IL-20R2 mRNA and protein expression were detected from the skin of IL-20R2−/− mice. (a) Schematic diagrams of the IL-20R2 gene with intron/exon structures and primer locations for RT-PCR in the contest of the WT (left) and IL-20R2−/− (right) genetic loci. Seven exons (Exon 1–7) corresponding to the mRNA and protein-encoding domains of IL-20R2308 were indicated by gray rectangles. Known protein domains were marked by abbreviations: SS, signal peptide; FN, fibronectin-binding domain; P, primer binding site; UTR, untranslated region; TK-Neo, neomycin resistance gene under control of thymidine-kinase promoter. (b) Semi-quantitative RT-PCR analysis of IL-20R2 mRNA expression in the skin of WT and IL-20R2−/− BALB/c mice. DNA-free total RNA from the skin samples were reverse-transcribed followed by PCR using primer pairs as indicated. Although no IL-20R2 mRNA expression was seen in IL-20R2−/− mice with primers P1 and P3, which targeted the Exon I-containing transcript, IL-20R2 mRNA expression was detectable with primers P2 and P3, which targeted the Exon 2-containing transcripts. RPL-19 was used as internal control for equal RNA loading for the RT-PCR. (c) Fifty micrograms of total proteins from WT and IL-20R2−/− mouse skins were separated on non-reducing or reducing SDS-PAGE and analyzed by either western blot using mouse IL-20R2-specific antibody or in situ ligand affinity staining using mIL-24-AP. Antibody against GAPDH and AP alone were used as negative controls for equal sample loading and specificity in receptor binding, respectively. Non-reduced IL-20R2 protein was detectable in IL-20R2−/− mice, and the expression level appeared lower in IL-20R2−/− mice compared with WT mice.