Human TRPM5 Stable Cell Line - HEK293

Tetrameric cation channels of the transient receptor potential melastatin (TRPM) family are involved in a wide range of biological processes, spanning from temperature sensing and taste signal transduction to the regulation of cardiac function, inflammatory pain, and insulin secretion. The cytoplasmic domains of TRPM proteins are structurally highly conserved, accounting for more than 70% of the entire protein. To investigate how these cytoplasmic domains regulate channel gating, researchers employed electrophysiology and cryo-electron microscopy to study TRPM5, a channel primarily activated by intracellular Ca2+. The results demonstrate that the activation of mammalian TRPM5 channels is significantly influenced by Ca2+-dependent desensitization. Structural analysis of rat TRPM5 revealed a series of conformational changes triggered by Ca2+ binding, wherein the formation and dissociation of inter-subunit interfaces on the cytoplasmic side appear to regulate the processes of channel activation and desensitization. These studies elucidate the importance of cytoplasmic-side assembly for TRPM5 channel function and lay the groundwork for future research on other members of the TRPM family.

Here, researchers evaluated the responses of "inside-out" membrane patches from HEK293 cells expressing human, rat, mouse, or zebrafish TRPM5 channels to intracellular Ca2+ (Figure 1). Upon induction by 25 μM free Ca2+, all four orthologous channels generated similar TRPM5-specific outwardly rectifying currents. However, when exposed to 5.4 mM Ca2+, the currents peaked at similar amplitudes at both positive and negative membrane voltages before undergoing decay; this decay was more pronounced in the human, rat, and mouse channels than in the zebrafish ortholog (Figure 1 B-F). This marked difference in the extent of desensitization highlights a key distinction in gating properties between mammalian and zebrafish TRPM5 channels.

Figure 1. Mammalian and zebrafish TRPM5 channels possess a distinct activation profile. (Karuppan S, et al., 2024)