scholarly journals Myosin motor proteins are involved in the final stages of the secretory pathways

2011 ◽  
Vol 39 (5) ◽  
pp. 1115-1119 ◽  
Author(s):  
Lisa M. Bond ◽  
Hemma Brandstaetter ◽  
James R. Sellers ◽  
John Kendrick-Jones ◽  
Folma Buss
Keyword(s):  
Plasma Membrane ◽  
Recent Work ◽  
Secretory Pathway ◽  
Motor Proteins ◽  
Myosin Ii ◽  
Secretory Vesicles ◽  
Secretory Pathways ◽  
Unconventional Myosin ◽  
Myosin Motor ◽  
Muscle Myosin

In eukaryotes, the final steps in both the regulated and constitutive secretory pathways can be divided into four distinct stages: (i) the ‘approach’ of secretory vesicles/granules to the PM (plasma membrane), (ii) the ‘docking’ of these vesicles/granules at the membrane itself, (iii) the ‘priming’ of the secretory vesicles/granules for the fusion process, and, finally, (iv) the ‘fusion’ of vesicular/granular membranes with the PM to permit content release from the cell. Recent work indicates that non-muscle myosin II and the unconventional myosin motor proteins in classes 1c/1e, Va and VI are specifically involved in these final stages of secretion. In the present review, we examine the roles of these myosins in these stages of the secretory pathway and the implications of their roles for an enhanced understanding of secretion in general.

scholarly journals Secretory Pathway-Dependent Localization of the Saccharomyces cerevisiae Rho GTPase-Activating Protein Rgd1p at Growth Sites

2012 ◽  
Vol 11 (5) ◽  
pp. 590-600 ◽  
Author(s):  
Fabien Lefèbvre ◽  
Valérie Prouzet-Mauléon ◽  
Michel Hugues ◽  
Marc Crouzet ◽  
Aurélie Vieillemard ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Cell Cycle Progression ◽  
Secretory Pathway ◽  
Rho Gtpase ◽  
Secretory Vesicles ◽  
Gtpase Activating Protein ◽  
Content Type

ABSTRACT Establishment and maintenance of cell polarity in eukaryotes depends upon the regulation of Rho GTPases. In Saccharomyces cerevisiae , the Rho GTPase activating protein (RhoGAP) Rgd1p stimulates the GTPase activities of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively. Consistent with the distribution of Rho3p and Rho4p, Rgd1p is found mostly in areas of polarized growth during cell cycle progression. Rgd1p was mislocalized in mutants specifically altered for Golgi apparatus-based phosphatidylinositol 4-P [PtdIns(4)P] synthesis and for PtdIns(4,5)P 2 production at the plasma membrane. Analysis of Rgd1p distribution in different membrane-trafficking mutants suggested that Rgd1p was delivered to growth sites via the secretory pathway. Rgd1p may associate with post-Golgi vesicles by binding to PtdIns(4)P and then be transported by secretory vesicles to the plasma membrane. In agreement, we show that Rgd1p coimmunoprecipitated and localized with markers specific to secretory vesicles and cofractionated with a plasma membrane marker. Moreover, in vivo imaging revealed that Rgd1p was transported in an anterograde manner from the mother cell to the daughter cell in a vectoral manner. Our data indicate that secretory vesicles are involved in the delivery of RhoGAP Rgd1p to the bud tip and bud neck.

scholarly journals Dominant Negative Alleles ofSEC10Reveal Distinct Domains Involved in Secretion and Morphogenesis in Yeast

1998 ◽  
Vol 9 (7) ◽  
pp. 1725-1739 ◽  
Author(s):  
Dagmar Roth ◽  
Wei Guo ◽  
Peter Novick
Keyword(s):  
Plasma Membrane ◽  
Cell Cycle Progression ◽  
Secretory Pathway ◽  
Dominant Negative ◽  
Secretory Vesicles ◽  
Cycle Progression ◽  
Vesicle Docking ◽  
Amino Terminal ◽  
Exocyst Complex ◽  
Carboxy Terminal

The accurate targeting of secretory vesicles to distinct sites on the plasma membrane is necessary to achieve polarized growth and to establish specialized domains at the surface of eukaryotic cells. Members of a protein complex required for exocytosis, the exocyst, have been localized to regions of active secretion in the budding yeastSaccharomyces cerevisiae where they may function to specify sites on the plasma membrane for vesicle docking and fusion. In this study we have addressed the function of one member of the exocyst complex, Sec10p. We have identified two functional domains of Sec10p that act in a dominant-negative manner to inhibit cell growth upon overexpression. Phenotypic and biochemical analysis of the dominant-negative mutants points to a bifunctional role for Sec10p. One domain, consisting of the amino-terminal two-thirds of Sec10p directly interacts with Sec15p, another exocyst component. Overexpression of this domain displaces the full-length Sec10 from the exocyst complex, resulting in a block in exocytosis and an accumulation of secretory vesicles. The carboxy-terminal domain of Sec10p does not interact with other members of the exocyst complex and expression of this domain does not cause a secretory defect. Rather, this mutant results in the formation of elongated cells, suggesting that the second domain of Sec10p is required for morphogenesis, perhaps regulating the reorientation of the secretory pathway from the tip of the emerging daughter cell toward the mother–daughter connection during cell cycle progression.

scholarly journals A novel coordinated function of Myosin II with GOLPH3 controls centralspindlin localization during cytokinesis in Drosophila

2020 ◽  
Vol 133 (21) ◽  
pp. jcs252965
Author(s):  
Stefano Sechi ◽  
Anna Frappaolo ◽  
Angela Karimpour-Ghahnavieh ◽  
Roberta Fraschini ◽  
Maria Grazia Giansanti
Keyword(s):  
Plasma Membrane ◽  
Heavy Chain ◽  
Light Chain ◽  
Animal Cell ◽  
Myosin Ii ◽  
Contractile Ring ◽  
Ring Assembly ◽  
Missense Allele ◽  
Phosphatidylinositol 4 ◽  
Muscle Myosin

ABSTRACTIn animal cell cytokinesis, interaction of non-muscle myosin II (NMII) with F-actin provides the dominant force for pinching the mother cell into two daughters. Here we demonstrate that celibe (cbe) is a missense allele of zipper, which encodes the Drosophila Myosin heavy chain. Mutation of cbe impairs binding of Zipper protein to the regulatory light chain Spaghetti squash (Sqh). In dividing spermatocytes from cbe males, Sqh fails to concentrate at the equatorial cortex, resulting in thin actomyosin rings that are unable to constrict. We show that cbe mutation impairs localization of the phosphatidylinositol 4-phosphate [PI(4)P]-binding protein Golgi phosphoprotein 3 (GOLPH3, also known as Sauron) and maintenance of centralspindlin at the cell equator of telophase cells. Our results further demonstrate that GOLPH3 protein associates with Sqh and directly binds the centralspindlin subunit Pavarotti. We propose that during cytokinesis, the reciprocal dependence between Myosin and PI(4)P–GOLPH3 regulates centralspindlin stabilization at the invaginating plasma membrane and contractile ring assembly.

scholarly journals Rab7-harboring vesicles are carriers of the transferrin receptor through the biosynthetic secretory pathway

2021 ◽  
Vol 7 (2) ◽  
pp. eaba7803
Author(s):  
Maika S. Deffieu ◽  
Ieva Cesonyte ◽  
François Delalande ◽  
Gaelle Boncompain ◽  
Cristina Dorobantu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Transport ◽  
Transferrin Receptor ◽  
Intracellular Trafficking ◽  
Secretory Pathway ◽  
Gene Editing ◽  
The Other ◽  
Secretory Vesicles ◽  
Important Intermediate ◽  
Intermediate Compartment

The biosynthetic secretory pathway is particularly challenging to investigate as it is underrepresented compared to the abundance of the other intracellular trafficking routes. Here, we combined the retention using selective hook (RUSH) to a CRISPR-Cas9 gene editing approach (eRUSH) and identified Rab7-harboring vesicles as an important intermediate compartment of the Golgi–to–plasma membrane transport of neosynthesized transferrin receptor (TfR). These vesicles did not exhibit degradative properties and were not associated to Rab6A-harboring vesicles. Rab7A was transiently associated to neosynthetic TfR-containing post–Golgi vesicles but dissociated before fusion with the plasma membrane. Together, our study reveals a role for Rab7 in the biosynthetic secretory pathway of the TfR, highlighting the diversity of the secretory vesicles’ nature.

scholarly journals Promiscuity in Rab–SNARE Interactions

1999 ◽  
Vol 10 (12) ◽  
pp. 4149-4161 ◽  
Author(s):  
Eric Grote ◽  
Peter J. Novick
Keyword(s):  
Plasma Membrane ◽  
Secretory Pathway ◽  
Snare Complex ◽  
Free Form ◽  
Rab Proteins ◽  
Secretory Vesicles ◽  
Rab Protein ◽  
Target Membrane ◽  
Low Efficiency

Fusion of post-Golgi secretory vesicles with the plasma membrane in yeast requires the function of a Rab protein, Sec4p, and a set of v- and t-SNAREs, the Snc, Sso, and Sec9 proteins. We have tested the hypothesis that a selective interaction between Sec4p and the exocytic SNAREs is responsible for ensuring that secretory vesicles fuse with the plasma membrane but not with intracellular organelles. Assembly of Sncp and Ssop into a SNARE complex is defective in asec4-8 mutant strain. However, Snc2p binds in vivo to many other syntaxin-like t-SNAREs, and binding of Sncp to the endosomal/Golgi t-SNARE Tlg2p is also reduced in sec4-8cells. In addition, binding of Sncp to Ssop is reduced by mutations in two other Rab genes and four non-Rab genes that block the secretory pathway before the formation of secretory vesicles. In an alternate approach to look for selective Rab–SNARE interactions, we report that the nucleotide-free form of Sec4p coimmunoprecipitates with Ssop. However, Rab–SNARE binding is nonselective, because the nucleotide-free forms of six Rab proteins bind with similar low efficiency to three SNARE proteins, Ssop, Pep12p, and Sncp. We conclude that Rabs and SNAREs do not cooperate to specify the target membrane.

scholarly journals Bem1p contributes to secretory pathway polarization through a direct interaction with Exo70p

2014 ◽  
Vol 207 (1) ◽  
pp. 59-72 ◽  
Author(s):  
Dongmei Liu ◽  
Peter Novick
Keyword(s):  
Plasma Membrane ◽  
Secretory Pathway ◽  
Direct Interaction ◽  
Scaffold Protein ◽  
Synergistic Interaction ◽  
Genetic Interactions ◽  
Secretory Vesicles ◽  
Binding Partners ◽  
Actin Cables ◽  
Multiple Domains

The exocyst serves to tether secretory vesicles to cortical sites specified by polarity determinants, in preparation for fusion with the plasma membrane. Although most exocyst components are brought to these sites by riding on secretory vesicles as they are actively transported along actin cables, Exo70p displays actin-independent localization to these sites, implying an interaction with a polarity determinant. Here we show that Exo70p directly and specifically binds to the polarity determinant scaffold protein Bem1p. The interaction involves multiple domains of both Exo70p and Bem1p. Mutations in Exo70p that disrupt its interaction with Bem1, without impairing its interactions with other known binding partners, lead to the loss of actin-independent localization. Synthetic genetic interactions confirm the importance of the Exo70p–Bem1p interaction, although there is some possible redundancy with Sec3p and Sec15p, other exocyst components that also interact with polarity determinants. Similar to Sec3p, the actin-independent localization of Exo70p requires a synergistic interaction with the phosphoinositide PI(4,5)P2.

scholarly journals In vitro fusion between Saccharomyces cerevisiae secretory vesicles and cytoplasmic-side-out plasma membrane vesicles

2003 ◽  
Vol 370 (2) ◽  
pp. 641-649 ◽  
Author(s):  
Lorena ARRASTUA ◽  
Eider SAN SEBASTIAN ◽  
Ana F. QUINCOCES ◽  
Claude ANTONY ◽  
Unai UGALDE
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Secretory Pathway ◽  
Membrane Vesicles ◽  
Fusion Process ◽  
Temperature Sensitive ◽  
Secretory Vesicles ◽  
Plasma Membrane Vesicles ◽  
Fusion Event ◽  
Cytoplasmic Side

The final step in the secretory pathway, which is the fusion event between secretory vesicles and the plasma membrane, was reconstructed using highly purified secretory vesicles and cytoplasmic-side-out plasma membrane vesicles from the yeast Saccharomyces cerevisiae. Both organelle preparations were obtained from a sec 6-4 temperature-sensitive mutant. Fusion was monitored by means of a fluorescence assay based on the dequenching of the lipophilic fluorescent probe octadecylrhodamine B-chloride (R18). The probe was incorporated into the membrane of secretory vesicles, and it diluted in unlabelled cytoplasmic-side-out plasma membrane vesicles as the fusion process took place. The obtained experimental dequenching curves were found by mathematical analysis to consist of two independent but simultaneous processes. Whereas one of them reflected the fusion process between both vesicle populations as confirmed by its dependence on the assay conditions, the other represented a non-specific transfer of the probe. The fusion process may now be examined in detail using the preparation, validation and analytical methods developed in this study.

scholarly journals Drosophila non-muscle myosin II motor activity determines the rate of tissue folding

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Claudia G Vasquez ◽  
Sarah M Heissler ◽  
Neil Billington ◽  
James R Sellers ◽  
Adam C Martin
Keyword(s):  
Motor Activity ◽  
Molecular Motor ◽  
Myosin Ii ◽  
Cell Contractility ◽  
Myosin Motor ◽  
Muscle Myosin ◽  
Shape Changes ◽  
Drosophila Embryos

Non-muscle cell contractility is critical for tissues to adopt shape changes. Although, the non-muscle myosin II holoenzyme (myosin) is a molecular motor that powers contraction of actin cytoskeleton networks, recent studies have questioned the importance of myosin motor activity cell and tissue shape changes. Here, combining the biochemical analysis of enzymatic and motile properties for purified myosin mutants with in vivo measurements of apical constriction for the same mutants, we show that in vivo constriction rate scales with myosin motor activity. We show that so-called phosphomimetic mutants of the Drosophila regulatory light chain (RLC) do not mimic the phosphorylated RLC state in vitro. The defect in the myosin motor activity in these mutants is evident in developing Drosophila embryos where tissue recoil following laser ablation is decreased compared to wild-type tissue. Overall, our data highlights that myosin activity is required for rapid cell contraction and tissue folding in developing Drosophila embryos.

scholarly journals Two Motors and One Spring: Hypothetic Roles of Non-Muscle Myosin II and Submembrane Actin-Based Cytoskeleton in Cell Volume Sensing

2021 ◽  
Vol 22 (15) ◽  
pp. 7967
Author(s):  
Nadezhda Barvitenko ◽  
Muhammad Aslam ◽  
Alfons Lawen ◽  
Carlota Saldanha ◽  
Elisaveta Skverchinskaya ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Ionic Strength ◽  
Cell Volume ◽  
Molecular Motors ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Regulatory Volume Decrease ◽  
Membrane Curvature ◽  
Actin Cortex ◽  
Muscle Myosin

Changes in plasma membrane curvature and intracellular ionic strength are two key features of cell volume perturbations. In this hypothesis we present a model of the responsible molecular apparatus which is assembled of two molecular motors [non-muscle myosin II (NMMII) and protrusive actin polymerization], a spring [a complex between the plasma membrane (PM) and the submembrane actin-based cytoskeleton (smACSK) which behaves like a viscoelastic solid] and the associated signaling proteins. We hypothesize that this apparatus senses changes in both the plasma membrane curvature and the ionic strength and in turn activates signaling pathways responsible for regulatory volume increase (RVI) and regulatory volume decrease (RVD). During cell volume changes hydrostatic pressure (HP) changes drive alterations in the cell membrane curvature. HP difference has opposite directions in swelling versus shrinkage, thus allowing distinction between them. By analogy with actomyosin contractility that appears to sense stiffness of the extracellular matrix we propose that NMMII and actin polymerization can actively probe the transmembrane gradient in HP. Furthermore, NMMII and protein-protein interactions in the actin cortex are sensitive to ionic strength. Emerging data on direct binding to and regulating activities of transmembrane mechanosensors by NMMII and actin cortex provide routes for signal transduction from transmembrane mechanosensors to cell volume regulatory mechanisms.

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