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358 Cell-Penetrating Peptides: Processes and Applications
valent display of functional domains leads to enhanced binding avidity and functional
capacity, as compared to linear PPL analogs. These synthetic peptides penetrate cells
and locate in the nucleus. At 4°C, loligomers do not enter the cells, but rather
associate with plasma membranes. 79 Interestingly, inhibitors of ATP synthesis, like
2-deoxyglucose and Na-azide, did not inhibit uptake of loligomers, leaving the type
of uptake uncovered.
Conjugation of NLS sequences directs loligomers to the nucleus. Such constructs
have been successfully used in gene transfer in vitro. Singh et al. 80 have demonstrated
the use of loligomer 4 in transmembrane delivery of various plasmids. Loligomer 4
contains 8 NLS derived from SV40 large T antigene and eight pentalysine stretches.
16.5 CONCLUSIONS
Current developments in genomic research will rapidly lead to expansion in identification
of defective genes causing a variety of diseases and disclose numerous novel
therapeutic targets. Treatment of such diseases may include strategies ranging from
gene delivery and replacement to antisense approaches. For the foreseeable future,
the development of a nontoxic, easy-to-make, high-efficient vector should remain a
major focus of ongoing research. Several reports reviewed here demonstrate successful
applications of CPPs as nucleic acid delivery vehicles in various test systems.
It seems that these vectors are powerful ON and gene delivery tools, often transcending
the efficiency, in terms of gene transfer and integration (up to >99%), of
other common transfection vectors.
ABBREVIATIONS
Ac acetyl
APP amyloid precursor protein
CD circular dichroism
CPP cell-penetrating peptide
ds double stranded
EGFP enhanced green fluorescent protein
FACS fluorescence activated cell sorting
FISH fluorescent in situ hybridization
LDL low density lipoprotein
MPM membrane-permeable motif
MTS membrane translocating sequence
NLS nuclear localization signal
ODN oligodeoxynucleotide
ON oligonucleotide
pAntp antennapedia peptide
PLL poly-lysine
PNA peptide nucleic acid
pVEC peptide from vascular endothelial cadherin
RT-PCR reverse transcriptase polymerase chain reaction
S–S disulphide bond