This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Keller, P. J. Articles by Cox, A. D. Search for Related Content PubMed PubMed Citation Articles by Keller, P. J. Articles by Cox, A. D.

Rac3-Mediated Transformation Requires Multiple Effector Pathways

Departments of ¹ Pharmacology, ² Biology, and ³ Radiation Oncology and ⁴ Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

Requests for reprints: Adrienne D. Cox, Department of Radiation Oncology, University of North Carolina at Chapel Hill, CB #7512, Chapel Hill, NC 27599-7512. Phone: 919-966-7713; Fax: 919-966-7681; E-mail: adrienne_cox{at}med.unc.edu.

Our initial characterization of Rac3, a close relative of the small GTPase Rac1, established its ability to promote membrane ruffling, transformation, and activation of c-jun transcriptional activity. The finding that Rac3 is transforming, and its similarity to Rac1, a protein that has a well-established connection to many processes important for cancer progression, prompted further investigation into Rac3 transformation. We used effector domain mutants (EDMs) to explore the relationship among Rac signaling, transformation, and effector usage. All Rac3 EDMs tested (N26D, F37L, Y40C, and N43D) retained the ability to promote membrane ruffling and focus formation. In contrast, only the N43D mutant promoted anchorage independence. This differs from Rac1, where both N26D and N43D mutants were impaired in both types of transformation. To learn more about the signaling pathways involved, we did luciferase reporter assays and glutathione S-transferase pull-down assays for effector binding. We found evidence for a functional link between activation of phospholipase Cß₂ by Rac3 and signaling to the serum response factor (SRF). Surprisingly, we also found that Rac3 binds poorly to the known Rac1 effectors mixed lineage kinases 2 and 3 (MLK2 and MLK3). Transcription of cyclin D1 was the only pathway that correlated with growth in soft agar. Our experiments show that activation of membrane ruffling and transcriptional activation of c-jun, SRF, or E2F are not sufficient to promote anchorage-independent growth mediated by Rac3. Instead, multiple effector pathways are required for Rac3 transformation, and these overlap partially but not completely with those used by Rac1.

This article has been cited by other articles:

				A. Hajdo-Milasinovic, S. I. J. Ellenbroek, S. van Es, B. van der Vaart, and J. G. Collard Rac1 and Rac3 have opposing functions in cell adhesion and differentiation of neuronal cells J. Cell Sci., February 15, 2007; 120(4): 555 - 566. [Abstract] [Full Text] [PDF]

				K. Kimura, K. Kawamoto, S. Teranishi, and T. Nishida Role of rac1 in fibronectin-induced adhesion and motility of human corneal epithelial cells. Invest. Ophthalmol. Vis. Sci., October 1, 2006; 47(10): 4323 - 4329. [Abstract] [Full Text] [PDF]