TY - JOUR
T1 - Modulation of nucleotide sensitivity of ATP-sensitive potassium channels by phosphatidylinositol-4-phosphate 5-kinase
AU - Shyng, S. L.
AU - Barbieri, A.
AU - Gumusboga, A.
AU - Cukras, C.
AU - Pike, L.
AU - Davis, J. N.
AU - Stahl, P. D.
AU - Nichols, C. G.
PY - 2000/1/18
Y1 - 2000/1/18
N2 - ATP-sensitive potassium channels (K(ATP) channels) regulate cell excitability in response to metabolic changes. K(ATP) channels are formed as a complex of a sulfonylurea receptor (SURx), a member of the ATP-binding cassette protein family, and an inward rectifier K+ channel subunit (Kir6.x). Membrane phospholipids, in particular phosphatidylinositol (PI) 4,5- bisphosphate (PIP2), activate K(ATP) channels and antagonize ATP inhibition of K(ATP) channels when applied to inside-out membrane patches. To examine the physiological relevance of this regulatory mechanism, we manipulated membrane PIP2 levels by expressing either the wild-type or an inactive form of PI-4-phosphate 5-kinase (PIP5K) in COSm6 cells and examined the ATP sensitivity of coexpressed K(ATP) channels. Channels from cells expressing the wild-type PIP5K have a 6-fold lower ATP sensitivity (K(1/2), the half maximal inhibitory concentration, 60 μM) than the sensitivities from control cells (K(1/2) ≃ 10 μM). An inactive form of the PIP5K had little effect on the K(1/2) of wild-type channels but increased the ATP-sensitivity of a mutant K(ATP) channel that has an intrinsically lower ATP sensitivity (from K(1/2) ≃ 450 μM to K(1/2) ≃ 100 μM), suggesting a decrease in membrane PIP2 levels as a consequence of a dominant-negative effect of the inactive PIP5K. These results show that PIP5K activity, which regulates PIP2 and PI- 3,4,5-P3 levels, is a significant determinant of the physiological nucleotide sensitivity of K(ATP) channels.
AB - ATP-sensitive potassium channels (K(ATP) channels) regulate cell excitability in response to metabolic changes. K(ATP) channels are formed as a complex of a sulfonylurea receptor (SURx), a member of the ATP-binding cassette protein family, and an inward rectifier K+ channel subunit (Kir6.x). Membrane phospholipids, in particular phosphatidylinositol (PI) 4,5- bisphosphate (PIP2), activate K(ATP) channels and antagonize ATP inhibition of K(ATP) channels when applied to inside-out membrane patches. To examine the physiological relevance of this regulatory mechanism, we manipulated membrane PIP2 levels by expressing either the wild-type or an inactive form of PI-4-phosphate 5-kinase (PIP5K) in COSm6 cells and examined the ATP sensitivity of coexpressed K(ATP) channels. Channels from cells expressing the wild-type PIP5K have a 6-fold lower ATP sensitivity (K(1/2), the half maximal inhibitory concentration, 60 μM) than the sensitivities from control cells (K(1/2) ≃ 10 μM). An inactive form of the PIP5K had little effect on the K(1/2) of wild-type channels but increased the ATP-sensitivity of a mutant K(ATP) channel that has an intrinsically lower ATP sensitivity (from K(1/2) ≃ 450 μM to K(1/2) ≃ 100 μM), suggesting a decrease in membrane PIP2 levels as a consequence of a dominant-negative effect of the inactive PIP5K. These results show that PIP5K activity, which regulates PIP2 and PI- 3,4,5-P3 levels, is a significant determinant of the physiological nucleotide sensitivity of K(ATP) channels.
UR - http://www.scopus.com/inward/record.url?scp=0034681119&partnerID=8YFLogxK
U2 - 10.1073/pnas.97.2.937
DO - 10.1073/pnas.97.2.937
M3 - Article
C2 - 10639183
AN - SCOPUS:0034681119
SN - 0027-8424
VL - 97
SP - 937
EP - 941
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 2
ER -