N-terminus-mediated dimerization of ROCK-I is required for RhoE binding and actin reorganization.
ROCK-I (Rho-associated kinase 1) is a serine/threonine kinase that can be activated by RhoA and inhibited by RhoE. ROCK-I has an N-terminal kinase domain, a 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. In the present study, 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.
Garg
Ritu
R
Ludwig Institute for Cancer Research, Royal Free and University College School of Medicine, 91 Riding House Street, London W1W 7BS, UK.
Riento
Kirsi
K
Keep
Nicholas
N
Morris
Jonathan D H
JD
Ridley
Anne J
AJ
D000199:Actins / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000378:metabolism; D019281:Dimerization; D010766:Phosphorylation; D011485:Protein Binding; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins