Transmembrane proteins tetraspanin 4 and CD9 sense membrane curvature

Abstract

Multiple membrane shaping and remodelling processes are associated with tetraspanin proteins by yet unknown mechanisms. Tetraspanins constitute a family of proteins with four transmembrane domains present in high copy numbers in every cell type. Prominent examples are tetraspanin4 and CD9 that are required for the fundamental cellular processes of migrasome formation and fertilization, respectively. These proteins are enriched in curved membrane structures, such as cellular retraction fibers and oocyte microvilli. The factors driving this enrichment are, however, unknown. Here we revealed that tetrasapnin4 and CD9 are curvature sensors with a preference for positive membrane curvature. To this end we used a biomimetic system emulating membranes of cell retraction fibers and oocyte microvilli by membrane tubes pulled out of giant plasma membrane vesicles with controllable membrane tension and curvature. We developed a simple thermodynamic model for the partitioning of curvature sensors between flat and tubular membranes, which allowed us to estimate the individual intrinsic curvatures of the two proteins. Overall, our findings illuminate the process of migrasome formation and oocyte microvilli shaping and provide insight into the role of tetraspanin proteins in membrane remodelling processes.

Extracellular domain 2 of TSPAN4 governs its functions

“…Previously, we demonstrated that TSPAN4 is sensitive to membrane curvature and undergoes significant enrichment in membranes with positive membrane curvature ( 14 ). We generated giant plasma membrane vesicles (GPMVs) from HEK293T cells expressing TSPAN4-GFP and labeled them with the plasma membrane dye DiI-C12 ( Fig.…”

Supported Natural Membranes on Microspheres for Protein–Protein Interaction Studies

“…To compensate for the fluorescence yield difference between OG and GFP, the fluorescent intensities of water-solvated OG and GFP were measured. 42 The mole fraction of the protein in the GPMV was calculated as follows: where I microsphere OG is the intensity of the microspheres coated with liposomes containing known concentration of OG (Figure S6).…”

Transmembrane proteins tetraspanin 4 and CD9 sense membrane curvature

“…Raw data have been deposited in the OSF ( https://osf.io/p47c8/?view_only=963a1c0c7a744eb8b7e57daf98e23d07 ) ( 37 ).…”