Oncogenic RET Receptors Display Different Autophosphorylation Sites and Substrate Binding Specificities

doi:10.1074/jbc.271.10.5309

Oncogenic RET Receptors Display Different Autophosphorylation Sites and Substrate Binding Specificities (*)

From the (1)Departments of Biological Chemistry,
(2)Surgery, and
(3)Pathology, University of Michigan School of Medicine, Ann Arbor, Michigan 48109

^§ To whom correspondence should be addressed:
Dept. of Biological Chemistry, University of Michigan Medical School, Rm. 5416 Medical Science I, Ann Arbor, MI 48109-0606
. Tel.: 313-764-8154; Fax: 313-763-4581.

Abstract

The c-ret proto-oncogene encodes a receptor tyrosine kinase which plays an important role in neural crest as well as kidney development. Genetic studies have demonstrated that germ line mutations in the ret oncogene are the direct cause of multiple endocrine neoplasia (MEN) 2A and 2B, familial medullary thyroid carcinoma (FMTC), and Hirschsprung's disease. However, despite the large body of genetic and biological evidence suggesting the importance of RET in development and neoplastic processes, the signal transduction mechanisms of RET remain unknown. To begin to understand the molecular mechanisms of the disease states caused by mutations in RET, the patterns of autophosphorylation of the wild-type RET and the MEN mutants were studied using site-directed mutagenesis and phosphopeptide mapping. Among the 6 autophosphorylation sites found in the wild-type RET receptor, the MEN2B mutant lacked phosphorylation at Tyr-1096, leading to decreased Grb2 binding, while simultaneously creating a new phosphorylation site. These changes in autophosphorylation suggest that the MEN2B mutation may result in the more aggressive MEN2B phenotype by altering the receptor's signaling capabilities.

Footnotes

↵* This work was supported by the Cancer Research Foundation of America (to X. L.), the National Kidney Foundation (to Q. C. V.), NARSAD (to C. A. W.), American Cancer Society Grant VM-73A (to R. A. D.), National Institutes of Health Grants DK02176 (to R. A. D.) and DK18849 and DK18024 (to J. E. D.), and a grant from the Walther Cancer Institute (to J. E. D.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

FMTC

familial medullary thyroid carcinoma

MEN

multiple endocrine neoplasia

PAGE

polyacrylamide gel electrophoresis

GST

glutathione S-transferase.
- Received November 10, 1995.
- Revision received December 19, 1995.