N-terminus-mediated dimerization of ROCK-I is required for RhoE binding and actin reorganization

Ritu Garg , Kirsi Riento , Nicolas H Keep , Jonathan Dh Morris , Anne J Ridley (1)

1 Randall Division of Cell and Molecular Biophysics

ROCK-I is a serine/threonine kinase that can be activated by RhoA and inhibited by RhoE. ROCK-I has an N-terminal kinase domain, central coiled-coil region, and a RhoA-binding domain near the C-terminus. We have previously shown that RhoE binds to the N-terminal 420 amino acids of ROCK-I, which includes the kinase domain as well as N-terminal and C-terminal extensions. Here, we show that N-terminus-mediated dimerization of ROCK-I is required for RhoE binding. The central coiled-coil domain can also dimerize ROCK-I in cells, but this is insufficient in the absence of the N-terminus to allow RhoE binding. The kinase activity of ROCK-I 1-420 is required for dimerization and RhoE binding, however, inclusion of part of the coiled-coil domain compensates for lack of kinase activity, allowing RhoE to bind. N-terminus-mediated dimerization is also required for ROCK-I to induce the formation of stellate actin stress fibres in cells. These results indicate that dimerization via the N-terminus is critical for ROCK-I function in cells and for its regulation by RhoE.

Mots clés: Life Sciences

Ritu Garg, Kirsi Riento, Nicolas H Keep, Jonathan Dh Morris, Anne J Ridley. N-terminus-mediated dimerization of ROCK-I is required for RhoE binding and actin reorganization. Biochemical Journal, 2008, 411 (2), pp.407-414. ⟨10.1042/BJ20071342⟩. ⟨hal-00478888⟩