Differential phosphoinositide binding to components of the G protein-gated K+ channel.
The regulation of ion channels and transporters by anionic phospholipids is currently very topical. G protein-gated K(+) channels from the Kir3.0 family are involved in slowing the heart rate, generating late inhibitory postsynaptic potentials and controlling hormone release from neuroendocrine cells. There is considerable functional precedent for the control of these channels by phosphatidylinositol 4,5-bisphosphate. In this study, we used a biochemical assay to investigate the lipid binding properties of Kir3.0 channel domains. We reveal a differential binding affinity to a range of phosphoinositides between the C termini of the Kir3.0 isoforms. Furthermore, the N terminus in addition to the C terminus of Kir3.4 is necessary to observe binding and is decreased by the mutations R72A, K195A and R196A but not K194A. Protein kinase C phosphorylation of the Kir3.1 C-terminal fusion protein decreases anionic phospholipid binding. The differential binding affinity has functional consequences as the inhibition of homomeric Kir3.1, occurring after M3 receptor activation, recovers over minutes while homomeric Kir3.2 does not.
Thomas
Alison M
AM
Department of Medicine and BHF Laboratories, University College London, 5 University Street, London, WC1E 6JJ, United Kingdom. alison.thomas@ucl.ac.uk
Brown
Sean G
SG
Leaney
Joanne L
JL
Tinker
Andrew
A
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D058619:Maltose-Binding Proteins; D010716:Phosphatidylinositols; D011993:Recombinant Fusion Proteins; D011493:Protein Kinase C