An Argonaute 2 switch regulates circulating miR-210 to coordinate hypoxic adaptation across cells.

Abstract

Complex organisms may coordinate molecular responses to hypoxia by specialized avenues of communication across multiple tissues, but these mechanisms are poorly understood. Plasma-based, extracellular microRNAs have been described, yet their regulation and biological functions in hypoxia remain enigmatic. We found a unique pattern of release of the hypoxia-inducible microRNA-210 (miR-210) from hypoxic and reoxygenated cells. This microRNA is also elevated in human plasma in physiologic and pathologic conditions of altered oxygen demand and delivery. Released miR-210 can be delivered to recipient cells, and the suppression of its direct target ISCU and mitochondrial metabolism is primarily evident in hypoxia. To regulate these hypoxia-specific actions, prolyl-hydroxylation of Argonaute 2 acts as a molecular switch that reciprocally modulates miR-210 release and intracellular activity in source cells as well as regulates intracellular activity in recipient cells after miR-210 delivery. Therefore, Argonaute 2-dependent control of released miR-210 represents a unique communication system that integrates the hypoxic response across anatomically distinct cells, preventing unnecessary activity of delivered miR-210 in normoxia while still preparing recipient tissues for incipient hypoxic stress and accelerating adaptation.