Novel functions of Fanconi anemia proteins in selective autophagy and inflammation

Loss-of-function mutations in 19 Fanconi anemia (FA) pathway genes result in a variety of clinical manifestations such as birth defects, cognitive impairment, bone marrow failure (in up to 90% of FA patients within the first two decades of life), increased cancer risk, and accelerated aging [1]. Following DNA damage, proteins of the FA pathway act in a complex cascade to repair interstrand crosslinks (ICLs), which are caused by reactive oxygen species (ROS) or exposure to reactive aldehydes [2]. Although FA is a rare disease, somatic mutations or epigenetic silencing of several FA genes are found commonly in cancers in the general population (e.g. breast, ovarian, and pancreatic cancers). Furthermore, monoallelic germline mutations in at least five genes in the FA pathway, FANCD1/BRCA2, FANCS/BRCA1, BRIP1/FANCJ, PALB2/FANCN, and RAD51C/FANCO are associated with the development of cancer. Selective autophagy is a homeostatic “cellular housekeeping” pathway in which unwanted cytoplasmic cargos are targeted for lysosomal destruction. We discovered that Fanconi anemia genes represent a new class of selective autophagy factors [3, 4]. Our findings may help to explain some of the pathophysiological features of FA, particularly in regard to “environmental factors” [1] that modulate FA disease progression, and may lead to the identification of novel therapeutic targets for FA. We found that, while Fancc is dispensable for starvation-induced general macroautophagy, it is required for virophagy of two genetically unrelated neuronotropic viruses, Sindbis virus and herpes simplex virus type 1, and for host defense in vivo against lethal CNS infection with these viruses. FANCC is also required for Parkin-mediated mitophagy in vitro and for mitochondrial quality control in vivo. Thus, FANCC is required for two distinct forms of selective autophagy: virophagy and mitophagy (Figure 1). Rather than playing an indirect role in selective autophagy, FANCC is likely to function as an adaptor protein in both virophagy and mitophagy. FANCC is contained within membrane-bound autophagolysosomal structures together with Sindbis viral nucleocapsids and (similar to previously identified virophagy factors p62 [5] and SMURF1 [4]) FANCC interacts biochemically with Sindbis virus capsid protein. FANCC also interacts biochemically with Parkin and colocalizes with damaged mitochondria in a Parkin-dependent manner. Thus, Editorial