PTD–DRBD siRNA Delivery
A major hurdle in drug delivery today is for the drug to reach inside the cell to exert its biological effect. Many drug candidates are hydrophilic and are therefore not able to cross the hydrophobic plasma membrane, which serves to protect the cell from foreign molecules and pathogens. One promising drug candidate is the hydrophilic and negatively charged short-interfering RNA (siRNA), known to degrade target mRNA 1,000-fold more efficiently than small molecule drugs. The delivery capacity of small cationic peptides called protein transduction domains or cell-penetrating peptides, suggested them to be suitable delivery vehicles for siRNA. However, it has proven troublesome to utilize the PTD–siRNA conjugates for mRNA degradation due to the characteristics of siRNA, often resulting in precipitation and aggregation. This chapter describes a recently reported delivery strategy, PTD–DRBD fusion protein siRNA delivery, where a double-stranded RNA-binding domain expressed as a fusion protein together with three TAT PTDs binds the siRNA, thus masking the negatively charged backbone and preventing aggregation. This new protocol results in noncytotoxic mRNA degradation even more effective than lipofection.
Key wordsCPP PTD siRNA RNAi Double-stranded RNA binding domain
C.P.-A. was funded by a Knut & Alice Wallenberg’s Foundation Research Fellowship. A.E. was funded by a JSPS Research Fellowships for Young Scientists. This work was supported by the Leukemia and Lymphoma Society, the Pardee Foundation, California Institute of Regenerative Medicine, and Howard Hughes Medical Institute.
- 1.Frankel, A. D. and Pabo, C. O. (1988) Cellular uptake of the tat protein from human immunodeficiency virus. Cell 55, 1189–1193.Google Scholar