ABCC8 p.Glu128Cys
| Predicted by SNAP2: | A: D (66%), C: D (59%), D: D (85%), F: D (71%), G: D (85%), H: D (80%), I: D (75%), K: D (71%), L: D (75%), M: D (66%), N: D (85%), P: D (91%), Q: D (75%), R: D (80%), S: D (80%), T: D (80%), V: D (75%), W: D (80%), Y: D (71%), |
| Predicted by PROVEAN: | A: D, C: D, D: N, F: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: N, R: D, S: D, T: D, V: D, W: D, Y: D, |
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[hide] N-terminal transmembrane domain of SUR1 controls g... J Gen Physiol. 2011 Mar;137(3):299-314. Epub 2011 Feb 14. Pratt EB, Tewson P, Bruederle CE, Skach WR, Shyng SL
N-terminal transmembrane domain of SUR1 controls gating of Kir6.2 by modulating channel sensitivity to PIP2.
J Gen Physiol. 2011 Mar;137(3):299-314. Epub 2011 Feb 14., [PMID:21321069]
Abstract [show]
Functional integrity of pancreatic adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels depends on the interactions between the pore-forming potassium channel subunit Kir6.2 and the regulatory subunit sulfonylurea receptor 1 (SUR1). Previous studies have shown that the N-terminal transmembrane domain of SUR1 (TMD0) interacts with Kir6.2 and is sufficient to confer high intrinsic open probability (P(o)) and bursting patterns of activity observed in full-length K(ATP) channels. However, the nature of TMD0-Kir6.2 interactions that underlie gating modulation is not well understood. Using two previously described disease-causing mutations in TMD0 (R74W and E128K), we performed amino acid substitutions to study the structural roles of these residues in K(ATP) channel function in the context of full-length SUR1 as well as TMD0. Our results revealed that although R74W and E128K in full-length SUR1 both decrease surface channel expression and reduce channel sensitivity to ATP inhibition, they arrive there via distinct mechanisms. Mutation of R74 uniformly reduced TMD0 protein levels, suggesting that R74 is necessary for stability of TMD0. In contrast, E128 mutations retained TMD0 protein levels but reduced functional coupling between TMD0 and Kir6.2 in mini-K(ATP) channels formed by TMD0 and Kir6.2. Importantly, E128K full-length channels, despite having a greatly reduced P(o), exhibit little response to phosphatidylinositol 4,5-bisphosphate (PIP(2)) stimulation. This is reminiscent of Kir6.2 channel behavior in the absence of SUR1 and suggests that TMD0 controls Kir6.2 gating by modulating Kir6.2 interactions with PIP(2). Further supporting this notion, the E128W mutation in full-length channels resulted in channel inactivation that was prevented or reversed by exogenous PIP(2). These results identify a critical determinant in TMD0 that controls Kir6.2 gating by controlling channel sensitivity to PIP(2). Moreover, they uncover a novel mechanism of K(ATP) channel inactivation involving aberrant functional coupling between SUR1 and Kir6.2.
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No. Sentence Comment
129 Bars: horizontal, 10 s; vertical, 1,000 pA for WT and E128C, and 200 pA for the rest.
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ABCC8 p.Glu128Cys 21321069:129:54
status: NEW[hide] Engineered interaction between SUR1 and Kir6.2 tha... J Gen Physiol. 2012 Aug;140(2):175-87. doi: 10.1085/jgp.201210803. Epub 2012 Jul 16. Pratt EB, Zhou Q, Gay JW, Shyng SL
Engineered interaction between SUR1 and Kir6.2 that enhances ATP sensitivity in KATP channels.
J Gen Physiol. 2012 Aug;140(2):175-87. doi: 10.1085/jgp.201210803. Epub 2012 Jul 16., [PMID:22802363]
Abstract [show]
The ATP-sensitive potassium (K(ATP)) channel consisting of the inward rectifier Kir6.2 and SUR1 (sulfonylurea receptor 1) couples cell metabolism to membrane excitability and regulates insulin secretion. Inhibition by intracellular ATP is a hallmark feature of the channel. ATP sensitivity is conferred by Kir6.2 but enhanced by SUR1. The mechanism by which SUR1 increases channel ATP sensitivity is not understood. In this study, we report molecular interactions between SUR1 and Kir6.2 that markedly alter channel ATP sensitivity. Channels bearing an E203K mutation in SUR1 and a Q52E in Kir6.2 exhibit ATP sensitivity approximately 100-fold higher than wild-type channels. Cross-linking of E203C in SUR1 and Q52C in Kir6.2 locks the channel in a closed state and is reversible by reducing agents, demonstrating close proximity of the two residues. Our results reveal that ATP sensitivity in K(ATP) channels is a dynamic parameter dictated by interactions between SUR1 and Kir6.2.
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87 Fig. S5 illustrates that Q52C-Kir6.2//E128C-SUR1 channels show no evidence of cross-linking. Fig. S6 shows MgADP stimulation of Q52E-Kir6.2 channels.
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ABCC8 p.Glu128Cys 22802363:87:38
status: NEW206 However, no change in channel activity was observed in Q52C-Kir6.2//E128C-SUR1 than WT (Fig. 6), in contrast to the near 100-fold increase in ATP sensitivity observed in Q52E-Kir6.2// E203K-SUR1 (Fig. 2).
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ABCC8 p.Glu128Cys 22802363:206:68
status: NEW