Polyethylenimine-graft-chitosan (PEI-g-chitosan) was synthesized by performing cationic polymerization of aziridine in the presence of water-soluble oligo-chitosan (M(n) = 3400). The absolute molecular weight and chemistry of the PEI-g-chitosan obtained were characterized using GPC, 13C and 1H NMR, respectively. The results indicated that all the amines of chitosan were grafted with oligo-PEI, and the average length of the oligo-PEI side chains was determined by the feed molar ratio of aziridne/amine in chitosan. PEI-g-chitosan of M(n) = 7400 with a polydispersity index (PDI) of 1.50, and PEI side chains of M(n) = 206 was prepared for gene delivery. Gel electrophoresis showed that DNA migration was retarded completely at a N/P ratio of 2.5/1, indicating good DNA condensation capability of PEI-g-chitosan. The sizes and the zeta-potentials of the complexes of PEI-g-chitosan/DNA were characterized. The cytotoxicity of PEI-g-chiotsan was evaluated, and the results reflected that PEI-g-chitosan had a lower cytotoxicity than PEI (25 K). Gene transfection efficiency of PEI-g-chitosan in HepG2, HeLa, and primary hepatocytes cells and after administration in the common bile duct of rat liver was determined. Remarkably, PEI-g-chitosan showed a higher transfection efficiency than that of PEI (25 K) both in vitro and in vivo. The systematic distribution and the distribution in liver of the gene expression of the complexes of PEI-chitosan/DNA were determined as well.

Integrin-mediated focal adhesions connect the extracellular matrix and cytoskeleton to regulate cell responses, such as migration. Protein tyrosine phosphatase ␣ (PTP␣) regulates integrin signaling, focal adhesion formation, and migration, but its roles in these events are incompletely understood. The integrin-proximal action of PTP␣ activates Src family kinases, and subsequent phosphorylation of PTP␣ at Tyr789 acts in an unknown manner to promote migration. PTP␣-null cells were used in reconstitution assays to distinguish PTP␣-Tyr789-dependent signaling events. This showed that PTP␣-Tyr789 regulates the localization of PTP␣ and the scaffolding protein Cas to adhesion sites where Cas interacts with and is phosphorylated by Src to initiate Cas signaling. Linking these events, we identify BCAR3 as a molecular connector of PTP␣ and Cas, with phospho-Tyr789 PTP␣ serving as the first defined cellular ligand for the BCAR3 SH2 domain that recruits BCAR3-Cas to adhesions. Our findings reveal a novel role of PTP␣ in integrin-induced adhesion assembly that enables Src-mediated activation of the pivotal function of Cas in migration.