By contrast, co-expression of wild-type Cdk5 (K) or the required cofactor p35 (L) enhance AcnWT-induced roughness. Quantification of pS437 and polyQ-levels in eye discs. elife-30760-fig8-data1.xlsx (44K) DOI:?10.7554/eLife.30760.022 Figure 9source data 1: Quantification of pS437-Acn in neurodegenerative model eye discs. elife-30760-fig9-data1.xlsx (39K) DOI:?10.7554/eLife.30760.024 Supplementary file 1: Suppression of Acn-induced eye roughness by kinase knock down. The effect on eye morphology of GMR-Gal4-driven expression of UAS-RNAi transgenes with or without UAS-Acinus was scored and recorded as the number of flies with normal eyes (score?=?1), eye with mild errors (score?=?2), rough eyes (score?=?3) or severely rough eyes (score?=?4). The percentage suppression or enhancement was calculated from the average score for each RNAi transgene compared to UAS-Acn in the absence of RNAi transgenes. Positive or negative numbers indicate suppression and enhancement, respectively. Green or red colors highlight UAS-transgenes with more than 50% suppression or enhancement. Numbers in parenthesis indicated stock numbers of the Bloomington Drosophila stock center or, if starting with a V..’, from the Vienna Resource Center. All flies were raised at 28C. elife-30760-supp1.docx (27K) DOI:?10.7554/eLife.30760.025 Supplementary file 2: Genetic interactions of Acn with p38b and Cdk5/p35 loss and gain of function. The effect on eye morphology of GMR-Gal4-driven expression of UAS-transgenes with or without UAS-Acinus was scored and recorded as the number of flies with normal eyes (score?=?1), eye with mild errors (score?=?2), rough eyes (score?=?3) or severely rough eyes (score?=?4). The percentage suppression or enhancement was calculated from the average score for each RNAi transgene compared to UAS-Acn in the absence of RNAi transgenes. Positive or negative numbers indicate suppression and enhancement, respectively. Green or red colors highlight UAS-transgenes with more than 50% suppression or enhancement. Numbers in parenthesis indicated stock numbers of the Bloomington Drosophila stock center. All flies were raised at 28C. elife-30760-supp2.docx (111K) DOI:?10.7554/eLife.30760.026 Supplementary file 3: Methazathioprine Genotypes of flies used for each figure. Relevant genotypes are listed for all Figures. elife-30760-supp3.docx (36K) DOI:?10.7554/eLife.30760.027 Supplementary file 4: Key resources table. elife-30760-supp4.xlsx (17K) DOI:?10.7554/eLife.30760.028 Transparent reporting form. elife-30760-transrepform.docx (245K) DOI:?10.7554/eLife.30760.029 Abstract Cdk5 is a post-mitotic kinase with complex roles in maintaining neuronal health. The various mechanisms by which Cdk5 inhibits and promotes neurodegeneration are still poorly understood. Here, we show that in Cdk5 regulates Methazathioprine basal autophagy, a key mechanism suppressing neurodegeneration. In a targeted screen, Cdk5 genetically interacted with Acinus (Acn), a primarily nuclear protein, which promotes starvation-independent, basal autophagy. Loss of Cdk5, or its required cofactor p35, reduces S437-Acn phosphorylation, whereas Cdk5 gain-of-function increases pS437-Acn levels. The phospho-mimetic S437D mutation stabilizes Acn and promotes basal autophagy. In mutants, basal autophagy and lifespan are reduced, but restored to near wild-type levels in the presence of stabilized AcnS437D. Expression of aggregation-prone polyQ-containing proteins or the Amyloid-42 peptide, but not alpha-Synuclein, enhances Cdk5-dependent phosphorylation of S437-Acn. Our data indicate that Cdk5 is required to maintain the protective role of basal autophagy in the initial responses to a subset of neurodegenerative challenges. (Haberman et al., 2010; Nandi et al., 2014). Mammalian Acn had originally been identified as a caspase target aiding in chromatin modifications in apoptotic cells (Sahara et al., 1999; Joselin et al., 2006). In mammalian and can elevate its levels in a cell type-specific manner (Nandi et al., 2014). An unexpected consequence of such elevated Acn was an increase in basal, starvation-independent autophagy. High-level Acn overexpression by the Gal4/UAS system triggers autophagy-dependent death in (Haberman et al., 2010). By contrast, Acn levels were modestly increased by the AcnD527A mutation that interferes with its Caspase-mediated cleavage or by phospho-mimetic mutations in two AKT1 target sites that reduce this cleavage (Nandi et al., 2014). Such mildly elevated Acn levels yielded elevated basal autophagy with beneficial outcomes including enhanced starvation resistance, prolonged life span and reduced loads of polyQ aggregates in a model of Huntingtons disease (Nandi et al., 2014). Here, we show that similar benefits are gained by phosphorylation of Acn at serine 437. We identify Cdk5 as the kinase which mediates this phosphorylation and show that Cdk5 activity is enhanced in the presence of multiple aggregation-prone proteins, including Huntingtin-Q93 (Htt.Q93), SCA3.Q78, and Amyloid-beta peptide 42 (A42). These findings offer new insights into the complex mechanisms balancing the effects of loss and gain-of-function of Cdk5 on neurodegenerative diseases. Results Rabbit polyclonal to GRB14 Phosphorylation of conserved serine 437 stabilizes Acn Phosphorylation of conserved C-terminal Akt1-target sites (Figure 1A) regulates Acn levels Methazathioprine in flies and mammalian cells (Hu et.