Table 1.

Nucleotide and phosphoinositide regulation of KATP channel subtypes

Tissue location (cell type)aSubunit config.ATP inhibition (IC50)MgATP regulation (EC50/IC50; µM)MgADP activation (EC50; µM)PIP2 affinity (ΔΔG; kJ/mol)Refs
Pancreas (β cell) Kir6.2/SUR1 10–20 112–124b 8–11 38 Proks et al. (2010), (2014), Foster and Coetzee (2016), Pipatpolkai et al. (2020)  
Heart (cardiac myocyte) Kir6.2/SUR2A 21–100 541b 18 n.d.d Aguilar-Bryan and Bryan (1999), Tammaro and Ashcroft (2007), Pratt et al. (2012), Proks et al. (2014), Foster and Coetzee (2016), Pipatpolkai et al. (2020)  
Vasculature (smooth muscle) Kir6.1/SUR2B 29–200 n.d.b 96c n.d.e Davies et al. (2010), Foster and Coetzee (2016)  
a

Note the possibility for a range of KATP isoforms to be expressed in an individual tissue, and that the listed isoforms may be found in other tissues, for example, the “pancreatic” Kir6.2/SUR1 form of the channel is also found in neurons.

b

Italicized text denotes IC50 values. Note that mutant channels (Kir6.2-G334D, Kir6.2-F333I) with reduced ATP sensitivity were used to reveal MgATP sensitivities, as the effects of MgATP are normally strongly masked by inhibitory effects of free ATP. Similar mutants are needed to study MgATP regulation of Kir6.1 containing channels in detail.

c

Measured in the presence of 10 µM pinacidil.

d

Likely similar to Kir6.2/SUR1, above, as PIP2 binding free energy for Kir6.2 alone is 33 kJ/mol.

e

Likely higher than for Kir6.1, as inferred from indirect measures in Quinn et al. (2003).

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