FIGURE 3.

SALM1 C-terminal domain regulates surface expression. A, sequence of SALM1 C-terminal region. Myc-SALM1 was truncated by inserting a stop codon at Lys-558 (S1MΔCT), Glu-608 (608 stop), Pro-680 (680 stop), Gly-691 (691 stop), Ala-704 (704 stop), Glu-716 (716 stop), Tyr-741 (741 stop), or Val-788 (S1Δ1), as indicated in the diagram. The motif responsible for intracellular retention is underlined. TM, transmembrane domain. B and C, representative immunofluorescent images of Myc-SALM1 deletion constructs transfected into HeLa cells. Surface staining was detected by anti-S1NT (Surface), and total SALM1 was detected using anti-Myc antibodies (Total). 691 stop is detected on the cell surface (B, last panel), whereas 704 stop is not (C, first panel), suggesting a putative retention motif between residues 691 and 704 (boxed region). Scale bar, 20 μm.