Phosphatidylinositol [correction] 4,5-bisphosphate signals underlie receptor-specific Gq/11-mediated modulation of N-type Ca2+ channels.
Modulation of voltage-gated Ca2+ channels via G-protein-coupled receptors is a prime mechanism regulating neurotransmitter release and synaptic plasticity. Despite extensive studies, the molecular mechanism underlying Gq/11-mediated modulation remains unclear. We found cloned and native N-type Ca2+ channels to be regulated by phosphatidylinositol [correction] 4,5-bisphosphate (PIP2). In inside-out oocyte patches, PIP2 greatly attenuated or reversed the observed rundown of expressed channels. In sympathetic neurons, muscarinic M1 ACh receptor suppression of the Ca2+ current (ICa) was temporally correlated with PIP2 hydrolysis, blunted by PIP2 in whole-cell pipettes, attenuated by expression of PIP2-sequestering proteins, and became irreversible when PIP2 synthesis was blocked. We also probed mechanisms of receptor specificity. Although bradykinin also induced PIP2 hydrolysis, it did not inhibit ICa. However, bradykinin receptors became nearly as effective as M1 receptors when PIP2 synthesis, IP3 receptors, or the activity of neuronal Ca2+ sensor-1 were blocked, suggesting that bradykinin receptor-induced intracellular Ca2+ increases stimulate PIP2 synthesis, compensating for PIP2 hydrolysis. We suggest that differential use of PIP2 signals underlies specificity of Gq/11-coupled receptor actions on the channels
Gamper
Nikita
N
Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA.
Reznikov
Vitaliy
V
Yamada
Yoichi
Y
Yang
Jian
J
Shapiro
Mark S
MS
D019870:1-Phosphatidylinositol 4-Kinase / Q000502:physiology; D000818:Animals; D019470:Biolistics; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000737:chemistry / Q000502:physiology*; D020013:Calcium Signaling; D002135:Calcium-Binding Proteins / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000737:chemistry / Q000502:physiology*; D017136:Ion Transport; D007527:Isoenzymes / Q000502:physiology; D008297:Male; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009865:Oocytes; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000096:biosynthesis / Q000502:physiology*; D054803:Phospholipase C delta; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D017783:Superior Cervical Ganglion / Q000166:cytology; D014162:Transfection; D010738:Type C Phospholipases / Q000502:physiology; D014982:Xenopus laevis
D020864:Calcium Channels, N-Type; D002135:Calcium-Binding Proteins; D007527:Isoenzymes; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D011976:Receptors, Muscarinic; D011993:Recombinant Fusion Proteins; D019870:1-Phosphatidylinositol 4-Kinase; D010738:Type C Phospholipases; D054803:Phospholipase C delta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D001920:Bradykinin; D002118:Calcium