Functional metabotropic glutamate receptors on nuclei from brain and primary cultured striatal neurons. Role of transporters in delivering ligand.
G-protein-coupled receptors are well known for converting an extracellular signal into an intracellular response. Here we showed that the metabotropic glutamate receptor 5 (mGlu5) plays a dynamic intracellular role in signal transduction. Activation of endogenously expressed mGlu5 on striatal nuclear membranes leads to rapid, sustained calcium (Ca2+) responses within the nucleoplasm that can be blocked by receptor-specific antagonists. Extracellular ligands such as glutamate and quisqualate reach nuclear receptors via both sodium-dependent transporters and cystine glutamate exchangers. Inhibition of either transport system blocks radiolabeled agonist uptake as well as agonist-induced nuclear Ca2+ changes. Impermeable antagonists like LY393053 and LY367366 not only blocked [3H]quisqualate binding but also prevented nontransported agonists such as (RS)-3,5-dihydroxyphenylglycine from inducing intracellular Ca2+ changes in heterologous cells. In contrast, neither LY compound prevented quisqualate or glutamate from activating intracellular receptors leading to Ca2+ responses. Inasmuch as Ca2+ can enter the nucleoplasm via the nuclear pore complex or from the nuclear lumen, the presence of nuclear mGlu5 receptors appeared to amplify the latter process generating a faster nuclear response in heterologous cells. In isolated striatal nuclei, nuclear receptor activation results in the de novo appearance of phosphorylated CREB protein. Thus, activation of nuclear mGlu5 receptors initiates a signaling cascade that is known to alter gene transcription and regulate many paradigms of synaptic plasticity. These studies demonstrated that mGlu5 receptors play a dynamic role in signaling both on and off the plasma membrane.
Jong
Yuh-Jiin I
YJ
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Kumar
Vikas
V
Kingston
Ann E
AE
Romano
Carmelo
C
O'Malley
Karen L
KL
D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D004396:Coloring Agents / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D007150:Immunohistochemistry; D008024:Ligands; D008027:Light; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D010766:Phosphorylation; D011422:Propionates / Q000494:pharmacology; D011485:Protein Binding; D018094:Receptors, Metabotropic Glutamate / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D012964:Sodium / Q000737:chemistry; D013347:Subcellular Fractions / Q000378:metabolism; D013876:Thiophenes / Q000494:pharmacology; D013997:Time Factors
D004396:Coloring Agents; D004791:Enzyme Inhibitors; C404526:LY393053; D008024:Ligands; D011422:Propionates; D018094:Receptors, Metabotropic Glutamate; D011993:Recombinant Fusion Proteins; D013876:Thiophenes; C119517:alpha-thioxantylmethyl-4-carboxyphenylglycine; D018698:Glutamic Acid; D004533:Egtazic Acid; D012964:Sodium; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D003545:Cysteine; D002118:Calcium; D005998:Glycine