Fig. 1.

Tryptophan aspartate-containing coat protein (TACO; also known as CORO1A or coronin-1) suppresses Toll-like receptor (TLR) signalling. The human promonocytic cell line (THP-1) cells were transfected with a luciferase reporter plasmid, p5×nuclear factor (NF)-κB-luc, and incubated for 48 h before the addition of Mycobacterium leprae (multiplicity of infection: 10) or peptidoglycan (PGN) (2 µg/ml). Luciferase activity was measured 12 h after stimulation (a). Western blot analysis of CORO1A protein levels in human embryonic kidney 293 (HEK293) cells transfected with a CORO1A expression plasmid and in THP-1 cells (control) demonstrated that the same amount of cellular protein was present in both cell types (b). HEK293 cells were transfected with a luciferase reporter plasmid, p5×NF-κB-luc (c), pGL3-control (d) or pGL3-h interferon (IFN)-β (e) along with the indicated human TLR expression plasmid (TLR-2, TLR-3 or TLR-4) in the presence or absence of the CORO1A expression plasmid. PGN, poly(IC) and lipopolysaccharide (LPS) were used as specific TLR-2, TLR-3 and TLR-4 ligands. Each ligand or tumour necrosis factor (TNF)-α was added 36 h after transfection, and luciferase activity was measured 12 h after ligand stimulation. The results are presented as relative promoter activity in which luciferase activity in the absence of the CORO1A expression plasmid was set to 1·0 (c,d,e). The graph shows the mean ± standard deviation. One asterisk (*) indicates a value of P < 0·05, two asterisks (**) indicate a value of P < 0·01.