Intestinal ferritinophagy is regulated by HIF-2 and is essential for systemic iron homeostasis

Abstract

Iron is critical for many processes including oxygen transport and erythropoiesis. Transcriptomic analysis demonstrates that HIF-2 regulates over 90% of all transcripts induced following iron deficiency in the intestine. However, beyond divalent metal transporter 1 (DMT1), ferroportin 1 (Fpn1) and duodenal cytochrome b (Dcytb), no other genes/pathways have been critically assessed with respects to their importance in intestinal iron absorption. Ferritinophagy is associated with cargo specific autophagic breakdown of ferritin and subsequent release of iron. We show here that nuclear receptor co-activator 4 (NCOA4)-mediated intestinal ferritinophagy is integrated to systemic iron demand via HIF-2. Duodenal NCOA4 expression is regulated by HIF-2 during high systemic iron demands. Moreover, overexpression of intestinal HIF-2 is sufficient to activate NCOA4 and promote lysosomal degradation of ferritin. Promoter analysis revealed NCOA4 as a direct HIF-2 target. To demonstrate the importance of intestinal HIF-2/ferritinophagy axis in systemic iron homeostasis, whole body and intestine-specific NCOA4-null mouse lines were assessed. These analyses demonstrate an iron sequestration in the enterocytes, and significantly high tissue ferritin levels in the dietary iron deficiency and acute hemolytic anemia models. Together, our data suggests efficient ferritinophagy is critical for intestinal iron absorption and systemic iron homeostasis.