Gain-of-function screen identifies a role of the Sec61α translocon in Drosophila postmitotic neurotoxicity

To elucidate the intrinsic mechanisims of neurotoxicity induction, including those underlying neural cell death and neurodegeneration, we developed a gain-of-function screen for gene products causing neural cell loss. To identify novel genes with a cell-death-related function in neurons, we screened 4,964 Drosophila GS lines, in which one or two genes from much of the Drosophila genome can be overexpressed. Approximately 0.68% of the GS lines produced phenotypes involving a loss of postmitotic neurons. Of these, we identified and characterized the endd2 gene, which encodes the Drosophila ortholog of Sec61 alpha (DSec61 alpha), an endoplastnic reticulum protein with protein translocation activity. Ectopic expression of DSec61 alpha caused neural cell death accompanied by the accumulation of ubiquitinated proteins, which was mediated by DSec61 alpha's translocon activity. This supported our previous observation that the DSec61 alpha translocon contributes to expanded polyglutamine-mediated neuronal toxicity, which is also associated with ubiquitinated protein accumulation. These data suggest that the translocon may be a novel component of neural cell death and degeneration pathways. Our approach can be used to identify potential neurotoxic factors within the whole genome, which will increase our understanding of the molecular mechanisms of various types of cell death, including those associated with human neurodegenerative diseases. (c) 2005 Elsevier B.V. All rights reserved.