(A–C) Immunofluorescent images show colocalization of CEACAM16 (A, green, polyclonal anti-V5) with α-tectorin (B, red, anti-myc) in OK cells cotransfected with myc-Tecta+V5-Ceacam16. Images are merged in C. (Scale bar: 24 μm.) (D–H) Coimmunoprecipitation experiments. Cell lysates (input) and eluted proteins (output) were separated on 4–20% gradient gel. Anti-V5, anti-myc, anti-oncomodulin, anti-Flag, and anti-GFP were used to identify CEACAM16, α-tectorin, oncomodulin, CEACAM1, and prestin. (D and E) A plasmid encoding CEACAM16 was cotransfected into OK cells with GFP-prestin (CEACAM16+GFP-prestin) and Tecta (CEACAM16+Tecta) plasmids, respectively. CEACAM16 is pulled down with 2 μg of anti-V5/protein A Sepharose. α-Tectorin coimmunoprecipitates with CEACAM16, but prestin does not. (F and G) Plasmids encoding α-tectorin were cotransfected into HEK293T cells with oncomodulin (α-tectorin+oncomodulin) and CEACAM16 (α-tectorin +CEACAM16). Cell lysates were subjected to coimmunoprecipitation by using 2 μg of anti-myc protein A Sepharose (pulling down α-tectorin). CEACAM16 coimmunoprecipitates with α-tectorin but not with oncomodulin. (H) Plasmid encoding α-tectorin was cotransfected into OK cells with CEACAM1 (α-tectorin +CEACAM1). Cell lysates were subjected to coimmunoprecipitation by using 2 μg of anti-Flag/protein G Sepharose (pulling down CEACAM1). CEACAM1 did not coimmunoprecipitate with α-tectorin.