The ups and downs of Src regulation: Tumor suppression by Cbp

Tight control of the tyrosine kinase activity of c-Src is critical for regulating its oncogenic potential. In a recent issue of Molecular Cell, Oneyama et al. (2008a) report that the membrane-bound adaptor protein Cbp (also known as PAG) can suppress c-Src-mediated cell transformation and tumorigenesis by binding and sequestering c-Src within lipid rafts. Cbp is also a raft-associated binding partner for Csk, a negative regulator of c-Src. However, the authors show that Cbp-mediated Src suppression is Csk independent. These findings suggest that Cbp is a tumor suppressor whose expression is downregulated during Src-driven cancer progression.