title: Secretory mechanisms and intercellular transfer of microRNAs in living cells.
abstract: The existence of circulating microRNAs (miRNAs) in the blood of cancer patients has raised the possibility that miRNAs may serve as a novel diagnostic marker. However, the secretory mechanism and biological function of extracellular miRNAs remain unclear. Here, we show that miRNAs are released through a ceramide-dependent secretory machinery and that the secretory miRNAs are transferable and functional in the recipient cells. Ceramide, whose biosynthesis is regulated by neutral sphingomyelinase 2 (nSMase2), triggers secretion of small membrane vesicles called exosomes. The decreased activity of nSMase2 with a chemical inhibitor, GW4869, and a specific small interfering RNA resulted in the reduced secretion of miRNAs. Complementarily, overexpression of nSMase2 increased extracellular amounts of miRNAs. We also revealed that the endosomal sorting complex required for transport system is unnecessary for the release of miRNAs. Furthermore, a tumor-suppressive miRNA secreted via this pathway was transported between cells and exerted gene silencing in the recipient cells, thereby leading to cell growth inhibition. Our findings shed a ray of light on the physiological relevance of secretory miRNAs.
authors.affiliation: Section for Studies on Metastasis, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Kosaka
authors.forename: Haruhisa
authors.initials: H
authors.lastname: Iguchi
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yoshioka
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Takeshita
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Matsuki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ochiya
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D001597:Benzylidene Compounds / Q000494:pharmacology; D001692:Biological Transport; D014408:Biomarkers, Tumor / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D017077:Culture Media, Conditioned / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism
chemical_list: D000814:Aniline Compounds; D001597:Benzylidene Compounds; D014408:Biomarkers, Tumor; D017077:Culture Media, Conditioned; C468773:GW 4869; D035683:MicroRNAs; D034741:RNA, Small Interfering; D013108:Sphingomyelin Phosphodiesterase; C519633:SMPD2 protein, human