Inhibition of ras-induced germinal vesicle breakdown in Xenopus oocytes by rap-1B.
A cDNA clone (Krev-1) has recently been identified that possesses the ability to reverse the transformed phenotype when introduced into a K-ras-transformed NIH/3T3 cell line. The Krev-1 protein, also known as rap-1A, was found to share 50% homology with the ras proteins. The rap-1A protein has also been shown to block the interaction of ras with its GTPase activating protein in vitro, leading to speculation regarding its role in vivo. A closely related protein, rap-1B, has also been identified in platelets, human erythroleukemia cells, neutrophils, and aortic smooth muscle cells. Unlike rap-1A, rap-1B has been shown to be phosphorylated in platelets. Given the high degree of similarity between the amino acid sequences of rap-1A and rap-1B, we sought to investigate the effect of microinjected rap-1B on H-ras(Val12)-induced germinal vesicle breakdown in Xenopus laevis oocytes. In this assay system, equimolar concentrations of rap-1B were found to block germinal vesicle breakdown triggered by the oncogenic ras protein. However, in the presence of IGF-1, this inhibition was not observed. Moreover, rap-1B is readily phosphorylated in the oocytes.
Campa
M J
MJ
Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, NC 27709.
Chang
K J
KJ
Molina y Vedia
L
L
Reep
B R
BR
Lapetina
E G
EG
D000818:Animals; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics*; D006801:Humans; D006868:Hydrolysis; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism; D015689:Oncogene Protein p21(ras) / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D014170:Transformation, Genetic; D014407:Tumor Cells, Cultured; D014982:Xenopus laevis / Q000235:genetics*; D020668:rap GTP-Binding Proteins
D007334:Insulin-Like Growth Factor I; D019204:GTP-Binding Proteins; D015689:Oncogene Protein p21(ras); D020668:rap GTP-Binding Proteins