Functional dissection of lysine deacetylases reveals that HDAC1 and p300 regulate AMPK.

First identified as histone-modifying proteins, lysine acetyltransferases (KATs) and deacetylases (KDACs) antagonize each other through modification of the side chains of lysine residues in histone proteins. Acetylation of many non-histone proteins involved in chromatin, metabolism or cytoskeleton regulation were further identified in eukaryotic organisms, but the corresponding enzymes and substrate-specific functions of the modifications are unclear. Moreover, mechanisms underlying functional specificity of individual KDACs remain enigmatic, and the substrate spectra of each KDAC lack comprehensive definition. Here we dissect the functional specificity of 12 critical human KDACs using a genome-wide synthetic lethality screen in cultured human cells. The genetic interaction profiles revealed enzyme-substrate relationships between individual KDACs and many important substrates governing a wide array of biological processes including metabolism, development and cell cycle progression. We further confirmed that acetylation and deacetylation of the catalytic subunit of the adenosine monophosphate-activated protein kinase (AMPK), a critical cellular energy-sensing protein kinase complex, is controlled by the opposing catalytic activities of HDAC1 and p300. Deacetylation of AMPK enhances physical interaction with the upstream kinase LKB1, leading to AMPK phosphorylation and activation, and resulting in lipid breakdown in human liver cells. These findings provide new insights into previously underappreciated metabolic regulatory roles of HDAC1 in coordinating nutrient availability and cellular responses upstream of AMPK, and demonstrate the importance of high-throughput genetic interaction profiling to elucidate functional specificity and critical substrates of individual human KDACs potentially valuable for therapeutic applications.

Involvement of SDF1a and STAT3 in granulocyte colony-stimulating factor rescues optic ischemia-induced retinal function loss by mobilizing hematopoietic stem cells.

PURPOSE: Granulocyte colony-stimulating factor (G-CSF) has been applied clinically for several years. In this study, we used G-CSF to induce the mobilization of hematopoietic progenitor cells into peripheral blood in an ischemia-induced retinal degeneration model. METHODS: Male Sprague-Dawley rats received G-CSF treatment for 5 days following optic ligation. Histologic and functional evaluations were performed and results were compared with those from untreated rats. Real-time PCR, Western blotting, and immunohistochemical analyses were used to evaluate the expression of retinal cell markers and other substances. RESULTS: Retinal histology showed that transient optic ligation induced retinal cell loss. Postischemia, animals that received G-CSF treatment had a higher retinal cell survival rate than that of control animals. Analysis of apoptosis showed that retinas from G-CSF-treated animals exhibited fewer apoptotic cells than those from control retinas. Immunoblotting analyses indicated the presence of greater numbers of CD34-, but less chemokine receptor type 4 (CXCR4)-, and stromal cell-derived factor 1 alpha (SDF1α)-positive cells in the G-CSF-treated ischemic retinas than in ischemic retinas without treatment 14 days after ischemia. The ischemic retinas from G-CSF-treated animals displayed upregulated Thy1 and opsin expression compared with the retinas from untreated animals. Electroretinography indicated superior retinal function in animals treated with G-CSF than in untreated animals postischemia, and that STAT3 might play an important role. CONCLUSIONS: Our results suggest that G-CSF reduces optic ischemia-induced retinal cell loss, possibly through STAT3-regulated mobilization of hematopoietic progenitor cells to the retina.

Intraocular gene transfer of ciliary neurotrophic factor rescues photoreceptor degeneration in RCS rats.

Ciliary neurotrophic factor (CNTF) is known as an important factor in the regulation of retinal cell growth. We used both recombinant CNTF and an adenovirus carrying the CNTF gene to regulate retinal photoreceptor expression in a retinal degenerative animal, Royal College of Surgeons (RCS) rats. Cells in the outer nuclear layer of the retinae from recombinant-CNTF-treated, adenoviral-CNTF-treated, saline-operated, and contralateral untreated preparations were examined for those exhibiting CNTF photoreceptor protective effects. Cell apoptosis in the outer nuclear layer of the retinae was also detected. It was found that CNTF had a potent effect on delaying the photoreceptor degeneration process in RCS rats. Furthermore, adenovirus CNTF gene transfer was proven to be better at rescuing photoreceptors than that when using recombinant CNTF, since adenoviral CNTF prolonged the photoreceptor protection effect. The function of the photoreceptors was also examined by taking electroretinograms of different animals. Adenoviral-CNTF-treated eyes showed better retinal function than did the contralateral control eyes. This study indicates that adenoviral CNTF effectively rescues degenerating photoreceptors in RCS rats.