PMID: 11889571

Gupta J, Linsdell P
Point mutations in the pore region directly or indirectly affect glibenclamide block of the CFTR chloride channel.
Pflugers Arch. 2002 Mar;443(5-6):739-47. Epub 2001 Dec 8., [PubMed]
Sentences
No. Mutations Sentence Comment
4 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:4:57
status: NEW
view ABCC7 p.Thr338Ala details
ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:4:47
status: NEW
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Two mutations in the 6th transmembrane region, F337A and T338A, significantly weakened glibenclamide block, consistent with a direct interaction between glibenclamide and this region of the pore. Login to comment
5 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:5:63
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:5:74
status: NEW
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Interestingly, two mutations in the 12th transmembrane region (N1138A and T1142A) significantly strengthened block. Login to comment
63 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:63:187
status: NEW
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ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:63:177
status: NEW
view ABCC7 p.Phe337Ala details
ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:63:245
status: NEW
view ABCC7 p.Asn1138Ala details
ABCC7 p.Thr1134Ala
X
ABCC7 p.Thr1134Ala 11889571:63:52
status: NEW
view ABCC7 p.Thr1134Ala details
ABCC7 p.Ser1141Ala
X
ABCC7 p.Ser1141Ala 11889571:63:32
status: NEW
view ABCC7 p.Ser1141Ala details
ABCC7 p.Met1137Ala
X
ABCC7 p.Met1137Ala 11889571:63:63
status: NEW
view ABCC7 p.Met1137Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:63:256
status: NEW
view ABCC7 p.Thr1142Ala details
While block of the TM12 mutants S1141A (Fig. 1) and T1134A and M1137A (data not shown) was indistinguishable from wild-type, block was significantly weakened in the TM6 mutants F337A and T338A, and significantly strengthened in the TM12 mutants N1138A and T1142A (Fig. 1). Login to comment
69 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:69:150
status: NEW
view ABCC7 p.Thr338Ala details
ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:69:173
status: NEW
view ABCC7 p.Phe337Ala details
ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:69:161
status: NEW
view ABCC7 p.Asn1138Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:69:188
status: NEW
view ABCC7 p.Thr1142Ala details
Mean fraction of control current remaining following addition of 60 µM glibenclamide (I/I0) is shown as a function of voltage for wild-type (q), T338A (s), N1138A (s), F337A (ss) and T1142A (xx). Login to comment
70 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:70:269
status: NEW
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ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:70:259
status: NEW
view ABCC7 p.Phe337Ala details
ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:70:200
status: NEW
view ABCC7 p.Asn1138Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:70:211
status: NEW
view ABCC7 p.Thr1142Ala details
Mean of data from 5-10 patches, fitted by Eq. according to the mean parameters shown in Fig. 3 rent remaining following addition of glibenclamide (I/I0) was significantly reduced at all voltages in N1138A and T1142A (P<0.05), and significantly increased in F337A and T338A at negative membrane potentials (P<0.05). Login to comment
71 ABCC7 p.Thr1134Ala
X
ABCC7 p.Thr1134Ala 11889571:71:37
status: NEW
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ABCC7 p.Ser1141Ala
X
ABCC7 p.Ser1141Ala 11889571:71:55
status: NEW
view ABCC7 p.Ser1141Ala details
ABCC7 p.Met1137Ala
X
ABCC7 p.Met1137Ala 11889571:71:45
status: NEW
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In contrast, I/I0 was not altered in T1134A, M1137A or S1141A at any voltage (data not shown). Login to comment
75 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:75:92
status: NEW
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ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:75:82
status: NEW
view ABCC7 p.Phe337Ala details
ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:75:130
status: NEW
view ABCC7 p.Asn1138Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:75:141
status: NEW
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Consistent with the results shown in Fig. 2, Kd(0) was significantly increased in F337A and T338A, and significantly decreased in N1138A and T1142A (Fig. 3A). Login to comment
83 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:83:104
status: NEW
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ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:83:84
status: NEW
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The extracellular Cl-concentration had a similar effect on Kd(0) in the TM6 mutants F337A (Fig. 5A) and T338A (Figs. 4, 5A). Login to comment
84 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:84:155
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:84:175
status: NEW
view ABCC7 p.Thr1142Ala details
In contrast, reducing extracellular Cl-concentration from 154 mM to 10 mM had no significant effect on apparent glibenclamide affinity in the TM12 mutants N1138A (Fig. 5A) or T1142A (Figs. 4, 5A). Login to comment
85 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:85:112
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:85:238
status: NEW
view ABCC7 p.Thr1142Ala details
As a result, the effect of these two mutations on Kd(0) was dependent on the extracellular Cl-concentration: in N1138A, Kd(0) was reduced to 35% of the wild-type value with 154 mM Cl- but only to 61% of wild-type with 10 mM Cl-, while in T1142A, Kd(0) was 40% of wild-type with 154 mM Cl- and 50% with 10 mM Cl-. Login to comment
98 ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:98:50
status: NEW
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ABCC7 p.Thr338Ala
X
ABCC7 p.Thr338Ala 11889571:98:429
status: NEW
view ABCC7 p.Thr338Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:98:69
status: NEW
view ABCC7 p.Thr1142Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:98:448
status: NEW
view ABCC7 p.Thr1142Ala details
A Example I-V relationships for wild-type (left), T338A (center) and T1142A (right), recorded with 10 mM extracellular Clas described in Materials and methods, before (Ctrl) and immediately following addition of 60 µM glibenclamide (+Glib) to the intracellular solution. B Mean fraction of control current remaining following addition of glibenclamide, with 154 mM (q) or 10 mM (qq) extracellular Cl-, for wild-type (left), T338A (center) and T1142A (right). Login to comment
100 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:100:62
status: NEW
view ABCC7 p.Asn1138Ala details
A similar lack of extracellular Cl-dependence was observed in N1138A (data not shown) Discussion Glibenclamide causes a relatively high affinity block of CFTR [32, 34] and other Cl-channels [14, 29, 31, 42]. Login to comment
106 ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:106:22
status: NEW
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ABCC8 p.Thr338Ala
X
ABCC8 p.Thr338Ala 11889571:106:32
status: NEW
view ABCC8 p.Thr338Ala details
Two mutations in TM6, F337A and T338A, significantly weakened block by glibenclamide (Figs. 2, 3); this effect was apparently independent of the extracellu- 744 Fig. 5 Extracellular Cl-dependence of the apparent affinity and voltage dependence of glibenclamide block. Login to comment
112 ABCC7 p.Phe337Ala
X
ABCC7 p.Phe337Ala 11889571:112:79
status: NEW
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However, the increase in Kd(0) was modest in both cases (1.5-fold increase for F337A compared to wild-type, and 2.1-fold increase for T338A), and both mutants are still clearly blocked in a voltage-dependent manner by glibenclamide (Figs. 1, 2). Login to comment
115 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:115:77
status: NEW
view ABCC7 p.Asn1138Ala details
ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:115:88
status: NEW
view ABCC7 p.Thr1142Ala details
In contrast to the effects of these mutations in TM6, two mutations in TM12 (N1138A and T1142A) caused a significant increase in the apparent affinity of glibenclamide block (Figs. 2, 3). Login to comment
116 ABCC7 p.Thr1134Ala
X
ABCC7 p.Thr1134Ala 11889571:116:120
status: NEW
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ABCC7 p.Thr1134Ala
X
ABCC7 p.Thr1134Ala 11889571:116:121
status: NEW
view ABCC7 p.Thr1134Ala details
ABCC7 p.Ser1141Ala
X
ABCC7 p.Ser1141Ala 11889571:116:136
status: NEW
view ABCC7 p.Ser1141Ala details
ABCC7 p.Ser1141Ala
X
ABCC7 p.Ser1141Ala 11889571:116:137
status: NEW
view ABCC7 p.Ser1141Ala details
ABCC7 p.Met1137Ala
X
ABCC7 p.Met1137Ala 11889571:116:128
status: NEW
view ABCC7 p.Met1137Ala details
ABCC7 p.Met1137Ala
X
ABCC7 p.Met1137Ala 11889571:116:129
status: NEW
view ABCC7 p.Met1137Ala details
This does not appear to be a nonspecific effect of mutagenesis within TM12, since three other mutations in this region (T1134A, M1137A, S1141A) had no effect on glibenclamide block (Fig. 3). Login to comment
120 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:120:129
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:120:139
status: NEW
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Two kinds of interactions may underlie the ability of extracellular Cl- ions to weaken glibenclamide block of wild-type, but not N1138A or T1142A CFTR. Login to comment
122 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:122:14
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:122:25
status: NEW
view ABCC7 p.Thr1142Ala details
In this case, N1138A and T1142A might alter the structure of a binding site for both Cl- and glibenclamide, reducing its affinity for Cl- ions and thereby indirectly increasing glibenclamide occupancy of the pore. Login to comment
132 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:132:77
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:132:88
status: NEW
view ABCC7 p.Thr1142Ala details
However, it is interesting to note that both suggest that: (1) the mutations N1138A and T1142A can increase the apparent affinity of glibenclamide block without directly affecting the interaction between glibenclamide and the pore walls, and (2) these two mutations both interfere with Cl-binding within the pore. Login to comment
134 ABCC7 p.Asn1138Ala
X
ABCC7 p.Asn1138Ala 11889571:134:159
status: NEW
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ABCC7 p.Thr1142Ala
X
ABCC7 p.Thr1142Ala 11889571:134:170
status: NEW
view ABCC7 p.Thr1142Ala details
Furthermore, the suggestion that TM12 residues N1138 and T1142 contribute to Cl-binding within the pore conflicts with our previous finding that the mutations N1138A and T1142A have no effect on unitary Cl-conductance [10]. Login to comment
135 ABCC7 p.Thr1134Ala
X
ABCC7 p.Thr1134Ala 11889571:135:91
status: NEW
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ABCC7 p.Ser1141Ala
X
ABCC7 p.Ser1141Ala 11889571:135:107
status: NEW
view ABCC7 p.Ser1141Ala details
ABCC7 p.Met1137Ala
X
ABCC7 p.Met1137Ala 11889571:135:99
status: NEW
view ABCC7 p.Met1137Ala details
Interestingly, these two mutations did not affect SCN- block, although other TM12 mutants (T1134A, M1137A, S1141A) did [10], suggesting that Cl- and SCN- binding may be controlled by different structural features within TM12. Login to comment
147 ABCC7 p.Arg347Asp
X
ABCC7 p.Arg347Asp 11889571:147:99
status: NEW
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Am J Physiol 271:C628-C634 20. Linsdell P, Hanrahan JW (1997) Interaction of channel blockers with R347D-CFTR [abstract]. Login to comment