The gut microbiota affects nutrient acquisition and energy regulation of the host, and can influence the development of obesity, insulin resistance, and diabetes. During feeding, gut microbes produce short-chain fatty acids, which are important energy sources for the host. Here we show that the short-chain fatty acid receptor GPR43 links the metabolic activity of the gut microbiota with host body energy homoeostasis. We demonstrate that GPR43-deficient mice are obese on a normal diet, whereas mice overexpressing GPR43 specifically in adipose tissue remain lean even when fed a high-fat diet. Raised under germ-free conditions or after treatment with antibiotics, both types of mice have a normal phenotype. We further show that short-chain fatty acid-mediated activation of GPR43 suppresses insulin signalling in adipocytes, which inhibits fat accumulation in adipose tissue and promotes the metabolism of unincorporated lipids and glucose in other tissues. These findings establish GPR43 as a sensor for excessive dietary energy, thereby controlling body energy utilization while maintaining metabolic homoeostasis.

Over the last decade, DNA microarray technology has provided a great contribution to the life sciences. The MicroArray Quality Control (MAQC) project demonstrated the way to analyze the expression microarray. Recently, microarray technology has been utilized to analyze a comprehensive microRNA expression profiling. Currently, several platforms of microRNA microarray chips are commercially available. Thus, we compared repeatability and comparability of five different microRNA microarray platforms (Agilent, Ambion, Exiqon, Invitrogen and Toray) using 309 microRNAs probes, and the Taqman microRNA system using 142 microRNA probes. This study demonstrated that microRNA microarray has high intra-platform repeatability and comparability to quantitative RT-PCR of microRNA. Among the five platforms, Agilent and Toray array showed relatively better performances than the others. However, the current lineup of commercially available microRNA microarray systems fails to show good inter-platform concordance, probably because of lack of an adequate normalization method and severe divergence in stringency of detection call criteria between different platforms. This study provided the basic information about the performance and the problems specific to the current microRNA microarray systems.

Background: Runx2, formerly called PEBP2aA or Cbfa1, is a transcription factor whose deletion causes a complete lack of ossification. It directly regulates the expression of osteoblast-specific genes through the osteoblast-specific cis-acting element found in the promoter region of these genes.

Extracellular signal-regulated kinase 5 (ERK5), a member of the mitogen-activated protein kinase family, plays an important role in growth factor signaling to the nucleus. However, molecular mechanisms regulating subcellular localization of ERK5 have remained unclear. Here, we show that nucleocytoplasmic shuttling of ERK5 is regulated by a bipartite nuclear localization signal-dependent nuclear import mechanism and a CRM1-dependent nuclear export mechanism. Our results show that the N-terminal half of ERK5 binds to the C-terminal half and that this binding is necessary for nuclear export of ERK5. They further show that the activating phosphorylation of ERK5 by MEK5 results in the dissociation of the binding between the N-and C-terminal halves and thus inhibits nuclear export of ERK5, causing its nuclear import. These results reveal the mechanism by which the activating phosphorylation of ERK5 induces its nuclear import and suggest a novel example of a phosphorylation-dependent control mechanism for nucleocytoplasmic shuttling of proteins.The mitogen-activated protein kinase (MAPK) cascade, one of signaling modules ubiquitous among eukaryotes, transmits extracellular signals from cell surface receptors to specific targets within cells and regulates a wide variety of cellular functions, including cell proliferation, differentiation, and stress responses. The MAPK cascades are composed of three conserved kinases, MAPK, MAPK kinase (MAPKK), and MAPKK kinase. Extracellular stimuli, such as growth factors, induce sequential phosphorylation of the three kinases; stimulus-activated MAPKK kinase phosphorylates MAPKK, which in turn phosphorylates and activates MAPK. Phosphorylated and activated MAPK phosphorylates downstream targets, such as transcription factors, and modulates their function. To date, at least four subfamily members of the MAPK family have been identified: extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun-N-terminal kinases (JNKs), p38, and ERK5. Each molecule is activated by distinct pathways and transmits signals either independently or coordinately. ERK1/2 is activated mainly by mitogenic stimuli, whereas p38 and JNK are activated mainly by stress stimuli or inflammatory cytokines (2,6,8,19,28,31,32,34).ERK5, also known as big MAP kinase 1, is activated by oxidative stress, hyperosmolarity, and several growth factors (11, 13-15, 20, 22, 23, 25, 42). Unlike other MAPK members, ERK5 has a unique large C-terminal region, whose function is not fully elucidated. MEK5 is the upstream MAPKK that specifically phosphorylates and activates ERK5 (23,42). It has been shown that ERK5 directly interacts with, phosphorylates, and activates several transcription factors including c-Myc, Sap1a, c-Fos, Fra-1, and MEF2 family members (11,20,22,35,41). Moreover, ERK5 is shown to regulate transcription through a kinase-independent mechanism that involves its unique C-terminal half (21, 35). ERK5 is important for promoting cell proliferation (12, 23), differentiation (10), and neuronal survival (37). ERK5-null ...

Although protein folding, in principle is a spontaneous process which depends only upon the amino-acid sequence, the assistance of molecular chaperones is required for many proteins to achieve their final conformation in vivo. While Hsp90 is one of the major molecular chaperones, it has long been the most mysterious among them. Recent advances in our knowledge regarding Hsp90 structure and function, owing to both detailed biochemical and genetic characterizations of Hsp90 co-chaperones, as well as eminent structural studies have established Hsp90 as an ATPase-dependent chaperone, and have provided a paradigm of the Hsp90 chaperone cycle, which is sequentially tuned and coordinated by a variety of co-chaperones. Here we summarize the current knowledge regarding the structure and essential activities of Hsp90, which certainly promises a deeper understanding of the functions of Hsp90 in vivo.

ERK5 plays a crucial role in many biological processes by regulating transcription. ERK5 has a large C-terminal-half that contains a transcriptional activation domain. However, it has remained unclear how its transcriptional activation activity is regulated. Here, we show that the activated kinase activity of ERK5 is required for the C-terminal-half to enhance the AP-1 activity, and that the activated ERK5 undergoes autophosphorylation on its most C-terminal region. Changing these phosphorylatable threonine and serine residues to unphosphorylatable alanines significantly reduces the transcriptional activation activity of ERK5. Moreover, phosphomimetic mutants of the C-terminal-half of ERK5 without an N-terminal kinase domain are shown to be able to enhance the AP-1 activity in fibroblastic cells. These results reveal the role of the stimulus-induced ERK5 autophosphorylation in regulation of gene expression. The mitogen-activated protein kinase (MAPK)2 cascades play an essential role in transducing extracellular signals to cytoplasmic and nuclear effectors, and regulate a variety of cellular functions, including cell proliferation, differentiation, and stress responses. The MAPK cascades are composed of three classes of protein kinases: MAPK, MAPK kinase (MAPKK), and MAPKK kinase (MAPKKK). Each MAPK is activated by specific members of MAPKK, which are activated by MAPKKK (1-13). Four subfamily members of the MAPK family have been relatively well studied; extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38, and ERK5.ERK5 is activated by oxidative stress, hyperosmolarity, and several growth factors including epidermal growth factor and nerve growth factor (14 -18). MEK5 is the upstream MAPKK that specifically phosphorylates and activates ERK5 (16,19). It has been shown that ERK5 directly phosphorylates and activates several transcription factors including c-Myc, Sap1a, c-Fos, Fra-1, and MEF2 family members (15, 17, 20 -22). ERK5 knock-out mice die in embryonic stages with angiogenic failure and cardiovascular defects, and in the adult stages, ERK5 is required for endothelial cell survival and maintenance of blood vascular integrity (23-26). The targeted deletion of MEK5 also causes early embryonic death with cardiovascular defects (27). Moreover, knockdown studies in Xenopus have shown that ERK5 and MEK5 play an essential role in neural differentiation (28).ERK5 has a large, unique C-terminal-half not found in other MAPK family members (19,29). Because of this unique 400-amino acid extension, ERK5 is also called big MAP kinase 1 (BMK1). The C-terminal-half of ERK5 has two proline-rich domains and a bipartite NLS, and shares no high homology with other proteins (19,30,31). Kasler et al. (32) demonstrated that the C-terminal-half of ERK5 has a potent transcriptional activation domain. It was subsequently shown that the ERK5 C-terminal-half is essential for transactivation of MEF2C (30). Moreover, a recent study has shown that ERK5 has two transactivation domains in its C-termin...

Background : ERK5 is the newest subfamily member of the mitogen-activated protein kinase (MAPK) family, and is activated by various extracellular signals including growth factors. MEK5 is a specific activator of ERK5. c-Fos and Fra-1, well-known immediate early gene products, are members of the AP-1 family. We previously reported that activation of the MEK5-ERK5 pathway is able to induce expression of c-Fos.

ObjectiveTrastuzumab has been used for the treatment of HER2-positive breast cancer (BC). However, a subset of BC patients exhibited resistance to trastuzumab therapy. Thus, clarifying the molecular mechanism of trastuzumab treatment will be beneficial to improve the treatment of HER2-positive BC patients. In this study, we identified trastuzumab-responsive microRNAs that are involved in the therapeutic effects of trastuzumab.Methods and ResultsRNA samples were obtained from HER2-positive (SKBR3 and BT474) and HER2-negetive (MCF7 and MDA-MB-231) cells with and without trastuzumab treatment for 6 days. Next, we conducted a microRNA profiling analysis using these samples to screen those microRNAs that were up- or down-regulated only in HER2-positive cells. This analysis identified miR-26a and miR-30b as trastuzumab-inducible microRNAs. Transfecting miR-26a and miR-30b induced cell growth suppression in the BC cells by 40% and 32%, respectively. A cell cycle analysis showed that these microRNAs induced G1 arrest in HER2-positive BC cells as trastuzumab did. An Annexin-V assay revealed that miR-26a but not miR-30b induced apoptosis in HER2-positive BC cells. Using the prediction algorithms for microRNA targets, we identified cyclin E2 (CCNE2) as a target gene of miR-30b. A luciferase-based reporter assay demonstrated that miR-30b post-transcriptionally reduced 27% (p = 0.005) of the gene expression by interacting with two binding sites in the 3′-UTR of CCNE2.ConclusionIn BC cells, trastuzumab modulated the expression of a subset of microRNAs, including miR-26a and miR-30b. The upregulation of miR-30b by trastuzumab may play a biological role in trastuzumab-induced cell growth inhibition by targeting CCNE2.