Search results for "Endomembrane system"
showing 10 items of 13 documents
Systematic analysis of specific and nonspecific auxin effects on endocytosis and trafficking.
2021
Abstract The phytohormone auxin and its directional transport through tissues are intensively studied. However, a mechanistic understanding of auxin-mediated feedback on endocytosis and polar distribution of PIN auxin transporters remains limited due to contradictory observations and interpretations. Here, we used state-of-the-art methods to reexamine the auxin effects on PIN endocytic trafficking. We used high auxin concentrations or longer treatments versus lower concentrations and shorter treatments of natural indole-3-acetic acid (IAA) and synthetic naphthalene acetic acid (NAA) auxins to distinguish between specific and nonspecific effects. Longer treatments of both auxins interfere wi…
Molecular mechanisms of endomembrane trafficking in plants
2021
Abstract Endomembrane trafficking is essential for all eukaryotic cells. The best-characterized membrane trafficking organelles include the endoplasmic reticulum (ER), Golgi apparatus, early and recycling endosomes, multivesicular body, or late endosome, lysosome/vacuole, and plasma membrane. Although historically plants have given rise to cell biology, our understanding of membrane trafficking has mainly been shaped by the much more studied mammalian and yeast models. Whereas organelles and major protein families that regulate endomembrane trafficking are largely conserved across all eukaryotes, exciting variations are emerging from advances in plant cell biology research. In this review, …
Stitching proteins into membranes, not sew simple
2014
Abstract Most integral membrane proteins located within the endomembrane system of eukaryotic cells are first assembled co-translationally into the endoplasmic reticulum (ER) before being sorted and trafficked to other organelles. The assembly of membrane proteins is mediated by the ER translocon, which allows passage of lumenal domains through and lateral integration of transmembrane (TM) domains into the ER membrane. It may be convenient to imagine multi-TM domain containing membrane proteins being assembled by inserting their first TM domain in the correct orientation, with subsequent TM domains inserting with alternating orientations. However a simple threading model of assembly, with s…
Sjögren's autoimmunity: how perturbation of recognition in endomembrane traffic may provoke pathological recognition at the cell surface
1998
CD4 T cell antigen recognition requires presentation by major histocompatibility complex Class II molecules (MHC II). B cell surface immunoglobulins recognize antigens independently of MHC II, but activation typically requires CD4 cell cytokines as accessory signals. Plasma membrane-endomembrane traffic in lacrimal gland acinar cells, targets of autoimmune activity in Sjogren's syndrome, may satisfy both requirements. The Golgi protein galactosyltransferase and the lysosomal proteins cathepsin B and cathepsin D appear at the plasma membranes during sustained secretomotor stimulation. The RNA transcription termination factor La, a frequent target of Sjogren's autoantibodies, appears in the a…
Microbial strategies to exploit host cells
2005
The European Research Conference (EURESCO) on Spatial and Temporal Dynamics of the Endomembrane System was held in sunny San Feliu de Guixols, Spain, between 16 and 21 October 2004. The conference was organized by D. Holden and H. Stenmark ![][1] By bringing together scientists from the fields of microbiology and cell biology, the European Research Conference (EURESCO) on ‘Spatial and Temporal Dynamics of the Endomembrane System’ combined the best of both worlds at the intersection where intracellular pathogens and host cells meet. The mixture of studies, which focused on the molecular mechanisms behind endocytic and secretory transport, and the pathogenic microbes that exploit these pathwa…
Effects of Ga3 and Ca2+ on barley aleurone protoplasts: a freeze-fracture study
1988
Freeze-fracture electron microscopy was used to study changes in the endomembrane system of barley (Hordeum vulgare L. cv. Himalaya) aleurone protoplasts. Protoplasts were used for this study because their response to calcium and the plant hormone gibberellic acid (Ga3) can be monitored prior to rapid freezing of cells for electron microscopy. Protoplasts incubated in Ga3 plus Ca2+ secrete elevated levels of a-amylase relative to cells incubated in Ga3 or Ca2+ alone. The endoplasmic reticulum (ER) and Golgi apparatus of protoplasts incubated in Ga3 plus Ca2+ undergo changes that are well correlated with the synthesis and secretion of a-amylase. The ER, which appears as short, single sheets …
The Biogenesis of Vacuoles: Insights from Microscopy
1997
Publisher Summary Vacuoles of plant cells were discovered with the early light microscope and, as meant by the etymology of the word, were subsequently defined as the cell space empty of cytoplasmic matter. As usual in experimental science, methodological and instrumental progress has delineated differently the present definitions of vacuoles, which largely depend on the tools and concepts used for their study. This chapter discusses the biogenesis of vacuoles. Biochemistry and physiology of the vacuole have been made possible by the isolation of intact vacuoles. A specific, although yet incomplete, set of soluble and membrane proteins with unique properties have been specifically ascribed …
Out for a Walk Along the Secretory Pathway During Programmed Cell Death
2015
This chapter provides a comprehensive updated analysis on the role of the secretory pathway in the orchestration of cell’s demise, an emerging and promising research topic in the field of plant programmed cell death (PCD). Since my first review on this topic, a plethora of data has been published supporting the concept that endomembrane system-forming subcellular compartments cooperate to coordinate cellular responses to developmental and environmental cues and thereby can dictate a cell’s ultimate fate. Thus, the early secretory pathway, encompassing the endoplasmic reticulum and Golgi apparatus, can be involved in the perception of extrinsic and intrinsic stimuli. It can also be an active…
Folding and insertion of transmembrane helices at the ER
2021
In eukaryotic cells, the endoplasmic reticulum (ER) is the entry point for newly synthesized proteins that are subsequently distributed to organelles of the endomembrane system. Some of these proteins are completely translocated into the lumen of the ER while others integrate stretches of amino acids into the greasy 30 Å wide interior of the ER membrane bilayer. It is generally accepted that to exist in this non-aqueous environment the majority of membrane integrated amino acids are primarily non-polar/hydrophobic and adopt an α-helical conformation. These stretches are typically around 20 amino acids long and are known as transmembrane (TM) helices. In this review, we will consider how tra…
The membrane proteome of Medicago truncatula roots displays qualitative and quantitative changes in response to arbuscular mycorrhizal symbiosis
2014
International audience; Arbuscular mycorrhizal (AM) symbiosis that associates roots of most land plants with soil-borne fungi (Glomeromycota), is characterized by reciprocal nutritional benefits. Fungal colonization of plant roots induces massive changes in cortical cells where the fungus differentiates an arbuscule, which drives proliferation of the plasma membrane. Despite the recognized importance of membrane proteins in sustaining AM symbiosis, the root microsomal proteome elicited upon mycorrhiza still remains to be explored. In this study, we first examined the qualitative composition of the root membrane proteome of Medicago truncatula after microsome enrichment and subsequent in dep…