ABCMdb

ABCC7 p.Arg899Lys

Predicted by SNAP2:	A: N (87%), C: N (72%), D: N (61%), E: N (82%), F: N (66%), G: N (72%), H: N (93%), I: N (87%), K: N (97%), L: N (82%), M: N (82%), N: N (82%), P: N (78%), Q: N (87%), S: N (93%), T: N (93%), V: N (87%), W: D (63%), Y: N (72%),
Predicted by PROVEAN:	A: N, C: N, D: N, E: N, F: N, G: N, H: N, I: N, K: N, L: N, M: N, N: N, P: N, Q: N, S: N, T: N, V: N, W: N, Y: N,

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Publications
[hide] The cystic fibrosis transmembrane conductance regu... Pflugers Arch. 2015 Aug;467(8):1783-94. doi: 10.1007/s00424-014-1618-8. Epub 2014 Oct 4. Broadbent SD, Ramjeesingh M, Bear CE, Argent BE, Linsdell P, Gray MA
The cystic fibrosis transmembrane conductance regulator is an extracellular chloride sensor.
Pflugers Arch. 2015 Aug;467(8):1783-94. doi: 10.1007/s00424-014-1618-8. Epub 2014 Oct 4., [PMID:25277268]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl(-) channel that governs the quantity and composition of epithelial secretions. CFTR function is normally tightly controlled as dysregulation can lead to life-threatening diseases such as secretory diarrhoea and cystic fibrosis. CFTR activity is regulated by phosphorylation of its cytosolic regulatory (R) domain, and ATP binding and hydrolysis at two nucleotide-binding domains (NBDs). Here, we report that CFTR activity is also controlled by extracellular Cl(-) concentration ([Cl(-)]o). Patch clamp current recordings show that a rise in [Cl(-)]o stimulates CFTR channel activity, an effect conferred by a single arginine residue, R899, in extracellular loop 4 of the protein. Using NBD mutants and ATP dose response studies in WT channels, we determined that [Cl(-)]o sensing was linked to changes in ATP binding energy at NBD1, which likely impacts NBD dimer stability. Biochemical measurements showed that increasing [Cl(-)]o decreased the intrinsic ATPase activity of CFTR mainly through a reduction in maximal ATP turnover. Our studies indicate that sensing [Cl(-)]o is a novel mechanism for regulating CFTR activity and suggest that the luminal ionic environment is an important physiological arbiter of CFTR function, which has significant implications for salt and fluid homeostasis in epithelial tissues.

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No. Sentence Comment
82 Furthermore, introducing a lysine residue in place of arginine (R899K) maintained the response to [Cl- ]o (Fig. 2c) while mutating R899 to the negatively charged glutamic acid (R899E) did not, clearly showing that the positive charge at position 899 in ECL4 of CFTR is essential for [Cl- ]o sensing. Login to comment
112 To explore the role of phosphorylation further, we studied the effect of deleting the R domain from CFTR (residues 634-836) [12, 7], which removes all the major PKA/PKC Table 1 Summary of the FSK stimulation of whole cell currents and Erev shifts observed with the CFTR constructs used in this study CFTR Construct n FSK Stimulation (%&#b1;SEM) Erev shift (mV&#b1;SEM) WT (50 bc;M ATP) 5 180&#b1;96 15.0&#b1;3.6 WT (100 bc;M ATP) 6 12,000&#b1;6,000 15.2&#b1;3.0 WT (300 bc;M ATP) 8 1,200&#b1;600 17.0&#b1;3.0 WT (1 mM ATP) 24 13,000&#b1;6,000 23.7&#b1;1.8 WT (1.3 mM ATP) 9 1,400&#b1;900 16.7&#b1;2.6 WT (2 mM ATP) 24 6,100&#b1;5,300 16.7&#b1;1.6 WT (5 mM ATP) 7 1,600&#b1;1,000 20.1&#b1;4.4 WT (50 bc;M ATP + 50 bc;M P-ATP) 7 224&#b1;130 15.3&#b1;1.0 WT + Genistein 4 7,600&#b1;5,200 26.1&#b1;5.4 WT + AMP-PNP 5 2,800&#b1;2,500 21.8&#b1;5.5 WT (3 mM MgCl2) 7 28,000&#b1;17,000 18.3&#b1;3.1 R104Q 5 4,600&#b1;1,600 28.6&#b1;4.7 K114C 5 12,000&#b1;6,700 29.2&#b1;3.0 R117Q 4 33,000&#b1;20,000 30.1&#b1;3.4 K329A 5 13,000&#b1;10,000 33.7&#b1;2.1 R334Q 9 13,000&#b1;6,700 27.3&#b1;2.9 K335A 5 3,200&#b1;1,500 20.8&#b1;7.1 W401G 7 2,600&#b1;1,800 18.5&#b1;4.8 Delta-R (No Stim) 5 - 25.1&#b1;2.7 Delta-R (No FSK, Genistein) 5 140&#b1;13 22.7&#b1;3.0 Delta-R (FSK, No Genistein) 4 89&#b1;14 15.6&#b1;6.0 Delta-R (FSK + Genistein) 6 639&#b1;432 25.1&#b1;4.9 Delta-R-E1371S (No FSK) 9 - 21.4&#b1;4.8 Delta-R-E1371S (FSK) 4 2,600&#b1;1,400 15.3&#b1;4.7 K892Q 7 16,000&#b1;9,500 36.8&#b1;4.8 R899E 4 1,200&#b1;400 25.0&#b1;2.7 R899K 4 1,600&#b1;900 26.6&#b1;2.9 R899Q 7 5,400&#b1;2,800 30.0&#b1;1.3 R899Q + AMP-PNP 4 72,000&#b1;50,000 15.2&#b1;2.8 R899Q-E1371Q (No FSK) 4 - 18.4&#b1;5.9 R899Q-E1371Q (FSK) 6 107&#b1;48 15.6&#b1;3.0 R1128Q 6 14,000&#b1;6,100 41.1&#b1;4.2 Y1219G 6 3,200&#b1;2,500 19.2&#b1;3.3 E1371Q (No FSK) 6 - 25.5&#b1;3.5 E1371Q (FSK) 8 -28&#b1;9 22.3&#b1;4.0 E1371Q (FSK, No ATP, No GTP) 8 270&#b1;130 19.4&#b1;4.5 E1371Q + AMP-PNP (No FSK) 4 - 24.7&#b1;6.5 E1371Q + AMP-PNP (FSK) 8 180&#b1;170 17.4&#b1;4.0 Vector Control 4 15&#b1;38 - FSK stimulation was calculated as the percentage increase in current density at -60 mV from the Erev, after 5-min exposure to 10 bc;M FSK. Login to comment