The very many faces of presenilins and the γ-secretase complex

Presenilin is a central, catalytic component of the γ-secretase complex which conducts intramembrane cleavage of various protein substrates. Although identified and mainly studied through its role in the development of amyloid plaques in Alzheimer disease, γ-secretase has many other important functions. The complex seems to be evolutionary conserved throughout the Metazoa, but recent findings in plants and Dictyostelium discoideum as well as in archeons suggest that its evolution and functions might be much more diversified than previously expected. In this review, a selective survey of the multitude of functions of presenilins and the γ-secretase complex is presented. Following a brief overview of γ-secretase structure, assembly and maturation, three functional aspects are analyzed: (1) the role of γ-secretase in autophagy and phagocytosis; (2) involvement of the complex in signaling related to endocytosis; and (3) control of calcium fluxes by presenilins

Organismal view of a plant and a plant cell.

Cell walls are at the basis of a structural, four-dimensional framework of plant form and growth time. Recent rapid progress of cell wall research has led to the situation where the old, long-lasting juxtaposition: "living" protoplast - "dead" cell wall, had to be dropped. Various attempts of re-interpretation cast, however, some doubts over the very nature of plant cell and the status of the walls within such a cell. Following a comparison of exocellular matrices of plants and animals, their position in relation to cells and organisms is analysed. A multitude of perspectives of the biological organisation of living beings is presented with particular attention paid to the cellular and organismal theories. Basic tenets and resulting corollaries of both theories are compared, and evolutionary and developmental implications are considered. Based on these data, "The Plant Body" - an organismal concept of plants and plant cells is described

Fluorescence microscopy techniques in the research on the endomembrane system of plant cells

Gwałtowny rozwój technik mikroskopii fluorescencyjnej, w tym konfokalnej, w połączeniu z wykorzystaniem metod biologii molekularnej znacząco zdynamizowały rozwój molekularnej biologii komórki. Z wielu różnych względów, zwłaszcza znaczącej odmienności strukturalnej i funkcjonalnej, badania komórek roślinnych są nieco opóźnione. Artykuł podsumowuje stan badań systemu błon wewnętrznych komórek roślinnych z wykorzystaniem zróżnicowanych podejść i metod badawczych biologii komórki. Wskazuje na użycie różnego typu znaczników, tak chemicznych, jak i genetycznych, które umożliwiają lokalizację makrocząsteczek i procesów biologicznych. Omawia substancje chemiczne, które zaburzają funkcjonowanie systemu wewnątrzbłonowego, a więc pośrednio pozwalają wnioskować o roli uczestniczących w tych procesach białek. Wreszcie, pokazuje wykorzystanie nowych podejść i technik mikroskopowych do badań komórek roślinnych. Gdzie to jest stosowne, omawia także trudności wynikające ze swoistości składu, struktury i funkcji komórek roślinnych.Rapid development of fluorescence microscopy, including confocal microscopy, combined with the utilization of the methodologies of molecular biology, significantly accelerated the development of molecular cell biology. Research in plant cell biology slightly lags behind, mainly due to marked structural and functional dissimilarity of plant cells. This paper summarizes the current state of research on plant endomembrane system with respect to the utilization of differentiated approaches and methods of cell biology. The use of markers, both chemical and genetic, which enable localization of macromolecules and biological processes is indicated. Chemical substances perturbing the functioning of the endomembrane system and thus enabling to draw conclusions on the role of specific proteins are listed and discussed. Finally, use of novel approaches and microscopic techniques to the research of plant cells is demonstrated. Where applicable, problems arising due to the specific composition, structure and function of plant cells, are also considered

Journey from the Center of the Cell - the intra- and intercellular transport of mRNA

Transport and localized translation of mRNA is crucial for the proper spatiotemporal organization of proteins within cells. Distribution of RNAs to subcellular domains has recently emerged as a major mechanism for establishing functionally distinct compartments and structures in the cells. There is an emerging evidence that active transport of mRNA involves cytoskeleton and membrane trafficking pathways in fungi, plants and animals, suggesting that it is a common phenomenon among eukaryotes. The important highlights are that the RNA-binding proteins recognize the cargo mRNA and that RNPs are actively transported on the cytoskeletal tracks or co-transported with membranous compartments, such as the endoplasmic reticulum and endosomes. The interest of scientists has expanded over the past years in response to the discoveries that RNA can be exported from cells to play a role in the intercellular communication. In this review, we will focus on characterization of the RNA transport both, within a cell and between cells, and on the currently proposed mechanisms for RNA targeting

Collagenase as a useful tool for the analysis of plant cellular peripheries

A technique for the selective loosening of the cell wall structure and the isolation of proteins permanently knotted in the cell walls was elaborated. Following treatment with collagenase, some proteins, such as calreticulin (CRT) and auxin binding protein 1 (ABP1) were released from purified cell walls, most probably through destruction of respective interacting proteins. The results were confirmed by the immunolocalization of the ABP1 and CRT with confocal and electron microscopy. On the other hand, potential substrates of collagenase, among them annexin 1 have been recognized. Mass spectra of annexin 1 obtained after collagenase digestion and results from analysis of potential cleavage sites suggested that the mechanism of enzyme cleavage might not depend on the amino acid sequence. Summarizing, collagenase was found to be a very useful tool for exploring molecules involved in the functioning of cellular peripheries