Targeting of zyxin to sites of actin membrane interaction and to the nucleus

The localization of proteins to particular intracellular compartments often regulates their functions. Zyxin is a LIM protein found prominently at sit es of cell adhesion, faintly in leading lamellipodia, and transiently in ce ll nuclei. Here we have performed a domain analysis to identify regions in zyxin that are responsible for targeting it to different subcellular locati ons. The N-terminal proline-rich region of zyxin, which harbors binding sit es for alpha -actinin and members of the Ena/VASP family, concentrates in l amellipodial extensions and weakly in focal adhesions. The LIM region of zy xin displays robust targeting to focal adhesions. When overexpressed in cel ls, the LIM region of zyxin causes displacement of endogenous zyxin from fo cal adhesions. Upon mislocalization of full-length zyxin, at least one memb er of the Ena/VASP family is also displaced, and the organization of the ac tin cytoskeleton is perturbed. Zyxin also has the capacity to shuttle betwe en the nucleus and focal adhesion sites. When nuclear export is inhibited, zyxin accumulates in cell nuclei. The nuclear accumulation of zyxin occurs asynchronously with approximately half of the cells exhibiting nuclear loca lization of zyxin within 2.3 h of initiating leptomycin B treatment. Our re sults provide insight into the functions of different zyxin domains.