scholarly journals Mechanistic Framework for Establishment, Maintenance, and Alteration of Cell Polarity in Plants

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Pankaj Dhonukshe
Keyword(s):  
Plasma Membrane ◽  
Cell Polarity ◽  
Single Cells ◽  
Cell Types ◽  
Membrane Domains ◽  
Cell Transport ◽  
Agc Kinases ◽  
Polar Localization ◽  
Intact Plants ◽  
Polarity Establishment

Cell polarity establishment, maintenance, and alteration are central to the developmental and response programs of nearly all organisms and are often implicated in abnormalities ranging from patterning defects to cancer. By residing at the distinct plasma membrane domains polar cargoes mark the identities of those domains, and execute localized functions. Polar cargoes are recruited to the specialized membrane domains by directional secretion and/or directional endocytic recycling. In plants, auxin efflux carrier PIN proteins display polar localizations in various cell types and play major roles in directional cell-to-cell transport of signaling molecule auxin that is vital for plant patterning and response programs. Recent advanced microscopy studies applied to single cells in intact plants reveal subcellular PIN dynamics. They uncover the PIN polarity generation mechanism and identified important roles of AGC kinases for polar PIN localization. AGC kinase family members PINOID, WAG1, and WAG2, belonging to the AGC-3 subclass predominantly influence the polar localization of PINs. The emerging mechanism for AGC-3 kinases action suggests that kinases phosphorylate PINs mainly at the plasma membrane after initial symmetric PIN secretion for eventual PIN internalization and PIN sorting into distinct ARF-GEF-regulated polar recycling pathways. Thus phosphorylation status directs PIN translocation to different cell sides. Based on these findings a mechanistic framework evolves that suggests existence of cell side-specific recycling pathways in plants and implicates AGC3 kinases for differential PIN recruitment among them for eventual PIN polarity establishment, maintenance, and alteration.

Membrane microdomains: lessons from microscopy

1995 ◽  
Vol 53 ◽  
pp. 776-777
Author(s):  
J.M. Robinson ◽  
J.M Oliver
Keyword(s):  
Spatial Distribution ◽  
Plasma Membrane ◽  
Epithelial Cells ◽  
Plasma Membranes ◽  
Cell Types ◽  
Imaging Modalities ◽  
Membrane Microdomains ◽  
Membrane Domains ◽  
Lateral Heterogeneity ◽  
Functional Importance

Specialized regions of plasma membranes displaying lateral heterogeneity are the focus of this Symposium. Specialized membrane domains are known for certain cell types such as differentiated epithelial cells where lateral heterogeneity in lipids and proteins exists between the apical and basolateral portions of the plasma membrane. Lateral heterogeneity and the presence of microdomains in membranes that are uniform in appearance have been more difficult to establish. Nonetheless a number of studies have provided evidence for membrane microdomains and indicated a functional importance for these structures.This symposium will focus on the use of various imaging modalities and related approaches to define membrane microdomains in a number of cell types. The importance of existing as well as emerging imaging technologies for use in the elucidation of membrane microdomains will be highlighted. The organization of membrane microdomains in terms of dimensions and spatial distribution is of considerable interest and will be addressed in this Symposium.

scholarly journals Involvement of Raft-Like Plasma Membrane Domains of Entamoeba histolytica in Pinocytosis and Adhesion

2004 ◽  
Vol 72 (9) ◽  
pp. 5349-5357 ◽  
Author(s):  
Richard C. Laughlin ◽  
Glen C. McGugan ◽  
Rhonda R. Powell ◽  
Brenda H. Welter ◽  
Lesly A. Temesvari
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Entamoeba Histolytica ◽  
Fluid Phase ◽  
Cell Types ◽  
Cysteine Proteases ◽  
Membrane Domains ◽  
Cell Surface Molecule ◽  
Physiological Relevance ◽  
Plasma Membrane Domains

ABSTRACT Lipid rafts are highly ordered, cholesterol-rich, and detergent-resistant microdomains found in the plasma membrane of many eukaryotic cells. These domains play important roles in endocytosis, secretion, and adhesion in a variety of cell types. The parasitic protozoan Entamoeba histolytica, the causative agent of amoebic dysentery, was determined to have raft-like plasma membrane domains by use of fluorescent lipid analogs that specifically partition into raft and nonraft regions of the membrane. Disruption of raft-like membrane domains in Entamoeba with the cholesterol-binding agents filipin and methyl-β-cyclodextrin resulted in the inhibition of several important virulence functions, fluid-phase pinocytosis, and adhesion to host cell monolayers. However, disruption of raft-like domains did not inhibit constitutive secretion of cysteine proteases, another important virulence function of Entamoeba. Flotation of the cold Triton X-100-insoluble portion of membranes on sucrose gradients revealed that the heavy, intermediate, and light subunits of the galactose-N-acetylgalactosamine-inhibitible lectin, an important cell surface adhesion molecule of Entamoeba, were enriched in cholesterol-rich (raft-like) fractions, whereas EhCP5, another cell surface molecule, was not enriched in these fractions. The subunits of the lectin were also observed in high-density, actin-rich fractions of the sucrose gradient. Together, these data suggest that pinocytosis and adhesion are raft-dependent functions in this pathogen. This is the first report describing the existence and physiological relevance of raft-like membrane domains in E. histolytica.

scholarly journals Recent Experiments Support a Microemulsion Origin of Plasma Membrane Domains: Dependence of Domain Size on Physical Parameters

Membranes ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 167
Author(s):  
David W. Allender ◽  
M. Schick
Keyword(s):  
Plasma Membrane ◽  
Domain Size ◽  
Cell Types ◽  
Physical Parameters ◽  
Spontaneous Curvature ◽  
Membrane Domains ◽  
Physical Origin ◽  
Unsaturated Lipids ◽  
Bending Modulus ◽  
Different Cell Types

It is widely, but not universally, believed that the lipids of the plasma membrane are not uniformly distributed, but that “rafts” of sphingolipids and cholesterol float in a “sea” of unsaturated lipids. The physical origin of such heterogeneities is often attributed to a phase coexistence between the two different domains. We argue that this explanation is untenable for several reasons. Further, we note that the results of recent experiments are inconsistent with this picture. However, they are quite consistent with an alternate explanation, namely, that the plasma membrane is a microemulsion of the two kinds of regions. To show this, we briefly review a simplified version of this theory and its phase diagram. We also explicate the dependence of the predicted domain size on four physical parameters. They are the energy cost of gradients in the composition, the spontaneous curvature of the membrane, its bending modulus and its surface tension. Taking values of the latter two from experiment, we obtain domain sizes for several different cell types that vary from 58 to 88 nm.

Steps in the morphogenesis of a polarized epithelium. II. Disassembly and assembly of plasma membrane domains during reversal of epithelial cell polarity in multicellular epithelial (MDCK) cysts

1990 ◽  
Vol 95 (1) ◽  
pp. 153-165
Author(s):  
A.Z. Wang ◽  
G.K. Ojakian ◽  
W.J. Nelson
Keyword(s):  
Plasma Membrane ◽  
Suspension Culture ◽  
Cell Polarity ◽  
Collagen Gel ◽  
Preceding Paper ◽  
Fundamental Aspect ◽  
Membrane Domains ◽  
Polarized Cells ◽  
Plasma Membrane Domains ◽  
Polarized Epithelium

A fundamental aspect in the morphogenesis of a polarized epithelium is the formation of structurally and functionally distinct apical and basal-lateral domains of the plasma membrane. The formation of these membrane domains involves the accumulation of domain-specific proteins and removal of incorrectly localized proteins. The mechanisms involved in these processes are not well understood. We have approached this problem by detailed analysis of the distribution and fate of proteins specific for different membrane domains during reversal of epithelial polarity. In the preceding paper we showed that MDCK cells form multicellular cysts comprising a closed monolayer of polarized cells. The orientation of cell polarity depends upon whether cysts are formed in suspension culture or in a collagen gel. Here, we show that, when fully developed cysts formed in suspension culture are placed in a collagen gel, polarity is rapidly reversed without cell dissociation. We show that during the process of polarity reversal, plasma membrane domains are disassembled by uptake of proteins into cytoplasmic vesicles, followed by protein degradation that probably occurs in lysosomes. The disassembly and assembly of the apical and the basal-lateral membrane domains occur in a sequential order with different kinetics. Our results provide further insights into the establishment of protein specificity of plasma membrane domains in polarized cells.

scholarly journals The 'lipid raft' microdomain proteins reggie-1 and reggie-2 (flotillins) are scaffolds for protein interaction and signalling.

2005 ◽  
Vol 72 ◽  
pp. 109-118 ◽  
Author(s):  
Claudia A. O. Stuermer ◽  
Helmut Plattner
Keyword(s):  
Plasma Membrane ◽  
Lipid Raft ◽  
Ganglion Cells ◽  
Single Cells ◽  
Cell Types ◽  
Cellular Prion Protein ◽  
Surface Proteins ◽  
Current View ◽  
Specific Cell ◽  
Rna Knockdown

Reggie-1 and reggie-2 are two evolutionarily highly conserved proteins which are up-regulated in retinal ganglion cells during regeneration of lesioned axons in the goldfish optic nerve. They are located at the cytoplasmic face of the plasma membrane and are considered to be 'lipid raft' constituents due to their insolubility in Triton X-100 and presence in the 'floating fractions'; hence they were independently named flotillins. According to our current view, the reggies subserve functions as protein scaffolds which form microdomains in neurons, lymphocytes and many other cell types across species as distant as flies and humans. These microdomains are of a surprisingly constant size of less than or equal to 0.1 mm in all cell types, whereas the distance between them is variable. The microdomains co-ordinate signal transduction of specific cell-surface proteins and especially of GPI (glycosylphosphatidylinositol)-anchored proteins into the cell, as is demonstrated for PrPc (cellular prion protein) in T-lymphocytes. These cells possess a pre-formed reggie cap scaffold consisting of densely packed reggie microdomains. PrPc is targeted to the lymphocyte reggie cap when activated by antibody cross-linking, and induces a distinct Ca2+ signal. In developing zebrafish, reggies become concentrated in neurons and axon tracts, and their absence, after morpholino antisense RNA-knockdown, results in deformed embryos with reduced brains. Likewise, defects in Drosophila eye morphogenesis occur upon reggie overexpression in mutant flies. The defects observed in the organism, as well as in single cells in culture, indicate a morphogenetic function of the reggies, with emphasis on the nervous system. This complies with their role as scaffolds for the formation of multiprotein complexes involved in signalling across the plasma membrane.

scholarly journals Galectin–glycan lattices regulate cell-surface glycoprotein organization and signalling

2008 ◽  
Vol 36 (6) ◽  
pp. 1472-1477 ◽  
Author(s):  
Omai B. Garner ◽  
Linda G. Baum
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Targeted Delivery ◽  
Cell Types ◽  
Surface Glycoprotein ◽  
Membrane Domains ◽  
Cellular Functions ◽  
Cell Surface Glycoprotein

The formation of multivalent complexes of soluble galectins with glycoprotein receptors on the plasma membrane helps to organize glycoprotein assemblies on the surface of the cell. In some cell types, this formation of galectin–glycan lattices or scaffolds is critical for organizing plasma membrane domains, such as lipid rafts, or for targeted delivery of glycoproteins to the apical or basolateral surface. Galectin–glycan lattice formation is also involved in regulating the signalling threshold of some cell-surface glycoproteins, including T-cell receptors and growth factor receptors. Finally, galectin–glycan lattices can determine receptor residency time by inhibiting endocytosis of glycoprotein receptors from the cell surface, thus modulating the magnitude or duration of signalling from the cell surface. This paper reviews recent evidence in vitro and in vivo for critical physiological and cellular functions that are regulated by galectin–glycoprotein interactions.

scholarly journals Ultrastructural Analysis of Human Epidermal CD44 Reveals Preferential Distribution on Plasma Membrane Domains Facing the Hyaluronan-rich Matrix Pouches

1998 ◽  
Vol 46 (2) ◽  
pp. 241-248 ◽  
Author(s):  
Anna-Liisa Tuhkanen ◽  
Markku Tammi ◽  
Alpo Pelttari ◽  
Ulla M. Ågren ◽  
Raija Tammi
Keyword(s):  
Plasma Membrane ◽  
Basement Membrane ◽  
Intercellular Space ◽  
Plasma Membranes ◽  
Ultrastructural Localization ◽  
Cell Types ◽  
Membrane Domains ◽  
Immunogold Staining ◽  
Plasma Membrane Domains ◽  
Plasma Membrane Domain

We used immunogold staining and stereology to examine the ultrastructural localization and to estimate the relative content of CD44 in different strata and cell types of normal human epidermis. We found that CD44 existed almost exclusively on the plasma membranes; only rare labeling occurred on vesicular structures within the cytoplasm. Quantitation of the immunogold particles indicated that the labeling density of melanocytes corresponded to that of basal keratinocytes, and Langerhans cells displayed a labeling density of ∼10% that of the surrounding spinous cells. Among keratinocyte strata, the highest labeling density occurred on spinous cells, suggesting upregulation of CD44 after detachment from the basement membrane. The plasma membrane distribution of CD44 was compartmentalized, with little signal on cell–cell and cell-substratum contact sites such as desmosomes, the plasma membrane domain facing the basement membrane, and the close apposition of terminally differentiating granular cells. In contrast, CD44 was abundant on plasma membrane domains facing an open intercellular space, rich in hyaluronan. This distribution is in line with a role of CD44 as a hyaluronan receptor, important in the maintenance of the intercellular space for nutritional and cell motility functions in stratified epithelia.

scholarly journals Recent Experiments Support an Emulsion Origin of Plasma Membrane Domains: Dependence of Domain Size on Physical Parameters

2020 ◽  
Author(s):  
David W. Allender ◽  
M. Schick
Keyword(s):  
Plasma Membrane ◽  
Domain Size ◽  
Cell Types ◽  
Physical Parameters ◽  
Spontaneous Curvature ◽  
Membrane Domains ◽  
Physical Origin ◽  
Unsaturated Lipids ◽  
Bending Modulus ◽  
Different Cell Types

It is widely, but not universally, believed that the lipids of the plasma membrane are not uniformly distributed, but that "rafts'' of sphingolipids and cholesterol float in a "sea'' of unsaturated lipids. The physical origin of such heterogeneities is often attributed to a phase coexistence between the two different domains. We argue that this explanation is untenable for several reasons. Further we note that the results of recent experiments are inconsistent with this picture. However they are quite consistent with an alternate explanation, namely that the plasma membrane is an emulsion of the two kinds of regions. To show this, we briefly review a simplified version of this theory and its phase diagram. We also explicate the dependence of the predicted domain size on four physical parameters. Among them are the spontaneous curvature of the membrane and its bending modulus and surface tension. Taking values of the latter two from experiment, we obtain domain sizes for several different cell types that vary from 58 to 88 nm.

Protein trafficking and polarity in kidney epithelium: from cell biology to physiology

1996 ◽  
Vol 76 (1) ◽  
pp. 245-297 ◽  
Author(s):  
D. Brown ◽  
J. L. Stow
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Protein Trafficking ◽  
Cell Biology ◽  
Cell Types ◽  
Membrane Domains ◽  
Disease States ◽  
Target Membrane ◽  
Plasma Membrane Domains ◽  
Membrane Components

The transepithelial movement of fluids, electrolytes, and larger molecules is achieved by the activity of a host of specialized transporting proteins, including enzymes, receptors, and channels, that are located on either the apical, basal, or lateral plasma membrane domains of epithelial cells. In the kidney as well as in all other organs, this remarkable polarity of epithelial cells depends on the selective insertion of newly synthesized and recycling proteins and lipids into distinct plasma membrane domains and on the maintenance and modulation of these specialized domains once they are established during epithelial development. This review addresses the mechanisms by which epithelial cells control the movement of membrane components within the cell to ensure that they are delivered to the correct target membrane. Among the topics discussed are targeting signals within membrane proteins, the role of the cytoskeleton and the tight junctional barrier in cell polarity, and the requirement for accessory proteins in the targeting process, including GTP-binding proteins, and proteins that are involved in vesicle docking and fusion events. The final part of the review is devoted uniquely to the polarized targeting of functionally defined proteins in various kidney cell types. In concluding, examples of how a breakdown in these trafficking pathways may be related to some disease states are presented.

scholarly journals Troponin-I localizes selected apico-basal cell polarity signals

2018 ◽  
Author(s):  
Sergio Casas-Tintó ◽  
Alberto Ferrús
Keyword(s):  
Cell Polarity ◽  
Troponin I ◽  
Genome Instability ◽  
Cell Types ◽  
Wing Disc ◽  
Apical Region ◽  
Loss Of Function ◽  
Polar Localization ◽  
A Cell

AbstractBeyond its well characterized role in muscle contraction,DrosophilaTroponin I (TnI) is expressed in other cell types where it plays a role in proliferation control. TnI traffics between the nucleus and the cytoplasm through a sumoylation-dependent mechanism. We address here the role of TnI in the cytoplasm. TnI accumulates in the apical region of epidermal cells and neuroblasts. TnI helps to localize and co-immunoprecipitates with Par-3/Bazooka and with disc large (Dlg), two components of the apico-basal polarity system. By contrast, Scribbled is not affected by TnI depletion. In neuroblasts, TnI is required for the polar localization of Miranda while non-polar Dlg is not affected. TnI loss-of-function triggers genome instability, cell apoptosis and extrusion from wing disc epithelia. However, rescue from apoptosis by p35 does not prevent genome instability demonstrating that both features, apoptosis and genome instability, are mechanistically independent. While PI3K is known to contribute to apico-basal polarity of epithelia in vertebrates,DrosophilaPI3K depletion alters neither the apical localization of TnI or Par3/Bazooka, nor the basal localization of Dlg. However, the overexpression of PI3K prevents the polarity defects caused by TnI depletion. Thus, TnI binds certain apico-basal polarity signals in a cell type dependent context, and it unveils a hitherto unsuspected diversity of mechanisms to allocate cell polarity factors.

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