ABCMdb

ABCC7 p.Lys978Gln

ClinVar:	c.2932A>T , p.Lys978* D , Likely pathogenic
Predicted by SNAP2:	A: D (71%), C: D (75%), D: D (91%), E: D (85%), F: D (85%), G: D (80%), H: D (71%), I: D (75%), L: D (80%), M: D (63%), N: D (71%), P: D (91%), Q: D (75%), R: D (66%), S: D (66%), T: D (75%), V: D (80%), W: D (91%), Y: D (80%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: N, F: D, G: D, H: D, I: D, L: D, M: D, N: N, P: D, Q: N, R: N, S: N, T: D, V: D, W: D, Y: D,

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Publications
[hide] Regulation of CFTR chloride channel macroscopic co... Am J Physiol Cell Physiol. 2011 Jan;300(1):C65-74. Epub 2010 Oct 6. Li MS, Holstead RG, Wang W, Linsdell P
Regulation of CFTR chloride channel macroscopic conductance by extracellular bicarbonate.
Am J Physiol Cell Physiol. 2011 Jan;300(1):C65-74. Epub 2010 Oct 6., [PMID:20926782]

Abstract [show]
The CFTR contributes to Cl and HCO transport across epithelial cell apical membranes. The extracellular face of CFTR is exposed to varying concentrations of Cl and HCO in epithelial tissues, and there is evidence that CFTR is sensitive to changes in extracellular anion concentrations. Here we present functional evidence that extracellular Cl and HCO regulate anion conduction in open CFTR channels. Using cell-attached and inside-out patch-clamp recordings from constitutively active mutant E1371Q-CFTR channels, we show that voltage-dependent inhibition of CFTR currents in intact cells is significantly stronger when the extracellular solution contains HCO than when it contains Cl. This difference appears to reflect differences in the ability of extracellular HCO and Cl to interact with and repel intracellular blocking anions from the pore. Strong block by endogenous cytosolic anions leading to reduced CFTR channel currents in intact cells occurs at physiologically relevant HCO concentrations and membrane potentials and can result in up to approximately 50% inhibition of current amplitude. We propose that channel block by cytosolic anions is a previously unrecognized, physiologically relevant mechanism of channel regulation that confers on CFTR channels sensitivity to different anions in the extracellular fluid. We further suggest that this anion sensitivity represents a feedback mechanism by which CFTR-dependent anion secretion could be regulated by the composition of the secretions themselves. Implications for the mechanism and regulation of CFTR-dependent secretion in epithelial tissues are discussed.

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Sentences [show]
No. Sentence Comment
118 To investigate whether these positively charged residues influence the strength of channel block by cytosolic anions in intact cells, we neutralized these charges in an E1371Q background. Login to comment
119 Figure 6A shows macroscopic currents carried by K95Q/ E1371Q-, R303Q/E1371Q-, and K978Q/E1371Q-CFTR in Fig. 4. Login to comment

[hide] CFTR inhibition by glibenclamide requires a positi... Biochim Biophys Acta. 2007 Oct;1768(10):2438-46. Epub 2007 May 21. Melin P, Hosy E, Vivaudou M, Becq F
CFTR inhibition by glibenclamide requires a positive charge in cytoplasmic loop three.
Biochim Biophys Acta. 2007 Oct;1768(10):2438-46. Epub 2007 May 21., [PMID:17582383]

Abstract [show]
The sulfonylurea glibenclamide is widely used as an open-channel blocker of the CFTR chloride channel. Here, we used site-directed mutagenesis to identify glibenclamide site of interaction: a positively charged residue K978, located in the cytoplasmic loop 3. Charge-neutralizing mutations K978A, K978Q, K978S abolished the inhibition of forskolin-activated CFTR chloride current by glibenclamide but not by CFTR(inh)-172. The charge-conservative mutation K978R did not alter glibenclamide sensitivity of CFTR current. Mutations of the neighbouring R975 (R975A, R975S, R975Q) did not affect electrophysiological and pharmacological properties of CFTR. No alteration of halide selectivity was observed with any of these CFTR mutant channels. This study identifies a novel potential inhibitor site within the CFTR molecule, and suggests a novel role of cytoplasmic loop three, within the second transmembrane domain of CFTR protein. This work is the first to report on the role of a residue in a cytoplasmic loop in the mechanism of action of the channel blocker glibenclamide.

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No. Sentence Comment
2 Charge-neutralizing mutations K978A, K978Q, K978S abolished the inhibition of forskolin-activated CFTR chloride current by glibenclamide but not by CFTRinh-172. Login to comment
77 We investigated the role of the charged residue K978 in the sequence ILNRFSKD of CL3 (Fig. 1B) described as a region physically close to the pore [29] and examined the interaction of glibenclamide with mutated EGFP-CFTR channels: K978A, K978Q, K978R, Fig. 2. Login to comment
84 Similar effects in the presence of Fsk were recorded with cells expressing K978A, K978Q, K978R and K978S mutants CFTR. Login to comment
96 To investigate the role of the charge of the side chain of K978 in glibenclamide resistance, different amino acid substitutions were examined: K978A, K978Q, K978R. Login to comment
98 Fig. 4A presents the ratio Iglib/Ifsk, recorded at -100 mV, with 100 bc;M glibenclamide, for K978A, K978Q, K978R, K978S channels compared to CFTR-wt. Login to comment
108 neutralizing mutations (K978A, K978Q) rendered channels insensitive to inhibition by glibenclamide as demonstrated by the time course of current recorded at +40 mV (Fig. 4B). Login to comment
128 (B) Examples of time course of current densities (between +40 mVand -40 mV) from the charge neutralizing mutants CFTR-K978Q (a0;) and CFTR-K978A (ef;) in presence of Fsk 10 bc;M, and Fsk+Glib 100 bc;M, and Fsk+CFTRinh-172 10 bc;M. Login to comment
138 This was the case for the mutations that neutralized the charge of the side chain of the residue 978 (K978A, K978Q, K978S). Login to comment