Cell surface remodeling caused by the loss of the flippase subunit TMEM30A in immune cells

Abstract

ABSTRACT Plasma membrane lipid asymmetry is tightly regulated and fundamental to mammalian cell physiology. TMEM30A is the β-subunit of P4-ATPases, flippase enzymes that maintain strict phosphatidylserine (PS) asymmetry by pumping it from the outer to the cytosolic leaflet. Loss of TMEM30A function causes constitutive PS externalization and has been implicated in diseases such as diffuse large B-cell lymphoma and tumor immune evasion. Here, we systematically define the biophysical and molecular consequences of TMEM30A deletion in immune cells. Using a live-cell lipid reporter, membrane order probe, and surface proteome mapping, we show that TMEM30A-knockout cells display robust PS externalization accompanied by faster lateral diffusion of membrane constituents and decreased plasma membrane order. Surface proteome reorganization includes increased abundance of tetraspanins and CD47. Furthermore, TMEM30A loss triggers glycocalyx remodeling via ADAM10-dependent shedding, which removes major transmembrane mucins, including CD43 and CD162 (also known as SPN and SELPLG, respectively). Together, these data reveal a coordinated reorganization of lipids, glycans and proteins upon TMEM30A loss, suggesting mechanistic links between flippase dysfunction and increased plasma membrane dynamics and potential sensitization to immune therapy. Furthermore, our study provides an integrated surfaceome framework that might shed light on the relationship between TMEM30A expression and clinical outcomes in cancer.