Does water stress promote the proteome-wide adjustment of intrinsically disordered proteins in plants?

Plant response to water stress involves the activation of mechanisms expected to help them cope with water scarcity. Among these mechanisms, proteome-wide adjustment is well known. This includes actions to save energy, protect cellular and molecular components, and maintain vital functions of the cell. Intrinsically disordered proteins, which are proteins without a rigid three-dimensional structure, are seen as emerging multifunctional cellular components of proteomes. They are highly abundant in eukaryotic proteomes, and numerous functions for these proteins have been proposed. Here, we discuss several reasons why the collection of intrinsically disordered proteins in a proteome (disordome) could be subjected to an active regulation during conditions of water scarcity in plants. We also discuss the potential misinterpretations of disordome content estimations made so far due to bias-prone data and the need for reliable analysis based on experimental data in order to acknowledge the plasticity nature of the disordome.     

Neuroplastin-65 and a mimetic peptide derived from its homophilic binding site modulate neuritogenesis and neuronal plasticity

Neuroplastin-65 (Np65) is a brain-specific cell adhesion molecule belonging to the immunoglobulin superfamily. Homophilic trans-interaction of Np65 mediates adhesion between cells and modulates synaptic plasticity. This interaction solely occurs through the first immunoglobulin (Ig) module of Np65, but the exact binding mechanism has not yet been elucidated. In this study, we identify the homophilic binding motif of Np65 and show that a synthetic peptide modeled after this motif, termed enplastin, binds to Np65. We demonstrate that both Np65- and enplastin-induced intracellular signaling depends on fibroblast growth factor receptor, p38 mitogen-activated protein kinase, Ca(2+) /calmodulin-dependent protein kinase, and cytoplasmic Ca(2+) concentration. In addition, we show that interference with Np65 homophilic binding by enplastin has an inhibitory effect on Np65-mediated neurite outgrowth in vitro and on the initial phase of spatial learning in rats.     

Facilitation of AMPA receptor synaptic delivery as a molecular mechanism for cognitive enhancement

Cell adhesion molecules and downstream growth factor-dependent signaling are critical for brain development and synaptic plasticity, and they have been linked to cognitive function in adult animals. We have previously developed a mimetic peptide (FGL) from the neural cell adhesion molecule (NCAM) that enhances spatial learning and memory in rats. We have now investigated the cellular and molecular basis of this cognitive enhancement, using biochemical, morphological, electrophysiological, and behavioral analyses. We have found that FGL triggers a long-lasting enhancement of synaptic transmission in hippocampal CA1 neurons. This effect is mediated by a facilitated synaptic delivery of AMPA receptors, which is accompanied by enhanced NMDA receptor-dependent long-term potentiation (LTP). Both LTP and cognitive enhancement are mediated by an initial PKC activation, which is followed by persistent CaMKII activation. These results provide a mechanistic link between facilitation of AMPA receptor synaptic delivery and improved hippocampal-dependent learning, induced by a pharmacological cognitive enhancer.     

Expression of heat shock protein70 in pig oocytes: heat shock response during oocyte growth

The heat shock response of growing and fully-grown pig oocytes was analyzed in vitro by determining heat shock protein70 (HSP70) synthesis under both normal conditions (39 degrees C; 0 and 6h) and after heat shock (43 degrees C; 1, 4 and 6h). The expression of HSP70 in oocytes was detected by immunoblotting analysis. Growing oocytes measuring 80-99 microm synthesized a high number of HSP70 without heat shock effect, and these were capable of increasing the synthesis of HSP70 after heat shock to a maximum after 1h. Growing oocytes measuring 100-115 microm also synthesized HSP70 without heat shock and after it, but the HSP70 synthesis was not statistically changed by increasing duration of heat shock. In fully-grown oocytes, great amounts of HSP70 were found without heat shock treatment, and the contents of HSP70 significantly decreased after heat shock. These results indicate that growing oocytes are able to synthesize HSP70 after heat shock. This ability declines at the end of the growth period, and fully-grown oocytes are unable to induce HSP70 synthesis after heat shock. HSP70 is synthesized and stored during oocyte growth. The high HSP70 synthesis in non-heat-treated growing oocytes and a great amount of HSP70 in fully-grown oocytes support the hypothesis that HSP70 is important for oocyte growth and maturation.     

ERp19 and ERp46, new members of the thioredoxin family of endoplasmic reticulum proteins

Using a proteomic analysis of the luminal environment of the endoplasmic reticulum (ER), we have identified 141 proteins, of which 6 were previously unknown. Two newly discovered ER luminal proteins, designated ERp19 and ERp46, are related to protein disulphide isomerase. Western and Northern blot analyses revealed that both ERp19 and ERp46 and their respective mRNAs are highly expressed in the liver as compared with other tissues. Both proteins were enriched in purified liver ER vesicles and were localized specifically to the ER in McA-RH7777 hepatocytes. Functional analysis with yeast complementation studies showed that ERp46 but not ERp19 can substitute for protein disulphide isomerase function in vivo.     

Microenvironment Modulates Osteogenic Cell Lineage Commitment in Differentiated Embryonic Stem Cells

Background

Due to their self-renewal, embryonic stem cells (ESCs) are attractive cells for applications in regenerative medicine and tissue engineering. Although ESC differentiation has been used as a platform for generating bone in vitro and in vivo, the results have been unsatisfactory at best. It is possible that the traditional culture methods, which have been used, are not optimal and that other approaches must be explored.

Methodology/Principal Findings

ESCs were differentiated into osteoblast lineage using a micro-mass approach. In response to osteogenic differentiation medium, many cells underwent apoptosis, while others left the micro-mass, forming small aggregates in suspension. These aggregates were cultured in three different culture conditions (adhesion, static suspension, and stirred suspension), then examined for osteogenic potential in vitro and in vivo. In adhesion culture, ESCs primed to become osteoblasts recommitted to the adipocyte lineage in vitro. In a static suspension culture, resulting porous aggregates expressed osteoblasts markers and formed bone in vivo via intermembranous ossification. In a stirred suspension culture, resulting non-porous aggregates suppressed osteoblast differentiation in favor of expanding progenitor cells.

Conclusions/Significance

We demonstrate that microenvironment modulates cell fate and subsequent tissue formation during ESC differentiation. For effective tissue engineering using ESCs, it is important to develop optimized cell culture/differentiation conditions based upon the influence of microenvironment.     

Zinc-induced interactions of the metal-binding domain of beta-amyloid with nucleic acids and glycosaminoglycans

Zinc ions form complexes with β-amyloid peptides and play an important role in Alzheimer’s disease pathogenesis. It has been demonstrated by turbidimetry and correlation spectroscopy that synthetic peptide Aβ16 representing the metal-binding domain of β-amyloid is able to interact with nucleic acids, chondroitin polysulfate, and dextran sulfates in the presence of zinc ions. The amino acid D7H substitution enhanced the peptide binding to polyanions, whereas the H6R and H6A-H13A substitutions abolished this interaction. It is suggested that the metal-binding domain may serve as a zinc-dependent site of β-amyloid interaction with biological polyanions including DNA, RNA, and glycosaminoglycans.     

Genetic diversity of rodent species sold in South African pet shops

Murid rodents are considered globally important invasive species, yet they are still sold in the pet trade. Little is known about the genetic diversity of traded rodents, and many species are incorrectly identified in the pet trade. We used mitochondrial gene regions to assess the taxonomy and genetic diversity of 149 rodents sold in pet shops across eight South African provinces. We identified a total of 112 specimens as Mus musculus, while 31 were Rattus norvegicus, and six were identified as the southern African endemic, southern multimammate mouse Mastomys coucha. Phylogenetic analyses revealed that the three species were monophyletic. Mus musculus and R. norvegicus showed higher levels of genetic diversity, with 19 unique mtDNA haplotypes recovered for M. musculus and eight haplotypes for R. norvegicus. KwaZulu-Natal, Western Cape and Gauteng Provinces had the most unique haplotypes than other provinces. Our findings showed that non-native species are widely distributed in the South African pet trade industry, while M. coucha was not widely traded, although recorded in three provinces. This suggests that most provinces comply with the trade regulations on native species, but the threat of invasive rodents to South Africa's unique biodiversity is highlighted.     

Dimensions of responsibility in medical genetics: exploring the complexity of the “duty to recontact”

Discussion of a “duty to recontact” emerged as technological advances left professionals considering getting back in touch with patients they had seen in the past. While there has been much discussion of the duty to recontact as a matter of theory and ethics, there has been rather little empirically based analysis of what this “duty” consists of. Drawing on interviews with 34 professionals working in, or closely with, genetics services, this paper explores what the “duty to recontact” means for healthcare professionals involved in genetics. Using a discourse analytic framework, the paper identifies three system generated discourses on recontact (governance, legal and responsibilizing discourses) and three lifeworld discourses (situating recontact as a formal duty; more loosely as an obligation; and as a personal sense of responsibility). In summary, the paper shows that the “duty” to recontact involves a complex interplay of system responsibilities with professional duties, responsibilities and obligations.