Enhancement of Ca2+ channel currents in human neuroblastoma (SH-SY5Y) cells by phorbol esters with and without activation of protein kinase C.

Abstract

The effects of phorbol esters on Ca2+ channel currents in human neuroblastoma SH-SY5Y cells were studied using whole-cell patch-clamp recordings. Bath application of 12-O-tetradecanoylphorbol-13-acetate (TPA) or phorbol 12,13-dibutyrate (PDBu; 100 nM to 1 microM), known activators of protein kinase C (PKC), enhanced Ca2+ channel currents in a voltage-dependent manner similar to that of Bay K 8644. TPA also enhanced Ca2+ channel currents during cell dialysis with the PKC pseudosubstrate, PKC(19-36), and in cells which had been pre-incubated with 500 nM staurosporine, and which were exposed to staurosporine during recordings. Application of 4 alpha-phorbol-12,13-didecanoate (4 alpha-PDD; 100 nM), which does not activate PKC, caused current enhancement similar to the effects of TPA. However, intracellular dialysis of TPA was without effect on Ca2+ channel currents. Residual Ca2+ channel currents recorded after exposure to 1 microM omega-conotoxin GVIA were still enhanced by TPA, but in the presence of either Bay K 8644 (5 microM) or nifedipine (5 microM), TPA was without effect. When cells were pre-incubated for 10 min at 37 degrees C with 100 nM TPA, currents subsequently recorded in its absence were enhanced as compared to untreated cells; 5 microM nifedipine still inhibited currents to the same degree. This enhancement was not mimicked by 4 alpha-PDD, and was inhibited by staurosporine. Our results indicate that acute applications of phorbol esters (at concentrations commonly used to activate PKC) enhance L-type Ca2+ channel currents in SH-SY5Y cells via a PKC-independent mechanism which appears similar to that induced by Bay K 8644. By contrast, pre-incubation with TPA enhances both L- and N-type currents via activation of PKC.

• Authors: H L Reeve, P F Vaughan, C Peers
• Journal: Pflugers Archiv : European journal of physiology (Pflugers Arch) Vol. 429 Issue 5 Pg. 729-37 (Mar 1995) ISSN: 0031-6768 [Print] Germany
• PMID: 7540748 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Calcium Channel Agonists
• Calcium Channel Blockers
• Phorbol Esters
• 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
• Protein Kinase C

Topics

• 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester (pharmacology)
• Brain Neoplasms (metabolism)
• Calcium Channel Agonists (pharmacology)
• Calcium Channel Blockers (pharmacology)
• Electrophysiology
• Enzyme Activation (drug effects)
• Humans
• Neuroblastoma (metabolism)
• Patch-Clamp Techniques
• Phorbol Esters (pharmacology)
• Protein Kinase C (metabolism)
• Tumor Cells, Cultured