No abstract

Macroautophagy/autophagy is involved in myeloid cellular repair, destruction, and osteoclast differentiation; conversely, KLF2 (kruppel-like factor 2 [lung]) regulates myeloid cell activation and differentiation. To investigate the specific role of KLF2 in autophagy, osteoclastic differentiation was induced in monocytes in presence or absence of the autophagy inhibitor 3-methyladenine (3-MA), KLF2 inducer geranylgeranyl transferase inhibitor (GGTI298), and adenoviral overexpression of KLF2. We found that the number of autophagic cells and multinucleated osteoclasts were significantly decreased in presence of 3-MA, GGTI298, and KLF2 overexpressed cells indicating involvement of KLF2 in these processes. In addition, autophagy-related protein molecules were significantly decreased after induction of KLF2 during the course of osteoclastic differentiation. Furthermore, induction of arthritis in mice reduced the level of Klf2 in monocytes, and enhanced autophagy during osteoclastic differentiation. Mechanistically, knocking down of KLF2 increased the level of Beclin1 (BECN1) expression, and conversely, KLF2 over-expression reduced the level of BECN1 in monocytes. Moreover, 3-MA and GGTI298 both reduced myeloid cell proliferation concomitantly upregulating senescence-related molecules (CDKN1A/p21 and CDKN1B/p27 kip1). We further confirmed epigenetic regulation of Becn1 by modulating Klf2; knocking down of Klf2 increased the levels of histone activation marks H3K9 and H4K8 acetylation in the promoter region of Becn1; and overexpression of Klf2 decreased the levels of H4K8 and H3K9 acetylation. In addition, osteoclastic differentiation also increased levels of H3K9 and H4K8 acetylation in the promoter region of Becn1. Together these findings for the first time revealed that Klf2 critically regulates Becn1-mediated autophagy process during osteoclastogenesis.

SummaryIn the current era of genomic medicine, diseases are identified as manifestations of anomalous patterns of gene expression. Cancer is the principal example among such maladies. Although remarkable progress has been achieved in the understanding of the molecular mechanisms involved in the genesis and progression of cancer, its epigenetic regulation, particularly histone deacetylation, demands further studies. Histone deacetylases (HDACs) are one of the key players in the gene expression regulation network in cancer because of their repressive role on tumor suppressor genes. Higher expression and function of deacetylases disrupt the finely tuned acetylation homeostasis in both histone and non-histone target proteins. This brings about alterations in the genes implicated in the regulation of cell proliferation, differentiation, apoptosis and other cellular processes. Moreover, the reversible nature of epigenetic modulation by HDACs makes them attractive targets for cancer remedy. This review summarizes the current knowledge of HDACs in tumorigenesis and tumor progression as well as their contribution to the hallmarks of cancer. The present report also describes briefly various assays to detect histone deacetylase activity and discusses the potential role of histone deacetylase inhibitors as emerging epigenetic drugs to cure cancer. (J Histochem Cytochem 62:11-33, 2014)

To define the regulatory role of Kruppel-like factor 2 ( KLF2 ) during osteoblast (OB) differentiation of dental pulp-derived stem cell (DPSC)s, herein, we show that the levels of KLF2 and autophagy-related molecules were significantly increased in differentiated cells. Gain-of-function and loss-of-function approaches of KLF2 confirmed that KLF2 modulated autophagic and OB differentiation-related molecules. In addition, knockdown of the autophagic molecule ( ATG7 or BECN1 ) in DPSCs resulted in reduced levels of KLF2 and OB differentiation-related molecules. Conversely, the induction of autophagy increased levels of KLF2 and OB differentiation-related molecules. Moreover, OB differentiation induced mitophagy and mitochondrial membrane potential-related molecules. In addition, OB differentiation reduced the generation of total and mitochondrial ROS productions and induced intracellular Ca 2+ production. Measurements of glycolysis and oxidative phosphorylation simultaneously in live cells revealed that OB differentiation decreased the oxygen consumption rate, which is an indicator of mitochondrial respiration and reduced the level of ATP production. Furthermore, flux analysis also revealed that OB differentiation increased the extracellular acidification rate (ECAR) in the non-glycolytic acidification, and the glycolytic capacity conditions, increasing the lactate production and reducing the metabolic activity of the cells. Thus, a metabolic shift from mitochondrial respiration to the glycolytic pathway was observed during OB differentiation. Finally, chromatin immunoprecipitation (ChIP) analysis confirmed that the KLF2 and active epigenetic marks (H3K27Ac and H3K4me3) were upregulated in the promoter region of ATG7 during OB differentiation. These results provide evidence that the mitophagy process is important during OB differentiation, and KLF2 critically regulates it.