Stimulation of group I metabotropic glutamate receptors evokes calcium signals and c-jun and c-fos gene expression in human T cells.
To study if the activation of group I mGlu receptors in human T cells modifies intracellular Ca2+ concentration ([Ca2+](i)) and cell function, we measured [Ca2+](i) on cell suspensions (spectrofluorimetric method) or single cell (digital Ca2+ imaging system) using fura-2 as indicator. Early-inducible gene (c-jun and c-fos) expression was studied by reverse transcriptase-polymerase chain reaction assay as representative of Ca(2+)-sensitive gene expression. (1S,3R)-ACPD (100 microM), the selective mGlu receptor agonist, evoked a significant increase (34.1+/-4.9%) of [Ca2+](i), pharmacologically characterized as mediated by group I mGlu receptors, since both (S)-3,5-DHPG (100 microM), a selective group I mGlu receptor agonist and CHPG (1mM), the specific mGlu5 receptor agonist, reproduced the effects, that were abolished by AIDA (1mM), a selective group I mGlu receptor antagonist. (S)-3,5-DHPG-induced a rapid [Ca2+](i) rise (initial phase) followed by a slow decrease (second phase) to the baseline. Both extracellular Ca2+ and Ca2+ released from intracellular stores contribute to the [Ca2+](i) increase which depend on PLC activation. In a Ca(2+)-free buffer, the second phase rapidly return to the baseline; LaCl3 (1-10 microM), an inhibitor of extracellular Ca2+ influx, significantly reduced the second phase only; thapsigargin (1microM), by discharging intracellular Ca2+ stores, U 73122 (10 microM) and D609 (300 microM), by inhibiting PLC activity, prevented both phases. In our system, PTX pre-treatment increased (S)-3,5-DHPG effects, demonstrating that PXT-sensitive G(i/o) proteins are involved. Finally, specific stimulation of these receptors in Jurkat cells upregulates c-jun and c-fos gene expression, thus activating multiple downstream signalling regulating important T cell functions.
Miglio
Gianluca
G
DISCAFF, "Amedeo Avogadro" University of Eastern Piedmont, Via Bovio 6, 28100 Novara, Italy.
Varsaldi
Federica
F
Dianzani
Chiara
C
Fantozzi
Roberto
R
Lombardi
Grazia
G
D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D016762:Genes, fos / Q000187:drug effects / Q000502:physiology*; D016758:Genes, jun / Q000187:drug effects / Q000502:physiology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D019169:Jurkat Cells; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000378:metabolism*; D012118:Resorcinols / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*
D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; C104077:metabotropic glutamate receptor type 1; C079215:3,5-dihydroxyphenylglycine; D005998:Glycine