Fig. 8. Prevention of glycosylation of the Na,K-ATPase β₁ subunit decreases detergent resistance of E-cadherin and abolishes a swainsonine-induced increase in detergent resistance of E-cadherin.

A, Tight monolayers of MDCK cells expressing unglycosylated mutant of the Na,K-ATPase β₁ subunit were grown in the absence (lanes 1–4) or presence of swainsonine (lanes 5–8) and treated with Triton X-100 as described in the legend to Fig. 6. As expected, swainsonine did not change gel mobility of N123, but slightly increased gel mobility of E-cadherin. Swainsonine did not affect detergent stability of either E-cadherin or the mutated Na,K-ATPase β₁ subunit.

B–C, Quantification of the results shows that both unglycosylated mutant of the Na,K-ATPase β₁ subunit, N123 (B), and E-cadherin (C) resident in the basolateral plasma membrane are less resistant to extraction by Triton X-100 in the cell line expressing N123 mutant as compared to non-transfected MDCK cells (Fig. 6). Swainsonine did not change detergent resistance of the unglycosylated Na,K-ATPase β₁ subunit (B) and E-cadherin (C) in the mutant-expressing cell line, in contrast to the protective effect of the inhibitor in non-transfected cells (Fig. 6).

Error bars, ± s.d. (n=3). Significant difference with non-transfected MDCK cells: * P<0.05, Student’s t-test. ** - P<0.001, Student’s t-test.