Abstract

Filamin-A and a4ß1 Integrin are CD47-dependent Cargo Proteins in Extracellular Vesicles

Sukhbir Kaur, Staff Scientist,

CD47 is a ubiquitously expressed membrane protein that functions as a receptor for thrombospondin-1 and the counter receptor for signal regulatory protein alpha in phagocytes. CD47 is expressed on a subset of extracellular vesicles (EVs) that contain a distinct population of RNAs {Kaur, 2018 #1}. CD47 colocalizes predominantly with CD81 and a4ß1 integrin on Jurkat T cell-derived EVs but not with classical EVs bearing CD63 or CD9 {Kaur, 2022 #2}. CD47 and its cytoplasmic adapter ubiquilin-1 regulate which RNAs are packaged into T cell EVs via physical interactions with components of the exportin-1/Ran nuclear export complex and its known cargos {Kaur, 2022 #3}. Here, we report that disruption of CD47 in Jurkat T lymphoblast and PC3 prostate carcinoma cells impairs the sorting of filamin A and a4ß1 integrin into EVs. Targeted mass spectrometry and coimmunoprecipitation analyses indicate that CD47 indirectly interacts with filamin A either via ubiquilin-1/Exportin-1 or ß1 Integrin. Filamin A may thereby play an important role in CD47-dependent sorting of protein and RNA cargoes into specific subsets of EVs.

Conclusions: CD47 and ubiquilin-1 interact with filamin A, which is known to interact with the cytoplasmic domain of ß1 integrins to regulate integrin function. Less filamin A and a4ß1 integrin sort into EV in the absence of CD47, suggesting that CD47 promotes filamin A and integrin sorting into EV, mediated through ubiquilin1 and/or exportin-1.