Recently, we have proposed a new system of gene regulation called 'drug or gene delivery system responding to cellular signals' (D-RECS). In this system, transgene expression is activated in response to intracellular target protein kinases or proteases for safe, cell-specific gene delivery by using peptide-polymer conjugates. Here we applied this system to an intracellular Rho-associated coiled-coil kinase (ROCK) signal, which is activated abnormally in cardiovascular diseases. A ROCK responsive polymer consisting of neutral polymers in main chain and cationic ROCK substrate peptides in side chains was prepared and could form the complex with plasmid DNA. The complex was transferred into NIH3T3 cells with or without L-α-lysophosphatidic acid (LPA) that increases ROCK activity. At an N/P ratio of 2.0, a significant increase of the gene expression was identified in LPA-treated NIH3T3 cells, but was disappeared in NIH3T3 cells treated with ROCK specific inhibitor, Y-27632. These results suggest that the ROCK responsive polymer can regulate gene expression in response to ROCK activity.
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