Table 2.

Measurement of Cx43 Turnover^a

pcDNA3.1 derivative	percentage of Cx43 remaining
pcDNA3.1	85 ± 2 (5)
Flag-CIP85wt	54 ± 5 (4)
Flag-CIP85ΔSH3	79 ± 6 (4)
Flag-CIP85wt + NH4Cl	89 ± 2 (5)
Flag-CIP85wt + MG132	66 ± 2 (3)

^aHela cells stably expressing Cx43 were transiently transfected with pcDNA3.1 alone or Flag-CIP85 constructs (wild type or the SH3 domain deletion mutant). The cells were pulse-labeled with [³⁵S]Met/Cys at 100 μCi/mL for 45 min and chased for 3 h without or with 10 mM NH₄Cl or 40 μM MG132. [³⁵S]-labeled Cx43 proteins were immunoprecipitated and quantitatively measured by densitometry of the autoradiographs. The mean values ± SEM (t test) represent the percentages of Cx43 remaining after 3 h-chases compared to 0 h-chase controls. The numbers of independent experiments are indicated in parentheses. Compared to the value of the vector alone in a two-tailed Student's t test, the value of CIP85wt is significantly different (P < 0.013), whereas the value of CIP85ΔSH3 is not significantly different (P > 0.1). Compared to the value of CIP85wt without inhibitor in a two-tailed Student's t test, the value of CIP85wt pulsed and chased with NH₄Cl is significantly different (P < 0.004), whereas the value of CIP85wt pulsed and chased with MG132 is not significantly different (P > 0.1).