Structural Role of Stomatin in Organizing Functional Membrane Microdomains

Abstract

Stomatin, originally discovered in red blood cells, is a member of the SPFH (Stomatin, Prohibitin, Flotillin, and HflK/C) protein family, which has long been proposed to scaffold functional membrane microdomains (FMMs) enriched in saturated lipids such as cholesterol and sphingomyelin. Stomatin has been reported to associate with a variety of proteins involved in diverse physiological processes, including ion channel regulation, membrane fusion, mechanosensory regulation and vesicle trafficking; however, the mechanisms by which it modulates these interactions remain poorly understood. Here, we determined the cryo-electron microscopy (cryo-EM) structures of stomatin, revealing its hexadecameric assemblies. The SPFH1 domains insert into the cytosolic leaflet of membranes and, together with the N-terminal hairpin, form a potential cholesterol-binding pocket. Liposome reconstitution experiments demonstrated that stomatin self-organizes into clusters, and Spectrum and Polarization Optical Tomography (SPOT) further showed that these clusters enhance membrane lipid order, supporting the proposed role of stomatin in organizing functional membrane microdomains (FMMs). Proteomic mass spectrometry analysis identified numerous stomatin-associated cargo proteins, including solute carrier (SLC) transporters, RAB GTPases, and integrins, suggesting that stomatin regulates solute transport and contributes to vesicle trafficking and cell migration. Together, these findings elucidate the structural and functional roles of stomatin and underscore its potential as a therapeutic target for modulating cancer cell migration and metastasis.