Murine embryonic stem cell line CGR8 expresses all subtypes of muscarinic receptors and multiple nicotinic receptor subunits: Down-regulation of α4- and β4-subunits during early differentiation

Non-neuronal acetylcholine mediates its cellular effects via stimulation of the G-protein-coupled muscarinic receptors and the ligand-gated ion channel nicotinic receptors. The murine embryonic stem cell line CGR8 synthesizes and releases non-neuronal acetylcholine. In the present study a systematic investigation of the expression of nicotinic receptor subunits and muscarinic receptors was performed, when the stem cells were grown in the presence or absence of LIF, as the latter condition induces early differentiation. CGR8 cells expressed multiple nicotinic receptor subtypes (α3, α4, α7, α9, α10, β1, β2, β3, β4, γ, δ, ε) and muscarinic receptors (M1, M3, M4, M5); M2 was detected only in 2 out of 8 cultures. LIF removal caused a down-regulation only of the α4- and β4-subunit. In conclusion, more or less the whole repertoire of cholinergic receptors is expressed on the murine embryonic stem cell line CGR8 for mediating cellular signaling of non-neuronal acetylcholine which acts via auto- and paracrine pathways. During early differentiation of the murine CGR8 stem cell signaling via nicotinic receptors containing α4- or β4 subunits is reduced. Thus, the so-called neuronal α4 nicotine receptor composed of these subunits may be involved in the regulation of pluripotency in this murine stem cell line.