAII to the cytoplasm. Expression of AKAP45 markedly decreased thyroglobulin mRNA levels and inhibited accumulation of C-PKA in the nucleus. Our results suggest that: 1) The localization of PKAII influences cAMP signaling to the nucleus; 2) Ras alters the localization and the expression of PKAII; 3) Translocation of PKAII to the cytoplasm reduces nuclear C-PKA accumulation, resulting in decreased expression of cAMP-dependent genes, including RIIbeta, TSH receptor, and thyroglobulin. The loss of RIIbeta permanently down-regulates thyroid-specific gene expression.
Feliciello
A
A
Dipartimento Biologia e Patologia Molecolare e Cellulare, Centro di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Facoltà di Medicina, Università Federico II, Napoli, Italy.
Giuliano
P
P
Porcellini
A
A
Garbi
C
C
Obici
S
S
Mele
E
E
Angotti
E
E
Grieco
D
D
Amabile
G
G
Cassano
S
S
Li
Y
Y
Musti
A M
AM
Rubin
C S
CS
Gottesman
M E
ME
Avvedimento
E V
EV
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D000242:Cyclic AMP / Q000494:pharmacology; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000378:metabolism*; D017931:DNA Primers; D015971:Gene Expression Regulation, Enzymologic; D011905:Genes, ras; D008361:Mannosidases / Q000096:biosynthesis; D015689:Oncogene Protein p21(ras) / Q000096:biosynthesis; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011989:Receptors, Thyrotropin / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction; D013954:Thyroglobulin / Q000096:biosynthesis; D014162:Transfection; D043323:alpha-Mannosidase
D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; C415703:Akap5 protein, rat; D002352:Carrier Proteins; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D017931:DNA Primers; C517839:Prkar2b protein, rat; D011506:Proteins; D011989:Receptors, Thyrotropin; D011994:Recombinant Proteins; D013954:Thyroglobulin; D000242:Cyclic AMP; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D008361:Mannosidases; D043323:alpha-Mannosidase; D015689:Oncogene Protein p21(ras)