Bacterial RNA sensing by TLR8 requires RNase 6 processing and is inhibited by RNA 2'O-methylation

Area of Science:

• Immunology
• Molecular Biology
• RNA Biology

Background:

• Toll-like receptor 8 (TLR8) recognizes single-stranded RNA (ssRNA).
• RNase T2 and RNase A family members process ssRNA, releasing activating fragments.
• RNase 6 is highly expressed in monocytes but its role in TLR8 activation by bacterial RNA is unknown.

Purpose of the Study:

• To investigate the role of RNase 6 in TLR8 activation by bacterial RNA.
• To determine if RNase 6 processes bacterial RNA to generate TLR8-activating fragments.

Main Methods:

• Utilized BLaER1 cells and primary human monocytes with and without RNASE6 deficiency.
• Stimulated cells with bacterial RNA (bRNA) and live bacteria.
• Assessed TLR8-dependent responses.
• Treated bRNA with recombinant RNase 6.
• Investigated the effect of 2'O-RNA methyl modification on RNase 6 processing and TLR8 activation.

Main Results:

• Monocytes deficient in RNase 6 exhibited a reduced TLR8 response to bacterial RNA and live bacteria.
• Recombinant RNase 6 treatment generated TLR8-stimulating fragments from bacterial RNA.
• RNase 6 processing of bacterial RNA was impaired by 2'O-RNA methyl modification at the first uridine, dampening TLR8 stimulation.

Conclusions:

• RNase 6 plays a significant role in TLR8 activation by bacterial RNA.
• RNase 6 processes bacterial RNA into uridine-terminated fragments that activate TLR8.
• RNase 6 activity is modulated by RNA modifications like 2'O-methylation.