Non-coplanar 2,2',3,5',6-pentachlorobiphenyl (PCB 95) amplifies ionotropic glutamate receptor signaling in embryonic cerebellar granule neurons by a mechanism involving ryanodine receptors.
The mechanisms by which non-coplanar 2,2',3,5',6-pentachlorobiphenyl (PCB 95) and rapamycin interact with ryanodine receptor (RyR) complexes to alter Ca2+ signaling, were explored in intact cerebellar granule neurons. PCB 95 (10 microM, 20 min) significantly increased the number of neurons responding to caffeine. PCB 95 sensitization of RyR-mediated responses was further supported by the observations that ryanodine pretreatment blocked response to caffeine and coplanar 2,4,4',5-tetrachlorobiphenyl (PCB 66), which lacks RyR activity, failed to sensitize neurons. PCB 95 did not significantly alter levels of resting cytosolic Ca2+ nor thapsigargin-sensitive Ca2+ stores, suggesting a more complex mechanism than sensitization from increased cytosolic Ca2+ or an increased endoplasmic reticulum/cytosolic Ca2+ gradient. The immunosuppressant, rapamycin, sensitized neurons to caffeine in a manner similar to PCB 95, suggesting a common mechanism. PCB 95 or rapamycin significantly enhanced Ca2+ responses following N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl4-isoxasolepropiate (AMPA) receptor activation. Store depletion or direct block of RyR with ryanodine enhanced responses to NMDA. PCB 95 further enhanced these responses to NMDA. These results suggest that PCB 95 and rapamycin enhance NMDA- and AMPA-mediated Ca2+ signals by modifying a functional association of the FKBP12/RyR complex that results in amplification of glutamate signaling in cultured cerebellar granule neurons in culture.
Gafni
Juliette
J
Department of Molecular Biosciences, and Center for Children's Environmental Health and Disease Prevention, University of California, Davis, California 95616, USA.
Wong
Patty W
PW
Pessah
Isaac N
IN
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002531:Cerebellum / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004347:Drug Interactions; D007166:Immunosuppressive Agents / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009603:Nitroso Compounds / Q000494:pharmacology; D009924:Organ Culture Techniques; D011078:Polychlorinated Biphenyls / Q000378:metabolism / Q000494:pharmacology*; D018091:Receptors, AMPA / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D020123:Sirolimus / Q000494:pharmacology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D007166:Immunosuppressive Agents; D009603:Nitroso Compounds; D018091:Receptors, AMPA; D019837:Ryanodine Receptor Calcium Release Channel; C032904:2,2',3,5',6-pentachlorobiphenyl; C008651:4-nitrosodimethylaniline; D012433:Ryanodine; D002110:Caffeine; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D011078:Polychlorinated Biphenyls; D002118:Calcium; D020123:Sirolimus