title: Differential regulation of metabotropic glutamate receptor 5-mediated phosphoinositide hydrolysis and extracellular signal-regulated kinase responses by protein kinase C in cultured astrocytes.
abstract: The metabotropic glutamate receptor 5 (mGluR5) exhibits a rapid loss of receptor responsiveness to prolonged or repeated agonist exposure. This receptor desensitization has been seen in a variety of native and recombinant systems, and is thought to result from receptor-mediated, protein kinase C (PKC)-dependent phosphorylation of the receptor, uncoupling it from the G protein in a negative feedback regulation. We have investigated the rapid PKC-mediated desensitization of mGluR5 in cortical cultured astrocytes by measuring downstream signals from activation of mGluR5. These include activation of phosphoinositide (PI) hydrolysis, intracellular calcium transients, and extracellular signal-regulated kinase 2 (ERK2) phosphorylation. We present evidence that PKC plays an important role in rapid desensitization of PI hydrolysis and calcium signaling, but not in ERK2 phosphorylation. This differential regulation of mGluR5-mediated responses suggests divergent signaling and regulatory pathways which may be important mechanisms for dynamic integration of signal cascades.
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006868:Hydrolysis / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D054799:Phospholipase C beta; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D012118:Resorcinols / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; C578937:Grm5 protein, rat; D007527:Isoenzymes; D010716:Phosphatidylinositols; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; C079215:3,5-dihydroxyphenylglycine; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D005998:Glycine