Golgi Outpost Synthesis Impaired by Toxic Polyglutamine Proteins Contributes to Dendritic Pathology in Neurons

Dendrite aberration is a common feature of neurodegenerative diseases caused by protein toxicity, but the underlying mechanisms remain largely elusive. Here, we show that nuclear polyglutamine (polyQ) toxicity resulted in defective terminal dendrite elongation accompanied with a loss of Golgi outposts (GOPs) and decreased supply of plasma membrane (PM) in Drosophila Class IV da (C4da) neurons. mRNA sequencing revealed that down-regulated genes by polyQ proteins included many secretory pathway-related genes, including COPII genes regulating GOP synthesis. Transcription factor enrichment analysis identified CREB3L1/CrebA, which regulates COPII gene expression. CrebA overexpression in C4da neurons restored the dysregulation of COPII genes, GOP synthesis, and PM supply. The ChIP-PCR assay revealed that CrebA expression was regulated by CBP, which was sequestered by polyQ proteins. Furthermore, co-overexpression of CrebA and Rac1 synergistically restored the polyQ-induced dendrite pathology. Collectively, our results suggest that GOPs impaired by polyQ proteins contribute to dendrite pathology through the CBP-CrebA-COPII pathway. Overall design: mRNA expression profiles of the heads of Drosophila melanogaster with or without expressing MJDtr-78Q were examined by Illumina Hi-seq 2500.