Table 2.
Mutations of the pore-lining residues of MEC-4 alter channel activity
Xenopus oocytes were injected with cRNA mixtures of WT MEC-10, MEC-2, and MEC-6 in the presence of the indicated MEC-4 constructs. Whole-cell basal currents (before the initiation of LSS stimulation) were measured at −60 mV by perfusing oocytes with NaCl-110 TEV solution. At the end of each recording, 20 μm benzamil was added to the bath to determine the leak current. n indicates the number of measurements for each group. Significant changes in whole-cell Na+ currents when compared with MEC-4 A713T (MEC-4d) are noted (**, p < 0.01; ***, p < 0.01; ****, p < 0.0001; ns, not significant), determined with one-way ANOVA followed by a Bonferroni test).
| Mutation | INa+ | S.D. | n | p |
|---|---|---|---|---|
| μA | μA | |||
| Ala713 (WT) | −0.12 | 0.08 | 12 | **** |
| A713C | −0.48 | 0.85 | 17 | **** |
| A713D | −0.83 | 0.96 | 18 | **** |
| A713V | −0.59 | 0.26 | 18 | **** |
| A713T (MEC-4d) | −4.31 | 2.90 | 90 | |
| N710C/A713T | −1.13 | 0.51 | 20 | **** |
| L711C/A713T | −4.19 | 1.96 | 22 | NS |
| L712C/A713T | −2.76 | 1.39 | 22 | ** |
| A713T/D714C | −0.60 | 0.39 | 17 | **** |
| A713T/F715C | −1.51 | 1.19 | 16 | **** |
| A713T/G716C | −1.66 | 1.41 | 11 | **** |
| A713T/G717C | −0.42 | 0.18 | 19 | **** |
| A713T/Q718C | −2.91 | 3.07 | 16 | NS |
| A713T/L719C | −5.62 | 3.40 | 16 | NS |
| A713T/G720C | −0.03 | 0.02 | 12 | **** |
| A713T/L721C | −1.77 | 1.38 | 16 | **** |
| A713T/W722C | −0.05 | 0.08 | 11 | **** |
| A713T/G724C | −0.02 | 0.02 | 12 | **** |
| A713T/I725C | −2.31 | 1.64 | 20 | *** |
| A713T/S726C | −0.02 | 0.02 | 12 | **** |
| A713T/F727C | −0.54 | 0.46 | 12 | **** |
| A713T/L728C | −2.26 | 1.28 | 12 | ** |
| A713T/T729C | 0.00 | 0.01 | 11 | **** |