Effect of connective tissue growth factor (CCN2/CTGF) on proliferation and differentiation of mouse periodontal ligament-derived cells

Background: CCN2/CTGF is known to be involved in tooth germ development and periodontal tissue remodeling, as well as in mesenchymal tissue development and regeneration. In this present study, we investigated the roles of CCN2/CTGF in the proliferation and differentiation of periodontal ligament cells (murine periodontal ligament-derived cell line: MPL) in vitro. Results: In cell cultures of MPL, the mRNA expression of the CCN2/CTGF gene was stronger in sparse cultures than in confluent ones and was significantly enhanced by TGF-β. The addition of Recombinant CCN2/CTGF (rCCN2) to MPL cultures stimulated DNA synthesis and cell growth in a dose-dependent manner. Moreover, rCCN2 addition also enhanced the mRNA expression of alkaline phosphatase (ALPase), type I collagen, and periostin, the latter of which is considered to be a specific marker of the periosteum and periodontium; whereas it showed little effect on the mRNA expression of typical osteoblastic markers, e.g., osteopontin and osteocalcin. Finally, rCCN2/CTGF also stimulated ALPase activity and collagen synthesis. Conclusion: These results taken together suggest important roles of CCN2/CTGF in the development and regeneration of periodontal tissue including the periodontal ligament.</p

Insulin receptor substrate-1 (IRS-1) forms a ribonucleoprotein complex associated with polysomes

AbstractInsulin receptor substrates (IRSs) are known to play important roles in mediating intracellular insulin-like growth factors (IGFs)/insulin signaling. In this study, we identified components of messenger ribonucleoprotein (mRNP) as IRS-1-associated proteins. IRS-1 complex formation analysis revealed that IRS-1 is incorporated into the complexes of molecular mass more than 1000kDa, which were disrupted by treatment with RNase. Furthermore, oligo(dT) beads precipitated IRS-1 from cell lysates, showing that the IRS-1 complexes contained messenger RNA. Taken together with the data that IRS-1 was fractionated into the polysome-containing high-density fractions, we concluded that IRS-1 forms the novel complexes with mRNPs

Trk-fused gene (TFG) regulates pancreatic beta cell mass and insulin secretory activity

The Trk-fused gene (TFG) is reportedly involved in the process of COPII-mediated vesicle transport and missense mutations in TFG cause several neurodegenerative diseases including hereditary motor and sensory neuropathy with proximal dominant involvement (HMSN-P). The high coincidence ratio between HMSN-P and diabetes mellitus suggests TFG to have an important role(s) in glucose homeostasis. To examine this possibility, β-cell specific TFG knockout mice (βTFG KO) were generated. Interestingly, βTFG KO displayed marked glucose intolerance with reduced insulin secretion. Immunohistochemical analysis revealed smaller β-cell masses in βTFG KO than in controls, likely attributable to diminished β-cell proliferation. Consistently, β-cell expansion in response to a high-fat, high-sucrose (HFHS) diet was significantly impaired in βTFG KO. Furthermore, glucose-induced insulin secretion was also markedly impaired in islets isolated from βTFG KO. Electron microscopic observation revealed endoplasmic reticulum (ER) dilatation, suggestive of ER stress, and smaller insulin crystal diameters in β-cells of βTFG KO. Microarray gene expression analysis indicated downregulation of NF-E2 related factor 2 (Nrf2) and its downstream genes in TFG depleted islets. Collectively, TFG in pancreatic β-cells plays a vital role in maintaining both the mass and function of β-cells, and its dysfunction increases the tendency to develop glucose intolerance.This study was partly supported by a Grant-in-Aid for Research Activity Start-up (JSPS KAKENHI Grant Number JP15H06427) (to T.Y.) from the Ministry of Education, Science, Sports and Culture, Japan, and grants from Mitsubishi Tanabe Pharma (to T.Y.), Novartis Pharma (to T.Y.), Takeda Science Foundation (to Y.N.), Asahi Life Foundation (to Y.N.) and The Uehara Memorial Foundation (to Y.N.)

Five isoforms of the phosphatidylinositol 3-kinase regulatory subunit exhibit different associations with receptor tyrosine kinases and their tyrosine phosphorylations

AbstractThere are five isoforms of the regulatory subunit for the heterodimeric type of phosphatidylinositol 3-kinase. These five regulatory subunit isoforms were overexpressed using an adenovirus transfection system, and their own tyrosine phosphorylations and associations with various tyrosine kinase receptors were investigated. When overexpressed in CHO-PDGFR cells, the associations of these regulatory subunit isoforms with the platelet-derived growth factor receptor were similar. However, when overexpressed in CHO-IR cells, p55γ exhibited a significantly lower ability to bind with IRS-1 upon insulin stimulation, as compared with other regulatory subunit isoforms. Furthermore, p55α and p55γ were found to be tyrosine-phosphorylated. Finally, interestingly, when overexpressed in CHO-EGFR cells or A431 cells and stimulated with epidermal growth factor (EGF), phosphorylated EGF receptor was detected in p85α, p85β and p50α immunoprecipitates, but not in p55α and p55γ immunoprecipitates. In addition, EGF-induced tyrosine phosphorylation was observed in p85α, p85β, p55α and p55γ, but not in p50α, immunoprecipitates. Thus, each regulatory subunit exhibits specific responses regarding both the association with tyrosine-phosphorylated substrates and its own tyrosine phosphorylation. These results suggest that each isoform possesses specific roles in signal transduction, based on its individual tyrosine kinase receptor

Palmitoylation of the canine histamine H2 receptor occurs at Cys305 and is important for cell surface targeting

AbstractTo determine the presence and functional role of the histamine H2 receptor (H2R) palmitoylation, a receptor with a Cys305 to Ala (A305 receptor) mutation was generated. Wild-type (WT) and A305 receptors were tagged at their N-termini with a hemagglutinin (HA) epitope. WT, but not A305, receptors incorporated [3H]palmitate by metabolic labeling, indicating that the H2R is palmitoylated at Cys305. Immunocytochemistry of WT and A305 receptors expressed in COS7 cells revealed WT receptors to be distributed at the plasma membrane, while the majority of A305 receptors were localized intracellularly with only a small portion being at the plasma membrane. However, the affinity of the A305 receptor for tiotidine was comparable to that of the WT receptor. In addition, when the amounts of cell surface receptors as determined by anti-HA antibody binding were equivalent, A305 receptors mediated production of more cAMP than WT receptors. Preincubation of COS7 cells expressing each receptor with 10−5 M histamine for 30 min reduced subsequent cAMP production in response to histamine via the receptors to similar extents, indicating that palmitoylation is not necessary for desensitization. In addition, cell surface A305 receptors were capable of being internalized from the cell surface at a rate and extent similar to those of WT receptors. Finally, CHO cell lines stably expressing either WT or A305 receptors were incubated with 10−5 M histamine for 1, 6, 12 and 24 h. Total amounts of WT and A305 receptors, as determined by tiotidine binding, were reduced by incubation, indicating downregulation. Downregulation of the A305 receptor was more extensive than that of the WT receptor. Thus, palmitoylation of the H2R might be important for targeting to the cell surface and stability

Involvement of resistin-like molecule β in the development of methionine-choline deficient diet-induced non-alcoholic steatohepatitis in mice

Resistin-like molecule β (RELMβ) reportedly has multiple functions including local immune responses in the gut. In this study, we investigated the possible contribution of RELMβ to non-alcoholic steatohepatitis (NASH) development. First, RELMβ knock-out (KO) mice were shown to be resistant to methionine-choline deficient (MCD) diet-induced NASH development. Since it was newly revealed that Kupffer cells in the liver express RELMβ and that RELMβ expression levels in the colon and the numbers of RELMβ-positive Kupffer cells were both increased in this model, we carried out further experiments using radiation chimeras between wild-type and RELMβ-KO mice to distinguish between the contributions of RELMβ in these two organs. These experiments revealed the requirement of RELMβ in both organs for full manifestation of NASH, while deletion of each one alone attenuated the development of NASH with reduced serum lipopolysaccharide (LPS) levels. The higher proportion of lactic acid bacteria in the gut microbiota of RELMβ-KO than in that of wild-type mice may be one of the mechanisms underlying the lower serum LPS level the former. These data suggest the contribution of increases in RELMβ in the gut and Kupffer cells to NASH development, raising the possibility of RELMβ being a novel therapeutic target for NASH

Prolyl Isomerase Pin1 Regulates Mouse Embryonic Fibroblast Differentiation into Adipose Cells

isomerase, Pin1, regulates insulin signal transduction. Pin1 reduces responses to insulin stimulation by binding CRTC2 (CREB-regulated transcriptional co-activator 2) and PPARγ (peroxisome prolifereator- activated receptor γ), but conversely enhances insulin signaling by binding IRS-1 (insulin receptor substrate-1), Akt kinase, and Smad3. Therefore, it is still unclear whether Pin1 inhibits or enhances adipose cell differentiation. mice was restored by increasing expression of Pin1. We found that Pin1 binds to phosphoThr172- and phosphoSer271-Pro sites in CREB suppress the activity in COS-7 cells.Pin1 enhanced the uptake of triglycerides and the differentiation of MEF cells into adipose cells in response to insulin stimulation. Results of this study suggest that Pin1 down-regulation could be a potential approach in obesity-related dysfunctions, such as high blood pressure, diabetes, non-alcoholic steatohepatitis