Noninvasive intracellular delivery of functional peptides and proteins

In order to probe intracellular signaling based on interactions of thousand s of proteins expressed in the living cell, new methods of noninvasive deli very of functional peptides and proteins to cells have been developed. Thes e include cellular import of peptides and proteins based on the cell-membra ne-permeable properties of the hydrophobic region of a signal peptide seque nce. The prototypical cell-permeable SN50 peptide, which contains the nucle ar localization signal sequence of NK-kappa B p50, has been applied in mult iple cell types to block nuclear import of this and other transcription fac tors. Further developments, including site-specific ligation of bipartite i mport peptides and production of import-competent recombinant proteins, pro vide the means for easy and rapid delivery of peptides and proteins to a wi de spectrum of cells in order to regulate intracellular pathways involved i n adhesion, signaling and trafficking to the nucleus.