A zinc-binding citrus protein metallothionein can act as a plant defense factor by controlling host-selective ACR-toxin production

Metallothionein is a small cysteine-rich protein known to have a metal-binding function. We isolated three different lengths of rough lemon cDNAs encoding a metallothionein (RlemMT1, RlemMT2 and RlemMT3), and only RlemMT1-recombinant protein had zinc-binding activity. Appropriate concentration of zinc is an essential micronutrient for living organisms, while excess zinc is toxic. Zinc also stimulates the production of host-selective ACR-toxin for citrus leaf spot pathogen of Alternaria alternata rough lemon pathotype. Trapping of zinc by RlemMT1-recombinant protein or by a zinc-scavenging agent in the culture medium caused suppression of ACR-toxin production by the fungus. Since ACR-toxin is the disease determinant for A. alternata rough lemon pathotype, addition of RlemMT1 to the inoculum suspension led to a significant decrease in symptoms on rough lemon leaves as a result of reduced ACR-toxin production from the zinc trap around infection sites. RlemMT1-overexpression mutant of A. alternata rough lemon pathotype also produced less ACR-toxin and reduced virulence on rough lemon. This suppression was caused by an interruption of zinc absorption by cells from the trapping of the mineral by RlemMT1 and an excess supplement of ZnSO₄ restored toxin production and pathogenicity. Based on these results, we propose that zinc adsorbents including metallothionein likely can act as a plant defense factor by controlling toxin biosynthesis via inhibition of zinc absorption by the pathogen.     

TGF-β family signaling in stem cells

Background

The diversity of cell types and tissue types that originate throughout development derives from the differentiation potential of embryonic stem cells and somatic stem cells. While the former are pluripotent, and thus can give rise to a full differentiation spectrum, the latter have limited differentiation potential but drive tissue remodeling. Additionally cancer tissues also have a small population of self-renewing cells with stem cell properties. These cancer stem cells may arise through dedifferentiation from non-stem cells in cancer tissues, illustrating their plasticity, and may greatly contribute to the resistance of cancers to chemotherapies.

Scope of review

The capacity of the different types of stem cells for self-renewal, the establishment and maintenance of their differentiation potential, and the selection of differentiation programs are greatly defined by the interplay of signaling molecules provided by both the stem cells themselves, and their microenvironment, the niche. Here we discuss common and divergent roles of TGF-β family signaling in the regulation of embryonic, reprogrammed pluripotent, somatic, and cancer stem cells.

Major conclusions

Increasing evidence highlights the similarities between responses of normal and cancer stem cells to signaling molecules, provided or activated by their microenvironment. While TGF-β family signaling regulates stemness of normal and cancer stem cells, its effects are diverse and depend on the cell types and physiological state of the cells.

General significance

Further mechanistic studies will provide a better understanding of the roles of TGF-β family signaling in the regulation of stem cells. These basic studies may lead to the development of a new therapeutic or prognostic strategies for the treatment of cancers. This article is part of a Special Issue entitled Biochemistry of Stem Cells.     

Significant association of urokinase plasminogen activator Pro141Leu with serum lipid profiles in a Japanese population

Urokinase plasminogen activator (uPA) plays important physiological and pathological roles in fibrinolysis, cancer metastasis, and atherosclerosis. One study suggested that uPA also has a major role in cholesterol biosynthesis in humans via its receptor uPAR. Thus, we investigated the associations of functional uPA polymorphism (plasminogen activator, urokinase; PLAU Pro141Leu, rs2227564) with serum lipid profiles in a Japanese cohort. The study included 5152 participants (1465 male, 3687 female; age range, 35–69 years) of the Daiko Study, a part of the Japan Multi-Institutional Collaborative Cohort Study (J-MICC Study). Subjects were enrolled at the Daiko Medical Center from June 2008 to May 2010. Low-density lipoprotein cholesterol (LDL-C) and non-HDL-C (subtraction of high-density lipoprotein cholesterol from total cholesterol) in fasting blood of participants were each classified into two groups, < or ≥ 140 mg/dL, and < or ≥ 170 mg/dL, respectively. Genotype frequencies of PLAU Pro141Leu (rs2227564) were 59.1% for ProPro, 35.6% for ProLeu, and 5.3% for LeuLeu, and were in Hardy–Weinberg equilibrium (p = 0.789). The allele frequencies were 0.769 for Pro and 0.231 for Leu. The multivariate-adjusted odd ratios (ORs) and 95% confidence intervals (CIs) for high LDL-C and non-HDL-C were 1.11 (95%CI; 1.00–1.23) and 1.16 (95%CI; 1.03–1.30) for those with Leu allele relative to ProPro. This study suggested that PLAU Pro141Leu (rs2227564) is significantly associated with serum lipid levels in a Japanese population.     

Validity and reliability of a visual scoring method for masticatory ability using test gummy jelly

Background: For quantitative evaluation of masticatory ability of the elderly patients, there should be a simple and reliable method without special techniques and instruments. Objective: The purpose of this study was to examine the validity and reliability of a visual scoring method for assessing masticatory performance. Materials and Methods: A 10‐stage scale for visually scoring was rated based on the range of the glucose concentration dissolved from comminuted jelly. Photographic images of comminuted jellies were produced as a standard material for each score. Fifty subjects were recruited as raters who graded the visual score for 50 photographic images of comminuted jellies on the screen of a lap‐top three times in random order. Results: There were strong correlations (rs = 0.911– 0.981, Spearman’s rank coefficient) between the actual scores determined from the glucose concentration and the visual scores graded by subjects in all three measurements. The intraclass correlation coefficients (ICCs) of the inter‐rater reliability and the ICCs of the intra‐rater reliability of the visual scoring ranged from 0.946 to 0.947 and from 0.860 to 0.987 in three measurements, respectively. Conclusions: These results indicated that the visual scoring method was valid and reliable for evaluation of masticatory performance.     

Abrogation of neutral cholesterol ester hydrolytic activity causes adrenal enlargement

We have previously demonstrated that neutral cholesterol ester hydrolase 1 (Nceh1) regulates foam cell formation and atherogenesis through the catalytic activity of cholesterol ester hydrolysis, and that Nceh1 and hormone-sensitive lipase (Lipe) are responsible for the majority of neutral cholesterol ester hydrolase activity in macrophages. There are several cholesterol ester-metabolizing tissues and cells other than macrophages, among which adrenocortical cells are also known to utilize the intracellular cholesterol for steroidogenesis. It has been believed that the mobilization of intracellular cholesterol ester in adrenal glands was facilitated solely by Lipe. We herein demonstrate that Nceh1 is also involved in cholesterol ester hydrolysis in adrenal glands. While Lipe deficiency remarkably reduced the neutral cholesterol ester hydrolase activity in adrenal glands as previously reported, additional inactivation of Nceh1 gene completely abrogated the activity. Adrenal glands were enlarged in proportion to the degree of reduced neutral cholesterol ester hydrolase activity, and the enlargement of adrenal glands and the accumulation of cholesterol esters were most pronounced in the Nceh1/Lipe double-deficient mice. Thus Nceh1 is involved in the adrenal cholesterol metabolism, and the cholesterol ester hydrolytic activity in adrenal glands is associated with the organ enlargement.     

KRAS-induced actin-interacting protein is required for the proper localization of inositol 1,4,5-trisphosphate receptor in the epithelial cells

Three inositol 1,4,5-trisphosphate receptor (IP₃R) subtypes are differentially expressed among tissues and function as the Ca²⁺ release channel on specialized endoplasmic reticulum (ER) membranes. The proper subcellular localization of IP₃R is crucial for its proper function, but this molecular mechanism is unclear. KRAS-induced actin-interacting protein (KRAP) was originally identified as a cancer-related molecule, and is involved in the regulation of whole-body energy homeostasis and pancreatic exocrine system. We herein identified IP₃R as an associated molecule with KRAP in vivo, and the association was validated by the co-immunoprecipitation and confocal immunostaining studies in mouse tissues including liver and pancreas. The association of KRAP with IP₃R was also observed in the human epithelial cell lines including HCT116, HeLa and HEK293 cells. Intriguingly, KRAP interacts with distinct subtypes of IP₃R in a tissue-dependent manner, i.e. IP₃R1 and IP₃R2 in the liver and IP₃R2 and IP₃R3 in the pancreas. The NH₂-terminal amino acid residues 1–610 of IP₃R are critical for the association with KRAP and KRAP–IP₃R complex resides in a specialized ER but not a typical reticular ER. Furthermore, the localization of particular IP₃R subtypes in tissues from KRAP-deficient mice is obviously disturbed, i.e. IP₃R1 and IP₃R2 in the liver and IP₃R2 and IP₃R3 in the pancreas. These findings demonstrate that KRAP physically associates with IP₃R and regulates the proper localization of IP₃R in the epithelial cells in vivo and cultured cells, and might shed light on the Ca²⁺ signaling underlying physiological cellular programs, cancer development and metabolism-related diseases.