The Small GTP-Binding Protein RhoA Regulates c-Jun by a ROCK-JNK Signaling Axis

This is the authors' abstract. We don't add key points for this paper.

RhoA regulates the actin cytoskeleton and the expression of genes associated with cell proliferation. This includes c-fos and c-jun, which are members of the AP1 family of transcription factors that play a key role in normal and aberrant cell growth. Whereas RhoA stimulates the c-fos SRE by a recently elucidated mechanism that is dependent on actin treadmilling, how RhoA regulates c-jun is still poorly understood. We found that RhoA stimulates c-jun expression through ROCK, but independently from the ability of ROCK to promote actin polymerization. Instead, we found that ROCK activates JNK, which then phosphorylates c-Jun and ATF2 when bound to the c-jun promoter. Thus, ROCK represents a point of signal divergence downstream from RhoA, as it promotes actin reorganization and the consequent expression from the c-fos SRE, while a parallel pathway connects ROCK to JNK, thereby stimulating c-jun expression. Ultimately, these pathways converge in the nucleus to regulate AP1 activity.