Inhibition of SALM4 clustering by an antibody to LRR. A,
Myc-SALM4 was transfected into HeLa cells, and surface expression was detected
using an antibody directed against the SALM leucine-rich repeats (anti-LRR).
Intracellular SALM4 was detected with anti-Myc (see Total). Surface
staining indicates that the LRR antibody recognizes SALM4 intercellular
clusters (arrowhead). B, HeLa cells transiently transfected
with Myc-SALM4 were treated for 24 h with antisera directed against the SALM
LRR or SALM4 C terminus (anti-S4CT), which served as a control. SALM4 surface
staining was detected by anti-Myc, and intracellular SALM4 was detected by
anti-S4CT antibodies. SALM4 cluster formation is largely inhibited by anti-LRR
(1:250). However, SALM4 surface clustering is not disrupted by application of
anti-S4CT (1:250). C, treatment of Myc-SALM4-transfected HeLa cells
with anti-Myc antibodies (1:1000) for 24 h enhances SALM4 clustering
(arrowheads). Anti-Myc antibodies also induce clustering of the SALM2
C terminus (arrowheads, bottom panel) in HeLa cells transfected with
full-length Myc-SALM2 (detected with anti-S2CT).