Circulating TNFR1 exosome-like vesicles partition with the LDL fraction of human plasma.
Extracellular type I tumor necrosis factor receptors (TNFR1) are generated by two mechanisms, proteolytic cleavage of TNFR1 ectodomains and release of full-length TNFR1 in the membranes of exosome-like vesicles. Here, we assessed whether TNFR1 exosome-like vesicles circulate in human blood. Immunoelectron microscopy of human serum demonstrated TNFR1 exosome-like vesicles, with a diameter of 27-36nm, while Western blots of human plasma showed a 48-kDa TNFR1, consistent with a membrane-associated receptor. Gel filtration chromatography revealed that the 48-kDa TNFR1 in human plasma co-segregated with LDL particles by size, but segregated independently by density, demonstrating that they are distinct from LDL particles. Furthermore, the 48-kDa exosome-associated TNFR1 in human plasma contained a reduced content of N-linked carbohydrates as compared to the 55-kDa membrane-associated TNFR1 from human vascular endothelial cells. Thus, a distinct population of TNFR1 exosome-like vesicles circulate in human plasma and may modulate TNF-mediated inflammation.
Zhang
Jing
J
Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Hawari
Feras I
FI
Shamburek
Robert D
RD
Adamik
Barbara
B
Kaler
Maryann
M
Islam
Aminul
A
Liao
Da-Wei
DW
Rouhani
Farshid N
FN
Ingham
Matthew
M
Levine
Stewart J
SJ
D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure*; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood*; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000097:blood*; D022161:Transport Vesicles / Q000648:ultrastructure*
D008077:Lipoproteins, LDL; D047888:Receptors, Tumor Necrosis Factor, Type I