The ulcerative colitis risk gene adenylyl cyclase 7 restrains the T-helper 2 phenotype and Class II antigen presentation.

Background and aims: Genome-wide association studies have shown that the most risk-conferring genetic polymorphism for ulcerative colitis (UC) outside the human leukocyte antigen locus is the amino acid substitution p.Asp439Glu in the adenylyl cyclase 7 gene (ADCY7). ADCY7 is the main isoform in the hematopoietic system and produces the second messenger cyclic AMP (cAMP) downstream of G protein-coupled receptor signaling. Our aim was to determine the contribution of this polymorphism to UC risk by analyzing its effect on ADCY7 function in cell-based assays.

Methods: We characterized the p.Asp439Glu variant in cell lines using western blots, immunofluorescence, cAMP assay, and luciferase assay. We modeled this variant using siRNA knock-down in human primary CD4+ T cells and characterized them by RNA-seq, viability assay, flow cytometry, cAMP assay, and ELISA.

Results: The p.Asp439Glu variant is deficient in protein expression but retains membrane localization. This results in a 40% reduction in cAMP synthesis and luciferase reporter expression. Knock-down of ADCY7 in T cells reduces the expression of ribosomal proteins and cAMP signaling proteins, while skewing cytokine production toward a T-helper 2 pattern and upregulating antigen presentation accompanied by increased surface expression of major histocompatibility complex Class II and CD86.

Conclusions: The UC risk-conferring variant, p.Asp439Glu, in ADCY7 reduces cyclic AMP signaling, leading to modifications in cytokine profile and antigen presentation. Medications that enhance cyclic AMP by direct activation of ADCY7 or by phosphodiesterase inhibition may be beneficial in this disease.