Nod2-Nodosome in a Cell-Free System: Implications in Pathogenesis and Drug Discovery for Blau Syndrome and Early-Onset Sarcoidosis

Figure 2

Construction of Nod2-nodosome containing the BS/EOS-associated mutation in a cell-free system. Synthetic protein-protein interactions were detected by pull-down assay and amplified luminescent proximity homogeneous assay (ALPHA). (a) Biotinylated-Nod2-WT (Nod2-WT-Btn) and 1 μg FLAG-tagged RICK-WT (FLAG-RICK-WT) lysed in 300 μL NP-40 buffer were precipitated with 20 μL streptavidin-conjugated agarose beads with or without MDP. The precipitations were subjected to SDS-PAGE and immunoblotting. Detection on the blotting membranes was performed using anti-FLAG mAb M2 or anti-Nod2 mAb. (b) A total of 100 ng of each protein indicated was incubated with 5 μg/mL anti-FLAG mAb M2, 16.67 μg/mL protein-A-conjugated ALPHA acceptor beads, and 16.67 μg/mL streptavidin-conjugated ALPHA donor beads for 24 hours, with or without 5.33 mg/mL MDP or 5 mg/mL N-Acetylmuramyl-D-Alanyl-D-Isoglutamine (MDP-D-isomer). Responses (counts) were measured using the EnSpire™ Multimode Plate Reader. (c) Activation of Nod2-nodosome in a cell-free system by MDP degradation components. Interactions between Nod2-WT-Btn and FLAG-RICK-WT were detected by ALPHA. A total of 100 ng of Nod2-WT-Btn and FLAG-RICK-WT were incubated with 5 μg/mL anti-FLAG mAb M2, 16.67 μg/mL protein-A-conjugated ALPHA acceptor beads and 16.67 μg/mL streptavidin-conjugated ALPHA donor beads for 24 hours, without or with 5.33 mg/mL MDP, 5.33 mg/mL MDP (D-isomer), 5.33 mg/mL N-acetylglucosamine (GlcNAc), 5.33 mg/mL L-alanine (L-Ala), or 5.33 mg/mL D-isoglutamine (D-isoGlu). Responses (counts) were measured using the EnSpire Multimode Plate Reader. The results are representative of three independent experiments and given as means ± standard deviation from triplicate wells. (d) A total of 100 ng of Nod2-WT-Btn, or Nod2-R334W-Btn, or Nod2-N670K-Btn with FLAG-RICK-WT was incubated with 5 μg/mL anti-FLAG mAb M2, 16.67 μg/mL protein-A-conjugated ALPHA acceptor beads, and 16.67 μg/mL streptavidin-conjugated ALPHA donor beads for 24 hours, with or without 5.33 mg/mL or 13.33 mg/mL MDP or 13.33 mg/mL MDP-D-isomer. The results are representative of three independent experiments and given as means ± standard deviation from triplicate wells. CARD, caspase recruitment domain; MDP, muramyl dipeptide; WT, wild-type; P, precipitation; WB, western blot. value < 0.05 and value < 0.01 were considered statistically significant using Student’s -test.

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