title: Dual regulation of voltage-gated calcium channels by PtdIns(4,5)P2.
abstract: Voltage-gated calcium channels (VGCCs) conduct calcium into cells after membrane depolarization and are vital for diverse biological events. They are regulated by various signalling pathways, which has profound functional consequences. The activity of VGCCs decreases with time in whole-cell and inside-out patch-clamp recordings. This rundown reflects persistent intrinsic modulation of VGCCs in intact cells. Although several mechanisms have been reported to contribute to rundown of L-type channels, the mechanism of rundown of other types of VGCC is poorly understood. Here we show that phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2), an essential regulator of ion channels and transporters, is crucial for maintaining the activity of P/Q- and N-type channels. Activation of membrane receptors that stimulate hydrolysis of PtdIns(4,5)P2 causes channel inhibition in oocytes and neurons. PtdIns(4,5)P2 also inhibits P/Q-type channels by altering the voltage dependence of channel activation and making the channels more difficult to open. This inhibition is alleviated by phosphorylation by protein kinase A. The dual actions of PtdIns(4,5)P2 and the crosstalk between PtdIns(4,5)P2 and protein kinase A set up a dynamic mechanism through which the activity of VGCCs can be finely tuned by various neurotransmitters, hormones and trophic factors.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Wu
authors.forename: Claudia S
authors.initials: CS
authors.lastname: Bauer
authors.forename: Xiao-guang
authors.initials: XG
authors.lastname: Zhen
authors.forename: Cheng
authors.initials: C
authors.lastname: Xie
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004553:Electric Conductivity; D004789:Enzyme Activation; D006868:Hydrolysis; D015640:Ion Channel Gating / Q000187:drug effects; D008954:Models, Biological; D009154:Mutation; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000172:deficiency / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation; D011817:Rabbits; D011892:Rana catesbeiana; D051381:Rats; D020917:Receptor, trkA / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D015220:Calcium Channels; D019269:Phosphatidylinositol 4,5-Diphosphate; D000255:Adenosine Triphosphate; D020917:Receptor, trkA; D017868:Cyclic AMP-Dependent Protein Kinases