Molecular and Cellular Biology

Ras Signaling Output

Science's STKE  22 Jan 2002:
Vol. 2002, Issue 116, pp. tw39
DOI: 10.1126/stke.2002.116.tw39

The small guanosine triphosphatase Ras transduces signals that regulate many diverse cellular processes, likely as a result of its dynamic interaction with various effector molecules. Wang et al. show that two effector proteins, Raf and Rin1, compete with each other to bind Ras in vitro and in vivo. Although activated Ras and its downstream effectors can induce cell transformation in fibroblasts, Ras-Rin1 interaction was antagonistic to this process. The protein 14-3-3 interacts with both Raf and Rin1. The authors further identify a serine residue in Rin1 that is critical for 14-3-3 interaction, and when mutated, allowed more Rin1 to localize to cellular membranes and activate Ras. In addition, protein kinase D (PKD) was shown to phosphorylate this serine residue in vitro. The authors propose that phosphorylation of Rin1 by PKD promotes interaction of Rin1 with 14-3-3. This could negatively regulate Rin1 by blocking its translocation to the membrane, thus preventing access by Ras. Ras interaction with Rin1 would otherwise block Raf activation and direct signaling through Rin1 downstream effectors.

Y. Wang, R. T. Waldron, A. Dhaka, A. Patel, M. M. Riley, E. Rozengurt, J. Colicelli, The RAS effector RIN1 directly competes with RAF and is regulated by 14-3-3 proteins. Mol. Cell. Biol. 22, 916-926 (2002). [Abstract] [Full Text]