Annexins Laohavisit, Anuphon; Davies, Julia M.
The New phytologist,
January 2011, Letnik:
189, Številka:
1
Journal Article
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Annexins are multifunctional lipid-binding proteins. Plant annexins are expressed throughout the life cycle and are under environmental control. Their association or insertion into membranes may be ...governed by a range of local conditions (Ca²⁺, pH, voltage or lipid identity) and nonclassical sorting motifs. Protein functions include exocytosis, actin binding, peroxidase activity, callose synthase regulation and ion transport. As such, annexins appear capable of linking Ca²⁺, redox and lipid signalling to coordinate development with responses to the biotic and abiotic environment. Significant advances in plant annexin research have been made in the past 2 yr. Here, we review the basis of annexin multifunctionality and suggest how these proteins may operate in the life and death of a plant cell.
Plant cyclic nucleotide-gated channels (CNGCs) are tetrameric cation channels which may be activated by the cyclic nucleotides (cNMPs) adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine ...3',5'-cyclic monophosphate (cGMP). The genome of
encodes 20 CNGC subunits associated with aspects of development, stress response and immunity. Recently, it has been demonstrated that CNGC subunits form heterotetrameric complexes which behave differently from the homotetramers produced by their constituent subunits. These findings have widespread implications for future signalling research and may help explain how specificity can be achieved by CNGCs that are known to act in disparate pathways. Regulation of complex formation may involve cyclic nucleotide-gated channel-like proteins.
The transient elevation of cytosolic free calcium concentration (Ca2+cyt) induced by cold stress is a well‐established phenomenon; however, the underlying mechanism remains elusive. Here, we report ...that the Ca2+‐permeable transporter ANNEXIN1 (AtANN1) mediates cold‐triggered Ca2+ influx and freezing tolerance in Arabidopsis thaliana. The loss of function of AtANN1 substantially impaired freezing tolerance, reducing the cold‐induced Ca2+cyt increase and upregulation of the cold‐responsive CBF and COR genes. Further analysis showed that the OST1/SnRK2.6 kinase interacted with and phosphorylated AtANN1, which consequently enhanced its Ca2+ transport activity, thereby potentiating Ca2+ signaling. Consistent with these results and freezing sensitivity of ost1 mutants, the cold‐induced Ca2+cyt elevation in the ost1‐3 mutant was reduced. Genetic analysis indicated that AtANN1 acts downstream of OST1 in responses to cold stress. Our data thus uncover a cascade linking OST1‐AtANN1 to cold‐induced Ca2+ signal generation, which activates the cold response and consequently enhances freezing tolerance in Arabidopsis.
Synopsis
How cold stress generates and controls transient elevation of calcium in the cytosol of plant cells is ill‐defined. Cold‐activated OST1 kinase promotes freezing tolerance in Arabidopsis by potentiating ANNEXIN1‐dependent calcium signaling.
ANNEXIN1 (AtANN1) mediates the generation of cold‐triggered Ca2+ signals.
Cold‐activated OST1 kinase phosphorylates AtANN1 to enhance its Ca2+ transport activity, thereby amplifying Ca2+ signaling.
OST1‐AtANN1 module regulates the expression of cold responsive CBF and COR genes and plant freezing tolerance.
Cold‐activated OST1 kinase phosphorylates ANNEXIN1 to boost calcium ion uptake and thus promotes expression of COR genes that enhance cold stress responses in Arabidopsis.
The effects of psycholinguistic variables are critical to the evaluation of theories about the cognitive reading system. However, reading research has tended to focus on the impact of key variables ...on average performance. We report the first investigation examining variation in psycholinguistic effects across the life span, from childhood into old age. We analyzed the performance of a sample of 535 readers, aged 8-83 years in lexical decision and pronunciation tasks. Our findings show that the effects on reading of two key variables, frequency and AoA, decrease in size with increasing age over the life span. We observed the systematic modulation by age and reading ability of these and other psycholinguistic effects alongside a global U-shaped effect of age. Diffusion model analyses suggest that developmental speed-up in decision responses can be attributed to the increasing quality of evidence accumulation in reaction to words, while the ageing-related slowing can be attributed to decreasing efficiency of stimulus encoding or response execution processes. An analysis of spoken response durations furnishes a consistent picture in which the slowing of pronunciation responses with age can be attributed to slowing articulatory processes. We think our findings can be explained by theoretical accounts that incorporate learning as the basis for the development of structure in the reading system. However, an adequate theory shall have to include assumptions about both developmental learning and later ageing. Our results warrant a life span theory of reading.
Roots are subjected to a range of abiotic stresses as they forage for water and nutrients. Cytosolic free calcium is a common second messenger in the signaling of abiotic stress. In addition, roots ...take up calcium both as a nutrient and to stimulate exocytosis in growth. For calcium to fulfill its multiple roles must require strict spatio-temporal regulation of its uptake and efflux across the plasma membrane, its buffering in the cytosol and its sequestration or release from internal stores. This prompts the question of how specificity of signaling output can be achieved against the background of calcium's other uses. Threats to agriculture such as salinity, water availability and hypoxia are signaled through calcium. Nutrient deficiency is also emerging as a stress that is signaled through cytosolic free calcium, with progress in potassium, nitrate and boron deficiency signaling now being made. Heavy metals have the capacity to trigger or modulate root calcium signaling depending on their dose and their capacity to catalyze production of hydroxyl radicals. Mechanical stress and cold stress can both trigger an increase in root cytosolic free calcium, with the possibility of membrane deformation playing a part in initiating the calcium signal. This review addresses progress in identifying the calcium transporting proteins (particularly channels such as annexins and cyclic nucleotide-gated channels) that effect stress-induced calcium increases in roots and explores links to reactive oxygen species, lipid signaling, and the unfolded protein response.
Thalidomide maintenance has the potential to modulate residual multiple myeloma (MM) after an initial response. This trial compared the effect of thalidomide maintenance and no maintenance on ...progression-free survival (PFS) and overall survival (OS) in MM patients. After intensive or nonintensive induction therapy, 820 newly diagnosed MM patients were randomized to open-label thalidomide maintenance until progression, or no maintenance. Interphase FISH (iFISH) analysis was performed at study entry. Median PFS was significantly longer with thalidomide maintenance (log-rank P < .001). Median OS was similar between regimens (log-rank P = .40). Patients with favorable iFISH showed improved PFS (P = .004) and a trend toward a late survival benefit. Patients with adverse iFISH receiving thalidomide showed no significant PFS benefit and worse OS (P = .009). Effective relapse therapy enhanced survival after progression, translating into a significant OS benefit. Meta-analysis of this and other studies show a significant late OS benefit (P < .001, 7-year difference hazard ratio = 12.3; 95% confidence interval, 5.5-19.0). Thalidomide maintenance significantly improves PFS and can be associated with improved OS. iFISH testing is important in assessing the clinical impact of maintenance therapy. Overview analysis demonstrated that thalidomide maintenance was associated with a significant late OS benefit. This trial was registered at www.isrctn.org as #ISRCTN68454111.
IMPORTANCE: The World Health Organization is developing a global strategy to eliminate cervical cancer, with goals for screening prevalence among women aged 30 through 49 years. However, evidence on ...prevalence levels of cervical cancer screening in low- and middle-income countries (LMICs) is sparse. OBJECTIVE: To determine lifetime cervical cancer screening prevalence in LMICs and its variation across and within world regions and countries. DESIGN, SETTING, AND PARTICIPANTS: Analysis of cross-sectional nationally representative household surveys carried out in 55 LMICs from 2005 through 2018. The median response rate across surveys was 93.8% (range, 64.0%-99.3%). The population-based sample consisted of 1 136 289 women aged 15 years or older, of whom 6885 (0.6%) had missing information for the survey question on cervical cancer screening. EXPOSURES: World region, country; countries’ economic, social, and health system characteristics; and individuals’ sociodemographic characteristics. MAIN OUTCOMES AND MEASURES: Self-report of having ever had a screening test for cervical cancer. RESULTS: Of the 1 129 404 women included in the analysis, 542 475 were aged 30 through 49 years. A country-level median of 43.6% (interquartile range IQR, 13.9%-77.3%; range, 0.3%-97.4%) of women aged 30 through 49 years self-reported to have ever been screened, with countries in Latin America and the Caribbean having the highest prevalence (country-level median, 84.6%; IQR, 65.7%-91.1%; range, 11.7%-97.4%) and those in sub-Saharan Africa the lowest prevalence (country-level median, 16.9%; IQR, 3.7%-31.0%; range, 0.9%-50.8%). There was large variation in the self-reported lifetime prevalence of cervical cancer screening among countries within regions and among countries with similar levels of per capita gross domestic product and total health expenditure. Within countries, women who lived in rural areas, had low educational attainment, or had low household wealth were generally least likely to self-report ever having been screened. CONCLUSIONS AND RELEVANCE: In this cross-sectional study of data collected in 55 low- and middle-income countries from 2005 through 2018, there was wide variation between countries in the self-reported lifetime prevalence of cervical cancer screening. However, the median prevalence was only 44%, supporting the need to increase the rate of screening.
Lysine acetylation (AcK), a posttranslational modification wherein a two-carbon acetyl group binds covalently to a lysine residue, occurs prominently on mitochondrial proteins and has been linked to ...metabolic dysfunction. An emergent theory suggests mitochondrial AcK occurs via mass action rather than targeted catalysis. To test this hypothesis, we performed mass spectrometry-based acetylproteomic analyses of quadriceps muscles from mice with skeletal muscle-specific deficiency of carnitine acetyltransferase (CrAT), an enzyme that buffers the mitochondrial acetyl-CoA pool by converting short-chain acyl-CoAs to their membrane permeant acylcarnitine counterparts. CrAT deficiency increased tissue acetyl-CoA levels and susceptibility to diet-induced AcK of broad-ranging mitochondrial proteins, coincident with diminished whole body glucose control. Sub-compartment acetylproteome analyses of muscles from obese mice and humans showed remarkable overrepresentation of mitochondrial matrix proteins. These findings reveal roles for CrAT and L-carnitine in modulating the muscle acetylproteome and provide strong experimental evidence favoring the nonenzymatic carbon pressure model of mitochondrial AcK.
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•Mitochondrial matrix proteins are susceptible to nutrient-induced lysine acetylation•Carnitine acetyltransferase (CrAT) buffers the mitochondrial pool of acetyl-CoA•CrAT deficiency in muscle increased acetylation of mitochondrial matrix proteins•Results support the nonenzymatic model of mitochondrial protein acetylation
Davies et al. show that mitochondrial matrix proteins in skeletal muscle are highly susceptible to nutrient-induced lysine acetylation, a PTM linked to metabolic disease. Nutrient-induced acetylation of mitochondrial proteins is offset by the acetyl-CoA buffering action of carnitine acetyltransferase, suggesting this PTM occurs via mass action rather than targeted catalysis.
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