Unusual properties of α7 nicotinic acetylcholine receptor ion channels in B lymphocyte-derived SP-2/0 cells

Oleksandr Tarasenko; Sergiy Voytenko; Lyudmyla Koval; Olena Lykhmus; Olena Kalashnyk; Maryna Skok

doi:10.1016/j.intimp.2020.106373

Unusual properties of α7 nicotinic acetylcholine receptor ion channels in B lymphocyte-derived SP-2/0 cells

Int Immunopharmacol. 2020 Mar 9:82:106373. doi: 10.1016/j.intimp.2020.106373. Online ahead of print.

Authors

Oleksandr Tarasenko¹, Sergiy Voytenko², Lyudmyla Koval³, Olena Lykhmus⁴, Olena Kalashnyk⁴, Maryna Skok⁵

Affiliations

¹ Bogomoletz Institute of Physiology, 4, Bogomoletz Str, 01024 Kyiv, Ukraine. Electronic address: tar@biph.kiev.ua.
² Bogomoletz Institute of Physiology, 4, Bogomoletz Str, 01024 Kyiv, Ukraine.
³ Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine. Electronic address: lkoval@biochem.kiev.ua.
⁴ Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine.
⁵ Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine. Electronic address: skok@biochem.kiev.ua.

PMID: 32163855
DOI: 10.1016/j.intimp.2020.106373

Abstract

This study demonstrates the presence of α7 nicotinic acetylcholine receptors (nAChR) in B lymphocyte-derived SP-2/0 cells by means of flow cytometry and immunocytochemistry. According to lectin and sandwich ELISA, the α7 subunits expressed in SP-2/0 cells are more glycosylated compared to those expressed in the brain or normal B lymphocytes and are combined with β2 subunits. At zero and negative pipette potentials, either acetylcholine or α7-specific agonist PNU282987 stimulated the ion channel activity in SP-2/0 cells revealed by single channel patch-clamp recordings. The conductivity was within the range of 19 to 39 pS and reversal potential was between -17 mV and +28 mV, the currents were potentiated by α7-specific positive allosteric modulator PNU120596 and were partially blocked by α7-specific antagonist methyllicaconitine (MLA). However, they were oriented downwards suggesting that the channels mediated the cation outflux rather than influx. As shown by Ca²⁺ imaging studies, PNU282987 did not stimulate immediate Ca²⁺ influx into SP-2/0 cells. Instead, Ca²⁺ influx through Ca-release-activated channels (CRACs) was observed within minutes after either PNU282987 or MLA application. It is concluded that SP-2/0 express α7β2 nAChRs, which mediate the cation outflux under negative pipette potentials applied, possibly, due to depolarized membrane or negative surface charge formed by carbohydrate residues. In addition, α7β2 nAChRs may influence CRACs in ion-independent way.

Keywords: B lymphocytes-derived cell line; CRACs; Ca(2+) influx; Ion channel; α7 nicotinic acetylcholine receptor.