Donnerstag, 13. August 2015

Exosome and microRNA transfer from paracrine & endocrine to cross-kingdom communication

Exosome and microRNA transfer
from paracrine & endocrine to cross-kingdom communication

In multicellular organisms, the cell-to-cell communication is of particular importance for any physiological process, and the proper organization of the entire organism. Numerous studies over the past decade suggest a horizontal transfer of cellular secreted microRNAs between cells, tissues and organs. Hence extracellular RNAs (primarily small non-coding RNAs) represent a novel form of inter-cellular communication by transferring genetic information from a donor cell to a recipient cell. This points to an important new role for small RNAs in inter-cellular communication on the paracrine- and endocrine-level.

Para- and endocrine communication
Small RNAs (primary microRNAs, piRNAs and other small RNA families) can be exported out of the donor cells and transported by various carriers, e.g. membrane-derived vesicles (exosomes, microvesicles, ectosomes, apoptotic bodies, and more), microRNA-binding protein complexes (RBP), or high density lipoproteins (HDL). Secreted microRNAs can be delivered into recipient cells where they function as endogenous microRNAs, simultaneously regulating multiple target genes or signaling pathways.

Cross-kingdom communication
In prokaryotes, this molecular signaling is typically referred to as quorum sensing, whereas in eukaryotic cells, the molecular communication occurs through hormones and cytokines. Recently various publications report that microRNAs can also be transmitted from one species to another, inducing signal interference in distant species, even in a cross-kingdom manner. This new mode of cross-species communication might mediate symbiotic and pathogenic relationships between various organisms. 
This can be of enormous importance in the inter-species communication of microorganisms and their hosts or by diet-derived small RNAs. Higher organisms are constantly under attack from pathogens, resulting in severe consequences on global human or veterinary health. Hence small RNA mediated RNA interference (RNAi) is a conserved regulatory mechanism that is involved in almost all eukaryotic cellular processes, including host immunity and pathogen virulence. Recent evidence supports the significant contribution of small RNAs and RNAi to the communication between hosts and some eukaryotic pathogens or symbiotic microorganisms. Mobile silencing signals - most likely small RNAs - are capable of translocating from the host to its interacting organism, and vice versa.

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