Cdc25A Regulation: To Destroy or Not to Destroy,Is That the Only Question?

No abstract available.     

Two Cys or Not Two Cys? That Is the Question; Alternative Oxidase in the Thermogenic Plant Sacred Lotus

Sacred lotus (Nelumbo nucifera) regulates temperature in its floral chamber to 32°C to 35°C across ambient temperatures of 8°C to 40°C with heating achieved through high alternative pathway fluxes. In most alternative oxidase (AOX) isoforms, two cysteine residues, Cys₁ and Cys₂, are highly conserved and play a role in posttranslational regulation of AOX. Further control occurs via interaction of reduced Cys₁ with α-keto acids, such as pyruvate. Here, we report on the in vitro regulation of AOX isolated from thermogenic receptacle tissues of sacred lotus. AOX protein was mostly present in the reduced form, and only a small fraction could be oxidized with diamide. Cyanide-resistant respiration in isolated mitochondria was stimulated 4-fold by succinate but not pyruvate or glyoxylate. Insensitivity of the alternative pathway of respiration to pyruvate and the inability of AOX protein to be oxidized by diamide suggested that AOX in these tissues may lack Cys₁. Subsequently, we isolated two novel cDNAs for AOX from thermogenic tissues of sacred lotus, designated as NnAOX1a and NnAOX1b. Deduced amino acid sequences of both confirmed that Cys₁ had been replaced by serine; however, Cys₂ was present. This contrasts with AOXs from thermogenic Aroids, which contain both Cys₁ and Cys₂. An additional cysteine was present at position 193 in NnAOX1b. The significance of the sequence data for regulation of the AOX protein in thermogenic sacred lotus is discussed and compared with AOXs from other thermogenic and nonthermogenic species.

Thermogenesis in Sacred Lotus

Sacred lotus (Nelumbo nucifera) is a thermogenic plant that regulates the temperature of its floral chamber between 32°C and 35°C for up to 4 d (Seymour and Schultze-Motel, 1996). Heating of plant tissues has been described as an adaptation to attract insect pollinators either by volatilization of scent compounds (Meeuse, 1975) or by providing a heat reward (Seymour et al., 1983), protect floral parts from low temperatures (Knutson, 1974), or provide the optimum temperature for floral development (Ervik and Barfod, 1999; Seymour et al., 2009). In sacred lotus, heat is produced by high rates of alternative pathway respiration (Watling et al., 2006; Grant et al., 2008); however, the mechanisms of heat regulation, which likely occur at a cellular level, remain unclear.

Alternative Oxidase

Alternative pathway respiration is catalyzed by the alternative oxidase protein (AOX), which acts as a terminal oxidase in the electron transport chain but, unlike the energy conserving cytochrome pathway (COX), complexes III and IV are bypassed and energy is released as heat. Traditionally, AOX activity was measured using oxygen consumption of tissue, cells, or isolated mitochondria in the presence or absence of AOX and COX inhibitors. However, this method does not accurately measure activity in vivo but does indicate the capacity of the alternative pathway (Ribas-Carbo et al., 1995; Day et al., 1996). The only method to date to accurately determine AOX activity, that is, flux of electrons through the AOX pathway in vivo, is to use oxygen isotope discrimination techniques (for review, see Robinson et al., 1995). Determining AOX activity in vivo is important because heat production in plants could be due to activity of either the AOX and/or plant uncoupling proteins. Using oxygen fractionation techniques, we have shown that flux through the AOX pathway is responsible for heating in sacred lotus (Watling et al., 2006; Grant et al., 2008). Furthermore, we were unable to detect any uncoupling protein in these tissues (Grant et al., 2008). AOX protein content within the sacred lotus receptacle increases markedly prior to thermogenesis, but it remains constant during heating (Grant et al., 2008), suggesting that regulation of heating occurs through posttranslational modification of the protein.

Posttranslational Regulation of AOX Protein

The plant AOX is a cyanide-insensitive dimeric protein located in the inner mitochondrial membrane (Day and Wiskich, 1995). The dimer subunits (monomers) can be linked via a noncovalent association (reduced protein) or covalently through the formation of a disulfide bridge (oxidized protein; Umbach and Siedow, 1993). The reduced protein when run on SDS-PAGE has a molecular mass of approximately 30 to 35 kD and the oxidized protein 60 to 71 kD; this holds true for AOX from a number of species, including soybean (Glycine max) roots and cotyledons (Umbach and Siedow, 1993), tobacco (Nicotiana tabacum) leaf (Day and Wiskich, 1995), and the thermogenic spadix of Arum maculatum (Hoefnagel and Wiskich, 1998).Regulation of AOX has been well studied in nonthermogenic plant species, and two mechanisms have been identified. Most AOX isoforms have two highly conserved Cys residues, Cys₁ and Cys₂ (defined in Berthold et al., 2000 and Holtzapffel et al., 2003), located near the N-terminal hydrophilic domain of the protein. In these isoforms, Cys₁ can either be reduced on both subunits of the AOX dimer, or the Cys₁ sulfhydryl groups can be oxidized to form a disulfide bridge (Rhoads et al., 1998). Reduction/oxidation modulation of AOX in vitro can be achieved using the sulfhydryl reductant dithiothreitol (DTT) to reduce the protein or diamide to oxidize the Cys residues. The reduced dimer can be further activated via the interaction of Cys₁ with α-keto acids, principally pyruvate (Rhoads et al., 1998; see McDonald [2008] for a model of posttranslational regulation of AOX). In addition, Cys₂ may also be involved in regulating AOX activity through interaction with the α-keto acid glyoxylate (which can also stimulate activity at Cys₁; Umbach et al., 2002).Recently, however, AOX proteins with different regulatory properties have been reported. Naturally occurring AOX proteins without the two regulatory Cys residues have been identified and, along with site-directed mutagenesis studies, used to further elucidate the specific roles of Cys₁ and Cys₂. The LeAOX1b isoform from tomato (Lycopersicon esculentum), which has a Ser residue at the position of Cys₁ and thus does not form disulfide linked dimers, is also activated by succinate rather than pyruvate when expressed in Saccharomyces cerevisiae (Holtzapffel et al., 2003). In Arabidopsis (Arabidopsis thaliana), uncharged or hydrophobic amino acid substitutions of either Cys result in an inactive enzyme, while positively charged substitutions produce an enzyme with higher than wild type basal activity but that is insensitive to pyruvate or succinate (Umbach et al., 2002). Single substitutions at Cys₁ or Cys₂ have revealed that glyoxylate can activate AOX via both Cys residues, but only one is needed for glyoxylate stimulation (Umbach et al., 2002, 2006). Double substitution mutants were not stimulated by either pyruvate or glyoxylate (Umbach et al., 2006).Previously, we determined that thermogenesis via the AOX pathway in the sacred lotus receptacle is precisely regulated through changes in AOX flux rather than changes to protein content (Grant et al., 2008). In this study, we investigated the nature of this regulation in mitochondria isolated from heating receptacles. Our aim was to elucidate the reduction/oxidation behavior of the AOX protein and the mechanisms of activation of cyanide-resistant respiration in sacred lotus receptacles to provide insights into the mechanism(s) of heat regulation in this species. We further investigated AOX regulation by determining the amino acid sequence of two novel AOX genes isolated from thermogenic receptacle tissue of sacred lotus.     

Clathrin‐Dependent or Not: Is It Still the Question?

Whether the endocytic uptake of a given molecule is mediated through clathrin-coated pits or not is a classical criterion used to characterize its endocytic pathway(s). Hence, clathrin-dependent endocytosis has been associated with highly selective and efficient uptake, whereas clathrin-independent endocytosis appeared to be confined to bulk uptake of fluid-phase markers. This scholastic view has recently been challenged using newly developed molecular tools that allow for the first time a functional and mechanistic analysis of these less well-characterized clathrin-independent pathways, including caveolar uptake and macropinocytosis. Furthermore, several studies point to a critical role of lateral lipid asymmetry – lipid rafts/microdomains – in membrane sorting. We will discuss the potential role of these structures in endocytosis and the possibility that differential sorting at the plasma membrane predisposes the ensuing intracellular fate of a given molecule as well as its physiological function.     

On the Mechanism of Cationic Amphiphile-mediated Transfection. To Fuse or not to Fuse: Is that the Question?

Due to charge interaction, cationic lipids spontaneously associate with nucleic acids, resulting in the formation of so-called lipoplexes. Lipoplexes are membranous structures that are capable of transducing genes into cells, eventually leading to expression of the genes (transfection). The mechanism involved in the cellular uptake of lipoplexes is most likely endocytosis, which occurs after nonspecific charge-mediated binding to cellular receptors. An important step in the transfection process following the actual internalization of lipoplexes is the release of the lipoplex and/or its DNA into the cytoplasm in order to evade lysosomal degradation. Here, the membranous nature of the lipoplex seems to be crucial in that it allows the exchange of lipids between the endosomal membrane and the lipoplex, which results in membrane perturbations that are a prerequisite in the endosomal escape of DNA. Interestingly, a hexagonal phase of the lipoplexes has been correlated with efficient transfection and it can be envisaged that such a phase could be instrumental in the creation of membrane perturbations. Subsequent to its release into the cytoplasm, the DNA has to be transferred into the nucleus. The nuclear import of DNA is most likely a protein-mediated process. In addition, the nuclear uptake of DNA may be facilitated at the time of nuclear envelope disassembly during mitosis. Currently, cationic liposomes are widely used as gene carrier system to deliver nucleic acids into cells in culture to study the cell-biological functioning of genes plus accompanying proteins. Ultimately, cationic lipids may be used in gene therapeutic protocols.     

Split Personality of a Potyvirus: To Specialize or Not to Specialize?

Bean yellow mosaic virus (BYMV), genus Potyvirus, has an extensive natural host range encompassing both dicots and monocots. Its phylogenetic groups were considered to consist of an ancestral generalist group and six specialist groups derived from this generalist group during plant domestication. Recombination was suggested to be playing a role in BYMV''s evolution towards host specialization. However, in subsequent phylogenetic analysis of whole genomes, group names based on the original hosts of isolates within each of them were no longer supported. Also, nine groups were found and designated I-IX. Recombination analysis was conducted on the complete coding regions of 33 BYMV genomes and two genomes of the related Clover yellow vein virus (CYVV). This analysis found evidence for 12 firm recombination events within BYMV phylogenetic groups I–VI, but none within groups VII–IX or CYVV. The greatest numbers of recombination events within a sequence (two or three each) occurred in four groups, three which formerly constituted the single ancestral generalist group (I, II and IV), and group VI. The individual sequences in groups III and V had one event each. These findings with whole genomes are consistent with recombination being associated with expanding host ranges, and call into question the proposed role of recombination in the evolution of BYMV, where it was previously suggested to play a role in host specialization. Instead, they (i) indicate that recombination explains the very broad natural host ranges of the three BYMV groups which infect both monocots and dicots (I, II, IV), and (ii) suggest that the three groups with narrow natural host ranges (III, V, VI) which also showed recombination now have the potential to reduce host specificity and broaden their natural host ranges.     

To B,or not to B: Is calcium the answer?

B lymphocytes are an important component of the adaptive and innate immune system because of their ability to secrete antibodies and to present antigens to T cells, which is critical for immune responses to many pathogens. Abnormal B cell function is the cause of diseases including autoimmune, paraneoplastic, and immunodeficiency disorders. The development, survival, and function of B cells depend on signaling through the B cell receptor (BCR) and costimulatory receptors. One of the signaling pathways induced by antigen binding to the BCR is store-operated Ca²⁺ entry (SOCE), which depends on the Ca²⁺ channel ORAI1 and its activators stromal interaction molecule (STIM) 1 and 2. A recent study by Berry et al. [1] reports that B cells lacking STIM1 and STIM2 fail to survive and proliferate because abolished SOCE results in impaired expression of two key anti-apoptotic genes and blunted activation of mTORC1 and c-Myc signaling. The associated Ca²⁺ regulated checkpoints of B cell survival and proliferation can be bypassed, at least partially, by costimulation through CD40 or TLR9. This study provides important new insights on how SOCE controls B cell function.     

The Brain’s Response to the Human Voice Depends on the Incidence of Autistic Traits in the General Population

Optimal brain sensitivity to the fundamental frequency (F0) contour changes in the human voice is important for understanding a speaker’s intonation, and consequently, the speaker’s attitude. However, whether sensitivity in the brain’s response to a human voice F0 contour change varies with an interaction between an individual’s traits (i.e., autistic traits) and a human voice element (i.e., presence or absence of communicative action such as calling) has not been investigated. In the present study, we investigated the neural processes involved in the perception of F0 contour changes in the Japanese monosyllables “ne” and “nu.” “Ne” is an interjection that means “hi” or “hey” in English; pronunciation of “ne” with a high falling F0 contour is used when the speaker wants to attract a listener’s attention (i.e., social intonation). Meanwhile, the Japanese concrete noun “nu” has no communicative meaning. We applied an adaptive spatial filtering method to the neuromagnetic time course recorded by whole-head magnetoencephalography (MEG) and estimated the spatiotemporal frequency dynamics of event-related cerebral oscillatory changes in beta band during the oddball paradigm. During the perception of the F0 contour change when “ne” was presented, there was event-related de-synchronization (ERD) in the right temporal lobe. In contrast, during the perception of the F0 contour change when “nu” was presented, ERD occurred in the left temporal lobe and in the bilateral occipital lobes. ERD that occurred during the social stimulus “ne” in the right hemisphere was significantly correlated with a greater number of autistic traits measured according to the Autism Spectrum Quotient (AQ), suggesting that the differences in human voice processing are associated with higher autistic traits, even in non-clinical subjects.     

To Coil,or Not to – Activity Associated Ambiguity in Defense Responses of Millipedes

Arthropods, like most other animals, generally exhibit strong defense responses to predatory threats. This communication aims to demonstrate that the intensity of expression of a particular defense response may be affected by the kind of activity an arthropod is currently performing. Millipedes coil when threatened, and we analyzed coiling responses in the millipede Phyllogonostreptus nigrolabiatus during feeding, resting and walking. Further, variation in response was also quantified with respect to the inclination of the body – horizontal on ground and perpendicular on stems of trees. The millipedes (n = 199) were tapped on their bodies with a short stick to elicit the response. Three levels of responses were obtained – complete, partial and nil. On ground, although most millipedes tended to show complete coiling, the responses alternated between the two extremes among the feeding ones; resting and walking millipedes predominantly displayed complete response. On trees however, most millipedes were non-responsive, although walking millipedes tended to show relatively greater proportion of complete response. These results prove that different activities can elicit variation in a defense response, and so does body inclination in millipedes.     

Hepatitis B Virus Infection in Human Immunodeficiency Virus Infected Southern African Adults: Occult or Overt – That Is the Question

Hepatitis B virus (HBV) and human immunodeficiency virus (HIV) share transmission routes and are endemic in sub-Saharan Africa. The objective of the present study was to use the Taormina definition of occult HBV infection, together with stringent amplification conditions, to determine the prevalence and characteristics of HBV infection in antiretroviral treatment (ART)-naïve HIV^+ve adults in a rural cohort in South Africa. The presence of HBV serological markers was determined by enzyme linked immunoassay (ELISA) tests. HBV DNA-positivity was determined by polymerase chain reaction (PCR) of at least two of three different regions of the HBV genome. HBV viral loads were determined by real-time PCR. Liver fibrosis was determined using the aspartate aminotransferase-to-platelet ratio index. Of the 298 participants, 231 (77.5%) showed at least one HBV marker, with 53.7% HBV DNA^−ve (resolved) and 23.8% HBV DNA^+ve (current) [8.7% HBsAg^+ve: 15.1% HBsAg^−ve]. Only the total number of sexual partners distinguished HBV DNA^+ve and HBV DNA^−ve participants, implicating sexual transmission of HBV and/or HIV. It is plausible that sexual transmission of HBV and/or HIV may result in a new HBV infection, superinfection and re-activation as a consequence of immunesuppression. Three HBsAg^−ve HBV DNA^+ve participants had HBV viral loads <200 IU/ml and were therefore true occult HBV infections. The majority of HBsAg^−ve HBV DNA^+ve participants did not differ from HBsAg^+ve HBV DNA^+ve (overt) participants in terms of HBV viral loads, ALT levels or frequency of liver fibrosis. Close to a quarter of HIV^+ve participants were HBV DNA^+ve, of which the majority were HBsAg^−ve and were only detected using nucleic acid testing. Detection of HBsAg^−ve HBV DNA^+ve subjects is advisable considering they were clinically indistinguishable from HBsAg^+ve HBV DNA^+ve individuals and should not be overlooked, especially if lamivudine is included in the ART.     

Straight but Not Narrow; Within-Gender Variation in the Gender-Specificity of Women’s Sexual Response

Gender differences in the specificity of sexual response have been a primary focus in sexual psychophysiology research, however, within-gender variability suggests sexual orientation moderates category-specific responding among women; only heterosexual women show gender-nonspecific genital responses to sexual stimuli depicting men and women. But heterosexually-identified or “straight” women are heterogeneous in their sexual attractions and include women who are exclusively androphilic (sexually attracted to men) and women who are predominantly androphilic with concurrent gynephilia (sexually attracted to women). It is therefore unclear if gender-nonspecific responding is found in both exclusively and predominantly androphilic women. The current studies investigated within-gender variability in the gender-specificity of women’s sexual response. Two samples of women reporting concurrent andro/gynephilia viewed (Study 1, n = 29) or listened (Study 2, n = 30) to erotic stimuli varying by gender of sexual partner depicted while their genital and subjective sexual responses were assessed. Data were combined with larger datasets of predominantly gyne- and androphilic women (total N = 78 for both studies). In both studies, women reporting any degree of gynephilia, including those who self-identified as heterosexual, showed significantly greater genital response to female stimuli, similar to predominantly gynephilic women; gender-nonspecific genital response was observed for exclusively androphilic women only. Subjective sexual arousal patterns were more variable with respect to sexual attractions, likely reflecting stimulus intensity effects. Heterosexually-identified women are therefore not a homogenous group with respect to sexual responses to gender cues. Implications for within-gender variation in women’s sexual orientation and sexual responses are discussed.     

Human Taeniasis in the Republic of Korea: Hidden or Gone?

History and current status of human taeniasis in the Republic of Korea, due to Taenia solium, Taenia asiatica, and Taenia saginata, are briefly reviewed. Until the 1980s, human taeniasis had been quite common in various localities of Korea. A study from 1924 reported 12.0% egg prevalence in fecal examinations. Thereafter, the prevalence of Taenia spp. ranged from 3% to 14% depending on the time and locality. Jeju-do, where pigs were reared in a conventional way, was the highest endemic area of taeniasis. An analysis of internal transcribed spacer 2 and mitochondrial cytochrome c oxidase 1 genes of 68 taeniasis cases reported from 1935 to 2005 in Korea by a research group revealed the relative occurrence of the 3 Taenia spp. as follows: T. solium (4.4%), T. asiatica (75.0%), and T. saginata (20.6%). However, national surveys on intestinal helminths conducted every 5 years on randomly selected people revealed that the Taenia egg prevalence dropped from 1.9% in 1971 to 0.02% in 1997 and finally to 0.0% in 2004. With the exception of 3 egg-positive cases reported in 2008 and 2 worm-proven cases in 2011, no more cases have been officially recorded. Based on these surveys and also on other literature, it can be concluded that taeniasis has virtually disappeared from Korea, although a few sporadic cases may remain hidden. Human cysticercosis is also expected to disappear within a couple of decades in Korea.     

Sex-Independent Cognition Improvement in Response to Kaempferol in the Model of Sporadic Alzheimer’s Disease

Neurochemical Research - Alzheimer’s disease (AD) is associated with neural oxidative stress and inflammation, and it is assumed to affect more women than men with unknown mechanisms....     

Human grief: Is its intensity related to the reproductive value of the deceased?

Thurstone's method of comparative judgement was used to measured the intensity of grief that parents of high-, moderate-, and low-reproductive value were expected to experience at the death of male and female children of different ages. The results were correlated with reproductive values for male and female British Columbians and for !Kung Bushwomen. Grief ratings were more highly correlated with reproductive value than with age and more highly correlated with reproductive values of !King Bushwomen than with those of British Columbians. The correlations were higher for male- than for female-stimulus children. The correlations of female ratings with reproductive value were higher than male ratings with reproductive value, although not as high as expected. However, the correlation between grief ratings and reproductive value did not increase as the reproductive value of the raters declined.     

State Transition,Is It a Photochemical or Non-photochemical Process in Leaf in Response to Irradiance?

The response of steady-state fluorescence (Fs) to irradiance in apple (Malus pumila Mill. cv. Tengmu No.1/Malus hupehensis Rehd.) leaf increased and decreased at light levels below and above 400 mmol.m-2.s-1 photosynthetic photon flux density (PPFD), respectively, while the light-adapted maximal fluorescence (Fm') and minimal fluorescence (Fo') decreased constantly with the increasing PPFD, and the closure of photosystem Ⅱ reaction center (PSⅡ RC) increased continuously, reflected by the chlorophyll fluorescence parameter of (Fs-Fo')/(Fm'-Fo'). These facts indicated that decrease of Fs above 400 mmol.m-2.s-1 PPFD was not caused by closure of PSⅡ RC, but was mainly resulted from the process of light transfer from light-harvesting complexⅡ (LHCⅡ) to PSⅡ RC. In the presence of N-ethylmaleimide (NEM), an inhibitor of photosynthetic state transition, Fs kept on increasing in apple leaf at light levels from 400 to 700 mmol.m-2.s-1, which was the photosynthetic saturation irradiance of apple leaves. In addition, Fs still increased at light levels over 700 mmol.m-2.s-1 in apple leaf pre-treated with dithiothreitol (DTT), an inhibitor of xanthophyll cycle. These changes showed that state transition and xanthophyll cycle caused a decrease of Fs in apple leaf at light levels below and above the photosynthetic saturation irradiance, respectively. When apple leaf was pre-treated with NEM, the PSⅡ apparent rate of photochemical reaction (P-rate) and photochemical quenching (qP) decreased significantly in the light range of 600-800 mmol.m-2.s-1, but the non-photochemical quenching (qN) existed a small increase at 600-800 mmol.m-2.s-1 and a decrease above 800 mmol.m-2.s-1. These phenomena suggested that state transition was mainly a photochemical and a non-photochemical process in apple leaf responding to light lower and higher than photosynthetic saturation irradiance, respectively.