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The proteasome metabolizes peptide-mediated nonviral gene delivery systems
Journal article   Peer reviewed

The proteasome metabolizes peptide-mediated nonviral gene delivery systems

J KIM, C.-P CHEN and K. G RICE
Gene therapy, Vol.12(21), pp.1581-1590
2005
DOI: 10.1038/sj.gt.3302575
PMID: 16034460

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Abstract

The proteasome is a multisubunit cytosolic protein complex responsible for degrading cytosolic proteins. Several studies have implicated its involvement in the processing of viral particles used for gene delivery, thereby limiting the efficiency of gene transfer. Peptide-based nonviral gene delivery systems are sufficiently similar to viral particles in their size and surface properties and thereby could also be recognized and metabolized by the proteasome. The present study utilized proteasome inhibitors (MG 115 and MG 132) to establish that peptide DNA condensates are metabolized by the proteasome, thereby limiting their gene transfer efficiency. Transfection of HepG2 or cystic fibrosis/T1 (CF/T1) cells with CWK18 DNA condensates in the presence of MG 115 or MG 132 resulted in significantly enhanced gene expression. MG 115 and MG 132 increased luciferase expression 30-fold in a dose-dependent manner in HepG2 and CF/T1. The enhanced gene expression correlated directly with proteasome inhibition, and was not the result of lysosomal enzyme inhibition. The enhanced transfection was specific for peptide DNA condensates, whereas Lipofectamine- and polyethylenimine-mediated gene transfer were significantly blocked. A series of novel gene transfer peptides containing intrinsic GA proteasome inhibitors (CWK18(GA)n, where n=4, 6, 8 and 10) were synthesized and found to inhibit the proteasome. The gene transfer efficiency mediated by these peptides in four different cell lines established that a GA repeat of four is sufficient to block the proteasome and significantly enhance the gene transfer. Together, these results implicate the proteasome as a previously undiscovered route of metabolism of peptide-based nonviral gene delivery systems and provide a rationale for the use of proteasome inhibition to increase gene transfer efficiency.
 Biotechnology Gene Therapy Fundamental and applied biological sciences. Psychology Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy Health. Pharmaceutical industry Industrial applications and implications. Economical aspects Transfusions. Complications. Transfusion reactions. Cell and gene therapy Applied cell therapy and gene therapy Biological and medical sciences Medical sciences

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