Figure 5.

The C-terminal part of Ecto-ColXVII (Ser⁹⁷⁸-Pro¹⁴⁹⁷) is essential for ECM interactions. A: Schematic structure of the collagen XVII deletion mutants used in this study. B: The shed ectodomains of all the mutants were detected by the Ab NC16A-3 in the culture medium of transfected HEK 293 cells seeded on Matrigel. The molecular weight of the truncated ectodomains corresponded to the calculated sizes. Immunoblotting (B) and IIF (C) with the Ab HK139 demonstrated that the longer ectodomains of mutants COL3 and NC6 were deposited in the ECM (C; arrows) but that those of mutants COL11 and COL15 were not, indicating that the region spanning amino acids Ser⁹⁷⁸ to Pro¹⁴⁹⁷ is necessary for binding of collagen XVII to the ECM. The mutant ΔPro⁹⁹⁷-Gly¹¹⁵² with an internal deletion also binds to the ECM (B; arrow). TM, transmembrane; aa, amino acid; red, rhodamine phalloidin; blue, DAPI; and green, the Ab HK139 in C. Scale bars = 40 μm.