GPR110 transcripts and isoform 1 polypeptide. (A) Schematic of the four human GPR110 transcript isoforms, as gleaned from the UCSC genome web browser (chromosome 6, March 2006 version of the hg18 assembly). Isoform 1 encodes the full-length protein containing 14 exons. Isoform 2 contains an alternative splicing of exon 6 to exon 7a. Locations of in frame stop codons are shown for isoforms 3 and 4. (B) Relative expression of GPR110 isoforms 1-3 in human cell line PC-3. Transcript levels of isoforms 1 through 3 were measured by SYBR qPCR. Expression values were calculated relative to isoform 3 expression. Although qPCR analysis of the three GPR110 isoforms was done on the three prostate cells lines mentioned, as well as the three lung cell lines used in this study (A549, H460 and H23), we detected Isoform 2 only in PC-3 and LNCaP; and Isoform 3 only in PC-3. Thus, the data for all 3 isoforms are shown only for PC-3. (C) Schematic representation of the primary polypeptide structure of GPR110. SEA, SEA domain; GSIVA, amino acid sequence with potential for cleavage; GPS, GPS domain, with predicted cleavage at amino acid sequence HLT; 7TM, seven-span transmembrane domain. Blue triangles, predicted cleavage sites in the SEA and GPS domains; red triangles, locations of HA tags in isoform 1. Scale indicates peptide size, in kiloDaltons (kD).