Induction of cortical endoplasmic reticulum by dimerization of a coatomer-binding peptide anchored to endoplasmic reticulum membranes

Cortical endoplasmic reticulum (cER) is a permanent feature of yeast cells but occurs transiently in most animal cell types. Ist2p is a transmembrane protein that permanently localizes to the cER in yeast. When Ist2 is expressed in mammalian cells, it induces abundant cER containing Ist2. Ist2 cytoplasmic C-terminal peptide is necessary and sufficient to induce cER. This peptide sequence resembles classic coat protein complex I (COPI) coatomer protein-binding KKXX signals, and indeed the dimerized peptide binds COPI in vitro. Controlled dimerization of this peptide induces cER in cells. RNA interference experiments confirm that coatomer is required for cER induction in vivo, as are microtubules and the microtubule plus-end binding protein EB1. We suggest that Ist2 dimerization triggers coatomer binding and clustering of this protein into domains that traffic at the microtubule growing plus-end to generate the cER beneath the plasma membrane. Sequences similar to the Ist2 lysine-rich tail are found in mammalian STIM proteins that reversibly induce the formation of cER under calcium control.The current view of the yeast endoplasmic reticulum (ER) discriminates perinuclear ER from cortical ER (cER), which forms a circular structure apposed to the plasma membrane (PM) (1). Both structures are connected by tubulated membranes (2, 3), at least transiently, because ER membranes undergo continuous fission and fusion events (4, 5). cER is a much less prominent feature of most mammalian cells (6). The best-characterized function of cER is its role in the store-operated calcium entry, an ubiquitous Ca²⁺ influx pathway activated in response to depletion of intracellular calcium stores (7).Ist2 is a “yeast peripheral” protein involved in osmotic stress tolerance. It was initially believed to be located at the plasma membrane (8–11), and its cytosolic tail (Ist2ct) has been shown to carry the peripheral targeting signal (8). Ist2ct includes a dimerization domain (amino acids 878–928) and a lysine-rich carboxy terminal tail containing a KKXX-like motif that has been proposed to interact with the PM (11, 12). The nature of the peripheral Ist2 resident sites remains a matter of debate, however. It was once thought that Ist2 reached the PM in a new Golgi-independent manner (10), but more recently it has been concluded that the major residence site is in fact the cER (11).To gain insight into the biogenesis of cER in mammalian cells, we investigated whether Ist2, when expressed in a heterologous system, can serve as a useful marker for this compartment. Interestingly, enrichment of Ist2 chimeric protein at the cER appears to directly modulate the formation and/or maintenance of this ER subdomain. These dynamic changes in peripheral ER structure are absolutely dependent on both microtubules and coat protein complex I (COPI) and suggest a different role of COPI than its classical one.     

A longitudinal study for investigating the exposure level of anesthetics that impairs neurobehavioral performance

There is conflicting evidence on the level of anesthetics that impairs neurobehavioral performance, leading to differences in exposure standards (25 or 50 ppm for N(2)O). Thirty-eight operating room nurses and 23 unexposed nurses were asked to provide information on confounding variables: age, gender, years of schooling, alcohol and coffee consumption, smoking, length of work, symptoms (Euroquest) and results of Block Design test. Afterward, all workers were repeatedly examined (on Monday and Friday of a working week, before and after workshift) for stress and arousal (Mood Scale) and complex reaction times (Color Word Vigilance, CWV), the latter being the outcome. Individual exposure was assessed through urinary end-shift concentrations of nitrous oxide (N(2)O) and isoflurane. According to the highest value of urinary excretion of N(2)O in the week, exposed workers were subdivided in three groups (<13; > or =13 and <27; and > or = 27 microg/l). The values of 13 and 27 microg/l correspond to environmental concentrations of 25 and 50 ppm, respectively. In order to take into account the pre-existing abilities of exposed and reference workers, and investigate the neurobehavioral changes over time, longitudinal data were analyzed by a two-stage regression model and analysis of variance for repeated measures (MANOVA). The former method, controlling for confounding factors and Monday morning CWV (which conveyed the pre-existing ability of the subjects), showed that, with respect to unexposed nurses, reaction times were significantly (p<0.020) higher only in workers with urinary N(2)O> or = 27 microg/l. Therefore, at MANOVA, all subjects were categorized in two classes (N(2)O urinary concentrations or = 27 microg/l), and CWV results were adjusted for the confounding variables and effects of stress and arousal, taken concurrently with CWV. CWV significantly (p<0.039) decreased over a working week (indicating a learning effect) in workers with urinary N(2)O<27 microg/l, while remained steady (indicating impairment of neurobehavioral performance) in those with urinary N(2)O> 27 microg/l.     

Fetal blood-brain barrier P-glycoprotein contributes to brain protection during human development

During brain development and blood-brain barrier (BBB) differentiation the expression of P-glycoprotein (P-gp) may complement the protective function of the placental barrier against xenobiotic substances. To establish an immunohistochemical procedure for P-gp detection, different anti-P-gp monoclonal antibodies were first tested on a fibrosarcoma cell line and colonic carcinoma tissue. The protocol was then tested on adult human brains as a BBB-P-gp tissue-specific control and for double labeling with anti-P-gp and the astroglia marker glial fibrillary acidic protein (GFAP). The protocol was then used to analyze the expression and localization of P-gp in human fetuses during cerebral cortex formation. At the earliest examined stage, 12 weeks of gestation (wg), P-gp was detectable as diffuse cytoplasmic labeling of the endothelial cells lining the primary cortex microvessels. At 18 wg, a punctate P-gp staining pattern was detected on cortex and subcortical vessels and on their side branches. At 22 wg, P-gp staining was linear and concentrated on endothelial cell membranes. In all examined ages, GFAP-positive radial glial cells and astrocytes did not stain for P-gp, even at their perivascular processes, whereas faint P-gp labeling was seen on vimentin-reactive radial glia at the earliest examined fetal age. At midgestation, P-gp colocalized with caveolin-pY14 on the abluminal endothelial cell membrane. These results demonstrate that P-gp is expressed early during human cerebral cortical microvessel development, and suggest that at midgestation there may be efflux activity that is regulated by interactions with the caveolar endothelial cell compartment.     

High level of messenger RNA for BRMS1 in primary breast carcinomas is associated with poor prognosis

BRMS1 is regarded as a metastasis suppressor gene for its ability to reduce metastatic potential of human and murine breast cancer cells as well as human melanoma cells. However, BRMS1 association to human tumor progression is not clearly understood. In the present study we analyzed BRMS1 mRNA expression in tumor progression and its potential prognostic value for breast carcinoma. BRMS1 mRNA expression level was quantified by real-time PCR in 47 tumoral, in 14 peritumoral and in 15 metastatic microdissected cellular populations from 47 breast cancer patients with 10-year follow up. We found BRMS1 expression to be higher in carcinoma cells than in matching normal epithelial cell populations in 10 out of 14 cases (p = 0.0005), while lymph-nodal carcinoma cells showed lower BRMS1 expression in 9 out of 15 cases (p = 0.001). Using both in vivo (human mammary breast carcinomas) and in vitro systems (breast cancer cell lines) we were able to demonstrate that BRMS1 overexpression was not a bias effect induced by cell proliferation rate. BRMS1 expression levels did not correlate with standard breast cancer prognostic factors but BRMS1 higher expression was associated with patient shorter disease-free and overall survival. Our findings are apparently inconsistent with the concept of BRMS1 as a metastasis suppressor gene. One possible explanation is that epithelial cells increase their BRMS1 expression as a compensatory response to tumor formation or metastasis progression, which is elevated in proportion to tumor aggressiveness, whereas those cells of the primary tumor that cannot upregulate BRMS1 escape to form metastasis.     

Novel types of polysaccharidic assemblies

New types of polysaccharidic assemblies based on chitosan and uncharged or charged derivatives of scleroglucan are presented. Macroscopic assemblies having a spherical skinlike shape were prepared by controlled mixing of two polyelectrolyte solutions. Hydrogels based exclusively on the above natural derivatized polysaccharides crosslinked via simple chemical processes, avoiding the use of extraneous reticulating agents and organic solvents, are also described. These biocompatible materials may, eventually, be used in drug release formulations or for the incapsulation of bioactive macromolecules. The interesting possibility exists to study the micelle formation of amphiphiles within the spherical skins.     

A phase II trial of paclitaxel (Taxol®) as first line treatment in advanced breast cancer

Summary Paclitaxel (Taxol®) is a natural product with a broad spectrum of activity against various solid tumors. This report includes nineteen patients with advanced breast cancer who have not previously received chemotherapy for metastatic disease. Fifteen patients had received adjuvant chemotherapy, eight of which were doxorubicin based. Patients were treated with 135 mg/m² over 24 hours by continuous infusion given every 21 days. There were 2 complete and 4 partial responses for an objective response rate of 32% (95% C.I.: 14%, 57%) and eight patients or 42% with stable disease. Three of eight patients (38%) who had received adjuvant doxorubicin did respond to paclitaxel. Responses occurred in lung, liver, and soft tissue. The primary toxicity was hematologic with 13 hospitalizations for febrile neutropenia in 180 cycles (7%). Paclitaxel has moderate activity in a small number of patients with metastatic breast cancer at the dose of 135 mg/m² over 24 hours in this study.