Heterologous sensitization of adenylate cyclase is protein kinase A-dependent in Cath.a differentiated (CAD)-D2L cells
Article first published online: 3 FEB 2004
Journal of Neurochemistry
Volume 82, Issue 5, pages 1087–1096, September 2002
How to Cite
Johnston, C. A., Beazely, M. A., Vancura, A. F., Wang, J. K. T. and Watts, V. J. (2002), Heterologous sensitization of adenylate cyclase is protein kinase A-dependent in Cath.a differentiated (CAD)-D2L cells. Journal of Neurochemistry, 82: 1087–1096. doi: 10.1046/j.1471-4159.2002.01033.x
- Issue published online: 3 FEB 2004
- Article first published online: 3 FEB 2004
- Received February 18, 2002; revised manuscript received May 9, 2002; accepted May 13, 2002.
- adenylate cyclase;
- D2 dopamine receptor;
- heterologous sensitization;
- neuronal cell line;
- protein kinase A;
Persistent activation of Gαi/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 D2L 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 D2L dopamine receptor (CAD-D2L). Long-term 18 h treatment with the D2 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-D2L 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-D2L cells.