scholarly journals Lethal giant larvae proteins interact with the exocyst complex and are involved in polarized exocytosis

2005 ◽  
Vol 170 (2) ◽  
pp. 273-283 ◽  
Author(s):  
Xiaoyu Zhang ◽  
Puyue Wang ◽  
Akanksha Gangar ◽  
Jian Zhang ◽  
Patrick Brennwald ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cell ◽  
Membrane Fusion ◽  
Cell Polarity ◽  
Rho Gtpases ◽  
Critical Role ◽  
Cell Polarization ◽  
Snare Proteins ◽  
Exocyst Complex ◽  
Lethal Giant Larvae

The tumor suppressor lethal giant larvae (Lgl) plays a critical role in epithelial cell polarization. However, the molecular mechanism by which Lgl carries out its functions is unclear. In this study, we report that the yeast Lgl proteins Sro7p and Sro77p directly interact with Exo84p, which is a component of the exocyst complex that is essential for targeting vesicles to specific sites of the plasma membrane for exocytosis, and that this interaction is important for post-Golgi secretion. Genetic analyses demonstrate a molecular pathway from Rab and Rho GTPases through the exocyst and Lgl to SNAREs, which mediate membrane fusion. We also found that overexpression of Lgl and t-SNARE proteins not only improves exocytosis but also rescues polarity defects in exocyst mutants. We propose that, although Lgl is broadly distributed in the cells, its localized interaction with the exocyst and kinetic activation are important for the establishment and reenforcement of cell polarity.

scholarly journals A bidirectional antagonism between aPKC and Yurt regulates epithelial cell polarity

2014 ◽  
Vol 204 (4) ◽  
pp. 487-495 ◽  
Author(s):  
Clémence L. Gamblin ◽  
Émilie J.-L. Hardy ◽  
François J.-M. Chartier ◽  
Nicolas Bisson ◽  
Patrick Laprise
Keyword(s):  
Epithelial Cell ◽  
Cell Polarity ◽  
Cell Polarization ◽  
Membrane Domains ◽  
Epithelial Cell Polarity ◽  
Kinase C ◽  
The Stability ◽  
Regulatory Loop ◽  
Late Stages ◽  
Apical Localization

During epithelial cell polarization, Yurt (Yrt) is initially confined to the lateral membrane and supports the stability of this membrane domain by repressing the Crumbs-containing apical machinery. At late stages of embryogenesis, the apical recruitment of Yrt restricts the size of the apical membrane. However, the molecular basis sustaining the spatiotemporal dynamics of Yrt remains undefined. In this paper, we report that atypical protein kinase C (aPKC) phosphorylates Yrt to prevent its premature apical localization. A nonphosphorylatable version of Yrt dominantly dismantles the apical domain, showing that its aPKC-mediated exclusion is crucial for epithelial cell polarity. In return, Yrt counteracts aPKC functions to prevent apicalization of the plasma membrane. The ability of Yrt to bind and restrain aPKC signaling is central for its role in polarity, as removal of the aPKC binding site neutralizes Yrt activity. Thus, Yrt and aPKC are involved in a reciprocal antagonistic regulatory loop that contributes to segregation of distinct and mutually exclusive membrane domains in epithelial cells.

scholarly journals Phosphatidylinositol 4,5-bisphosphate Directs Spermatid Cell Polarity and Exocyst Localization in Drosophila

2010 ◽  
Vol 21 (9) ◽  
pp. 1546-1555 ◽  
Author(s):  
Lacramioara Fabian ◽  
Ho-Chun Wei ◽  
Janet Rollins ◽  
Tatsuhiko Noguchi ◽  
J. Todd Blankenship ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Plasma Membrane ◽  
Cell Polarity ◽  
The Other ◽  
Biosynthetic Enzyme ◽  
Loss Of Function ◽  
Partial Loss ◽  
Sperm Tail ◽  
Low Level ◽  
Exocyst Complex

During spermiogenesis, Drosophila melanogaster spermatids coordinate their elongation in interconnected cysts that become highly polarized, with nuclei localizing to one end and sperm tail growth occurring at the other. Remarkably little is known about the signals that drive spermatid polarity and elongation. Here we identify phosphoinositides as critical regulators of these processes. Reduction of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2) by low-level expression of the PIP2 phosphatase SigD or mutation of the PIP2 biosynthetic enzyme Skittles (Sktl) results in dramatic defects in spermatid cysts, which become bipolar and fail to fully elongate. Defects in polarity are evident from the earliest stages of elongation, indicating that phosphoinositides are required for establishment of polarity. Sktl and PIP2 localize to the growing end of the cysts together with the exocyst complex. Strikingly, the exocyst becomes completely delocalized when PIP2 levels are reduced, and overexpression of Sktl restores exocyst localization and spermatid cyst polarity. Moreover, the exocyst is required for polarity, as partial loss of function of the exocyst subunit Sec8 results in bipolar cysts. Our data are consistent with a mechanism in which localized synthesis of PIP2 recruits the exocyst to promote targeted membrane delivery and polarization of the elongating cysts.

scholarly journals Girdin is a component of the lateral polarity protein network restricting cell dissemination

2019 ◽  
Author(s):  
Cornélia Biehler ◽  
Li-Ting Wang ◽  
Myriam Sévigny ◽  
Alexandra Jetté ◽  
Clémence Gamblin ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Cell Polarity ◽  
Cancer Progression ◽  
Cell Polarization ◽  
Protein Network ◽  
Poor Overall Survival ◽  
Lung Cancers ◽  
Epithelial Cancers ◽  
Human Ortholog ◽  
Cell Dissemination

AbstractEpithelial cell polarity defects support cancer progression. It is thus crucial to decipher the functional interactions within the polarity protein network. Here we show that Drosophila Girdin and its human ortholog (GIRDIN) sustain the function of crucial lateral polarity proteins by inhibiting the apical kinase aPKC. Loss of GIRDIN expression is also associated with overgrowth of disorganized cell cysts. Moreover, we observed cell dissemination from GIRDIN knockdown cysts and tumorspheres, thereby showing that GIRDIN supports the cohesion of multicellular epithelial structures. Consistent with these observations, alteration of GIRDIN expression is associated with a poor overall survival in subtypes of breast and lung cancers. Overall, we discovered a core mechanism contributing to epithelial cell polarization from flies to humans. Our data also indicate that GIRDIN has the potential to impair the progression of epithelial cancers by preserving cell polarity and restricting cell dissemination.

scholarly journals Apical targeting of syntaxin 3 is essential for epithelial cell polarity

2006 ◽  
Vol 173 (6) ◽  
pp. 937-948 ◽  
Author(s):  
Nikunj Sharma ◽  
Seng Hui Low ◽  
Saurav Misra ◽  
Bhattaram Pallavi ◽  
Thomas Weimbs
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cell ◽  
Membrane Trafficking ◽  
Cell Polarization ◽  
Apical Plasma Membrane ◽  
Membrane Expression ◽  
Tight Junction Formation ◽  
Necessary And Sufficient ◽  
Syntaxin 3

In polarized epithelial cells, syntaxin 3 localizes to the apical plasma membrane and is involved in membrane fusion of apical trafficking pathways. We show that syntaxin 3 contains a necessary and sufficient apical targeting signal centered around a conserved FMDE motif. Mutation of any of three critical residues within this motif leads to loss of specific apical targeting. Modeling based on the known structure of syntaxin 1 revealed that these residues are exposed on the surface of a three-helix bundle. Syntaxin 3 targeting does not require binding to Munc18b. Instead, syntaxin 3 recruits Munc18b to the plasma membrane. Expression of mislocalized mutant syntaxin 3 in Madin-Darby canine kidney cells leads to basolateral mistargeting of apical membrane proteins, disturbance of tight junction formation, and loss of ability to form an organized polarized epithelium. These results indicate that SNARE proteins contribute to the overall specificity of membrane trafficking in vivo, and that the polarity of syntaxin 3 is essential for epithelial cell polarization.

scholarly journals Turnover Regulation of the Rho GTPase Cdc42 by Heat Shock Protein Chaperones and the MAPK Pathway Scaffold Bem4

2021 ◽  
Author(s):  
Paul J Cullen ◽  
Beatriz Gonzalez
Keyword(s):  
Heat Shock ◽  
Cell Polarity ◽  
Rho Gtpases ◽  
Rho Gtpase ◽  
Mapk Pathway ◽  
Cell Types ◽  
Cell Polarization ◽  
Extrinsic Cues ◽  
Dependent Cell ◽  
Map Kinase Pathway

All cells maintain an axis of polarity that directs the orientation of growth. Cell polarity can be reorganized during development and in response to extrinsic cues to produce new cell types. Rho GTPases are central regulators of cell polarity and signal-dependent cell differentiation. We show here that one of the best understood Rho GTPases, the highly conserved yeast Cdc42p, is turned over by members of the Heat Shock family of Proteins (HSPs). The Hsp40p chaperone, Ydj1p, was required for turnover of Cdc42p by the NEDD4 E3 ubiquitin ligase, Rsp5p, in the proteosome. Cdc42p turnover was regulated by HSPs at high temperatures, and in aging cells where the protein formed aggregates, implicating HSPs in Rho GTPase quality control. We also show that Cdc42pQ61L, which mimics the active (GTP-bound) conformation of the protein, was turned over at elevated levels by Ydj1p and Rsp5p. A turnover-defective version of Cdc42pQ61L led to multibudding phenotypes, implicating Cdc42 turnover in singularity in cell polarization. Cdc42p turnover also impacted MAP kinase pathway specificity. A pathway-specific scaffold, Bem4p, stabilized Cdc42p levels, which biased Cdc42p function in one MAPK pathway over another. Turnover regulation of Rho GTPases by HSPs and scaffolds provides new dimensions to the regulation of cell polarity and signal-dependent morphogenesis.

scholarly journals The mesoscale organization of syntaxin 1A and SNAP25 is determined by SNARE-SNARE-interactions

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jasmin Mertins ◽  
Jérôme Finke ◽  
Ricarda Antonia Sies ◽  
Kerstin Rink ◽  
Jan Hasenauer ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Fusion ◽  
Secretory Pathway ◽  
Snare Proteins ◽  
Strong Interactions ◽  
Dependent Manner ◽  
Syntaxin 1A ◽  
Membrane Area ◽  
Cellular Processes ◽  
Domain Interactions

SNARE proteins have been described as the effectors of fusion events in the secretory pathway more than two decades ago. The strong interactions between SNARE-domains are clearly important in membrane fusion, but it is unclear whether they are involved in any other cellular processes. Here, we analyzed two classical SNARE proteins, syntaxin 1A and SNAP25. Although they are supposed to be engaged in tight complexes, we surprisingly find them largely segregated in the plasma membrane. Syntaxin 1A only occupies a small fraction of the plasma membrane area. Yet, we find it is able to redistribute the far more abundant SNAP25 on the mesoscale by gathering crowds of SNAP25 molecules onto syntaxin-clusters in a SNARE-domain dependent manner. Our data suggests that SNARE-domain interactions are not only involved in driving membrane fusion on the nanoscale, but also play an important role in controlling the general organization of proteins on the mesoscale. Further, we propose this mechanisms preserves active syntaxin 1A-SNAP25 complexes at the plasma membrane.

scholarly journals A Second SNARE Role for Exocytic SNAP25 in Endosome Fusion

2006 ◽  
Vol 17 (5) ◽  
pp. 2113-2124 ◽  
Author(s):  
Yoshikatsu Aikawa ◽  
Kara L. Lynch ◽  
Kristin L. Boswell ◽  
Thomas F.J. Martin
Keyword(s):  
Plasma Membrane ◽  
Membrane Fusion ◽  
Secretory Vesicle ◽  
Neuroendocrine Cells ◽  
Snare Complex ◽  
Snare Proteins ◽  
Recycling Endosome ◽  
Protein Receptor ◽  
Interfering Rna

Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins play key roles in membrane fusion, but their sorting to specific membranes is poorly understood. Moreover, individual SNARE proteins can function in multiple membrane fusion events dependent upon their trafficking itinerary. Synaptosome-associated protein of 25 kDa (SNAP25) is a plasma membrane Q (containing glutamate)-SNARE essential for Ca2+-dependent secretory vesicle–plasma membrane fusion in neuroendocrine cells. However, a substantial intracellular pool of SNAP25 is maintained by endocytosis. To assess the role of endosomal SNAP25, we expressed botulinum neurotoxin E (BoNT E) light chain in PC12 cells, which specifically cleaves SNAP25. BoNT E expression altered the intracellular distribution of SNAP25, shifting it from a perinuclear recycling endosome to sorting endosomes, which indicates that SNAP25 is required for its own endocytic trafficking. The trafficking of syntaxin 13 and endocytosed cargo was similarly disrupted by BoNT E expression as was an endosomal SNARE complex comprised of SNAP25/syntaxin 13/vesicle-associated membrane protein 2. The small-interfering RNA-mediated down-regulation of SNAP25 exerted effects similar to those of BoNT E expression. Our results indicate that SNAP25 has a second function as an endosomal Q-SNARE in trafficking from the sorting endosome to the recycling endosome and that BoNT E has effects linked to disruption of the endosome recycling pathway.

scholarly journals Distribution of Integrins During Human Fetal Lung Development

1998 ◽  
Vol 46 (7) ◽  
pp. 803-810 ◽  
Author(s):  
Christelle Coraux ◽  
Aurélie Delplanque ◽  
Jocelyne Hinnrasky ◽  
Bruno Peault ◽  
Edith Puchelle ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Lung Development ◽  
Plasma Membranes ◽  
Branching Morphogenesis ◽  
Cell Polarization ◽  
Surface Epithelium ◽  
Secretory Cells ◽  
Stage Of Development

Interactions between epithelial cells and the extracellular matrix through integrins play a key role in the development of the lung by modulating branching morphogenesis, epithelial cell polarization, and differentiation. To determine the role of integrins during the different stages of lung development, we investigated the distribution of eight integrin subunits in the trachea and lung from human fetuses. In distal airways, during the early pseudoglandular stage of development, the α2-, α5-, α6-, αv-, and β1-subunits were detected in all epithelial cell plasma membranes, and polarized but undifferentiated tracheal epithelial cells expressed α3-, α6-, and β1-subunits in the plasma membrane of the cells facing the basement membrane. The α6- and β4-chains were detected along the basal plasma membrane of the basal cells in differentiated tracheal epithelia. The α4-subunit was detected in all respiratory cells throughout fetal development. In the submucosal glands, myoepithelial cells expressed the integrin subunits found in the undifferentiated cells of the developing airways, whereas the secretory cells expressed only α2-, α3-, α4-, α6-, and β1-subunits. These results demonstrate differential expression of integrins during lung development and suggest that integrins may play multiple roles in organogenesis and maturation of respiratory surface epithelium and glands.

scholarly journals Fission yeast NDR/LATS kinase Orb6 regulates exocytosis via phosphorylation of exocyst complex

2018 ◽  
Author(s):  
Ye Dee Tay ◽  
Marcin Leda ◽  
Christos Spanos ◽  
Juri Rappsilber ◽  
Andrew B. Goryachev ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Cell Polarity ◽  
Membrane Trafficking ◽  
Critical Role ◽  
Control Cell ◽  
Small Gtpase ◽  
Nucleotide Exchange ◽  
Exocyst Complex ◽  
Growing Cell

ABSTRACTNDR/LATS kinases regulate multiple aspects of cell polarity and morphogenesis from yeast to mammals, but few of their substrates are known. Fission yeast NDR/LATS kinase Orb6 has been proposed to control cell polarity via spatial regulation of Gef1, a guanine nucleotide exchange factor for the small GTPase Cdc42. Here we show that Orb6 plays a critical role as a positive regulator of exocytosis, independent of Gef1. Through Orb6 inhibition in vivo and quantitative global phosphoproteomics, we identify several proteins involved in membrane trafficking as Orb6 targets, and we confirm Sec3 and Sec5, conserved components of the exocyst complex, as substrates of Orb6 both in vivo and in vitro. Our results suggest that Orb6 kinase activity is crucial for exocyst localization to actively-growing cell tips and for exocyst activity during septum dissolution after cytokinesis. We further show that Orb6 phosphorylation of Sec3 serine-201 contributes to exocyst function in parallel with exocyst protein Exo70. We propose that Orb6 contributes to polarized growth by regulating membrane trafficking at multiple levels.

Sign in / Sign up

Export Citation Format

Share Document