Intraluminal Vesicles as Transfection Intermediaries

Area of Science:

• Molecular Biology
• Cell Biology
• Biotechnology

Background:

• Protein architecture-based transfection systems are explored to manage hepatotropic distribution and toxicity.
• Attenuated anthrax toxin (aATx) serves as a scaffold for a novel transfection system utilizing intraluminal vesicles (ILVs) for cytosolic delivery.
• Small interfering RNA (siRNA) attached to LFn-PKR is not a predicted substrate for the aATx translocase (protective antigen (PA)).

Purpose of the Study:

• To quantify the intracellular localization of siRNA delivered by aATx and correlate it with gene silencing activity.
• To investigate the role of ILVs in aATx-mediated cytosolic translocation of siRNA.
• To assess the efficacy of aATx-based siRNA delivery compared to traditional transfection methods.

Main Methods:

• Radioactive (32P-labeled) siRNA was used to track intracellular distribution after transfection with aATx in MCF-7 cells.
• Gene silencing efficacy was measured by targeting STAT3 gene expression via Western analysis.
• Inhibition of ILV formation using hypertonic sucrose or wheat germ agglutinin (WGA) was employed to study its effect on siRNA translocation.

Main Results:

• aATx-mediated transfection resulted in 77% ± 2.5% of cell-associated siRNA in the cytosol, compared to 45% ± 3.2% with Lipofectamine.
• aATx delivery led to a significant reduction in STAT3 expression (64.04% ± 14.17%).
• Inhibition of ILV formation by WGA (75.23% ± 0.06%) or sucrose (74.58% ± 7.76%) markedly reduced STAT3 gene knockdown.

Conclusions:

• The protective antigen (PA) pore insertion into endosomal membranes does not compromise membrane integrity, preventing vesicular bursting.
• Intraluminal vesicles (ILVs) play a critical role in the translocase activity of the aATx system.
• The aATx system demonstrates efficient cytosolic delivery of siRNA, leading to effective gene silencing, with ILVs being essential for this process.