E3 Ubiquitin Ligases: Key Regulators of TGFβ Signaling in Cancer Progression

Transforming growth factor beta (TGF beta) is a secreted growth and differentiation factor that influences vital cellular processes like proliferation, adhesion, motility, and apoptosis. Regulation of the TGF beta signaling pathway is of key importance to maintain tissue homeostasis. Perturbation of this signaling pathway has been implicated in a plethora of diseases, including cancer. The effect of TGF beta is dependent on cellular context, and TGF beta can perform both anti- and pro-oncogenic roles. TGF beta acts by binding to specific cell surface TGF beta type I and type II transmembrane receptors that are endowed with serine/threonine kinase activity. Upon ligand-induced receptor phosphorylation, SMAD proteins and other intracellular effectors become activated and mediate biological responses. The levels, localization, and function of TGF beta signaling mediators, regulators, and effectors are highly dynamic and regulated by a myriad of post-translational modifications. One such crucial modification is ubiquitination. The ubiquitin modification is also a mechanism by which crosstalk with other signaling pathways is achieved. Crucial effector components of the ubiquitination cascade include the very diverse family of E3 ubiquitin ligases. This review summarizes the diverse roles of E3 ligases that act on TGF beta receptor and intracellular signaling components. E3 ligases regulate TGF beta signaling both positively and negatively by regulating degradation of receptors and various signaling intermediates. We also highlight the function of E3 ligases in connection with TGF beta's dual role during tumorigenesis. We conclude with a perspective on the emerging possibility of defining E3 ligases as drug targets and how they may be used to selectively target TGF beta-induced pro-oncogenic responses.

Automated summary

TGFβ is a crucial factor influencing cell growth and differentiation, playing a key role in maintaining tissue homeostasis. Disruption of the TGFβ signaling pathway is associated with various diseases, including cancer, and its effects are dependent on cellular context. Ubiquitination modification is an important mechanism influencing TGFβ signaling.