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Characterization of the metabotropic glutamate receptors mediating phospholipase C activation and calcium release in cerebellar granule cells: calcium‐dependence of the phospholipase C response
Author(s) -
Masgrau Roser,
Servitja JoanMarc,
Young Kenneth W.,
Pardo Raul,
Sarri Elisabet,
Nahorski Stefan R.,
Picatoste Fernando
Publication year - 2001
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.0953-816x.2000.01384.x
Subject(s) - metabotropic glutamate receptor , metabotropic glutamate receptor 1 , glutamate receptor , metabotropic glutamate receptor 6 , ryanodine receptor , metabotropic glutamate receptor 5 , metabotropic glutamate receptor 7 , metabotropic receptor , bapta , microbiology and biotechnology , chemistry , calcium , extracellular , biochemistry , biology , receptor , organic chemistry
In this study we have determined the metabotropic glutamate receptors (mGluRs) involved in the glutamate activation of phospholipase C (PLC) and Ca 2+ mobilization in cerebellar granule cells at 9 days in vitro; and studied the Ca 2+ modulation of the PLC response. Both PLC activation and Ca 2+ signalling were found to be mediated exclusively by the mGluR1 subtype, although both group I mGluRs, mGluR1α and mGluR5, could be detected in cell extracts. Exposure of cells to medium devoid of Ca 2+ for various times before agonist stimulation reduced the PLC response, which was quickly recovered following the re‐exposure of cells to Ca 2+ ‐containing medium. The extent of the glutamate response correlated well with changes in the cytosolic Ca 2+ concentration. On the other hand, loading of the intracellular Ca 2+ stores by a transient depolarization followed by washing in nondepolarizing buffer, allowed glutamate to release stored Ca 2+ in the majority of cells and enhanced glutamate activation of PLC. Under such conditions, the absence of extracellular Ca 2+ during stimulation and the chelation of cytosolic Ca 2+ with BAPTA/AM inhibited both glutamate‐elicited Ca 2+ response and PLC activation. Overall, these results indicate that the mGluR‐mediated activation of PLC depends on the presence of extracellular Ca 2+ and can be modulated by moderate changes of cytosolic Ca 2+ . Furthermore, ryanodine reduced PLC stimulation by glutamate in predepolarized cells but not in control cells, suggesting that ryanodine receptors could play a role in the potentiation of the mGluR‐mediated activation of PLC by Ca 2+ release in predepolarized cells.