Abstract
Spontaneous transmitter release was studied at frog neuromuscular junctions exposed to the tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA), a specific activator of protein kinase C (PrkC). TPA at concentrations between 10−7 and 10−6 M induced a dose-dependent increase in miniature end-plate potential frequency. This frequency increase was enhanced by raising [Ca]0, diminished by lowering the temperature of the bath and virtually abolished in Ca2+-free Ringer. The TPA effect was only poorly reversible after washing. TPA was ineffective in increasing spontaneous release of transmitter at phosphatidylcholine-pretreated neuromuscular junctions. It is suggested that PrkC might play a role in neuromuscular transmission processes.
Similar content being viewed by others
References
Castagna M, Takai Y, Kaibuchi K, Sano K, Kikkawa U, Nishizuka Y (1982) Direct activation of calcium-activated, phospholipid-dependent protein kinase by tumor-promoting phorbol esters. Biol Chem 257:7847–7851
Cohen P (1982) The role of protein phosphorylation in neural and hormonal control of cellular activity. Nature (Lond) 296:613–620
Erulkar SD (1983) The modulation of neurotransmitter release at synaptic junctions. Rev Physiol Biochem Pharmacol 98:63–175
Kaibuchi K, Takai Y, Nishizuka Y (1981) Cooperative roles of various membrane phospholipids in the activation of calciumactivated, phospholipid-dependent protein kinase. J Biol Chem 256:7146–7149
Katz B, Miledi R (1965) Propagation of electric activity in motor nerve terminals. Proc R Soc Lond Biol 161:453–482
Katz B, Miledi R (1968) The role of calcium in neuromuscular facilitation. J Physiol (Lond) 195:481–492
Nestler EJ, Walaas, SI, Greengard P (1984) Neuronal phosphoprotein: physiological and clinical implications. Science 225:1357–1364
Nishizuka Y (1984a) Turnover of inositol phospholipids and signal transduction. Science 225:1365–1370
Nishizuka Y (1984b) The role of protein kinase C in cell surface signal transduction and tumour promotion. Nature 308:693–698
Pozzan T, Gatti G, Dozio N, Vicentini LM, Meldolesi J (1984) Ca-dependent and independent release of neurotransmitters from PC12 cells: a role for protein kinase C activation? J Cell Biol 99:628–638
Szoka F Jr, Papahadjopoulos D (1978) Procedure for preparation of liposomes with large internal aqueous space and high capture by reverse-phase evaporation. Proc Natl Acad Sci USA 75:4194–4198
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Eusebi, F., Molinaro, M. & Caratsch, C.G. Effects of phorbol ester on spontaneous transmitter release at frog neuromuscular junction. Pflugers Arch. 406, 181–183 (1986). https://doi.org/10.1007/BF00586680
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00586680