An intracytoplasmic IL-10 receptor variant permits rapid reduction in STAT3 activation

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Two common variants in the interleukin-10 receptor 1 (IL10R1) gene, SNP3 (S138G) and SNP4 (G330R), are linked to diseases and considered loss-of-function alleles.
• The precise molecular mechanism of the G330R variant's impact remains unclear.

Purpose of the Study:

• To investigate the molecular consequences of the G330R variant on IL10R1 surface expression and signal transducer and activator of transcription (STAT) phosphorylation dynamics.
• To elucidate the role of the G330R mutation in the IL10R1 signaling pathway.

Main Methods:

• HeLa cells expressing wild-type (WT) or variant IL10R1 haplotypes were stimulated with interleukin-10 (IL-10).
• IL10R1 surface expression and STAT (STAT1 and STAT3) phosphorylation were analyzed following IL-10 stimulation, continuous incubation, and pulsed IL-10 treatment.
• Janus kinase 1 (JAK1) activation was also assessed.

Main Results:

• IL10R1 surface expression showed a significant reduction after IL-10 ligand binding, returning to baseline within 3-9 hours upon IL-10 pulse, irrespective of haplotype.
• STAT3 phosphorylation was rapid and sustained with continuous IL-10 in both WT and variant cells.
• However, STAT3 phosphorylation declined rapidly in cells expressing IL10R1-G330R upon IL-10 pulse, unlike WT or S138G variants. Similar dynamics were observed for STAT1 phosphorylation.
• No differences in JAK1 activation were detected between WT and variant IL10R1 cells.

Conclusions:

• The IL10R1-G330R variant does not affect IL10R1 surface expression dynamics.
• The G330R mutation specifically alters the duration of STAT phosphorylation, indicating its crucial role in stabilizing STAT signals.
• This suggests that the G330 position is critical for the sustained signaling output of the IL10R1 pathway.