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Stress-induced Cdk5 activity enhances cytoprotective basal autophagy in Drosophila melanogaster by phosphorylating acinus at serine437.

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 Drosophila melanogaster Cdk5 regulates 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 p35 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.

SUBMITTER: Nandi N

PROVIDER: S-EPMC5760206 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Stress-induced Cdk5 activity enhances cytoprotective basal autophagy in Drosophila melanogaster by phosphorylating acinus at serine437.

Nandi Nilay N Tyra Lauren K LK Stenesen Drew D Krämer Helmut H

eLife 20171211

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 Drosophila melanogaster Cdk5 regulates 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 requir ...[more]

PMID: 29227247

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Project description:Although the treatment of brain tumors by targeting kinase-regulated macroautophagy/autophagy, is under investigation, the precise mechanism underlying autophagy initiation and its significance in glioblastoma (GBM) remains to be defined. Here, we report that PAK1 (p21 [RAC1] activated kinase 1) is significantly upregulated and promotes GBM development. The Cancer Genome Atlas analysis suggests that the oncogenic role of PAK1 in GBM is mainly associated with autophagy. Subsequent experiments demonstrate that PAK1 indeed serves as a positive modulator for hypoxia-induced autophagy in GBM. Mechanistically, hypoxia induces ELP3-mediated PAK1 acetylation at K420, which suppresses the dimerization of PAK1 and enhances its activity, thereby leading to subsequent PAK1-mediated ATG5 (autophagy related 5) phosphorylation at the T101 residue. This event not only protects ATG5 from ubiquitination-dependent degradation but also increases the affinity between the ATG12-ATG5 complex and ATG16L1 (autophagy related 16 like 1). Consequently, ELP3-dependent PAK1 (K420) acetylation and PAK1-mediated ATG5 (T101) phosphorylation are required for hypoxia-induced autophagy and brain tumorigenesis by promoting autophagosome formation. Silencing PAK1 with shRNA or small molecule inhibitor FRAX597 potentially blocks autophagy and GBM growth. Furthermore, SIRT1-mediated PAK1-deacetylation at K420 hinders autophagy and GBM growth. Clinically, the levels of PAK1 (K420) acetylation significantly correlate with the expression of ATG5 (T101) phosphorylation in GBM patients. Together, this report uncovers that the acetylation modification and kinase activity of PAK1 plays an instrumental role in hypoxia-induced autophagy initiation and maintaining GBM growth. Therefore, PAK1 and its regulator in the autophagy pathway might represent potential therapeutic targets for GBM treatment.Abbreviations: 3-MA: 3-methyladenine; Ac-CoA: acetyl coenzyme A; ATG5: autophagy related 5; ATG16L1, autophagy related 16 like 1; BafA1: bafilomycin A1; CDC42: cell division cycle 42; CGGA: Chinese Glioma Genome Atlas; CHX, cycloheximide; ELP3: elongator acetyltransferase complex subunit 3; GBM, glioblastoma; HBSS: Hanks balanced salts solution; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MAP2K1: mitogen-activated protein kinase kinase 1; MAPK14, mitogen-activated protein kinase 14; PAK1: p21 (RAC1) activated kinase 1; PDK1: pyruvate dehydrogenase kinase 1; PGK1, phosphoglycerate kinase 1; PTMs: post-translational modifications; RAC1: Rac family small GTPase 1; SQSTM1: sequestosome 1; TCGA, The Cancer Genome Atlas.

Dataset Information

Stress-induced Cdk5 activity enhances cytoprotective basal autophagy in Drosophila melanogaster by phosphorylating acinus at serine437.

Publications

Stress-induced Cdk5 activity enhances cytoprotective basal autophagy in <i>Drosophila melanogaster</i> by phosphorylating acinus at serine<sup>437</sup>.

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