[Probing of the target molecules of Rho-kinase and its function in neuronal cells]

Genome project terminated and post-genome project started, one of which aim is to understand the function and its regulation mechanism(s) of the molecules in living cells. Protein phosphorylation is one of the most common reactions responsive to extracellular stimulants. It is well understood about the involvement of Rho/Rho-kinase and Cdc42/p21-activated kinase (PAK) in the functions of muscle and non-muscle cells, but in neuronal cells little or poorly is understood. This is due to poor evidences about the target molecules of Rho-kinase and PAK and its functions in neuronal cells. We have revealed using a phosphorylation site-specific antibody that PAK targets synapsin Ia at Ser603 in vitro and in neuronal cells in culture, which is recognized as CaMKII site. This is reasonable, because the 600RQAS603 around Ser603 is also consensus motif for the phosphorylation of PAK and Rho-kinase besides CaMKII. Like this, we have tried to define the target molecules of Rho-kinase in neuronal cells. In this symposium, I would present that both Rho-kinase and PAK target MARCKS at Ser159 in vitro and in neuronal cells stimulated with LPA and bradykinin, respectively. Moreover, we would address the role of phosphorylation of MARCKS at Ser159 in neuronal functions.