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Heterologous sensitization of adenylate cyclase is protein kinase A‐dependent in Cath.a differentiated (CAD)‐D 2L cells
Author(s) -
Johnston Christopher A.,
Beazely Michael A.,
Vancura Amanda F.,
Wang James K. T.,
Watts Val J.
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2002.01033.x
Subject(s) - adenylate kinase , sensitization , heterologous , cyclase , protein kinase a , microbiology and biotechnology , chemistry , biology , kinase , neuroscience , biochemistry , enzyme , gene
Persistent activation of Gα i/o ‐coupled receptors results in a paradoxical enhancement of subsequent drug‐stimulated adenylate cyclase activity. The exact mechanism of this up‐regulation in the cyclic AMP signaling pathway, known as heterologous sensitization, remains undefined. The present study was designed to investigate the involvement of cyclic AMP‐dependent protein kinase in D 2L receptor–mediated sensitization in a neuronal cellular environment. The current studies were conducted in the Cath.a differentiated (CAD) cell line transfected stably with the D 2L dopamine receptor (CAD‐D 2L ). Long‐term 18 h treatment with the D 2 receptor agonist, quinpirole, resulted in a two‐fold enhancement of forskolin‐stimulated cyclic AMP accumulation. Similarly, long‐term treatment with the PKA inhibitors, H89 or Rp‐8Br‐cAMP, also enhanced adenylate cyclase activity. In contrast, long‐term activation of protein kinase A (PKA) by forskolin, isobutylmethylxanthine (IBMX), or dibutyryl cyclic AMP caused a significant reduction in subsequent forskolin‐stimulated cyclic AMP accumulation and reduced both quinpirole‐ and H89‐induced heterologous sensitization. The effects of PKA inhibitors and activators did not involve changes in PKA subunit expression. RT‐PCR analysis of adenylate cyclase isoform expression patterns revealed the expression of mRNA for ACVI and ACIX in CAD‐D 2L cells. The ability of ACVI to be negatively regulated by PKA is consistent with the observation that inhibition of PKA results in heterologous sensitization of adenylate cyclase activity in CAD‐D 2L cells.