Functional Changes in Potassium Conductances of the Human Neuroblastoma Cell Line SH-SY5Y During In Vitro Differentiation

Tosetti, Patrizia, Vanni Taglietti, and Mauro Toselli. Functional sium channel (hPCN1) was expressed and studied in Xenochanges in potassium conductances of the human neuroblastoma pus oocytes (Philipson et al. 1991). A Shaker potassium cell line SH-SY5Y during in vitro differentiation. J. Neurophysiol. channel, classified as Kv1.5, was cloned from human heart 79: 648–658, 1998. The electrophysiological properties of voltageand transfected in a mouse cell line (Snyders et al. 1993; dependent outward currents were investigated under voltage-clamp Tamkun et al. 1991). The gene for h-DRK1, the human conditions in the human neuroblastoma cell line SH-SY5Y before homologous of rat DRK1 (Frech et al. 1989) and mouse and after in vitro differentiation with retinoic acid, by using the mShab (Pak et al. 1991), was recently cloned from a human whole cell variant of the patch-clamp technique. Voltage steps to genomic DNA library (Albrecht et al. 1993) and its electrodepolarizing potentials from a holding level of 090 mV elicited, physiological properties were investigated after cDNA injecin both undifferentiated and differentiated cells, outward potassium currents that were blocked by tetraethylammonium, but were unaftion in Xenopus oocytes (Benndorf et al. 1994). Because it fected by 4-aminopyridine, cadmium, and by shifts of the holding is possible that host cells used for transfection confer to potentials to 040 mV. These currents activated rapidly and inactiexpressed exogenous channels properties that are not present vated slowly in a voltage-dependent manner. In undifferentiated in native channels (see also Shi et al. 1994), it is of interest cells the threshold for current activation was about 030 mV, with to examine the properties of channels in their tissue of origin. a steady-state half activation potential of 19.5 mV. Maximum conA quantitative study of potassium channels in native tissues ductance was 4.3 nS and mean conductance density was 0.34 mS/ however, is sometimes complicated by the presence of multicm. Steady-state half inactivation potential was 013.8 mV and ple overlapping ionic currents. Ç10% of the current was resistant to inactivation. Both activation The human neuroblastoma cell line SH-SY5Y, established and inactivation kinetics were voltage dependent. In differentiated by repetitive subcloning of the SK-N-SH cell line (Biedler cells the threshold for current activation was about 020 mV, with a half potential for steady-state activation of 37.0 mV. Maximum et al. 1978), exhibits the morphological and biochemical conductance was 15.2 nS and mean conductance density was 0.78 features of cells derived from the neural crest, like sympamS/cm. Steady-state half inactivation potential was 09.7 mV and thetic neurons (Barnes et al. 1981; Ross et al. 1981). These Ç37% of the current was resistant to inactivation. Both activation cells can be induced to acquire a neuronal phenotype by and inactivation kinetics were voltage dependent. This diversity in prolonged treatment, with the differentiating agent retinoic potassium channel properties observed between undifferentiated acid (Påhlman et al. 1984). Because of their capacity to and differentiated cells was related to differences in cell excitabildifferentiate in mature ganglion-like cells and to their celluity. Under current-clamp conditions, the action potential repolarizalar homogeneity, SH-SY5Y cells are a highly suitable model tion rate in differentiated cells was about threefold faster than that for studying the role ion channels play in the excitability of of the abortive action potentials elicitable in undifferentiated cells. cells of human origin. The use of this cell line would also Furthermore, during prolonged stimulation, trains of spikes could permit to combine molecular biological and electrophysiobe generated in some differentiated cells but not in undifferentiated