title: A novel dual kinase function of the RET proto-oncogene negatively regulates activating transcription factor 4-mediated apoptosis.
abstract: The RET proto-oncogene, a tyrosine kinase receptor, is widely known for its essential role in cell survival. Germ line missense mutations, which give rise to constitutively active oncogenic RET, were found to cause multiple endocrine neoplasia type 2, a dominant inherited cancer syndrome that affects neuroendocrine organs. However, the mechanisms by which RET promotes cell survival and prevents cell death remain elusive. We demonstrate that in addition to cytoplasmic localization, RET is localized in the nucleus and functions as a tyrosine-threonine dual specificity kinase. Knockdown of RET by shRNA in medullary thyroid cancer-derived cells stimulated expression of activating transcription factor 4 (ATF4), a master transcription factor for stress-induced apoptosis, through activation of its target proapoptotic genes NOXA and PUMA. RET knockdown also increased sensitivity to cisplatin-induced apoptosis. We observed that RET physically interacted with and phosphorylated ATF4 at tyrosine and threonine residues. Indeed, RET kinase activity was required to inhibit the ATF4-dependent activation of the NOXA gene because the site-specific substitution mutations that block threonine phosphorylation increased ATF4 stability and activated its targets NOXA and PUMA. Moreover, chromatin immunoprecipitation assays revealed that ATF4 occupancy increased at the NOXA promoter in TT cells treated with tyrosine kinase inhibitors or the ATF4 inducer eeyarestatin as well as in RET-depleted TT cells. Together these findings reveal RET as a novel dual kinase with nuclear localization and provide mechanisms by which RET represses the proapoptotic genes through direct interaction with and phosphorylation-dependent inactivation of ATF4 during the pathogenesis of medullary thyroid cancer.
authors: From the Department of Endocrine Neoplasia and Hormonal Disorders, ryarmand@mdanderson.org.
authors: Rozita
authors: R
authors: Bagheri-Yarmand
authors: From the Department of Endocrine Neoplasia and Hormonal Disorders.
authors: Krishna M
authors: KM
authors: Sinha
authors: the Department of Neurosurgery.
authors: Anupama E
authors: AE
authors: Gururaj
authors: the Department of Biochemistry and Molecular Biology and Center for Biomolecular Structure and Function, and.
authors: Zamal
authors: Z
authors: Ahmed
authors: From the Department of Endocrine Neoplasia and Hormonal Disorders.
authors: Yasmeen Q
authors: YQ
authors: Rizvi
authors: From the Department of Endocrine Neoplasia and Hormonal Disorders.
authors: Su-Chen
authors: SC
authors: Huang
authors: the Department of Biochemistry and Molecular Biology and Center for Biomolecular Structure and Function, and.
authors: John E
authors: JE
authors: Ladbury
authors: the Department of Neurosurgery.
authors: Oliver
authors: O
authors: Bogler
authors: the Department of Pathology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.
authors: Michelle D
authors: MD
authors: Williams
authors: From the Department of Endocrine Neoplasia and Hormonal Disorders.
authors: Gilbert J
authors: GJ
authors: Cote
authors: From the Department of Endocrine Neoplasia and Hormonal Disorders.
authors: Robert F
authors: RF
authors: Gagel
mesh_terms: D051701:Activating Transcription Factor 4 / Q000737:chemistry / Q000378:metabolism*; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D051096:Proto-Oncogene Proteins c-ret / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; C000715470:MAS1 protein, human; C498702:PMAIP1 protein, human; D047428:Protein Kinase Inhibitors; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051701:Activating Transcription Factor 4; D013912:Threonine; D051096:Proto-Oncogene Proteins c-ret; D002945:Cisplatin
keywords: Apoptosis; Thyroid; Transcription Regulation; Transcription Repressor; Tyrosine-Protein Kinase (Tyrosine Kinase); Ubiquitylation (Ubiquitination)