scholarly journals Macrophage podosomes assemble at the leading lamella by growth and fragmentation

2003 ◽  
Vol 161 (4) ◽  
pp. 697-705 ◽  
Author(s):  
James G. Evans ◽  
Ivan Correia ◽  
Olga Krasavina ◽  
Nicki Watson ◽  
Paul Matsudaira
Keyword(s):  
Cell Adhesion ◽  
Turnover Rate ◽  
De Novo ◽  
Critical Role ◽  
Leading Edge ◽  
Cell Periphery ◽  
Close Apposition ◽  
Cluster Precursor ◽  
Microtubule Inhibitors ◽  
In Cells

Podosomes are actin- and fimbrin-containing adhesions at the leading edge of macrophages. In cells transfected with β-actin–ECFP and L-fimbrin–EYFP, quantitative four-dimensional microscopy of podosome assembly shows that new adhesions arise at the cell periphery by one of two mechanisms; de novo podosome assembly, or fission of a precursor podosome into daughter podosomes. The large podosome cluster precursor also appears to be an adhesion structure; it contains actin, fimbrin, integrin, and is in close apposition to the substratum. Microtubule inhibitors paclitaxel and demecolcine inhibit the turnover and polarized formation of podosomes, but not the turnover rate of actin in these structures. Because daughter podosomes and podosome cluster precursors are preferentially located at the leading edge, they may play a critical role in continually generating new sites of cell adhesion.

scholarly journals Signal-mediated localization of Candida albicans pheromone response pathway components

2020 ◽  
Author(s):  
Anna Carolina Borges Pereira Costa ◽  
Raha Parvizi Omran ◽  
Chris Law ◽  
Vanessa Dumeaux ◽  
Malcolm Whiteway
Keyword(s):  
Candida Albicans ◽  
Map Kinase ◽  
Nuclear Localization ◽  
Map Kinases ◽  
Critical Role ◽  
Cell Periphery ◽  
Pheromone Response ◽  
Pheromone Response Pathway ◽  
Localization Signal ◽  
In Cells

Abstract Candida albicans opaque cells release pheromones to stimulate cells of opposite mating type to activate their pheromone response pathway. Although this fungal pathogen shares orthologous proteins involved in the process with Saccharomyces cerevisiae, the pathway in each organism has unique characteristics. We have used GFP-tagged fusion proteins to investigate the localization of the scaffold protein Cst5, as well as the MAP kinases Cek1 and Cek2, during pheromone response in C. albicans. In wild-type cells, pheromone treatment directed Cst5-GFP to surface puncta concentrated at the tips of mating projections. These puncta failed to form in cells defective in either the Gα or β subunits. However, they still formed in response to pheromone in cells missing Ste11, but with the puncta distributed around the cell periphery in the absence of mating projections. These puncta were absent from hst7Δ/Δ cells, but could be detected in the ste11Δ/Δ hst7Δ/Δ double mutant. Cek2-GFP showed a strong nuclear localization late in the response, consistent with a role in adaptation, while Cek1-GFP showed a weaker, but early increase in nuclear localization after pheromone treatment. Activation loop phosphorylation of both Cek1 and Cek2 required the presence of Ste11. In contrast to Cek2-GFP, which showed no localization signal in ste11Δ/Δ cells, Cek1-GFP showed enhanced nuclear localization that was pheromone independent in the ste11Δ/Δ mutant. The results are consistent with CaSte11 facilitating Hst7-mediated MAP kinase phosphorylation and also playing a potentially critical role in both MAP kinase and Cst5 scaffold localization.

The beta1-Tubulin Binding Protein RanBP10 Plays a Critical Role for Platelet Discoid Shape and Hemostasis

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 414-414 ◽  
Author(s):  
Harald Schulze ◽  
Silke Fleischhauer ◽  
Imke Meyer ◽  
Martin Wannack ◽  
Stefan Kunert
Keyword(s):  
Bone Marrow ◽  
De Novo ◽  
Binding Protein ◽  
Blood Platelets ◽  
Critical Role ◽  
Positional Information ◽  
Blood Stream ◽  
Cell Periphery ◽  
Nucleotide Exchange ◽  
Tubulin Binding

Abstract Blood platelets in the circulation are released from megakaryocytes (MKs), their precursor cells in the bone marrow. Mature MKs are located at the blood vessels and release platelets into the blood stream by intermediate structures referred to as proplatelets. Every MK can release up to a thousand virtually identical platelets. During this fragmentation process every single platelet is equipped with a rather constant number of assorted granules and a peripheral microtubule ring consisting of several coiled filaments. 8–12 microtubule filaments are found on average in the coil, which is essential for maintaining the platelet discoid shape. Generating these dynamic microtubule filaments at the very cell periphery in the absence of classical microtubule nucleating factors is strictly dependent on de novo nucleation of filaments. Beta1-tubulin is a MK/platelet-specific and the predominant isoform present in proplatelets and platelets. Mice lacking beta1-tubulin are thrombocytopenic and reveal platelet spherocytosis. In humans, a Q43P mutation in the beta1-tubulin gene Tubb1 also leads to large and spheric platelets. We have recently identified RanBP10 as a cytoplasmic beta1-tubulin binding protein that is selectively expressed in hematopoietic tissues like bone marrow and MKs. RNA interference (RNAi)- mediated RanBP10 ablation in primary MKs resulted in the collapse of long microtubule filaments whereas retrovirally forced overexpression of RanBP10 led to a marked increase in microtubule filaments, most likely by number or augmented bundling. RanBP10 harbors guanine nucleotide exchange factor activity toward Ran by exchanging GDP with GTP. As a local increase in Ran-GTP precedes nucleation of non-centrosomal microtubules in other cell types this mechanism might explain how positional information about new microtubule filaments is provided in the cell periphery of mature and proplatelet elaborating MKs. We generated a gene trap-mediated mouse model for RanBP10 deficiency. MKs derived from nullizygous animals phenocopied the collapse of microtubule filaments found by RNAi. Although RanBP10 was dispensable for overall platelet biogenesis with counts about 90–95% of normal, the ultrastructural analysis revealed that loss of RanBP10 protein resulted in a significant decline in the elliptic coefficient: Mutant platelets were more spherical and electron micrographs showed a wider variety in both microtubule filament number and coil localization including additional and incomplete coiling. Most intriguingly, RanBP10- deficient mice demonstrated a markedly prolonged bleeding time compared to littermate controls in a standardized tail bleeding assay. Platelets from nullizygous animals failed to respond normally to ADP by CD62P expression in flow cytometry. Our data thus suggest that RanBP10 plays a critical role in maintaining the tightly controlled platelet shape and function and that RanBP10 is essential for hemostasis.

Recent Advances in the Function of the 67 kDa Laminin Receptor and its Targeting for Personalized Therapy in Cancer

2017 ◽  
Vol 23 (32) ◽  
pp. 4745-4757 ◽  
Author(s):  
Ada Pesapane ◽  
Pia Ragno ◽  
Carmine Selleri ◽  
Nunzia Montuori
Keyword(s):  
Cell Adhesion ◽  
Cancer Progression ◽  
Ribosome Biogenesis ◽  
Critical Role ◽  
Protein Translation ◽  
Basement Membranes ◽  
Laminin Receptor ◽  
Cell Surface Receptor ◽  
Future Application ◽  
Neoplastic Cells

The 67 kDa high affinity laminin receptor (67LR) is a non-integrin cell surface receptor for laminin, the major component of basement membranes. Interactions between 67LR and laminin play a major role in mediating cell adhesion, migration, proliferation and survival. 67LR derives from homo- or hetero-dimerization of a 37 kDa cytosolic precursor (37LRP), most probably by fatty acid acylation. Interestingly, 37LRP, also called p40 or OFA/iLR (oncofetal antigen/immature laminin receptor), is a multifunctional protein with a dual activity in the cytoplasm and in the nucleus. In the cytoplasm, 37LRP it is associated with the 40S subunit of ribosome, playing a critical role in protein translation and ribosome biogenesis while in the nucleus it is tightly associated with nuclear structures, and bound to components of the cytoskeleton, such as tubulin and actin. 67LR is mainly localized in the cell membrane, concentrated in lipid rafts. Acting as a receptor for laminin is not the only function of 67LR; indeed, it also acts as a receptor for viruses, bacteria and prions. 67LR expression is increased in neoplastic cells and correlates with an enhanced invasive and metastatic potential. The primary function of 67LR in cancer is to promote tumor cell adhesion to basement membranes, the first step in the invasion-metastasis cascade. Thus, 67LR is overexpressed in neoplastic cells as compared to their normal counterparts and its overexpression is considered a molecular marker of metastatic aggressiveness in cancer of many tissues, including breast, lung, ovary, prostate, stomach, thyroid and also in leukemia and lymphoma. Thus, inhibiting 67LR binding to laminin could be a feasible approach to block cancer progression. Here, we review the current understanding of the structure and function of this molecule, highlighting its role in cancer invasion and metastasis and reviewing the various therapeutic options targeting this receptor that could have a promising future application.

Ady3p Links Spindle Pole Body Function to Spore Wall Synthesis in Saccharomyces cerevisiae

Genetics ◽  
2002 ◽  
Vol 160 (4) ◽  
pp. 1439-1450
Author(s):  
Mark E Nickas ◽  
Aaron M Neiman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
De Novo ◽  
Spindle Pole Body ◽  
Leading Edge ◽  
Spindle Pole ◽  
Spore Wall ◽  
Pole Body ◽  
Prospore Membrane ◽  
Sporulation Efficiency ◽  
Spore Walls

Abstract Spore formation in Saccharomyces cerevisiae requires the de novo synthesis of prospore membranes and spore walls. Ady3p has been identified as an interaction partner for Mpc70p/Spo21p, a meiosis-specific component of the outer plaque of the spindle pole body (SPB) that is required for prospore membrane formation, and for Don1p, which forms a ring-like structure at the leading edge of the prospore membrane during meiosis II. ADY3 expression has been shown to be induced in midsporulation. We report here that Ady3p interacts with additional components of the outer and central plaques of the SPB in the two-hybrid assay. Cells that lack ADY3 display a decrease in sporulation efficiency, and most ady3Δ/ady3Δ asci that do form contain fewer than four spores. The sporulation defect in ady3Δ/ady3Δ cells is due to a failure to synthesize spore wall polymers. Ady3p forms ring-like structures around meiosis II spindles that colocalize with those formed by Don1p, and Don1p rings are absent during meiosis II in ady3Δ/ady3Δ cells. In mpc70Δ/mpc70Δ cells, Ady3p remains associated with SPBs during meiosis II. Our results suggest that Ady3p mediates assembly of the Don1p-containing structure at the leading edge of the prospore membrane via interaction with components of the SPB and that this structure is involved in spore wall formation.

scholarly journals Changes in E-cadherin rigidity sensing regulate cell adhesion

2017 ◽  
Vol 114 (29) ◽  
pp. E5835-E5844 ◽  
Author(s):  
Caitlin Collins ◽  
Aleksandra K. Denisin ◽  
Beth L. Pruitt ◽  
W. James Nelson
Keyword(s):  
Cell Adhesion ◽  
Signaling Molecules ◽  
Membrane Dynamics ◽  
Cell Contact ◽  
Adhesion Assay ◽  
Cell Periphery ◽  
Actin Organization ◽  
Rigidity Sensing ◽  
E Cadherin ◽  
Cell Cell

Mechanical cues are sensed and transduced by cell adhesion complexes to regulate diverse cell behaviors. Extracellular matrix (ECM) rigidity sensing by integrin adhesions has been well studied, but rigidity sensing by cadherins during cell adhesion is largely unexplored. Using mechanically tunable polyacrylamide (PA) gels functionalized with the extracellular domain of E-cadherin (Ecad-Fc), we showed that E-cadherin–dependent epithelial cell adhesion was sensitive to changes in PA gel elastic modulus that produced striking differences in cell morphology, actin organization, and membrane dynamics. Traction force microscopy (TFM) revealed that cells produced the greatest tractions at the cell periphery, where distinct types of actin-based membrane protrusions formed. Cells responded to substrate rigidity by reorganizing the distribution and size of high-traction-stress regions at the cell periphery. Differences in adhesion and protrusion dynamics were mediated by balancing the activities of specific signaling molecules. Cell adhesion to a 30-kPa Ecad-Fc PA gel required Cdc42- and formin-dependent filopodia formation, whereas adhesion to a 60-kPa Ecad-Fc PA gel induced Arp2/3-dependent lamellipodial protrusions. A quantitative 3D cell–cell adhesion assay and live cell imaging of cell–cell contact formation revealed that inhibition of Cdc42, formin, and Arp2/3 activities blocked the initiation, but not the maintenance of established cell–cell adhesions. These results indicate that the same signaling molecules activated by E-cadherin rigidity sensing on PA gels contribute to actin organization and membrane dynamics during cell–cell adhesion. We hypothesize that a transition in the stiffness of E-cadherin homotypic interactions regulates actin and membrane dynamics during initial stages of cell–cell adhesion.

scholarly journals Critical role of fractalkine (CX3CL1) in cigarette smoke-induced mononuclear cell adhesion to the arterial endothelium

Thorax ◽  
2012 ◽  
Vol 68 (2) ◽  
pp. 177-186 ◽  
Author(s):  
Cristina Rius ◽  
Chantal Company ◽  
Laura Piqueras ◽  
Jose Miguel Cerdá-Nicolás ◽  
Cruz González ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Cigarette Smoke ◽  
Mononuclear Cell ◽  
Critical Role ◽  
Arterial Endothelium

Localization and quantification of endoplasmic reticulum Ca(2+)-ATPase isoform transcripts

1995 ◽  
Vol 269 (3) ◽  
pp. C775-C784 ◽  
Author(s):  
K. D. Wu ◽  
W. S. Lee ◽  
J. Wey ◽  
D. Bungard ◽  
J. Lytton
Keyword(s):  
Endoplasmic Reticulum ◽  
Critical Role ◽  
Qualitative Assessment ◽  
Cell Physiology ◽  
Striated Muscles ◽  
Physiological Processes ◽  
Alternatively Spliced ◽  
Spleen Lymphocytes ◽  
Fast Twitch ◽  
In Cells

The Ca(2+)-adenosinetriphosphatase pump of the sarcoplasmic or endoplasmic reticulum (SERCA) plays a critical role in Ca2+ signaling and homeostasis in all cells and is encoded by a family of homologous and alternatively spliced genes. To understand more clearly the role the different isoforms play in cell physiology, we have undertaken a quantitative and qualitative assessment of the tissue distribution of transcripts encoding each SERCA isoform. SERCA1 expression is restricted to fast-twitch striated muscles, SERCA2a to cardiac and slow-twitch striated muscles, whereas SERCA2b is ubiquitously expressed. SERCA3 is expressed most abundantly in large and small intestine, thymus, and cerebellum and at lower levels in spleen, lymph node, and lung. In situ hybridization analyses revealed SERCA3 transcripts in cells of the intestinal crypt, the thymic cortex, and Purkinje cells in cerebellum. In addition, SERCA3 was expressed abundantly in isolated rat spleen lymphocytes, in various murine lymphoid cell lines, and in primary cultured microvascular endothelial cells. This analysis demonstrates that SERCA3 is expressed selectively in cells in which Ca2+ signaling plays a critical and sensitive role in regulating physiological processes.

scholarly journals Reevaluating αE-catenin monomer and homodimer functions by characterizing E-cadherin/αE-catenin chimeras

2015 ◽  
Vol 210 (7) ◽  
pp. 1065-1074 ◽  
Author(s):  
Julie M. Bianchini ◽  
Khameeka N. Kitt ◽  
Martijn Gloerich ◽  
Sabine Pokutta ◽  
William I. Weis ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Intercellular Adhesion ◽  
Dependent Cell ◽  
In Cells ◽  
E Cadherin ◽  
Cell Cell

As part of the E-cadherin–β-catenin–αE-catenin complex (CCC), mammalian αE-catenin binds F-actin weakly in the absence of force, whereas cytosolic αE-catenin forms a homodimer that interacts more strongly with F-actin. It has been concluded that cytosolic αE-catenin homodimer is not important for intercellular adhesion because E-cadherin/αE-catenin chimeras thought to mimic the CCC are sufficient to induce cell–cell adhesion. We show that, unlike αE-catenin in the CCC, these chimeras homodimerize, bind F-actin strongly, and inhibit the Arp2/3 complex, all of which are properties of the αE-catenin homodimer. To more accurately mimic the junctional CCC, we designed a constitutively monomeric chimera, and show that E-cadherin–dependent cell adhesion is weaker in cells expressing this chimera compared with cells in which αE-catenin homodimers are present. Our results demonstrate that E-cadherin/αE-catenin chimeras used previously do not mimic αE-catenin in the native CCC, and imply that both CCC-bound monomer and cytosolic homodimer αE-catenin are required for strong cell–cell adhesion.

scholarly journals Visualization of Intracellular Transport of Vesicular Stomatitis Virus Nucleocapsids in Living Cells

2006 ◽  
Vol 80 (13) ◽  
pp. 6368-6377 ◽  
Author(s):  
Subash C. Das ◽  
Debasis Nayak ◽  
You Zhou ◽  
Asit K. Pattnaik
Keyword(s):  
Vesicular Stomatitis Virus ◽  
Protein Function ◽  
Intracellular Transport ◽  
Fluorescent Protein ◽  
De Novo ◽  
Virus Production ◽  
Hinge Region ◽  
Cell Periphery ◽  
P Protein ◽  
Vesicular Stomatitis

ABSTRACT The phosphoprotein (P) of vesicular stomatitis virus (VSV) is a subunit of the viral RNA polymerase. In previous studies, we demonstrated that insertion of 19 amino acids in the hinge region of the protein had no significant effect on P protein function. In the present study, we inserted full-length enhanced green fluorescent protein (eGFP) in frame into the hinge region of P and show that the fusion protein (PeGFP) is functional in viral genome transcription and replication, albeit with reduced activity. A recombinant vesicular stomatitis virus encoding PeGFP in place of the P protein (VSV-PeGFP), which possessed reduced growth kinetics compared to the wild-type VSV, was recovered. Using the recombinant VSV-PeGFP, we show that the viral replication proteins and the de novo-synthesized RNA colocalize to sites throughout the cytoplasm, indicating that replication and transcription are not confined to any particular region of the cytoplasm. Real-time imaging of the cells infected with the eGFP-tagged virus revealed that, following synthesis, the nucleocapsids are transported toward the cell periphery via a microtubule (MT)-mediated process, and the nucleocapsids were seen to be closely associated with mitochondria. Treatment of cells with nocodazole or Colcemid, drugs known to inhibit MT polymerization, resulted in accumulation of the nucleocapsids around the nucleus and also led to inhibition of infectious-virus production. These findings are compatible with a model in which the progeny viral nucleocapsids are transported toward the cell periphery by MT and the transport may be facilitated by mitochondria.

scholarly journals Smurf1 regulates tumor cell plasticity and motility through degradation of RhoA leading to localized inhibition of contractility

2006 ◽  
Vol 176 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Erik Sahai ◽  
Raquel Garcia-Medina ◽  
Jacques Pouysségur ◽  
Emmanuel Vial
Keyword(s):  
Cell Migration ◽  
Tumor Cell ◽  
Rho Gtpases ◽  
Rho Kinase ◽  
Cell Movement ◽  
Leading Edge ◽  
Cell Periphery ◽  
Tumor Cell Migration ◽  
Tumor Cell Motility

Rho GTPases participate in various cellular processes, including normal and tumor cell migration. It has been reported that RhoA is targeted for degradation at the leading edge of migrating cells by the E3 ubiquitin ligase Smurf1, and that this is required for the formation of protrusions. We report that Smurf1-dependent RhoA degradation in tumor cells results in the down-regulation of Rho kinase (ROCK) activity and myosin light chain 2 (MLC2) phosphorylation at the cell periphery. The localized inhibition of contractile forces is necessary for the formation of lamellipodia and for tumor cell motility in 2D tissue culture assays. In 3D invasion assays, and in in vivo tumor cell migration, the inhibition of Smurf1 induces a mesenchymal–amoeboid–like transition that is associated with a more invasive phenotype. Our results suggest that Smurf1 is a pivotal regulator of tumor cell movement through its regulation of RhoA signaling.

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