INTRACELLULAR REGULATION OF MACROMOLECULES USING PH-SENSITIVE LIPOSOMES AND NUCLEAR-LOCALIZATION SIGNAL - QUALITATIVE AND QUANTITATIVE-EVALUATION OF INTRACELLULAR TRAFFICKING

The objective of this study is to present a rational strategy to targe t macromolecules to the nucleus via the endocytic pathway. The two maj or barriers in this route to the nucleus are known as endosomal escape and nuclear transport. pH-sensitive liposomes were used in order to a chieve endosomal escape under the conditions of low pH in endosomes. B ovine serum albumin (alb) served as a model compound to be delivered t o nucleus and was encapsulated into the pH-sensitive Liposomes. The li posomes are composed of dioleoyl phosphatidyl ethanolamine: cholestery lhemisuccinate. They were taken up by rat peritoneal macrophages via e ndocytosis and subsequently underwent degradation, principally by lyso somal enzymes. By using pH-sensitive liposomes, intracellular degradat ion was reduced by a significant extent, as expected, via endosomal es cape. Cytosolic delivery of FITC-labelled alb was also detected by con focal microscopy. Selective targeting to the nucleus was performed by adding the nuclear localization signal (NLS) of the SV-40 large T anti gen to the FITC-alb, which were then encapsulated into the pH-sensitiv e liposomes, Confocal microscopy revealed that FITC-alb, in the presen ce of NLS was successfully delivered into nucleus, while no transport was observed in the absence of NLS. These results provide a useful str ategy for the nuclear targeting of macromolecules using pH-sensitive L iposomes in conjunction with NLS, (C) 1998 Academic Press.