Quantitative proteomics identifies NCOA4 as the cargo receptor mediating ferritinophagy.
Autophagy, the process by which proteins and organelles are sequestered in double-membrane structures called autophagosomes and delivered to lysosomes for degradation, is critical in diseases such as cancer and neurodegeneration. Much of our understanding of this process has emerged from analysis of bulk cytoplasmic autophagy, but our understanding of how specific cargo, including organelles, proteins or intracellular pathogens, are targeted for selective autophagy is limited. Here we use quantitative proteomics to identify a cohort of novel and known autophagosome-enriched proteins in human cells, including cargo receptors. Like known cargo receptors, nuclear receptor coactivator 4 (NCOA4) was highly enriched in autophagosomes, and associated with ATG8 proteins that recruit cargo-receptor complexes into autophagosomes. Unbiased identification of NCOA4-associated proteins revealed ferritin heavy and light chains, components of an iron-filled cage structure that protects cells from reactive iron species but is degraded via autophagy to release iron through an unknown mechanism. We found that delivery of ferritin to lysosomes required NCOA4, and an inability of NCOA4-deficient cells to degrade ferritin led to decreased bioavailable intracellular iron. This work identifies NCOA4 as a selective cargo receptor for autophagic turnover of ferritin (ferritinophagy), which is critical for iron homeostasis, and provides a resource for further dissection of autophagosomal cargo-receptor connectivity.
1] Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA [2] Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA [3] Harvard Radiation Oncology Program, Boston, Massachusetts 02115, USA [4] Department of Radiation Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Joseph D
JD
Mancias
Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA.
Xiaoxu
X
Wang
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Steven P
SP
Gygi
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Wade
JW
Harper
Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA.
Alec C
AC
Kimmelman
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D001343:Autophagy; D000071190:Autophagy-Related Protein 8 Family; D001682:Biological Availability; D005293:Ferritins / Q000737:chemistry / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D007501:Iron / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D056918:Nuclear Receptor Coactivators / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010588:Phagosomes / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D040901:Proteomics; D013379:Substrate Specificity
D048868:Adaptor Proteins, Signal Transducing; D000071190:Autophagy-Related Protein 8 Family; C498698:GABARAPL2 protein, human; D008840:Microfilament Proteins; C111382:NCOA4 protein, human; D056918:Nuclear Receptor Coactivators; D005293:Ferritins; D007501:Iron