Inhibition of gene expression in Escherichia coli by antisense phosphorodiamidate morpholino oligomers

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Research

Background:

• Antisense phosphorodiamidate morpholino oligomers (PMOs) are investigated for gene expression inhibition.
• The outer membrane of Escherichia coli presents a barrier to PMO entry.
• Previous studies showed limited success of PMOs in Gram-negative bacteria.

Purpose of the Study:

• To evaluate the efficacy of PMOs in inhibiting gene expression in Escherichia coli.
• To assess the role of the bacterial outer membrane in PMO transport.
• To determine if peptide conjugation enhances PMO delivery and activity.

Main Methods:

• Testing PMOs targeting reporter genes (luciferase) and essential genes (16S rRNA, acpP, lacI) in E. coli.
• Utilizing an E. coli lpxA mutant with a defective outer membrane to assess PMO entry.
• Synthesizing and testing peptide-conjugated PMOs, including (KFF)(3)KC-PMO and CRRRQRRKKR-PMO conjugates.
• Quantifying gene inhibition and reporter gene activity (luciferase, beta-galactosidase) in response to PMO treatment.

Main Results:

• Unconjugated PMOs showed minimal inhibition in wild-type E. coli but significant inhibition in the lpxA mutant.
• Covalent attachment of the peptide (KFF)(3)KC to PMOs significantly enhanced gene inhibition in wild-type E. coli.
• (KFF)(3)KC-PMO conjugates demonstrated dose-dependent inhibition of target mRNA (luciferase, lacI).
• The conjugation site of the peptide influenced PMO efficiency, and a different peptide (CRRRQRRKKR) did not enhance activity.

Conclusions:

• The outer membrane of E. coli restricts the cellular entry of unconjugated PMOs.
• (KFF)(3)KC-PMO conjugates efficiently cross bacterial membranes and specifically inhibit target gene expression.
• Peptide conjugation represents a promising strategy for delivering antisense oligonucleotides into Gram-negative bacteria.