Neuronal-like features of TE671 cells: presence of a functional nicotinic cholinergic receptor

The human medulloblastoma cell line TE671 has been investigated and found to have several 'neuron-like' properties, including the presence of a functional nicotinic receptor. The cell line TE671 is composed of at least 5 stable morphologic cell types. Resting potentials recorded with intracellular microelectrodes were low (-17 mV to -31 mV) but all cell types were capable of generating Na+-dependent action potentials following anode-brake stimulation. Rare spontaneous hyperpolarizing potentials, suggestive of synaptic activity, were also observed. TE671 cells were completely unresponsive to iontophoresed GABA but did respond to acetylcholine (ACh). The most common response to ACh was a depolarization accompanied by an increase in membrane conductance. When large amounts of ACh were delivered, depolarization followed by hyperpolarization was frequently observed. Depolarizing responses to ACh are abolished in Na+-free solution while hyperpolarizing responses to ACh were still present following the removal of both Na+ and Cl- from the bathing solution. The depolarization to ACh is mediated through a nicotinic cholinergic receptor. Depolarization was completely blocked in the presence of 10(-6) M alpha-bungarotoxin, 4.4 x 10(-5) M D-tubocurarine, or 10(-4) M decamethonium. Atropine was only 50% effective at 10(-4) M and hexamethonium was ineffective at 10(-4) M. In vitro binding of receptor ligands to membranes prepared from TE671 cells revealed high levels of [125I]alpha-bungarotoxin (alpha-BuTx) binding sites, in addition to lower levels of other ligand binding sites. [125I]alpha-BuTx bound to a single, saturable high affinity site in either membrane preparations or intact TE671 cells. Binding was potently inhibited by the classical nicotinic acetylcholine receptor antagonists D-tubocurarine and decamethonium. Nicotine and carbamylcholine showed intermediate potencies in inhibiting binding while atropine and hexamethonium showed little ability to inhibit [125I]alpha-BuTx binding. The data obtained from [125I]alpha-BuTx binding studies agree qualitatively with the electrophysiological data on the depolarizing ACh response and together they provide strong evidence that TE671 cells possess a functional nicotinic acetylcholine receptor. This cell may therefore be useful as a stable source with which to characterize mammalian neuronal nicotinic acetylcholine receptors and membrane events related to its activation.