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Accumulating evidence highlights the role of histone acetyltransferase GCN5 in the regulation of cell metabolism in metazoans.Here, we report that GCN5 is a negative regulator of autophagy, a lysosome-dependent catabolic mechanism. In animal cells and Drosophila, GCN5 inhibits the biogenesis of autophagosomes and lysosomes by targeting TFEB, the master transcription factor for autophagy-and lysosome-related gene expression. We show that GCN5 is a specific TFEB acetyltransferase, and acetylation by GCN5 results in the decrease in TFEB transcriptional activity. Induction of autophagy inactivates GCN5, accompanied by reduced TFEB acetylation and increased lysosome formation. We further demonstrate that acetylation at K274 and K279 disrupts the dimerization of TFEB and the binding of TFEB to its target gene promoters. In a Tau-based neurodegenerative Drosophila model, deletion of dGcn5 improves the clearance of Tau protein aggregates and ameliorates the neurodegenerative phenotypes. Together, our results reveal GCN5 as a novel conserved TFEB regulator, and the regulatory mechanisms may be involved in autophagy-and lysosome-related physiological and pathological processes. ª 2019 The Authors. Published under the terms of the CC BY NC ND 4.0 license EMBO reports 21: e48335 | 2020 H LC3-II formation in GFP-GCN5-overexpressing HeLa cells. I GFP-p62 levels in HEK293 cells stably expressing GFP-p62. The cells were cultured with GCN5 siRNA with or without CQ. J PDLIM1 and IFT20 protein levels in GCN5 KO HEK293 cells with or without transfection of GFP-GCN5 and addition of CQ. KRepresentative images of mCherry-Atg8a (red) and DAPI (blue) in Drosophila larval fat body in which dGcn5 is overexpressed (OE) or silenced (KD) using the pan-fat body driver (cg-GAL4). Drosophila (cg-GAL4/+) was used as the control (graph represents data from three independent experiments with ≥ 30 cells per condition; mean AE SEM; *P < 0.05, ***P < 0.001, Student's t-test; Scale bars, 10 lm).

Nanotopographic cues from biomaterials exert powerful effects on the osteogenic differentiation of mesenchymal stem cells because of their niche-mimicking features. However, the biological mechanisms underlying cell lineage determination by surface nanotopography have not been clearly elucidated. Here, we explored the osteogenic behavior of human bone marrow mesenchymal stem cells (hBMSCs) on poly-l-lactide nanofibers with different orientations and monitored the dynamic changes in global gene expression triggered by topographical cues. RT-PCR analysis of osteogenic marker genes and ALP activity assays demonstrated that hBMSCs cultured on random nanofibers showed enhanced osteogenic-specific fate compared with those on aligned nanofibers. Microarray analysis demonstrated a similar temporal change in gene expression patterns between hBMSCs cultured on random nanofibers and those induced with an osteogenic supplement (OS). However, the extent of osteogenic differentiation on the fibrous scaffold was much lower than that driven by chemical OS. In-depth pathway analysis revealed that focal adhesion kinase, TGF-β, Wnt, and MAPK pathways were involved in the activation of osteogenic differentiation in hBMSCs on random nanofibers. These findings suggested that a lower extent but similar rhythm of dynamic cellular behavior was induced on random nanofibers when compared with the OS condition and that mechanotransduction could trigger nonspecific and multilevel responses in hBMSCs. This study provides insight into the regulation of osteogenesis directed by substratum surfaces.

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