MicroRNA-210 decreases heme levels by targeting ferrochelatase in cardiomyocytes.

Microrna-210 (mir-210) increases in hypoxia and regulates mitochondrial respiration through modulation of iron-sulfur cluster assembly proteins (iscu1/2),a protein that is involved in fe/s cluster synthesis. however,it is not known how mir-210 affects cellular iron levels or production of heme,another iron containing molecule that is also needed for cellular and mitochondrial function. to screen for micro-ribonucleic acids (mirnas) regulated by iron,we performed a mirna gene array in neonatal rat cardiomyocytes treated with iron chelators. levels of mir-210 are significantly increased with iron chelation,however,this response was mediated entirely through the hypoxia-inducible factor (hif) pathway. furthermore,mir-210 reduced cellular heme levels and the activity of mitochondrial and cytosolic heme-containing proteins by modulating ferrochelatase (fech),the last enzyme in heme biosynthesis. mutation of the 2 mir-210 binding sites in the 3' untranslated region (utr) of fech reversed the mir-210 response,while mutation of either binding site in isolation did not exert any effects. changes mediated by mir-210 in heme and fech were independent of iscu,as overexpression of an iscu construct lacking the 3' utr does not alter mir-210 regulation of heme and fech. finally,fech levels increased in hypoxia,and this effect was not reversed by mir-210 knockdown,suggesting that the effects of mir-210 on heme are restricted to normoxic conditions,and that the pathway is overriden in hypoxia. our results identify a role for mir-210 in the regulation of heme production by targeting and inhibiting fech under normoxic conditions.