WDR45 mutation dysregulates iron homeostasis by promoting the chaperone-mediated autophagic degradation of ferritin heavy chain in an ER stress/p38 dependent mechanism

Abstract

Ferritin is the main iron storage protein that plays a pivotal role in the regulation of iron homeostasis. Mutations in the autophagy protein WD repeat domain 45 (WDR45) that lead to iron overload is associated with the human β-propeller protein-associated neurodegeneration (BPAN). Previous studies have demonstrated that ferritin was decreased in WDR45 deficient cells, but the mechanism remains unclear. In this study, we have demonstrated that the ferritin heavy chain (FTH) could be degraded via chaperone-mediated autophagy (CMA) in ER stress/p38-dependent pathway. In HeLa cells, inducing the ER stress activated CMA, therefore facilitated the degradation of FTH, and increased the content of Fe²⁺. However, the increased CMA activity and Fe²⁺ as well as the decreased FTH by ER stress inducer were restored by pre-treatment with p38 inhibitor. Overexpression of a mutant WDR45 activated CMA thus promoted the degradation of FTH. Furthermore, inhibition of ER stress/p38 pathway resulted in reduced activity of CMA, which consequently elevated the protein level of FTH but reduced the Fe²⁺ level. Our results revealed that WDR45 mutation dysregulates iron homeostasis by activating CMA, and promotes FTH degradation through ER stress/p38 signaling pathway.

Keywords: BPAN; Chaperone-mediated autophagy; ER stress; FTH; Iron homeostasis; WDR45; p38.