WDR45 contributes to neurodegeneration through regulation of ER homeostasis and neuronal death.

ABSTRACT

Mutations in the macroautophagy/autophagy gene WDR45 cause ß-propeller protein-associated neurodegeneration (BPAN); however the molecular and cellular mechanism of the disease process is largely unknown. Here we generated constitutive wdr45 knockout (KO) mice that displayed cognitive impairments, abnormal synaptic transmission and lesions in several brain regions. Immunohistochemistry analysis showed loss of neurons in prefrontal cortex and basal ganglion in aged mice, and increased apoptosis in prefrontal cortex, recapitulating a hallmark of neurodegeneration. Quantitative proteomic analysis showed accumulation of endoplasmic reticulum (ER) proteins in KO mouse. At the cellular level, accumulation of ER proteins due to WDR45 deficiency resulted in increased ER stress and impaired ER quality control. The unfolded protein response (UPR) was elevated through ERN1/IRE1 or EIF2AK3/PERK pathway, and eventually led to neuronal apoptosis. Suppression of ER stress or activation of autophagy through MTOR inhibition alleviated cell death. Thus, the loss of WDR45 cripples macroautophagy machinery in neurons and leads to impairment in organelle autophagy, which provides a mechanistic understanding of cause of BPAN and a potential therapeutic strategy to treat this genetic disorder.Abbreviations 7-ADD 7-aminoactinomycin D; ASD autistic spectrum disorder; ATF6 activating transcription factor 6; ATG autophagy-related; BafA1 bafilomycin A1; BCAP31 B cell receptor associated protein 31; BPAN ß-propeller protein-associated neurodegeneration; CCCP carbonyl cyanide m-chlorophenylhydrazone; CDIPT CDP-diacylglycerol-inositol 3-phosphatidyltransferase (phosphatidylinositol synthase); DDIT3/CHOP DNA-damage inducible transcript 3; EIF2A eukaryotic translation initiation factor 2A; EIF2AK3/PERK eukaryotic translation initiation factor 2 alpha kinase 3; ER endoplasmic reticulum; ERN1/IRE1 endoplasmic reticulum to nucleus signaling 1; GFP green fluorescent protein; HIP hippocampus; HSPA5/GRP78 heat shock protein family A (HSP70) member 5; KO knockout; LAMP1 lysosomal-associated membrane 1; mEPSCs miniature excitatory postsynaptic currents; MG132 N-benzyloxycarbonyl-L-leucyl-L-leucyl-L-leucinal; MIB mid-brain; MTOR mechanistic target of rapamycin kinase; PCR polymerase chain reaction; PFA paraformaldehyde; PFC prefrontal cortex; PRM parallel reaction monitoring; RBFOX3/NEUN RNA binding protein, fox-1 homolog [C. elegans] 3; RTN3 reticulon 3; SEC22B SEC22 homolog B, vesicle trafficking protein; SEC61B SEC61 translocon beta subunit; SEM standard error of the mean; SNR substantia nigra; SQSTM1/p62 sequestosome 1; TH tyrosine hydroxylase; Tm tunicamycin; TMT tandem mass tag; TUDCA tauroursodeoxycholic acid; TUNEL terminal deoxynucleotidyl transferase dUTP nick-end labeling; UPR unfolded protein response; WDR45 WD repeat domain 45; WT wild type; XBP1 X-box binding protein 1.