Intracellular Calcium-Binding Proteins in Signal Transduction

Cell stimulation generates a Ca2+ signal, which is perceived by intracellular Ca2+-binding proteins. These proteins are made up of different units of a conserved structural motif, called the 2S domain, and composed mainly of four β-helices and two anti parallel β-strands. This 2S domain can bind 2 Ca2+ ions and is roughly cup-shaped in the Ca2+-bound configuration. The interior of the cup is lined with solvent-exposed hydrophobic residues. In Ca2+-binding proteins involved in cellular signal-response coupling, such as calmodulin and troponin C, the hydrophobic cup is essential for interaction with, and activation of the response proteins. The Ca2+-free state is characterized by a reorientation of the β-helices and shielding of the hydrophobic residues in the cup. In contrast, interaction with the target strongly stabilizes the hydrophobic cups. Ca2+-buffering proteins, such as parvalbumin and sarcoplasmic Ca2+-binding proteins, have intrinsically a stable conformation, since the strongly hydrophobic cups are stabilized by frontal self association of the 2S domains

Comparative molecular modeling of Amphioxus calcium vector protein with calmodulin and troponin C

Calcium vector protein (CaVP), a new protein isolated from Amphioxus muscle, binds in a Ca2+ -rgulated manner to a 27 kd target protein, named CaVPT, whose function has not been elucidated yet. CaVP bears significant sequence homology to both calmodulin and skeletal muscle troponin C, especially in the C-tenninal half of the molecule, which presumably contains the two functional Ca2+ sites. The N-terminal half contains two abortive EF-hands and is intramolecularly crosslinked with a disulfide bond. Using the crystallographic structures of calmodulin and striated muscle troponin C as a framework, we constructed two different three-dimensional models of CaVP and modeled the intramolecular disulfide bridge. The modeling based upon the coordinates of calmodulin yields a Ca2+ -filled sites configuration in the N-terminal half of the molecule, even though no Ca2+ is bound in this half, whereas the troponin C-derived model generates a Ca2+ -empty sites configuration. The models predict that neither in the Ca2+ nor in the Ca2+ -empty sites conformation is there any steric and/or energetic obstacle for the formation of the disulfide bridge and that the disulfide bond is poorly accessible to reducing reagents. The optical properties of the Trp and Tyr residues of CaVP indicate that the calmodulin-derived model represents the most plausible predictio

Genomic Structure of the Amphioxus Calcium Vector Protein

Calcium vector protein (CaVP) is an EF-hand Ca2+-binding protein, which is unique to the protochordate, amphioxus. CaVP is supposed to act as a Ca2+ signal transductor, but its exact function remains unknown. Not only its function but also its exact evolutionary relationship to other Ca2+-binding proteins is unclear. To investigate the evolution of CaVP, we have determined the complete sequences of CaVP cDNAs from two amphioxus species, Branchiostoma lanceolatum and B. floridae, whose open reading frame cDNA and amino acid sequences show 96.5 and 98.2% identity, respectively. We have also elucidated the structure of the gene of B. floridae Ca VP, which is made up of seven exons and six introns. The positions of four of the six introns (introns 1, 2, 3, and 5) are identical with those of calmodulin, troponin C, and the Spec protein of the sea urchin. These latter proteins belong to the so-called troponin C superfamily (TnC superfamily) and thus CaVP likely also belongs to this family. Intron 6 is positioned in the 3‘ noncoding region and is unique to CaVP, so it may represent a landmark of the CaVP lineage only. The position of intron 4 is not conserved in the genes of the TnC superfamily or CaVP, and seems to result from either intron sliding or the addition of an intron (randomly inserted into or close to domain HE) to the genes of the TnC superfamily during their evolutio

Diversity of the Troponin C Genes during Chordate Evolution

To elucidate the diversity of troponin C (TnC) during chordate evolution, we determined the organization of TnCs from the amphioxus, the lamprey, and the frog. Like the ascidian, the amphioxus possesses a single gene of TnC, and the fundamental gene structure is identical with the ascidian TnC. However, because alternative splicing does not occur in amphioxus, the potential for generation of TnC isoforms through this event arises only in the ascidian lineage. From the frog Xenopus laevis, two distinct cDNAs encoding fTnC isoforms and a single s/cTnC cDNA were determined. The duplication of the fTnC gene may be a character of only Xenopus or closely related species. The lamprey possesses two cDNAs each encoding fTnC and s/cTnC. The lamprey is the earliest diverged species among vertebrates, and thus it is supposed that the presence of both fTnC and s/cTnC is universal among vertebrate species, and that the gene duplication might have occurred at a vertebrate ancestor after the protochordate/vertebrate divergence. The position of the 4th intron is 3.24/0 in protochordate TnC genes, but at 3.11/2 in vertebrate fTnCs and s/cTnCs. It is suggested that the 4th intron sliding might have occurred prior to the gene duplicatio

Screening for cervical Cancer in high-risk populations: DNA pap test or hybrid capture II test alone?

This study was designed to evaluate whether Hybrid Capture II (HC2) test alone refer women to colposcopy as appropriately as DNA Papanicolaou (Pap) test, in the context of a high-risk group of women using the recently validated DNACitoliq LBC system. Women with suspected cervical disease were included in this crosssectional study at a tertiary center in São Paulo, Brazil, for further workup. All women had cervical material collected for LBC and HC2 for high-risk human papillomavirus (hrHPV)-DNA test. Irrespective of cytology and HC2 results, colposcopy, and cervical biopsy when applicable, was systematically performed. All tests were performed blindly. Sensitivity, specificity, positive and negative predictive values, and overall accuracy of both methods were computed in relation to histology. A total of 1,080 women were included: 36.4% (393/1080) had ACUS+, 10.2% (110/1080) were high-grade squamous intraepithelial lesions (HSIL) or cancer. Mean age was 33.5 years. All women underwent colposcopy, and cervical biopsies were performed in 38.4% (415/1080): 33% (137/415) of the biopsies were negative, 14.4% (155/415) were low-grade squamous intraepithelial lesions (LSIL), 10.7% (116/415) were HSIL, and 0.6% (7/415) were cancer. HC2 sensitivity to diagnose biopsy-proven HSIL was 100%. Because all HSIL cases had a positive HC2 test, sensitivity could not be improved by adding LBC. Specificity and positive and negative predictive values of DNA Pap were not significantly different from HC2 test alone when considering LSIL+ histology as ‘‘gold standard’’ and HSIL+ histology. As a screening strategy for women with high-risk for cervical cancer, DNA Pap test does not seem to add substantially to HC2 alone in terms of appropriately referring to colposcopy

Efficacy of adjuvant chemotherapy according to hormone receptor status in young patients with breast cancer: a pooled analysis

Introduction Breast cancer at a young age is associated with an unfavorable prognosis. Very young patients with breast cancer therefore are advised to undergo adjuvant chemotherapy irrespective of tumor stage or grade. However, chemotherapy alone may not be adequate in young patients with hormone receptor-positive breast cancer. Therefore, we studied the effect of adjuvant chemotherapy in young patients with breast cancer in relation to hormone receptor status. Methods Paraffin-embedded tumor material was collected from 480 early-stage breast cancer patients younger than 41 years who participated in one of four European Organization for Research and Treatment of Cancer trials. Using immunohistochemistry on the whole series of tumors, we assessed estrogen receptor (ER) status and progesterone receptor (PgR) status in a standardized way. Endpoints in this study were overall survival (OS) and distant metastasis-free survival (DMFS). The median follow-up period was 7.3 years. Results Overall, patients with ER-positive tumors had better OS rates (hazard ratio [HR] 0.63; P = 0.02) compared with those with ER-negative tumors. However, in the subgroup of patients who received chemotherapy, no significant difference in OS (HR 0.87; P = 0.63) and DMFS (HR 1.36; P = 0.23) was found between patients with ER-positive tumors or those with ER-negative tumors. These differences were similar for PgR status. Conclusion Young patients with hormone receptor-positive tumors benefit less from adjuvant systemic chemotherapy than patients with hormone receptor-negative tumors. These results confirm that chemotherapy alone cannot be considered optimal adjuvant systemic treatment in breast cancer patients 40 years old or younger with hormone receptor-positive tumors

The Neural Basis of Object-Context Relationships on Aesthetic Judgment

The relationship between contextual information and object perception has received considerable attention in neuroimaging studies. In the work reported here, we used functional magnetic resonance imaging (fMRI) to investigate the relationship between aesthetic judgment and images of objects in their normal contextual setting versus images of objects in abnormal contextual settings and the underlying brain activity. When object-context relationships are violated changes in visual perception and aesthetic judgment emerges that exposes the contribution of vision to interpretations shaped by previous experience. We found that effects of context on aesthetic judgment modulates different memory sub-systems, while aesthetic judgment regardless of context recruit medial and lateral aspects of the orbitofrontal cortex, consistent with previous findings. Visual cortical areas traditionally associated with the processing of visual features are recruited in normal contexts, irrespective of aesthetic ratings, while prefrontal areas are significantly more engaged when objects are viewed in unaccustomed settings

Computational and mathematical approaches to societal transitions

After an introduction of the theoretical framework and concepts of transition studies, this article gives an overview of how structural change in social systems has been studied from various disciplinary perspectives. This overview first leads to the conclusion that computational and mathematical approaches and their practical form, modeling, up till now, have been almost absent in the research and theorizing of structural change or transitions in social systems. Second, this review of the social science literature suggests numerous theoretical constructs relevant for transition modeling. Relevant concepts include the conceptualization of the micro-to-macro link, the importance of explaining both stability and change, quantitative and qualitative definitions of structural change, the use of dichotomies, synchronic and diachronic reasoning in explaining structural change, definitions of basic patterns of social change, the conceptualization of resistance to change and intentional and normative aspects of social change. This article employs these theoretical concepts to describe and discuss the models presented in this special issue in order to develop an understanding of what exactly entails a computational or mathematical approach to societal transitions

Does the Establishment of Sustainable Use Reserves Affect Fire Management in the Humid Tropics?

Tropical forests are experiencing a growing fire problem driven by climatic change, agricultural expansion and forest degradation. Protected areas are an important feature of forest protection strategies, and sustainable use reserves (SURs) may be reducing fire prevalence since they promote sustainable livelihoods and resource management. However, the use of fire in swidden agriculture, and other forms of land management, may be undermining the effectiveness of SURs in meeting their conservation and sustainable development goals. We analyse MODIS derived hot pixels, TRMM rainfall data, Terra-Class land cover data, socio-ecological data from the Brazilian agro-census and the spatial extent of rivers and roads to evaluate whether the designation of SURs reduces fire occurrence in the Brazilian Amazon. Specifically, we ask (1) a. Is SUR location (i.e., de facto) or (1) b. designation (i.e. de jure) the driving factor affecting performance in terms of the spatial density of fires?, and (2), Does SUR creation affect fire management (i.e., the timing of fires in relation to previous rainfall)? We demonstrate that pre-protection baselines are crucial for understanding reserve performance. We show that reserve creation had no discernible impact on fire density, and that fires were less prevalent in SURs due to their characteristics of sparser human settlement and remoteness, rather than their status de jure. In addition, the timing of fires in relation to rainfall, indicative of local fire management and adherence to environmental law, did not improve following SUR creation. These results challenge the notion that SURs promote environmentally sensitive fire-management, and suggest that SURs in Amazonia will require special attention if they are to curtail future accidental wildfires, particularly as plans to expand the road infrastructure throughout the region are realised. Greater investment to support improved fire management by farmers living in reserves, in addition to other fire users, will be necessary to help ameliorate these threats

The FANCM:p.Arg658* truncating variant is associated with risk of triple-negative breast cancer

Breast cancer is a common disease partially caused by genetic risk factors. Germline pathogenic variants in DNA repair genes BRCA1, BRCA2, PALB2, ATM, and CHEK2 are associated with breast cancer risk. FANCM, which encodes for a DNA translocase, has been proposed as a breast cancer predisposition gene, with greater effects for the ER-negative and triple-negative breast cancer (TNBC) subtypes. We tested the three recurrent protein-truncating variants FANCM:p.Arg658*, p.Gln1701*, and p.Arg1931* for association with breast cancer risk in 67,112 cases, 53,766 controls, and 26,662 carriers of pathogenic variants of BRCA1 or BRCA2. These three variants were also studied functionally by measuring survival and chromosome fragility in FANCM (-/-) patient-derived immortalized fibroblasts treated with diepoxybutane or olaparib. We observed that FANCM:p.Arg658* was associated with increased risk of ER-negative disease and TNBC (OR = 2.44, P = 0.034 and OR = 3.79; P = 0.009, respectively). In a country-restricted analysis, we confirmed the associations detected for FANCM:p.Arg658* and found that also FANCM:p.Arg1931* was associated with ER-negative breast cancer risk (OR = 1.96; P = 0.006). The functional results indicated that all three variants were deleterious affecting cell survival and chromosome stability with FANCM:p.Arg658* causing more severe phenotypes. In conclusion, we confirmed that the two rare FANCM deleterious variants p.Arg658* and p.Arg1931* are risk factors for ER-negative and TNBC subtypes. Overall our data suggest that the effect of truncating variants on breast cancer risk may depend on their position in the gene. Cell sensitivity to olaparib exposure, identifies a possible therapeutic option to treat FANCM-associated tumors