The essential role of sphingolipids in TRPC5 ion channel localization and functionality within lipid rafts

Abstract

Sphingolipids are critical components of cellular membranes that play a pivotal role in modulating ion channel function by forming lipid rafts that stabilize and localize these channels. These lipids regulate membrane fluidity and protein-lipid interactions, directly influencing ion channel activity, trafficking, and signaling pathways essential for maintaining cellular homeostasis. Despite their fundamental role, the impact of sphingolipids on ion channel functionality, particularly within the nervous system, remains insufficiently understood. This study addresses this gap by examining the influence of sphingolipids on transient receptor potential canonical 5 (TRPC5), a key brain ion channel involved in sensory transduction and linked to conditions such as obesity, anxiety, and postpartum depression when disrupted. In this study, we demonstrate that TRPC5 is localized within lipid rafts. Inhibition of sphingolipid synthesis through myrioncin (Myr), the sphingomyelin synthase 2 inhibitor Ly93, or D,L-erythro-PDMP hydrochloride (PMDP) significantly disrupts TRPC5 localization at the plasma membrane. Treatment with lipid raft disruptors methyl-β-cyclodextrin (MCD) or sphingomyelin phosphodiesterase 3 (SMPD3), in conjunction with sphingolipid synthesis inhibitors, led to decreased TRPC5-mediated calcium flux and currents. This highlights the critical importance of TRPC5 localization in lipid rafts for its functionality. Furthermore, LC-MS/MS-based sphingolipidomics has shown that a balanced sphingolipid profile is crucial for channel function. Alterations in sphingolipid metabolism, especially the deficiency of sphingomyelin and glycosphingolipids, may primarily disrupt lipid raft structure. Interactions between amino acid residues with phenyl ring side chains and lipids at the inner and outer plasma membrane edges serve as ‘fixators’, anchoring TRPC5 channels within lipid rafts. Given the structural similarities among TRP channels, we propose that sphingolipid metabolic homeostasis may universally influence TRP channel activity, potentially explaining diverse neurological disorder phenotypes associated with sphingolipid metabolism disruptions.