Cell polarity and locomotion, as well as endocytosis, depend on NSF

NEM-sensitive factor (NSF) is an essential protein required during membrane transport. We replaced part of the endogenous D. discoideum NSF gene (nsfA) by a PCR-mutagenised library and isolated 11 mutants temperature-sensitive (ts) for growth. Two of these have been studied in detail. As expected, both are ts for FITC-dextran uptake by macropinocytosis, for internalising their surface membrane (monitored with FM1-43) and for phagocytosis. However, after 10-20 minutes at 28°C, they round up and cease to chemotax, move or cap ConA receptors. They fully recover when returned to 22°C. These cells carry out a normal ‘cringe’ reaction in response to cAMP, indicating that the actin cytoskeleton and this signal transduction pathway are still functional at 28°C. The behaviour of these mutants shows that NSF-catalysed processes are required not only for the different endocytic cycles but also for the maintenance of cell polarity. As cell locomotion depends on a cell having a polarity, the mutants stop moving at high temperature. A tentative model is proposed to explain the surprising link between membrane recycling and cell polarity revealed here.

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Dishevelled is a component of the frizzled signaling pathway in Drosophila

Development ◽

10.1242/dev.121.12.4095 ◽

1995 ◽

Vol 121 (12) ◽

pp. 4095-4102 ◽

Cited By ~ 28

Author(s):

R.E. Krasnow ◽

L.L. Wong ◽

P.N. Adler

Keyword(s):

Signal Transduction ◽

Cell Polarity ◽

Signal Transduction Pathway ◽

Receptor Complex ◽

Transduction Pathway ◽

General Role ◽

Tissue Polarity ◽

Developmental Patterning ◽

Single Process ◽

Genetic Hierarchy

The tissue polarity genes in Drosophila are required to coordinate cell polarity within the plane of the epidermis. Evidence to date suggests that these genes may encode components of a novel signal transduction pathway. Three of the genes, frizzled (fz), dishevelled (dsh), and prickle (pk) share a similar tissue polarity phenotype, suggesting that they function together in a single process. dsh is also known to function as a mediator of wingless (wg) signaling in a variety of developmental patterning processes in the fly. In this study, we make use of a fz transgene and a hypomorphic fz allele as genetic tools in an attempt to order these genes in a genetic hierarchy. Our results argue that dsh encodes a dosage sensitive component required for fz function and that it likely acts downstream of fz in the generation of tissue polarity. Our findings suggest that dsh may have a general role in signal transduction, perhaps as a component of a receptor complex.

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CD40/CD154 ligation induces mononuclear cell adhesion to human renal proximal tubule cells via increased ICAM-1 expression

AJP Renal Physiology ◽

10.1152/ajprenal.00317.2004 ◽

2005 ◽

Vol 289 (1) ◽

pp. F145-F153 ◽

Cited By ~ 13

Author(s):

Hongye Li ◽

Edward P. Nord

Keyword(s):

Signal Transduction ◽

Cell Adhesion ◽

Proximal Tubule ◽

Mononuclear Cell ◽

Mononuclear Cells ◽

Gene Array ◽

Signal Transduction Pathway ◽

Renal Proximal Tubule ◽

Transduction Pathway ◽

A Cell

The role of CD40/CD154 ligation in the upregulation of genes of the proinflammatory nuclear factor-κB (NF-κB) signal transduction pathway was explored in primary cultures of human renal proximal tubule epithelial cells. Using a cDNA gene array specific for human NF-κB signal pathway genes, 38 genes were upregulated at 1 h, and 7 of these genes remained upregulated at 3 h. Of these genes, intercellular adhesion molecule-1 (ICAM-1) was explored in further detail. Quantitative real-time PCR for ICAM-1 mRNA expression confirmed the gene array findings. Western blot analysis and quantitative sandwich-enzyme ELISA confirmed this observation at the protein level. A cell-surface ELISA assay showed that ICAM-1 expression doubled by 48 h of CD154 exposure, and fluorescence-activated cell sorter analysis suggested that both the number of cells expressing ICAM-1 and the expression of ICAM-1 on these cells had increased. A cell adhesion assay using fluorescein-labeled human peripheral mononuclear cells showed that ICAM-1 upregulation resulted in increased mononuclear cell adhesion to the monolayer, which was abrogated by pretreatment of the monolayer with a neutralizing ICAM-1 antibody. The p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580 but not the extracellular signal-regulated kinase 1/2 inhibitor (PD-98059) nor the protein kinase C inhibitor (calphostin) blunted ICAM-1 expression and mononuclear cell adhesion to the monolayer. We conclude that, in human renal proximal tubule epithelial cells, CD40 activation upregulates ICAM-1 (and other NF-κB pathway genes) expression with concomitant enhanced adhesion of mononuclear cells, which is mediated via the p38 MAPK signal transduction pathway.

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