Height Changes Associated with Pigment Aggregation in Xenopus laevis Melanophores

2004 ◽  
Vol 24 (3) ◽  
pp. 203-214
Author(s):  
Charlotte Immerstrand ◽  
Harriet M. Nilsson ◽  
Margaretha Lindroth ◽  
Tommy Sundqvist ◽  
Karl-Eric Magnusson ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Xenopus Laevis ◽  
Leading Edge ◽  
Pigment Cells ◽  
Cell Height ◽  
Lower Vertebrates ◽  
Brownish Black ◽  
Height Increase ◽  
Pigment Aggregation ◽  
Cell Centre

Melanophores are pigment cells found in the skin of lower vertebrates. The brownish-black pigment melanin is stored in organelles called melanosomes. In response to different stimuli, the cells can redistribute the melanosomes, and thereby change colour. During melanosome aggregation, a height increase has been observed in fish and frog melanophores across the cell centre. The mechanism by which the cell increases its height is unknown. Changes in cell shape can alter the electrical properties of the cell, and thereby be detected in impedance measurements. We have in earlier studies of Xenopus laevis melanophores shown that pigment aggregation can be revealed as impedance changes, and therefore we were interested in investigating the height changes associated with pigment aggregation further. Accordingly, we quantified the changes in cell height by performing vertical sectioning with confocal microscopy. In analogy with theories explaining the leading edge of migrating cells, we investigated the possibility that the elevation of plasma membrane is caused by local swelling due to influx of water through HgC12-sensitive aquaporins. We also measured the height of the microtubule structures to assess whether they are involved in the height increase. Our results show that pigment aggregation in X. laevis melanophores resulted in a significant height increase, which was substantially larger when aggregation was induced by latrunculin than with melatonin. Moreover, the elevation of the plasma membrane did not correlate with influx of water through aquaporins or formation of new microtubules, Rather, the accumulation of granules seemed to drive the change in cell height.

Imaging of Xenopus laevis Oocyte Plasma Membrane in Physiological-Like Conditions by Atomic Force Microscopy

2013 ◽  
Vol 19 (5) ◽  
pp. 1358-1363 ◽  
Author(s):  
Massimo Santacroce ◽  
Federica Daniele ◽  
Andrea Cremona ◽  
Diletta Scaccabarozzi ◽  
Michela Castagna ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Plasma Membrane ◽  
High Resolution ◽  
Membrane Proteins ◽  
Xenopus Laevis ◽  
Functional Study ◽  
Xenopus Laevis Oocyte ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Imaging

AbstractXenopus laevis oocytes are an interesting model for the study of many developmental mechanisms because of their dimensions and the ease with which they can be manipulated. In addition, they are widely employed systems for the expression and functional study of heterologous proteins, which can be expressed with high efficiency on their plasma membrane. Here we applied atomic force microscopy (AFM) to the study of the plasma membrane of X. laevis oocytes. In particular, we developed and optimized a new sample preparation protocol, based on the purification of plasma membranes by ultracentrifugation on a sucrose gradient, to perform a high-resolution AFM imaging of X. laevis oocyte plasma membrane in physiological-like conditions. Reproducible AFM topographs allowed visualization and dimensional characterization of membrane patches, whose height corresponds to a single lipid bilayer, as well as the presence of nanometer structures embedded in the plasma membrane and identified as native membrane proteins. The described method appears to be an applicable tool for performing high-resolution AFM imaging of X. laevis oocyte plasma membrane in a physiological-like environment, thus opening promising perspectives for studying in situ cloned membrane proteins of relevant biomedical/pharmacological interest expressed in this biological system.

scholarly journals The MADD-3 LAMMER Kinase Interacts with a p38 MAP Kinase Pathway to Regulate the Display of the EVA-1 Guidance Receptor in Caenorhabditis elegans

PLoS Genetics ◽  
2016 ◽  
Vol 12 (4) ◽  
pp. e1006010 ◽  
Author(s):  
Serena A. D’Souza ◽  
Luckshi Rajendran ◽  
Rachel Bagg ◽  
Louis Barbier ◽  
Derek M. van Pel ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Caenorhabditis Elegans ◽  
Map Kinase ◽  
Motor Neurons ◽  
Leading Edge ◽  
P38 Map Kinase ◽  
Endosomal Trafficking ◽  
Guidance Cue ◽  
Map Kinase Pathway ◽  
Kinase Pathway

The proper display of transmembrane receptors on the leading edge of migrating cells and cell extensions is essential for their response to guidance cues. We previously discovered that MADD-4, which is an ADAMTSL secreted by motor neurons in Caenorhabditis elegans, interacts with an UNC-40/EVA-1 co-receptor complex on muscles to attract plasma membrane extensions called muscle arms. In nematodes, the muscle arm termini harbor the post-synaptic elements of the neuromuscular junction. Through a forward genetic screen for mutants with disrupted muscle arm extension, we discovered that a LAMMER kinase, which we call MADD-3, is required for the proper display of the EVA-1 receptor on the muscle’s plasma membrane. Without MADD-3, EVA-1 levels decrease concomitantly with a reduction of the late-endosomal marker RAB-7. Through a genetic suppressor screen, we found that the levels of EVA-1 and RAB-7 can be restored in madd-3 mutants by eliminating the function of a p38 MAP kinase pathway. We also found that EVA-1 and RAB-7 will accumulate in madd-3 mutants upon disrupting CUP-5, which is a mucolipin ortholog required for proper lysosome function. Together, our data suggests that the MADD-3 LAMMER kinase antagonizes the p38-mediated endosomal trafficking of EVA-1 to the lysosome. In this way, MADD-3 ensures that sufficient levels of EVA-1 are present to guide muscle arm extension towards the source of the MADD-4 guidance cue.

An ultrastructural study of the effects of wheat germ agglutinin (WGA) on cell cortex organization during the first cleavage of Xenopus laevis eggs. II. Cortical wound healing

1979 ◽  
Vol 37 (1) ◽  
pp. 59-67
Author(s):  
M. Geuskens ◽  
R. Tencer
Keyword(s):  
Wound Healing ◽  
Plasma Membrane ◽  
Electron Microscope ◽  
Xenopus Laevis ◽  
Ultrastructural Study ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Cell Cortex ◽  
Animal Pole ◽  
Annular Zone

Uncleaved fertilized eggs of Xenopus laevis treated with wheat germ agglutinin (WGA) have been pricked at the animal pole both inside and outside the regressed furrow region. The wounded cortex of both regions has been studied with the electron microscope and compared with the same region of wounded, untreated eggs. In all 3 cases, filaments are organized in an annular zone in the damaged cortex. When the surface is pricked outside the regressed furrow of WGA-treated embryos, bundles of microfilaments radiate from the ring and extend in deep folds which form a ‘star’ around the wound at the surface of the embryo. However, when the surface is pricked in the new membrane of the regressed furrow, filaments are intermingled with internalized portions of the plasma membrane. It is suggested that, when the surface is pricked outside the furrow region, more filaments are mobilized to counteract the tangential retraction of the membrane which has acquired more rigidity after WGA binding.

scholarly journals Protein kinase C activation antagonizes melatonin-induced pigment aggregation in Xenopus laevis melanophores.

1992 ◽  
Vol 119 (6) ◽  
pp. 1515-1521 ◽  
Author(s):  
D Sugden ◽  
S J Rowe
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Xenopus Laevis ◽  
Pigment Granule ◽  
Melatonin Receptors ◽  
Kinase C ◽  
Pigment Granules ◽  
Slow Aggregation ◽  
Pigment Aggregation ◽  
Induced Aggregation

The pineal hormone, melatonin (5-methoxy N-acetyltryptamine) induces a rapid aggregation of melanin-containing pigment granules in isolated melanophores of Xenopus laevis. Treatment of melanophores with activators of protein kinase C (PKC), including phorbol esters, mezerein and a synthetic diacylglycerol, did not affect pigment granule distribution but did prevent and reverse melatonin-induced pigment aggregation. This effect was blocked by an inhibitor of PKC, Ro 31-8220. The inhibitory effect was not a direct effect on melatonin receptors, per se, as the slow aggregation induced by a high concentration of an inhibitor of cyclic AMP-dependent protein kinase (PKA), adenosine 3',5'-cyclic monophosphothioate, Rp-diastereomer (Rp-cAMPS), was also reversed by PKC activation. Presumably activation of PKC, like PKA activation, stimulates the intracellular machinery involved in the centrifugal translocation of pigment granules along microtubules. alpha-Melanocyte stimulating hormone (alpha-MSH), like PKC activators, overcame melatonin-induced aggregation but this response was not blocked by the PKC inhibitor, Ro 31-8220. This data indicates that centrifugal translocation (dispersion) of pigment granules in Xenopus melanophores can be triggered by activation of either PKA, as occurs after alpha-MSH treatment, or PKC. The very slow aggregation in response to inhibition of PKA with high concentrations of Rp-cAMPS, suggests that the rapid aggregation in response to melatonin may involve multiple intracellular signals in addition to the documented Gi-mediated inhibition of adenylate cyclase.

Ultrastructural Changes in the Surface Layers of the Newt's Egg in Relation to the Mechanism of Its Cleavage

1970 ◽  
Vol 6 (1) ◽  
pp. 207-227 ◽  
Author(s):  
G. G. SELMAN ◽  
M. M. PERRY
Keyword(s):  
Plasma Membrane ◽  
Leading Edge ◽  
Ultrastructural Changes ◽  
Cortical Layers ◽  
Active Growth ◽  
Structural Modifications ◽  
Cell Cleavage ◽  
Surface Irregularities ◽  
Dense Band ◽  
10 Nm Filaments

The surface and cortical layers of an uncleaved newt egg have a characteristic ultrastructure which remains unaltered during cleavage; ultrastructural changes are confined to the region of the furrow. At the onset of cleavage there is a dipping inwards of the rough heavily pigmented animal surface to form a groove. Along the bottom of the groove the surface irregularities are reduced and a dense band (0.1 µm thick and 16 µm wide) is formed immediately below the plasma membrane. Within this band there are parallel filaments, 8-10 nm in diameter, oriented in the direction of the future furrow. No structural modifications were observed below the cortical layers of the leading part of the furrow apart from accumulations of granules and the mid-bodies of the spindle remnant. It is proposed that the dipping-in of the groove is due to contraction within the filamentous band, rather than contraction in a sheet of subcortical gel as proposed previously. The filamentous band persists below the furrow during the later stages of cleavage. The new unpigmented surface first forms as a strip across the animal surface and begins to grow at the bottom of the groove. Over most of its area, it is much smoother than the pigmented surface and has less material on the outside of the plasma membrane. There are microvilli along the bottom of the groove. The join between the new unpigmented and the old pigmented surface is abrupt. As the new unpigmented surface grows in extent, a narrow furrow forms below the lowest part of the groove and progresses towards the vegetal surface. For most of its length the furrow is between 10-nm and 0.5 µm wide, but at its leading edge it is 2 µ wide with microvilli on its surface and 10-nm filaments below the plasma membrane. It is concluded that the progressive formation of the furrow is due to active growth of new unpigmented cell surface. At late cleavage a ridge 10 µm high forms at the join between the new and old surface. After cleavage the ridges approach and meet to form the intercellular junction by which daughter blastomeres are held together along the animal surface. The mechanism of cell cleavage in the newt egg and in other forms is discussed in the light of the present observations.

scholarly journals CD13 tethers the IQGAP1-ARF6-EFA6 complex to the plasma membrane to promote ARF6 activation, β1 integrin recycling, and cell migration

2019 ◽  
Vol 12 (579) ◽  
pp. eaav5938 ◽  
Author(s):  
Mallika Ghosh ◽  
Robin Lo ◽  
Ivan Ivic ◽  
Brian Aguilera ◽  
Veneta Qendro ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Migration ◽  
Cell Adhesion ◽  
Cell Attachment ◽  
Leading Edge ◽  
Small Gtpase ◽  
Β1 Integrin ◽  
Recycling Endosomes ◽  
Cellular Processes ◽  
Early Endosomes

Cell attachment to the extracellular matrix (ECM) requires a balance between integrin internalization and recycling to the surface that is mediated by numerous proteins, emphasizing the complexity of these processes. Upon ligand binding in various cells, the β1 integrin is internalized, traffics to early endosomes, and is returned to the plasma membrane through recycling endosomes. This trafficking process depends on the cyclical activation and inactivation of small guanosine triphosphatases (GTPases) by their specific guanine exchange factors (GEFs) and their GTPase-activating proteins (GAPs). In this study, we found that the cell surface antigen CD13, a multifunctional transmembrane molecule that regulates cell-cell adhesion and receptor-mediated endocytosis, also promoted cell migration and colocalized with β1 integrin at sites of cell adhesion and at the leading edge. A lack of CD13 resulted in aberrant trafficking of internalized β1 integrin to late endosomes and its ultimate degradation. Our data indicate that CD13 promoted ARF6 GTPase activity by positioning the ARF6-GEF EFA6 at the cell membrane. In migrating cells, a complex containing phosphorylated CD13, IQGAP1, GTP-bound (active) ARF6, and EFA6 at the leading edge promoted the ARF6 GTPase cycling and cell migration. Together, our findings uncover a role for CD13 in the fundamental cellular processes of receptor recycling, regulation of small GTPase activities, cell-ECM interactions, and cell migration.

Phosphoinositide lipids and cell polarity: linking the plasma membrane to the cytocortex

2012 ◽  
Vol 53 ◽  
pp. 15-27 ◽  
Author(s):  
Michael P. Krahn ◽  
Andreas Wodarz
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Membrane Lipids ◽  
Leading Edge ◽  
Cell Types ◽  
Specific Protein ◽  
Molecular Organization ◽  
Apical Side ◽  
Cell Substrate ◽  
Basolateral Side

Many cell types in animals and plants are polarized, which means that the cell is subdivided into functionally and structurally distinct compartments. Epithelial cells, for example, possess an apical side facing a lumen or the outside environment and a basolateral side facing adjacent epithelial cells and the basement membrane. Neurons possess distinct axonal and dendritic compartments with specific functions in sending and receiving signals. Migrating cells form a leading edge that actively engages in pathfinding and cell-substrate attachment, and a trailing edge where such attachments are abandoned. In all of these cases, both the plasma membrane and the cytocortex directly underneath the plasma membrane show differences in their molecular composition and structural organization. In this chapter we will focus on a specific type of membrane lipids, the phosphoinositides, because in polarized cells they show a polarized distribution in the plasma membrane. They furthermore influence the molecular organization of the cytocortex by recruiting specific protein binding partners which are involved in the regulation of the cytoskeleton and in signal transduction cascades that control polarity, growth and cell migration.

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