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

✍ Scribed by Helen L. Reeve; Peter F. T. Vaughan; Chris Peers

• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 985 KB
• Volume: 429
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00373996

✦ Synopsis

The effects of phorbol esters on Ca 2 + 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 #M), known activators of protein kinase C (PKC), enhanced Ca 2 + channel currents in a voltage-dependent manner similar to that of Bay K 8644. TPA also enhanced Ca 2+ 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~-phorbol-12,13-didecanoate (4~-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 Ca 2+ channel currents. Residual Ca 2 + channel currents recorded after exposure to 1 #M co-conotoxin GVIA were still enhanced by TPA, but in the presence of either Bay K 8644 (5 #M) or nifedipine (5/~M), TPA was without effect. When cells were pre-incubated for 10 rain at 37~ with 100 nM TPA, currents subsequently recorded in its absence were enhanced as compared to untreated cells; 5/~M nifedipine still inhibited currents to the same degree. This enhancement was not mimicked by 4~-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 Ca 2+ channel currents in SH-SY5Y cells via a PKC-independent mechanism which appears similar to that induced by Bay K 8644. By contrast,