Role of microfilaments in asialoglycoprotein processing in adult and developing liver

1990 ◽  
Vol 259 (4) ◽  
pp. G639-G645
Author(s):  
S. S. Kaufman ◽  
P. L. Blain ◽  
J. H. Park ◽  
D. J. Tuma
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Rate Constant ◽  
Cytochalasin D ◽  
Ligand Complex ◽  
Receptor Ligand ◽  
Surface Receptor ◽  
Old Rats ◽  
Initial Movement

To assess the role of microfilaments in receptor-mediated endocytosis of asialoglycoproteins, hepatocytes isolated from adult and 6-day-old rats were treated with the antimicrofilamentous agent cytochalasin D and then incubated with 125I-asialoorosomucoid (ASOR). Cytochalasin D (50 microM) reduced degradation of continuously endocytosed ASOR (7.5 micrograms/ml) equally in adult and neonate to approximately 20% of control. Internalization of surface-bound ASOR suggested at least two discrete sites at which ligand translocation was inhibited by drug at both ages: 1) initial movement of receptor-ligand complex from cell surface to interior and 2) postinternalization ligand transit to lysosomes. Inhibition of plasma membrane translocation was confirmed by calculation of endocytotic rate constant (Ke) values, which were decreased to approximately 20-30% of control after cytochalasin D treatment. In contrast, the antimicrotubular drug colchicine did not reduce Ke values significantly nor did colchicine in combination with cytochalasin D impede lysosome-directed transport more than cytochalasin D alone. These results indicate that internalization of occupied asialoglycoprotein surface receptor is microfilament dependent irrespective of postnatal age and that subsequent participation of microfilaments in asialoglycoprotein trafficking is closely related to that of microtubules.

scholarly journals CYRI-A regulates macropinocytic cup maturation and mediates integrin uptake, limiting invasive migration

2020 ◽  
Author(s):  
Anh Hoang Le ◽  
Tamas Yelland ◽  
Nikki Paul ◽  
Loic Fort ◽  
Savvas Nikolaou ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Ewing Sarcoma ◽  
Negative Regulator ◽  
Cell Surface Receptor ◽  
Actin Dynamics ◽  
Surface Receptor ◽  
Sarcoma Cells ◽  
Wave Complex

The Scar/WAVE complex is the major driver of actin nucleation at the plasma membrane, resulting in lamellipodia and membrane ruffles. While lamellipodia aid migration, membrane ruffles can generate macropinosomes - cup-like structures - important for nutrient uptake and regulation of cell surface receptor levels. How macropinosomes are formed and the role of the actin machinery in their formation and resolution is still not well understood. Mammalian CYRI-B is a recently described negative regulator of the Scar/WAVE complex by RAC1 sequestration, but its other paralogue, CYRI-A has not been characterised. Here we implicate CYRI-A as a key regulator of macropinocytosis maturation and integrin internalisation from the cell surface. We find that CYRI-A is recruited to nascent macropinosomes in a transient but distinct burst, downstream of PIP3-mediated RAC1 activation to regulate actin polymerisation. CYRI-A precedes RAB5A recruitment to engulfed macropinocytic cups and departs as RAB5A is recruited, consistent with a role for CYRI-A as a local suppressor of actin dynamics, enabling the resolution of the macropinocytic cup. The suppression of integrin a5b1 uptake caused by the co-depletion of CYRI-A and B in Ewing sarcoma cells, leads to an enhancement of surface integrin levels and enhanced invasion and anchorage-independent growth in 3D. Thus CYRI-A is a dynamic regulator of integrin uptake via macropinocytosis, functioning together with CYRI-B to regulate integrin homeostasis on the cell surface.

scholarly journals Synthesis of end-labeled multivalent ligands for exploring cell-surface-receptor–ligand interactions

2000 ◽  
Vol 7 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Eva J Gordon ◽  
Jason E Gestwicki ◽  
Laura E Strong ◽  
Laura L Kiessling
Keyword(s):  
Cell Surface ◽  
Cell Surface Receptor ◽  
Receptor Ligand ◽  
Multivalent Ligands ◽  
Ligand Interactions ◽  
Surface Receptor

scholarly journals Unraveling the sugar code: the role of microbial extracellular glycans in plant–microbe interactions

2020 ◽  
Author(s):  
Alan Wanke ◽  
Milena Malisic ◽  
Stephan Wawra ◽  
Alga Zuccaro
Keyword(s):  
Cell Surface ◽  
Hydrolytic Enzymes ◽  
Cell Surface Receptor ◽  
Molecular Signatures ◽  
Receptor Proteins ◽  
Surface Receptor ◽  
Microbe Interactions ◽  
Cell Surface Glycoconjugates ◽  
Cell Surface Glycans

Abstract To defend against microbial invaders but also to establish symbiotic programs, plants need to detect the presence of microbes through the perception of molecular signatures characteristic of a whole class of microbes. Among these molecular signatures, extracellular glycans represent a structurally complex and diverse group of biomolecules that has a pivotal role in the molecular dialog between plants and microbes. Secreted glycans and glycoconjugates such as symbiotic lipochitooligosaccharides or immunosuppressive cyclic β-glucans act as microbial messengers that prepare the ground for host colonization. On the other hand, microbial cell surface glycans are important indicators of microbial presence. They are conserved structures normally exposed and thus accessible for plant hydrolytic enzymes and cell surface receptor proteins. While the immunogenic potential of bacterial cell surface glycoconjugates such as lipopolysaccharides and peptidoglycan has been intensively studied in the past years, perception of cell surface glycans from filamentous microbes such as fungi or oomycetes is still largely unexplored. To date, only few studies have focused on the role of fungal-derived cell surface glycans other than chitin, highlighting a knowledge gap that needs to be addressed. The objective of this review is to give an overview on the biological functions and perception of microbial extracellular glycans, primarily focusing on their recognition and their contribution to plant–microbe interactions.

scholarly journals Phospholipase D2 Mediates Acute Aldosterone Secretion in Response to Angiotensin II in Adrenal Glomerulosa Cells

Endocrinology ◽  
2010 ◽  
Vol 151 (5) ◽  
pp. 2162-2170 ◽  
Author(s):  
Haixia Qin ◽  
Michael A. Frohman ◽  
Wendy B. Bollag
Keyword(s):  
Plasma Membrane ◽  
Angiotensin Ii ◽  
Cell Surface ◽  
Phosphatidic Acid ◽  
Phospholipase D ◽  
Cell Interior ◽  
Aldosterone Secretion ◽  
Phospholipase D2 ◽  
Glomerulosa Cells

In primary bovine adrenal glomerulosa cells, the signaling enzyme phospholipase D (PLD) is suggested to mediate priming, the enhancement of aldosterone secretion after pretreatment with and removal of angiotensin II (AngII), via the formation of persistently elevated diacylglycerol (DAG). To further explore PLD’s role in priming, glomerulosa cells were pretreated with an exogenous bacterial PLD. Using this approach, phosphatidic acid (PA) is generated on the outer, rather than the inner, leaflet of the plasma membrane. Although PA is not readily internalized, the PA is nonetheless rapidly hydrolyzed by cell-surface PA phosphatases to DAG, which efficiently flips to the inner leaflet and accesses the cell interior. Pretreatment with bacterial PLD resulted in priming upon subsequent AngII exposure, supporting a role of DAG in this process, because the increase in DAG persisted after exogenous PLD removal. To determine the PLD isoform mediating aldosterone secretion, and presumably priming, primary glomerulosa cells were infected with adenoviruses expressing GFP, PLD1, PLD2, or lipase-inactive mutants. Overexpressed PLD2 increased aldosterone secretion by approximately 3-fold over the GFP-infected control under basal conditions, with a significant enhancement to about 16-fold over the basal value upon AngII stimulation. PLD activity was also increased basally and upon stimulation with AngII. In contrast, PLD1 overexpression had little effect on aldosterone secretion, despite the fact that PLD activity was enhanced. In both cases, the lipase-inactive PLD mutants showed essentially no effect on PLD activity or aldosterone secretion. Our results suggest that PLD2 is the isoform that mediates aldosterone secretion and likely priming.

scholarly journals In vivo invasion of modified chorioallantoic membrane by tumor cells: the role of cell surface-bound urokinase.

1988 ◽  
Vol 107 (6) ◽  
pp. 2437-2445 ◽  
Author(s):  
L Ossowski
Keyword(s):  
Cell Surface ◽  
Plasminogen Activator ◽  
Tumor Cells ◽  
Chorioallantoic Membrane ◽  
Human Tumor ◽  
Chick Embryo Chorioallantoic Membrane ◽  
Catalytically Active ◽  
Surface Receptor

The ability of the chick embryo chorioallantoic membrane (CAM) to withstand invasion by tumor cells can be intentionally compromised by altering its morphological integrity. Using a newly developed quantitative assay of invasion we showed that intact CAMs were completely resistant to invasion by tumor cells, wounded CAMs did not pose a barrier to penetration, and CAMs that were wounded and then allowed to reseal displayed partial susceptibility to invasion. The invasion of resealed CAMs required catalytically active plasminogen activator (PA) of the urokinase type (uPA); the invasive efficiency of tumor cells was reduced by 75% when tumor uPA activity or tumor uPA production was inhibited. The invasive ability of human tumor cells, which have surface uPA receptors but which do not produce the enzyme, could be augmented by saturating their receptors with exogenous uPA. The mere stimulation of either uPA or tissue plasminogen activator production, in absence of binding to cell receptors, did not result in an enhancement of invasiveness. These findings suggest that the increased invasive potential of tumor cells is correlated with cell surface-associated proteolytic activity stemming from the interaction between uPA and its surface receptor.

scholarly journals Neisseria gonorrhoeae Porin P1.B Induces Endosome Exocytosis and a Redistribution of Lamp1 to the Plasma Membrane

2002 ◽  
Vol 70 (11) ◽  
pp. 5965-5971 ◽  
Author(s):  
Patricia Ayala ◽  
Brandi Vasquez ◽  
Lee Wetzler ◽  
Magdalene So
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Cell Surface ◽  
Neisseria Gonorrhoeae ◽  
Bacterial Infection ◽  
Immunoglobulin A ◽  
Late Endosomes ◽  
A Cell ◽  
Iga Protease

ABSTRACT The immunoglobulin A (IgA) protease secreted by pathogenic Neisseria spp. cleaves Lamp1, thereby altering lysosomes in a cell and promoting bacterial intracellular survival. We sought to determine how the IgA protease gains access to cellular Lamp1 in order to better understand the role of this cleavage event in bacterial infection. In a previous report, we demonstrated that the pilus-induced Ca2+ transient triggers lysosome exocytosis in human epithelial cells. This, in turn, increases the level of Lamp1 at the plasma membrane, where it can be cleaved by IgA protease. Here, we show that porin also induces a Ca2+ flux in epithelial cells. This transient is similar in nature to that observed in phagocytes exposed to porin. In contrast to the pilus-induced Ca2+ transient, the porin-induced event does not trigger lysosome exocytosis. Instead, it stimulates exocytosis of early and late endosomes and increases Lamp1 on the cell surface. These results indicate that Neisseria pili and porin perturb Lamp1 trafficking in epithelial cells by triggering separate and distinct Ca2+-dependent exocytic events, bringing Lamp1 to the cell surface, where it can be cleaved by IgA protease.

scholarly journals Actin-based Motility during Endocytosis in Budding Yeast

2006 ◽  
Vol 17 (3) ◽  
pp. 1354-1363 ◽  
Author(s):  
Kyoungtae Kim ◽  
Brian J. Galletta ◽  
Kevin O. Schmidt ◽  
Fanny S. Chang ◽  
Kendall J. Blumer ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Force Production ◽  
Actin Assembly ◽  
Capping Protein ◽  
Actin Cables ◽  
Endocytic Vesicles ◽  
Initial Movement ◽  
Fluorescence Markers

Actin assembly nucleated by Arp2/3 complex has been implicated in the formation and movement of endocytic vesicles. The dendritic nucleation model has been proposed to account for Arp2/3-mediated actin assembly and movement. Here, we explored the model by examining the role of capping protein in vivo, with quantitative tracking analysis of fluorescence markers for different stages of endocytosis in yeast. Capping protein was most important for the initial movement of endocytic vesicles away from the plasma membrane, which presumably corresponds to vesicle scission and release. The next phase of endosome movement away from the plasma membrane was also affected, but less so. The results are consistent with the dendritic nucleation model's prediction of capping protein as important for efficient actin assembly and force production. In contrast, the movement of late-stage endocytic vesicles, traveling through the cytoplasm en route to the vacuole, did not depend on capping protein. The movement of these vesicles was found previously to depend on Lsb6, a WASp interactor, whereas Lsb6 was found here to be dispensable for early endosome movement. Thus, the molecular requirements for Arp2/3-based actin assembly differ in early versus later stages of endocytosis. Finally, acute loss of actin cables led to increased patch motility.

The generation of cell surface polarity in mouse 8-cell blastomeres: the role of cortical microfilaments analysed using cytochalasin D

Development ◽  
1986 ◽  
Vol 95 (1) ◽  
pp. 169-191
Author(s):  
T. P. Fleming ◽  
S. J. Pickering ◽  
F. Qasim ◽  
B. Maro
Keyword(s):  
Cell Surface ◽  
Alternative Model ◽  
Cytochalasin D ◽  
Apical Surface ◽  
Surface Polarity ◽  
Cell Cycles ◽  
Contact Areas ◽  
Microfilament System

The mechanism by which a surface pole of microvilli is generated in mouse 8-cell blastomeres has been investigated. 4-cell and 8-cell embryos (or cell couplets) were incubated for precise times during their respective cell cycles in medium containing cytochalasin D (CCD) to disrupt the microfilament system. The blastomeres were analysed immediately for the distribution and state of organization of their microvilli, using three morphological techniques. The results indicate that the surface pole, characterized by microvilli containing CCD-resistant core filaments, is not generated by the gradual segregation of stable microvilli to the apical surface. An alternative model is proposed, based upon (a) the stabilization of the apical cytocortex prior to the elongation of apical microvilli and (b) the destabilization of cytocortical elements in contact areas and the shortening and loss of basolateral microvilli.

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