Abstract:
N-type voltage-gated calcium (Ca
2+) channels (N-type VGCC, Ca
V2.2) mediate Ca
2+ influx in response to action potential at the presynaptic terminal, and play an important role in synaptogenesis, neurotransmitter release and nociceptive signal transduction. It is a new target for the development of drugs for the treatment of neuralgia (chronic pain) and other major diseases. Due to the difficulty of calcium channel expression
in vitro and the detection of channel current, there is a great lack of new drug screening models. In this study, we established and optimized the electrophysiological drug screening model using
Xenopus laevis oocytes for the recombinant expression of Ca
V2.2
in vitro (this study were reviewed and approved by the Ethics Committee of Guangxi University, approval number: GXU-2023-0249). Firstly, the linear plasmids encoding cDNA of major subunit
α1B and auxiliary subunits
α2
δ1 and
β3 of rat Ca
V2.2 were used as templates for
in vitro transcription to generate their related mRNA (cRNA), after which three kinds of cRNA were injected into
Xenopus laevis oocytes at the mass ratio of 2∶1∶1 for expression. The two-electrode voltage clamp (TEVC) technique was used to detect the inward current produced by Ca
V2.2. At the same time, the expression conditions of Ca
V2.2 were optimized, and its gating function was characterized from the aspects of channel activation and inactivation. The results showed that 3-5 days after cRNA microinjection, stable Ca
V2.2-mediated barium ion (Ba
2+) currents were successfully detected. The interference of endogenous potassium channels and Ca
2+-activated chloride channels can be eliminated by tetraethylammonium hydroxide (TEAOH) and 1, 2-bis(2-aminophenoxy)ethane-
N,
N,
N',
N'-tetraacetic acid tetrakis (BAPTA-AM) treatment. The maximum potential for Ca
V2.2 activation is 0 mV, and the current reverses to be outward when the membrane potential is greater than +50 mV. By fitting the steady-state activation and inactivation curves, the half-maximal activation potential and half-maximal inactivation potential of Ca
V2.2 are identified as -15.9 and -60.2 mV. In this study, a stable Ca
V2.2 expression system was established based on
Xenopus laevis oocytes. The
in vitro expression system can provide a new way for the screening of Ca
V2.2 active compounds or lead drugs.