L-cysteine modulates visceral nociception mediated by the CaV2.3 R-type calcium channels

Slobodan M Todorovic,Mackenzie Walz,Toni Schneider,Seyed Mohammadreza Ghodsi

doi:10.1007/s00424-022-02674-y

Abstract

CaV2.3 channels are subthreshold voltage-gated calcium channels that play crucial roles in neurotransmitter release and regulation of membrane excitability, yet modulation of these channels with endogenous molecules and their role in pain processing is not well studied. Here, we hypothesized that an endogenous amino acid l-cysteine could be a modulator of these channels and may affect pain processing in mice. To test this hypothesis, we employed conventional patch-clamp technique in the whole-cell configuration using recombinant CaV2.3 subunit stably expressed in human embryonic kidney (HEK-293) cells. We found in our in vitro experiments that l-cysteine facilitated gating and increased the amplitudes of recombinant CaV2.3 currents likely by chelating trace metals that tonically inhibit the channel. In addition, we took advantage of mouse genetics in vivo using the acetic acid visceral pain model that was performed on wildtype and homozygous Cacna1e knockout male littermates. In ensuing in vivo experiments, we found that l-cysteine administered both subcutaneously and intraperitoneally evoked more prominent pain responses in the wildtype mice, while the effect was completely abolished in knockout mice. Conversely, intrathecal administration of l-cysteine lowered visceral pain response in the wildtype mice, and again the effect was completely abolished in the knockout mice. Our study strongly suggests that l-cysteine-mediated modulation of CaV2.3 channels plays an important role in visceral pain processing. Furthermore, our data are consistent with the contrasting roles of CaV2.3 channels in mediating visceral nociception in the peripheral and central pain pathways.

Highlights

Voltage-gated calcium channels (VGCCs) play essential roles in the nervous system including gene expression (L-type), neurotransmitter release (N, P/Q, and R-type), and membrane depolarization (T-type)
Subsequent studies have shown that neuronal Cav2.3 channels in the periphery, spinothalamic, and thalamocortical tracts contribute to gene translation and cell membrane excitability [18]
Immunohistochemistry experiments have shown the abundance of CaV2.3 protein in the dorsal root ganglia (DRG) and reticular nucleus of thalamus (RTN), as well as neocortex, suggesting their possible role in peripheral and central nociception and underlying sensory processing [5, 18, 23]

Summary

Introduction

Voltage-gated calcium channels (VGCCs) play essential roles in the nervous system including gene expression (L-type), neurotransmitter release (N-, P/Q-, and R-type), and membrane depolarization (T-type). The Cav2.3 (former α1E-subunit) or R-type channel is a subtype of the VGCC family that was discovered and cloned. Subsequent studies have shown that neuronal Cav2.3 channels in the periphery, spinothalamic, and thalamocortical tracts contribute to gene translation and cell membrane excitability [18]. Immunohistochemistry experiments have shown the abundance of CaV2.3 protein in the dorsal root ganglia (DRG) and reticular nucleus of thalamus (RTN), as well as neocortex, suggesting their possible role in peripheral and central nociception and underlying sensory processing [5, 18, 23]. Electrophysiological studies have reported enhanced firing frequency in neurons in the presence of endogenous reducing amino acid l-cysteine [7]. Previous studies have suggested a few specific pathways for the action of these substances,

Methods

Results

Conclusion