Interaction of the Ras-Related Protein Associated with Diabetes Rad and the Putative Tumor Metastasis Suppressor NM23 Provides a Novel Mechanism of GTPase Regulation

• Published in: Proceedings of the National Academy of Sciences - PNAS 1999-12, Vol.96 (26), p.14911-14918
• Main Authors: Zhu, Jianhua, Tseng, Yu-Hua, Kantor, Jason D., Rhodes, Christopher J., Zetter, Bruce R., Moyers, Julie S., Kahn, C. Ronald
• Format: Article
• Language: English
• Subjects: Animals; Antibodies; Biological Sciences; Cell growth; Cell lines; Cellular biology; Diabetes; Diabetes Mellitus - metabolism; DNA - biosynthesis; Drosophila; Enzyme Activation; Gene expression regulation; Genes, Tumor Suppressor; Genetic mutation; Glucose - metabolism; GTP Phosphohydrolases - metabolism; GTPase-activating protein; Guanosine Triphosphate - metabolism; Humans; Hydrolysis; Immediate-Early Proteins - metabolism; Melanoma; Models, Biological; Monomeric GTP-Binding Proteins - genetics; Monomeric GTP-Binding Proteins - metabolism; Neoplasm Metastasis - genetics; nm23 gene; NM23 Nucleoside Diphosphate Kinases; Nucleoside-Diphosphate Kinase - genetics; Nucleoside-Diphosphate Kinase - metabolism; Nucleotides; Physiological regulation; Protein Binding; Proteins; Rad gene; Rad protein; ras Proteins - metabolism; Rats; Rats, Sprague-Dawley; Transcription Factors - genetics; Transcription Factors - metabolism; Tumors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.96.26.14911

Rad is the prototypic member of a new class of Ras-related GTPases. Purification of the GTPase-activating protein (GAP) for Rad revealed nm23, a putative tumor metastasis suppressor and a development gene in Drosophila. Antibodies against nm23 depleted Rad-GAP activity from human skeletal muscle cytosol, and bacterially expressed nm23 reconstituted the activity. The GAP activity of nm23 was specific for Rad, was absent with the S105N putative dominant negative mutant of Rad, and was reduced with mutations of nm23. In the presence of ATP, GDP-Rad was also reconverted to GTP-Rad by the nucleoside diphosphate (NDP) kinase activity of nm23. Simultaneously, Rad regulated nm23 by enhancing its NDP kinase activity and decreasing its autophosphorylation. Melanoma cells transfected with wild-type Rad, but not the S105N-Rad, showed enhanced DNA synthesis in response to serum; this effect was lost with coexpression of nm23. Thus, the interaction of nm23 and Rad provides a potential novel mechanism for bidirectional, bimolecular regulation in which nm23 stimulates both GTP hydrolysis and GTP loading of Rad whereas Rad regulates activity of nm23. This interaction may play important roles in the effects of Rad on glucose metabolism and the effects of nm23 on tumor metastasis and developmental regulation.