Preferential accumulation of apoproteins of the light-harvesting chlorophyll a/b-protein complex in greening barley leaves treated with 5-aminolevulinic acid

In order to study the coordinate accumulation of chlorophyll (Chl) and apoproteins of Chl-protein complexes (CPs) during chloroplast development, we examined changes in the accumulation of the apoproteins in barley (Hordeum vulgare L.) leaves when the rate of Chl synthesis was altered by feeding 5-aminolevulinic acid (ALA), a precursor of Chl biosynthesis. Pretreatment with ALA increased the accumulation of Chl a and Chl b 1.5- and 2.3-fold, respectively, after 12 cycles of intermittent light (2 min light followed by 28 min darkness). Apoproteins of the light-harvesting Chl a/b-protein complex of photosystem II (LHCII) were increased 2.4-fold with ALA treatment. However, apoproteins of the P700-Chl a-protein complex (CP1) and the 43-kDa apoprotein of a Chl a-protein complex of photosystem II (CPa) were not increased by ALA application. With respect to CPs themselves, LHCII was increased when Chl synthesis was raised by ALA feeding, whereas CP1 exhibited no remarkable increase. These results indicate that LHCII serves a role in maintaining the stoichiometry of Chl to apoproteins by acting as a temporary pool for Chl molecules.Abbreviations ALA 5-aminolevulinic acid - Chl chlorophyll - CP chlorophyll-protein complex - CPa chlorophyll a-protein complex of PSII - CP1 P700-chlorophyll a-protein complex - LDS lithium dodecyl sulfate - LHCII light-harvesting chlorophyll a/b-protein complex of PSII This work was supported by the Grants-in-Aid for Scientific Research (04304004) from the Ministry of Education, Science and Culture, Japan.     

Primary structure of profilins from two species of Echinoidea and Physarum polycephalum

Profilin is a small G-actin-binding protein, the amino acid sequence of which was previously reported for calf, human, Acanthamoeba and yeast. Here the amino acid sequences of three profilins obtained from eggs of two species of Echinoidea, Clypeaster japonicus (order, Clypeasteroida) and Anthocidaris crassispina (order, Echinoida), and plasmodium of Physarum polycephalum were determined. Two echinoid profilins were composed of 139 amino acid residues, N-termini were acylated and the molecular mass was calculated to be 14.6 kDa, slightly larger than that of 13 kDa estimated by SDS/PAGE [Mabuchi, I. & Hosoya, H. (1982) Biomed. Res. 3, 465-476]. On the other hand, Physarum profilin was composed of 124 amino acid residues, the N-terminus was acylated, and the calculated molecular mass was 13132 Da. The sequences of C. japonicus and A. crassispina profilins were homologous (84% identical). However, the similarity of these profilins with those form other organisms was low. The sequence of Physarum profilin was homologous with Acanthamoeba profilin isoforms (51% identical) and with yeast profilin (42% identical), but not with other profilins. The relatively conservative sequence of profilins from yeast, Physarum, Acanthamoeba, echinoid eggs and mammalian cells was found in the N-terminal region, which was suggested to be a common actin-binding region. The C-terminal region was also conserved, although to a lesser extent than the N-terminal region.     

LRRK2 regulates synaptic vesicle endocytosis

The leucine-rich repeat kinase 2 (LRRK2) has been identified as the defective gene at the PARK8 locus causing the autosomal dominant form of Parkinson's disease (PD). Although several LRRK2 mutations were found in familial as well as sporadic PD patients, its physiological functions are not clearly defined. In this study, using yeast two-hybrid screening, we report the identification of Rab5b as an LRRK2-interacting protein. Indeed, our GST pull down and co-immunoprecipitation assays showed that it specifically interacts with LRRK2. In addition, subcellular fractionation and immunocytochemical analyses confirmed that a fraction of both proteins co-localize in synaptic vesicles. Interestingly, we found that alteration of LRRK2 expression by either overexpression or knockdown of endogenous LRRK2 in primary neuronal cells significantly impairs synaptic vesicle endocytosis. Furthermore, this endocytosis defect was rescued by co-expression of functional Rab5b protein, but not by its inactive form. Taken together, we propose that LRRK2, in conjunction with its interaction with Rab5b, plays an important role in synaptic function by modulating the endocytosis of synaptic vesicles.     

Insulin use and weight maintenance in well-controlled type 2 diabetes: a prospective cohort study

Intensification of glycemic control is associated with weight gain, however, less is known about weight change during the maintenance phase of glycemic management. On the basis of current models of energy homeostasis, we hypothesize that insulin use will result in less weight gain than oral antidiabetic agents in patients with well-controlled diabetes. This is a prospective cohort nested within a randomized control trial at an academic clinic, with enrollment from June 2002 to January 2005. A total of 163 patients with type 2 diabetes were enrolled after obtaining glycemic control. Insulin use was assessed by self-report at baseline. Participants were weighed at baseline and five follow-up visits over 24 months. The weight change was compared between insulin users and noninsulin users. The average (s.d.) age was 55 (11), 44% are female and 21% are black. The median duration of diabetes was 5 (0.5-10) years. At baseline, 88 participants (54%) reported insulin use with an average of 69 (6) units/day. Baseline BMI in the insulin users was 35 (6) and 33 (6) in noninsulin patients. Over 24 months, noninsulin patients gained 2.3 additional kilograms compared with insulin users (2.8 kg (6.8) vs. 0.5 kg (6.5), P = 0.065). After adjusting for age, race, sex, baseline weight, intervention status, and change in A1C, insulin users had 2.5 kg less weight gain than noninsulin users (P = 0.033). Less weight gain was observed over 24 months in insulin-treated patients. Whether this effect may be due to central catabolic effects of insulin merits additional confirmatory study and mechanistic investigation.     

Waist circumference, not the metabolic syndrome, predicts glucose deterioration in type 2 diabetes

We sought to assess the relationship between the metabolic syndrome, abdominal obesity, and glucose deterioration amongst patients with type 2 diabetes. Our prospective cohort consisted of 164 adult patients with established diabetes who have a history of poor glycemic control, have just completed an intensive intervention aimed at improved control, and have demonstrated reduced HbA1c prior to enrollment. Waist circumference and presence of metabolic syndrome were assessed at baseline, and patients were followed up (median 24 months) for assessment of the study outcome, namely, time-to-hyperglycemic relapse, predefined as HbA1c >8% and >1% rise over baseline. Kaplan-Meier estimates of relapse-free glucose maintenance and multivariable Cox regression models were used for quantifying the independent effects of the metabolic syndrome and waist circumference on risk of glucose deterioration. The mean baseline waist circumference was 42.9 5.5 inches. Prevalence of the metabolic syndrome was 80%. During follow-up, 39 patients (24%) experienced hyperglycemic relapse. The metabolic syndrome was not associated with time-to-relapse (P = 0.15). The waist circumference component by itself, however, was associated with increased likelihood of hyperglycemic relapse with an unadjusted hazard ratio of 3.4 (95% confidence interval (CI) 1.2-9.7) and a hazard ratio of 3.2 (95% CI 1.1-9.1) after adjusting for age, gender, insulin use, weight change, and physical activity level. The National Cholesterol Education Program Adult Treatment Panel III (NCEP ATPIII) metabolic syndrome had limited ability to predict glucose deterioration in this type 2 diabetes cohort. Waist circumference by itself, however, is a strong predictor of future glucose control, and may be a parsimonious tool for risk stratification. BMI may also be a useful predictive tool.     

A morphological study of the mycorrhiza ofEntoloma clypeatum f.hybridum onRosa multiflora

Mycorrhizas ofEntoloma clypeatum f.hybridum onRosa multiflora in the field in Japan were studied by stereo, light and electron microscopy. In most mycorrhizas, the root cap, meristem, and apical region of the cortex disappeared, but in a few mycorrhizas, these tissues remained. Fungal hyphae of the mycorrhizas invaded root tissues and branched palmately. Hyphae in contact with cortical cells were larger than those far from the root cells and contained many mitochondria, cisternae of endoplasmic reticulum and transitional vesicles. Invading hyphae were undulate in the apical part of the mycorrhiza, and some of them lacked distinct organelles. Electron-dense granules accumulated in the root cells adjacent to the fungal hyphae. Both the remnants of the plant cells and the fungal hyphae were included in the amorphous materials on the tip of the stele. These observations suggest the destructive infection by fungal hyphae of the root cells and their collapse near the tip of the stele.     

Aven-dependent activation of ATM following DNA damage

BACKGROUND: In response to DNA damage, cells undergo either cell-cycle arrest or apoptosis, depending on the extent of damage and the cell's capacity for DNA repair. Cell-cycle arrest induced by double-stranded DNA breaks depends on activation of the ataxia-telangiectasia (ATM) protein kinase, which phosphorylates cell-cycle effectors such as Chk2 and p53 to inhibit cell-cycle progression. ATM is recruited to double-stranded DNA breaks by a complex of sensor proteins, including Mre11/Rad50/Nbs1, resulting in autophosphorylation, monomerization, and activation of ATM kinase. RESULTS: In characterizing Aven protein, a previously reported apoptotic inhibitor, we have found that Aven can function as an ATM activator to inhibit G2/M progression. Aven bound to ATM and Aven overexpressed in cycling Xenopus egg extracts prevented mitotic entry and induced phosphorylation of ATM and its substrates. Immunodepletion of endogenous Aven allowed mitotic entry even in the presence of damaged DNA, and RNAi-mediated knockdown of Aven in human cells prevented autophosphorylation of ATM at an activating site (S1981) in response to DNA damage. Interestingly, Aven is also a substrate of the ATM kinase. Mutation of ATM-mediated phosphorylation sites on Aven reduced its ability to activate ATM, suggesting that Aven activation of ATM after DNA damage is enhanced by ATM-mediated Aven phosphorylation. CONCLUSIONS: These results identify Aven as a new ATM activator and describe a positive feedback loop operating between Aven and ATM. In aggregate, these findings place Aven, a known apoptotic inhibitor, as a critical transducer of the DNA-damage signal.     

Progress in the pathogenesis and genetics of Parkinson's disease

Recent progresses in the pathogenesis of sporadic Parkinson's disease (PD) and genetics of familial PD are reviewed. There are common molecular events between sporadic and familial PD, particularly between sporadic PD and PARK1-linked PD due to alpha-synuclein (SNCA) mutations. In sporadic form, interaction of genetic predisposition and environmental factors is probably a primary event inducing mitochondrial dysfunction and oxidative damage resulting in oligomer and aggregate formations of alpha-synuclein. In PARK1-linked PD, mutant alpha-synuclein proteins initiate the disease process as they have increased tendency for self-aggregation. As highly phosphorylated aggregated proteins are deposited in nigral neurons in PD, dysfunctions of proteolytic systems, i.e. the ubiquitin-proteasome system and autophagy-lysosomal pathway, seem to be contributing to the final neurodegenerative process. Studies on the molecular mechanisms of nigral neuronal death in familial forms of PD will contribute further on the understanding of the pathogenesis of sporadic PD.     

Structural requirements for the stability of novel cephalosporins to AmpC beta-lactamase based on 3D-structure

AmpC beta-lactamase is one of the leading causes of Pseudomonas aeruginosa (P. aeruginosa) resistance to cephalosporins. FR259647 is a cephalosporin having a novel pyrazolium substituent at the 3-position and exhibits excellent activity (MIC=1 microg/mL) against the AmpC beta-lactamase overproducing P. aeruginosa FP1380 strain in comparison with the third-generation cephalosporins FK518 [Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 454; Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 455; Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 456; Abstracts of Papers, 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, GA, October 21-24, 1990, Abs. 457] (MIC=16 microg/mL) and ceftazidime (CAZ) (MIC=128 microg/mL). The stability of FR259647 and FK518 to AmpC beta-lactamase was evaluated using MIC assays against both the P. aeruginosa PAO1 strain and a PAO1 mutant strain overproducing AmpC beta-lactamase as a differential assay, which indicates that the main difference derives from their stability to AmpC beta-lactamase. A structural analysis using computer simulations indicated that the difference in stability may be due to steric hindrance of the 3-position substituents causing differential affinity. This steric hindrance may disturb entry of the cephalosporins into the binding pocket. We predicted the possibility of inhibition of entry as a potential means of enhancing stability by conformational analysis. In order to validate this speculation, novel FR259647 derivatives 4-9 were designed, calculated, synthesized, and evaluated. As a result, we demonstrated that their probability of entry correlated with the MIC ratio of the mutant strain to the parent strain and supports the validity of our model.