Figure 1. SMase C suppression of heretologously expressed and native CFTR currents.
(A) Sphingomyelin hydrolysis reactions catalyzed by SMases C and D. (B) and (C) Currents of an oocyte injected with cRNA encoding CFTR before or after activation with 50 µM forskolin and 1 mM IBMX in the bath solution (B) and activated CFTR currents pre- or post-application of SMase C from S.aureus (SaSMase C: 0.4 ng/μl) (C), elicited by stepping membrane voltage from the −30 mV holding potential to −80 mV and then to 50 mV. (D) Time course of normalized CFTR currents at 50 mV where the arrows indicate addition of forskolin plus IBMX (arrow 1) or SaSMase C (arrow 2) (mean ± s.e.m, n = 6). (E) Normalized current amplitude before or after activation by forskolin plus IBMX and post-SMase C treatment (mean ± s.e.m, n = 6). (F) and (G) Native currents of a Calu-3 cell before or after activation with 50 µM forskolin and 1 mM IBMX in the bath solution (F) and activated CFTR currents before and after addition of SaSMase C (G), elicited by stepping membrane voltage from the 0 mV holding potential to −80 mV and then to 80 mV. (H) Time course of normalized CFTR currents at 80 mV where the arrows indicate addition of forskolin plus IBMX (arrow 1) or SaSMase C (0.5 ng/μl; arrow 2) (mean ± s.e.m, n = 7). (I) Normalized current amplitude before or after activation by forskolin plus IBMX and post-SMase C treatment (mean ± s.e.m, n = 7).