Figure 3. An alternatively spliced STING isoform with 3 TM domains localizes in the plasma membrane of mouse splenocytes.

(A) Predicted exon structure and schematic of the functional domains in the C-terminus of mouse Tmem173 transcript variants based on NCBI’s GENE database. (B) Different STING isoforms were detected by immunoblotting in splenocytes from 3 individual C57BL/6 mice. (C) Two STING isoforms with a different N-terminus were detected by reverse transcription PCR (RT-PCR) in mouse spleen and thymus. (D) Predicted plasma membrane topology of detected mouse STING isoforms. (E) B16^{Tmem173–/–} cells transfected with erSTING-EGFP, pmSTING-EGFP, or EGFP were incubated with the indicated antibodies and then washed and lysed. Immunoblotting was performed to detect IgG in the cell lysate using a secondary antibody against rabbit IgG. (F and G) B16^{Tmem173–/–} cells were transfected with erSTING-Flag, pmSTING-Flag, or a vector plasmid, respectively. An antibody against Flag was used to detect Flag projecting outside cells using immunofluorescence (F) and flow cytometry (G), respectively. Scale bars: 20 μm.