ROOT GROWTH INHIBITING, a Rice Endo-1,4-β-d-Glucanase, Regulates Cell Wall Loosening and is Essential for Root Elongation

The molecular mechanism involved in cell wall dynamics has not been well clarified, although it is quite important for organ growth. We characterized a rice mutant, root growth inhibiting (rt), which is defective in root elongation. The rt mutant showed a severe defect in cell elongation at the root-elongating zone with additional collapse of epidermal and cortex cells at the root tip caused by the defect in the smooth exfoliation of root cap cells. Consistent with these phenotypes, expression of the RT gene, which encodes a member of the membrane-anchored endo-1,4-??-d-glucanase, was specifically localized in the root-elongating zone and at the junction between epidermal and root cap cells. The enzymatic analysis of root extracts from the wild-type and rt mutant indicated that RT hydrolyzes noncrystalline amorphous cellulose. The cellulose content was slightly increased but the crystallinity of cellulose was decreased in the rt root. In addition, the hemicellulose composition was different between wild-type and rt roots. The total extensibility was significantly lower in the rt root explants. Based on these results, we concluded that RT is involved in the disassembly of the cell wall for cell elongation in roots as well as for root cap exfoliation from the epidermal cell layer by hydrolyzing the noncrystalline amorphous cellulose fibers of cellulose microfibrils resulting in loosening of the hemicellulose and cellulose interaction.     

Annexin A4 is a possible biomarker for cisplatin susceptibility of malignant mesothelioma cells

Mesothelioma is a highly malignant tumor with a poor prognosis and limited treatment options. Although cisplatin (CDDP) is an effective anticancer drug, its response rate is only 20%. Therefore, discovery of biomarkers is desirable to distinguish the CDDP-susceptible versus resistant cases. To this end, differential proteome analysis was performed to distinguish between mesothelioma cells of different CDDP susceptibilities, and this revealed that expression of annexin A4 (ANXA4) protein was higher in CDDP-resistant cells than in CDDP-susceptible cells. Furthermore, ANXA4 expression levels were higher in human clinical malignant mesothelioma tissues than in benign mesothelioma and normal mesothelial tissues. Finally, increased susceptibility was observed following gene knockdown of ANXA4 in mesothelioma cells, whereas the opposite effect was observed following transfection of an ANXA4 plasmid. These results suggest that ANXA4 has a regulatory function related to the cisplatin susceptibility of mesothelioma cells and that it could be a biomarker for CDDP susceptibility in pathological diagnoses.     

Complement C1q activates canonical Wnt signaling and promotes aging-related phenotypes

Wnt signaling plays critical roles in development of various organs and pathogenesis of many diseases, and augmented Wnt signaling has recently been implicated in mammalian aging and aging-related phenotypes. We here report that complement C1q activates canonical Wnt signaling and promotes aging-associated decline in tissue regeneration. Serum C1q concentration is increased with aging, and Wnt signaling activity is augmented during aging in the serum and in multiple tissues of wild-type mice, but not in those of C1qa-deficient mice. C1q activates canonical Wnt signaling by binding to Frizzled receptors and subsequently inducing C1s-dependent cleavage of the ectodomain of Wnt coreceptor low-density lipoprotein receptor-related protein 6. Skeletal muscle regeneration in young mice is inhibited by exogenous C1q treatment, whereas aging-associated impairment of muscle regeneration is restored by C1s inhibition or C1qa gene disruption. Our findings therefore suggest the unexpected role of complement C1q in Wnt signal transduction and modulation of mammalian aging.     

STT3B-dependent posttranslational N-glycosylation as a surveillance system for secretory protein

The chemical identity and integrity of the genome is challenged by the incorporation of ribonucleoside triphosphates (rNTPs) in place of deoxyribonucleoside triphosphates (dNTPs) during replication. Misincorporation is limited by the selectivity of DNA replicases. We show that accumulation of ribonucleoside monophosphates (rNMPs) in the genome causes replication stress and has toxic consequences, particularly in the absence of RNase H1 and RNase H2, which remove rNMPs. We demonstrate that postreplication repair (PRR) pathways-MMS2-dependent template switch and Pol ζ-dependent bypass-are crucial for tolerating the presence of rNMPs in the chromosomes; indeed, we show that Pol ζ efficiently replicates over 1-4 rNMPs. Moreover, cells lacking RNase H accumulate mono- and polyubiquitylated PCNA and have a constitutively activated PRR. Our findings describe a crucial function for RNase H1, RNase H2, template switch, and translesion DNA synthesis in overcoming rNTPs misincorporated during DNA replication, and may be relevant for the pathogenesis of Aicardi-Goutières syndrome.     

Targeting of polyplex to human hepatic cells by bio-nanocapsules, hepatitis B virus surface antigen L protein particles

We have previously demonstrated that lipoplex, a complex of cationic liposomes and DNA, could be targeted to human hepatic cells in vitro and in vivo by conjugation with bio-nanocapsules (BNCs) comprising hepatitis B virus (HBV) surface antigen L protein particles. Because the BNC-lipoplex complexes were endowed with the human hepatic cell-specific infection machinery from HBV, the complexes showed excellent specific transfection efficiency in human hepatic cells. In this study, we have found that polyplex (a complex of polyethyleneimine (PEI) and DNA) could form stable complexes with BNCs spontaneously. The diameter and ζ-potential of BNC-polyplex complexes are about 240 nm and +3.54 mV, respectively, which make them more suitable for in vivo use than polyplex alone. BNC-polyplex complexes with an N/P ratio (the molar ratio of the amine group of PEI to the phosphate group of DNA) of 40 showed excellent transfection efficiency in human hepatic cells. When acidification of endosomes was inhibited by bafilomycin A1, the complexes showed higher transfection efficiency than polyplex itself, strongly suggesting that the complexes escaped from endosomes by both fusogenic activity of BNCs and proton sponge activity of polyplex. Furthermore, the cytotoxicity is comparable to that of polyplex of the same N/P value. Thus, BNC-polyplex complexes would be a promising gene delivery carrier for human liver-specific gene therapy.     

A possible association between aldosterone response to vasopressin and circadian change of aldosterone in the patients with aldosterone-producing adenoma

Vasopressin was reported to stimulate secretion of both cortisol and aldosterone through eutopic V1a receptors in adrenal gland. Recently, adrenal hyper-responsiveness of plasma cortisol to vasopressin with eutopic overexpession of V1a receptors has been reported in Cushing's syndrome, such as a majority of cases of ACTH-independent macronodular adrenal hyperplasia and some cases of Cushing's adenomas. There were a few reports regarding the aldosterone response to vasopressin in aldosterone-producing adenoma. The aim of our study was to investigate the aldosterone response to vasopressin and its pathophysiological roles in the patients with aldosterone-producing adenoma. Vasopressin-loading test was performed in 10 patients with aldosterone-producing adenoma, and in 16 patients with non-functioning adrenal tumors. The roles of the aldosterone response to vasopressin were analyzed in terms of hormonal secretion and the expression of V1a receptor mRNA on the operated adrenal gland in aldosterone-producing adenoma. We found that (1) a varying aldosterone response to vasopressin was observed, (2) absolute response of plasma aldosterone in aldosterone-producing adenoma was significantly higher than that in non-functioning tumor, (3) aldosterone response rate to vasopressin was significantly and negatively correlated with the decline rate (%) in plasma aldosterone from morning to evening in aldosterone-producing adenoma, (4) V1a receptor mRNA was expressed at various values in aldosterone-producing adenoma, and (5) surgical removal of aldosterone-producing adenoma eliminated the aldosterone response to vasopressin observed in patients with aldosterone-producing adenoma. These findings indicated that vasopressin might be involved in the coordination of aldosterone secretion through eutopic expression of V1a receptor in aldosterone-producing adenoma.