Euphorbiasteroid,a component of Euphorbia lathyris L., inhibits adipogenesis of 3T3‐L1 cells via activation of AMP‐activated protein kinase

The purpose of this study is to investigate the effects of euphorbiasteroid, a component of Euphorbia lathyris L., on adipogenesis of 3T3‐L1 pre‐adipocytes and its underlying mechanisms. Euphorbiasteroid decreased differentiation of 3T3‐L1 cells via reduction of intracellular triglyceride (TG) accumulation at concentrations of 25 and 50 μM. In addition, euphorbiasteroid altered the key regulator proteins of adipogenesis in the early stage of adipocyte differentiation by increasing the phosphorylation of AMP‐activated protein kinase (AMPK) and acetyl‐CoA carboxylase. Subsequently, levels of adipogenic proteins, including fatty acid synthase, peroxisome proliferator‐activated receptor‐γ and CCAAT/enhancer‐binding protein α, were decreased by euphorbiasteroid treatment at the late stage of adipocyte differentiation. The anti‐adipogenic effect of euphorbiasteroid may be derived from inhibition of early stage of adipocyte differentiation. Taken together, euphorbiasteroid inhibits adipogenesis of 3T3‐L1 cells through activation of the AMPK pathway. Therefore, euphorbiasteroid and its source plant, E. lathyris L., could possibly be one of the fascinating anti‐obesity agent. Copyright © 2015 John Wiley & Sons, Ltd.     

Expression of the Xenopus homologue of the receptor for activated C-kinase 1 (RACK1) in the Xenopus embryo

We have isolated the Xenopus homologue of the receptor for activated C-kinase 1 (RACK1), whose amino acid sequence shows significant similarity with other vertebrate RACK1s. XRACK1 is a maternally expressed gene and its zygotic expression is detected in the antero-dorsal region and dorsal midline in the late neurula. At tailbud stage, rather diffuse staining is seen in the somite and head. Later, XRACK1 mRNA is expressed highly in ventrally migrating abdominal muscle anlagen, where it remains expressed during subsequent stages.     

Protective effect of isoflavones against homocysteine-mediated neuronal degeneration in SH-SY5Y cells

Previously, we reported that isoflavones exert a protective effect against the endoplasmic reticulum (ER) stress-mediated neuronal degeneration, and ER stress-mediated homocysteine toxicity may play an important role in the pathogenesis of neurodegeneration. Therefore, in this study we investigated the effects of isoflavones (genistein and daidzein) against homocysteine-mediated neurotoxicity in SH-SY5Y human neuroblastoma cells. The treatment of cells with either 17β-estradiol or isoflavones significantly protected the cells against homocysteine-mediated apoptosis. Isoflavones repressed homocysteine-mediated ER stress, reflected in the reduced expression of the immunoglobin heavy chain-binding protein mRNA, spliced X-box-protein-1 mRNA and the phosphorylated form of eukaryotic translation initiation factor 2α protein. Homocysteine caused significant increases in intracellular S-adenosylhomocysteine (SAH) and DNA damage. Isoflavones significantly alleviated DNA damage, but did not change SAH levels. Furthermore, the treatment of cells with isoflavones significantly reduced the microtubule-associated protein tau hyperphosphorylation by inactivating glycogen synthase kinase-3β and activating serine/threonine-protein phosphatase 2A. These results clearly demonstrate that isoflavones alleviate the ER stress- and DNA damage-mediated neurodegeneration caused by homocysteine.     

Regulation of telomeric repeat binding factor 1 binding to telomeres by casein kinase 2-mediated phosphorylation

Telomere maintenance is essential for continued cell proliferation and chromosome stability. Telomeres are maintained by telomerase and a collection of associated proteins. The telomeric protein telomeric repeat binding factor 1 (TRF1) negatively regulates telomere length by inhibiting access of telomerase at telomere termini. Here we report that TRF1 interacts with the beta subunit of casein kinase 2 (CK2) and serves as a substrate for CK2. CK2-mediated phosphorylation is required for the efficient telomere binding of TRF1 in vitro and in vivo. Inhibition of CK2 by the CK2 inhibitor 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole decreased the ability of TRF1 to bind telomeric DNA. The resulting telomere-unbound form of TRF1 was then ubiquitinated and degraded by the proteasome. Partial knockdown of CK2 by small interfering RNA resulted in removal of TRF1 from telomeres and subsequent degradation of TRF1. Mapping of the CK2 target site identified threonine 122 as a substrate in TRF1. A threonine to alanine change at this position led to a diminished DNA binding due to reduced dimerization of TRF1. In addition, phosphorylation of threonine 122 seemed critical for TRF1-mediated telomere length control. Our findings suggest that CK2-mediated phosphorylation of TRF1 plays an important role in modulating telomere length homeostasis by determining the levels of TRF1 at telomeres.