Functional delivery of viral miRNAs via exosomes

Abstract

Noncoding regulatory microRNAs (miRNAs) of cellular and viral origin control gene expression by repressing the translation of mRNAs into protein. Interestingly, miRNAs are secreted actively through small vesicles called "exosomes" that protect them from degradation by RNases, suggesting that these miRNAs may function outside the cell in which they were produced. Here we demonstrate that miRNAs secreted by EBV-infected cells are transferred to and act in uninfected recipient cells. Using a quantitative RT-PCR approach, we demonstrate that mature EBV-encoded miRNAs are secreted by EBV-infected B cells through exosomes. These EBV-miRNAs are functional because internalization of exosomes by MoDC results in a dose-dependent, miRNAmediated repression of confirmed EBV target genes, including CXCL11/ ITAC, an immunoregulatory gene down-regulated in primary EBVassociated lymphomas. We demonstrate that throughout coculture of EBV-infected B cells EBV-miRNAs accumulate in noninfected neighboring MoDC and show that this accumulation is mediated by transfer of exosomes. Thus, the exogenous EBV-miRNAs transferred through exosomes are delivered to subcellular sites of gene repression in recipient cells. Finally, we show in peripheral blood mononuclear cells from patients with increased EBV load that, although EBV DNA is restricted to the circulating B-cell population, EBV BART miRNAs are present in both B-cell and non-B-cell fractions, suggestive of miRNA transfer. Taken together our findings are consistent with miRNA-mediated gene silencing as a potential mechanism of intercellular communication between cells of the immune system that may be exploited by the persistent human γ-herpesvirus EBV.

Exogenous plant MIR168a specifically targets mammalian LDLRAP1: evidence of cross-kingdom regulation by microRNA

“…Thus, secreted miRNAs can serve as a novel class of signaling molecules in mediating intercellular communication [15]. The novel and important functions of the secreted miRNAs were also reported by many other groups [18][19][20][21]. The identification of circulating miRNAs, mainly delivered by cell-secreted MVs, as stable and active signaling molecules opens a new field of research in intercellular and interorganelle signal transduction.…”

Unveiling the effects of the secretome of mesenchymal progenitors from the umbilical cord in different neuronal cell populations

“…However recent reports have increasingly shown that besides the traditional growth factors and cytokines as important players in the secretome, it now appears that most of the cells, including MSCs, secrete large amounts of micro and nano-vesicles, either constitutively or upon activation signals [24]. Although little is still known on the biogenesis and physiological role of these entities, their potential as mediators of cell interactions has been reported by different authors [25][26][27][28]. Indeed exosome or microvesicles can operate in a multitude of ways since they can be considered as complex vectors that can hold known biological molecules.…”

Towards mechanisms and standardization in extracellular vesicle and extracellular RNA studies: results of a worldwide survey

“…Ambivalence was apparent for the transport and uptake categories, with most votes in the middle of the range. These results suggest perceived unmet needs across all topics, but especially in cargo loading and cargo transfer.

10.1080/20013078.2018.1535745-F0002Figure 2.EV topics about which we know the “most” [1] to the “least” [5]. Respondents were required to rank the five topics from most [1] to least knowledge [2].

…”

“…Studies of extracellular vesicles (EVs) and RNA were united in the mid- to late-2000s by findings that RNA molecules were incorporated into EVs and thereby transferred from cell to cell [1-5]. Communication via extracellular RNA (exRNA) was soon accepted as a novel set of mechanisms to explain the increasingly appreciated paracrine effects of EVs.…”