Active Fragments from Pro- and Antiapoptotic BCL-2 Proteins Have Distinct Membrane Behavior Reflecting Their Functional Divergence

Background

The BCL-2 family of proteins includes pro- and antiapoptotic members acting by controlling the permeabilization of mitochondria. Although the association of these proteins with the outer mitochondrial membrane is crucial for their function, little is known about the characteristics of this interaction.

Methodology/Principal Findings

Here, we followed a reductionist approach to clarify to what extent membrane-active regions of homologous BCL-2 family proteins contribute to their functional divergence. Using isolated mitochondria as well as model lipid Langmuir monolayers coupled with Brewster Angle Microscopy, we explored systematically and comparatively the membrane activity and membrane-peptide interactions of fragments derived from the central helical hairpin of BAX, BCL-xL and BID. The results show a connection between the differing abilities of the assayed peptide fragments to contact, insert, destabilize and porate membranes and the activity of their cognate proteins in programmed cell death.

Conclusion/Significance

BCL-2 family-derived pore-forming helices thus represent structurally analogous, but functionally dissimilar membrane domains.     

Cell cytoskeleton and tether extraction

We perform a detailed investigation of the force × deformation curve in tether extraction from 3T3 cells by optical tweezers. Contrary to conventional wisdom about tethers extracted from cells, we find that actin filaments are present within them, so that a revised theory of tether pulling from cells is called for. We also measure steady and maximum tether force values significantly higher than previously published ones for 3T3 cells. Possible explanations for these differences are investigated. Further experimental support of the theory of force barriers for membrane tube extension is obtained. The potential of studies on tether pulling force × deformation for retrieving information on membrane-cytoskeleton interaction is emphasized.     

MiRNAs as regulators of the response to inhaled environmental toxins and airway carcinogenesis

miRNAs are a class of small, noncoding RNAs averaging 22 nucleotides in length that down-regulate gene expression by complimentary binding to the 3' UTR of target genes. A growing body of research suggests that these small RNA species play significant roles in modulating the cellular response to a variety of types of stress. In this review, we summarize the available literature regarding the general response of miRNA to cellular stress, and then specifically focus on the miRNA response to inhaled toxins. These miRNA responses to inhaled toxins appear to be recapitulated in lung carcinogenesis, opening the possibility that modulation of the miRNA response could be a novel strategy for chemoprevention.     

CDC28 protein kinase regulatory subunit 1B (CKS1B) expression and genetic status analysis in oral squamous cell carcinoma

CKS1B is a member of the highly conserved cyclin kinase subunit 1 (CKS1) protein family which interacts with cyclin-dependent kinases and plays a critical role in cell cycle progression. In oral squamous cell carcinoma (OSCC), as in other malignancies, CKS1B overexpression has been correlated with reduced survival. To our knowledge, no studies evaluating the genetic status of CKS1B gene in OSCC have been reported. Herein, genetic and protein status of CKS1B were analyzed by immunohistochemical (IHC) and fluorescence in situ hybridization (FISH) techniques in a series of primary OSCC (n=51) and lymph node OSCC metastases samples (n=14). The observed results were compared with those obtained in either inflammatory (oral lichen planus [OLP]) (n=13) and premalignant oral mucosal lesions (oral leukoplakia) (n=16). A significant CKS1B overexpression was observed in OSCC and lymph node metastases samples than in OLP and oral leukoplakia (mean 70% vs 35%, p<0.001). CKS1B overexpression correlated with p27 loss of expression (p=0.0013) and SKP2 overexpression (p<0.00). FISH study disclosed statistical differences in both gene amplifications and gains between samples corresponding to OSCC and metastases from those of OLP and leukoplakia (p<0.001). Amplifications were present in 53% of OSCC samples and 33% of lymph node metastases vs 14% of oral leukoplakia and 0% of OLP biopsy specimens (p=0.002). Polysomies of chromosome 1 were seen in 46% of OSCC, 33% of ganglionar metastases, 14% of oral leukoplakia and 10% of OLP (p=0.036). Correlation of CKS1B over-expression and gains (both polysomies and amplifications) determined by FISH was statistically significant (p<0.001). Our results indicate that a high CKS1B expression is a common finding in primary OSCC which correlates with p27 low expression and SKP2 overexpression. This phenomenon may be due either to numerical (chromosome 1 polysomy) or structural (amplifications) CKS1B genetic abnormalities. This phenotypical and cytogenetic profile is not observed in premalignant or inflammatory oral mucosal lesions.     

Representation of aquatic vegetation change by plant macrofossils in a small and shallow freshwater lake

We explored spatial and temporal relationships between contemporary aquatic vegetation and surface sediment macrofossil remains in a small, shallow, English lake (Green Plantation Pond). The aquatic vegetation of Green Plantation Pond underwent a marked compositional change after 2005 with a shift from Elodea spp.-Potamogeton pusillus-Chara spp. to Ceratophyllum spp.-Chara spp.-Potamogeton crispus dominance. By comparing macrophyte and plant macrofossil distributions at multiple, closely spaced points in Green Plantation Pond for 2000 and 2008–2009, we studied the ability of macrofossils to track this major aquatic vegetation change. Representation of macrophytes by macrofossils was high with 63 and 76 % of extant plant species recorded by macro-remains in the 2000 and 2009 sediment surveys respectively. Nevertheless, plants were both over-represented (Nitella flexilis, Chara spp. and Zannichellia palustris) and under-represented (Ranunculus sect. Batrachium, Potamogeton spp.) in the sediment record in terms of relative macrofossil abundances and the number of occupied sample points. The study also revealed a lack of preservation of Elodea spp. leaf remains in the second (2009) survey compared to the first (2000) probably due to a longer time interval (5 vs. 10 months) between macrophyte and sediment sampling. Nevertheless, the macrofossils reliably recorded both the main shift in the contemporary vegetation (e.g. especially increases in Ceratophyllum spp. and P. crispus abundance) and other more subtle floristic changes (e.g. increases in Myriophyllum spicatum and Lemna spp.) exceptionally well. This study highlights the huge potential of macrofossils for tracking sub-decadal changes in the aquatic vegetation of small, shallow lakes.     

Interleukin-dependent modulation of HLA-DR expression on CD4and CD8 activated T cells

Summary Interleukins (IL) regulate different T-cell surface Ag known as activation markers that have distinct functional roles. In this paper, while studying the influence of some cytokines(IL-12, IL-2 and IL-4) on the expression of several markers [CD69,CD25, CD26, CD3, human leukocyte antigen (HLA-DR), CD45R0] in in vitro activated human T lymphocytes, we observed two groups of donors responding to phytohaemagglutinin (PHA) activation with high or low HLA-DRAg expression. We also found that CD4 and CD8 populations had different HLA-DR densities under PHA activation (particularly the high HLA-DR-expressing group). Interleukins, in a dose-dependent manner (IL-2 partially),upregulated these HLA-DR levels. In 5 day cultures, IL-12 and IL-2 enhanced the CD8/CD4 ratio of activated T cells,which was responsible, in part, for the IL-dependent HLA-DR upregulation.IL-12 and IL-2 also upregulated the HLA-DR expression at the molecular level on CD8, and IL-12 downregulated it on CD4 cells. It seems that IL-4 upregulated HLA-DR by shortening the mitogen-dependent regulation kinetics. We hypothesize that the different effect of each IL on HLA-DR expression might be related to the regulation of the dose of antigenic peptide presentation and, thus, also influence TH1/TH2 dominance.     

Human gamma oscillations during slow wave sleep

Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS). At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30-50 Hz) and high (60-120 Hz) frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves ("IN-phase" pattern), confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave ("ANTI-phase" pattern). This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks.