A multi-domain protein for β1 integrin-tangeted DNA delivery

Department of Cell Biology, Erasmus University, Rotterdam, The Netherlands.
Gene Therapy (Impact Factor: 3.1). 10/2000; 7(17):1505-15. DOI: 10.1038/
Source: PubMed


The development of effective receptor-targeted nonviral vectors for use in vivo is complicated by a number of technical problems. One of these is the low efficiency of the conjugation procedures used to couple protein ligands to the DNA condensing carrier molecules. We have made and characterized a multi-domain protein (SPKR)4inv, that is designed to target plasmid DNA to beta1 integrins in remodeling tissue. It contains a nonspecific DNA-binding domain (SPKR)4, a rigid alpha-helical linker, and the C-terminal beta1 integrin binding domain (aa 793-987) of the Yersinia pseudotuberculosis invasin protein. (SPKR)4inv could be purified at high yields using a bacterial expression system. We show that (SPKR)4inv binds with high affinity to both plasmid DNA and beta1 integrins. In a cell attachment assay, the apparent affinity of (SPKR)4inv for beta1 integrins is three orders of magnitude higher than that of the synthetic peptide integrin ligand RGDS. (SPKR)4inv-plasmid complexes are not active in an in vitro transfection assay. However, transfection efficiencies of plasmid complexes with a cationic lipid micelle (DOTAP/Tween-20) or a cationic polymer (polyethylenimine), are significantly increased in combination with (SPKR)4inv. (SPKR)4inv-mediated transfection can be inhibited by a soluble form of beta1 integrin, which is evidence for its receptor specificity. In conclusion, (SPKR)4inv allows beta1 integrin-specific targeting of plasmid-carrier complexes, while avoiding inefficient and cumbersome coupling chemistry. The modular design of the expression vector allows production of similar multi-domain proteins with a different affinity. The further development of such complexes for use in vivo is discussed.

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    • "This has important consequences for the engineering of tissue supports that, to date, generally involves RGD conjugation to polymers in a random distribution or non-specific adsorption of collagen or fibronectin (Rowley et al 1999; Tan et al 2001; Yang et al 2001). Similarly, recombinant proteins and polypeptides binding integrin for targeted gene delivery via receptor-mediated endocytosis have focussed on monovalent RGD and invasin ligands, extended by cationic polypeptides binding DNA (Harbottle et al 1998; Fortunati et al 2000; Kunath et al 2003). As our understanding of integrin–ligand binding advances, it would appear timely to explore alternative polypeptide templates facilitating a clustered organisation of RGD ligands. "
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