Trends in Cell Biology
Volume 10, Issue 7, 1 July 2000, Pages 290-295
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Review
Protein transduction: unrestricted delivery into all cells?

https://doi.org/10.1016/S0962-8924(00)01771-2Get rights and content

Abstract

Several proteins can traverse biological membranes through protein transduction. Small sections of these proteins (10–16 residues long) are responsible for this. Linking these domains covalently to compounds, peptides, antisense peptide nucleic acids or 40-nm iron beads, or as in-frame fusions with full-length proteins, lets them enter any cell type in a receptor- and transporter-independent fashion. Moreover, several of these fusions, introduced into mice, were delivered to all tissues, even crossing the blood–brain barrier. These domains thus might let us address new questions and even help in the treatment of human disease.

Section snippets

Producing PTD-linked molecules

We do not have to understand the mechanism of transduction to appreciate its potential to mediate the delivery of almost any molecule into cells. There currently appears to be no restriction on the type of molecule that can be transduced into cells when covalently attached to a PTD: compounds, peptides, oligonucleotides, peptide nucleic acids and full-length proteins, including antibodies, enzymes and sequestering proteins, have all been transduced14, 15, 17, 18, 19, 20, 21, 22. Undoubtedly,

Applications to cells in culture

PTD-linked peptides and proteins can be transduced into cells simply by adding them to the tissue-culture medium. The constructs are internalized in a rapid, concentration-dependent manner that achieves maximum intracellular concentration in less than 15 min16, 22. Normally, final media concentrations of 25–200 nm provide biological activity, although concentrations in excess of 1 μm can be used.

TAT-mediated transduction provides several advantages over DNA transfection, the current standard

In vivo protein transduction: delivery into model organisms

As with any potential pharmacological approach, one must translate in vitro findings to animal models. Can PTDs deliver molecules into cells of entire organisms? Based on past and recent studies in model organisms, the answer is yes. In 1994, Fawell et al.15 demonstrated a limited but significant capacity of TAT fusions to enter tissues in vivo in mice. Schutze-Redelmeier et al.31 showed that intraperitoneal injection of an Antp–antigenic-peptide fusion activated endogenous T cells in mice, and

Engineering transducing molecules to combat human disease

An effective drug must be active only in the diseased cell. As transducing proteins can readily enter all cell types, specificity must be built into the molecule. The following are examples of how transducing molecules can be constructed to elicit their effects in specific cell populations.

Chemotherapy agents must be able to kill tumour cells selectively while leaving normal cells unharmed. This was accomplished by Chen et al.24, who fused the Antp PTD to a peptide domain that serves as a

Future directions and considerations

Although unrestricted access of proteins into cells is now possible, we have a poor grasp of how this technology works. Based on the whole-animal studies, all cells appear to be susceptible to protein transduction. At the molecular level, it is unclear how proteins behave when interacting with the cell membrane or if any particular molecule (such as a specific phospholipid) is necessary to mediate entry. From the limited data currently available, transduction across the cellular membrane is

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