Horizontal transfer of RNAs: exosomes as mediators of intercellular communication

Abstract

Multicellular organisms are similar to biological communities, consisting of various cell types; thus, inter-cell communication is critical for the functioning of the whole system that ultimately constitutes a living being. Conventional models of cellular exchange include signaling molecules and direct contact-mediated cell communications. Exosomes, small vesicles originating from an inward budding of the plasma membrane, represent a new avenue for signaling between cells. This interchange is achieved by packaging RNA species into exosomes endowed with specific cell surface-targeting motifs. The delivered RNA molecules are functional, and mRNA can be translated into new proteins, while microRNAs (miRNAs) target host mRNAs in the recipient cell. RNA involved in transmitting information or molecules between cells is called exosomal RNA (esRNA). This review summarizes the characteristics of exosomes, specifically focusing on their role in the horizontal transfer of cellular information.

Figure 1

Schematic diagram illustrates the model for sorting of cargo into MVB and fate of the exosomes. Sorting of exosomes followed by the biosynthetic pathway leads to miRNA processing, exocytosis, or back fusion with the plasma membrane/within an endosomal compartment or lysosomal degradation.

Figure 2

A model for horizontal transfer of biological information through exosomes. Components transported via exosomes include proteins, including receptors, antigenic peptides and other cargo proteins. Nucleic acids transferred through exosomes include RNA, specifically microRNAs that can further regulate the gene expression in the recipient cells.