scholarly journals Programmed ER fragmentation drives selective ER inheritance and degradation in budding yeast meiosis

2021 ◽  
Author(s):  
George M. Otto ◽  
Tia Cheunkarndee ◽  
Jessica M. Leslie ◽  
Gloria A. Brar
Keyword(s):  
Plasma Membrane ◽  
Cell Differentiation ◽  
Budding Yeast ◽  
Developmentally Regulated ◽  
Selective Degradation ◽  
Cell Plasma ◽  
Membrane Tethering ◽  
Membrane Bound ◽  
Yeast Meiosis ◽  
And Function

AbstractThe endoplasmic reticulum (ER) is a membrane-bound organelle with diverse, essential functions that rely on the maintenance of membrane shape and distribution within cells. ER structure and function are remodeled in response to changes in cellular demand, such as the presence of external stressors or the onset of cell differentiation, but mechanisms controlling ER remodeling during cell differentiation are not well understood. Here, we describe a series of developmentally regulated changes in ER morphology and composition during budding yeast meiosis, a conserved differentiation program that gives rise to gametes. During meiosis, the cortical ER undergoes fragmentation before collapsing away from the plasma membrane at anaphase II. This programmed collapse depends on the meiotic transcription factor Ndt80, conserved ER membrane structuring proteins Lnp1 and reticulons, and the actin cytoskeleton. A subset of ER is retained at the mother cell plasma membrane and excluded from gamete cells via the action of ER-plasma membrane tethering proteins. ER remodeling is coupled to ER degradation by selective autophagy, which is regulated by the developmentally timed expression of the autophagy receptor Atg40. Autophagy relies on ER collapse, as artificially targeting ER proteins to the cortically retained ER pool prevents their degradation. Thus, developmentally programmed changes in ER morphology determine the selective degradation or inheritance of ER subdomains by gametes.

scholarly journals Programmed cortical ER collapse drives selective ER degradation and inheritance in yeast meiosis

2021 ◽  
Vol 220 (12) ◽  
Author(s):  
George Maxwell Otto ◽  
Tia Cheunkarndee ◽  
Jessica Mae Leslie ◽  
Gloria Ann Brar
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Cellular Functions ◽  
Cell Plasma Membrane ◽  
Developmentally Regulated ◽  
Selective Autophagy ◽  
Selective Degradation ◽  
Cell Plasma ◽  
Membrane Tethering ◽  
Yeast Meiosis

The endoplasmic reticulum (ER) carries out essential and conserved cellular functions, which depend on the maintenance of its structure and subcellular distribution. Here, we report developmentally regulated changes in ER morphology and composition during budding yeast meiosis, a conserved differentiation program that gives rise to gametes. A subset of the cortical ER collapses away from the plasma membrane at anaphase II, thus separating into a spatially distinct compartment. This programmed collapse depends on the transcription factor Ndt80, conserved ER membrane structuring proteins Lnp1 and reticulons, and the actin cytoskeleton. A subset of ER is retained at the mother cell plasma membrane and excluded from gamete cells via the action of ER–plasma membrane tethering proteins. ER remodeling is coupled to ER degradation by selective autophagy, which relies on ER collapse and is regulated by timed expression of the autophagy receptor Atg40. Thus, developmentally programmed changes in ER morphology determine the selective degradation or inheritance of ER subdomains by gametes.

scholarly journals Cell Secretion: Current Structural and Biochemical Insights

2010 ◽  
Vol 10 ◽  
pp. 2054-2069 ◽  
Author(s):  
Saurabh Trikha ◽  
Elizabeth C. Lee ◽  
Aleksandar M. Jeremic
Keyword(s):  
Plasma Membrane ◽  
Secretory Vesicles ◽  
Intercellular Signaling ◽  
Cell Secretion ◽  
Membrane Structures ◽  
Calcium Dependent ◽  
Cell Plasma ◽  
Membrane Bound ◽  
And Control ◽  
Fusion Pores

Essential physiological functions in eukaryotic cells, such as release of hormones and digestive enzymes, neurotransmission, and intercellular signaling, are all achieved by cell secretion. In regulated (calcium-dependent) secretion, membrane-bound secretory vesicles dock and transiently fuse with specialized, permanent, plasma membrane structures, called porosomes or fusion pores. Porosomes are supramolecular, cup-shaped lipoprotein structures at the cell plasma membrane that mediate and control the release of vesicle cargo to the outside of the cell. The sizes of porosomes range from 150nm in diameter in acinar cells of the exocrine pancreas to 12nm in neurons. In recent years, significant progress has been made in our understanding of the porosome and the cellular activities required for cell secretion, such as membrane fusion and swelling of secretory vesicles. The discovery of the porosome complex and the molecular mechanism of cell secretion are summarized in this article.

scholarly journals Fusion pore or porosome: structure and dynamics

2003 ◽  
Vol 176 (2) ◽  
pp. 169-174 ◽  
Author(s):  
BP Jena
Keyword(s):  
Plasma Membrane ◽  
Neuroendocrine Cells ◽  
Fusion Pore ◽  
Secretory Cells ◽  
Force Microscopy ◽  
Membrane Pores ◽  
Atomic Force ◽  
Cell Plasma ◽  
Electrophysiological Measurements ◽  
Membrane Bound

Electrophysiological measurements on live secretory cells almost a decade ago suggested the presence of fusion pores at the cell plasma membrane. Membrane-bound secretory vesicles were hypothesized to dock and fuse at these sites, to release their contents. Our studies using atomic force microscopy on live exocrine and neuroendocrine cells demonstrate the presence of such plasma membrane pores, revealing their morphology and dynamics at near nm resolution and in real time.

scholarly journals Meiotic regulation of the Ndc80 complex composition and function

2021 ◽  
Author(s):  
Jingxun Chen ◽  
Elçin Ünal
Keyword(s):  
Chromosome Segregation ◽  
Budding Yeast ◽  
Complex Composition ◽  
The Past ◽  
Ndc80 Complex ◽  
Health And Disease ◽  
Yeast Meiosis ◽  
And Function ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

AbstractThis review describes the current models for how the subunit abundance of the Ndc80 complex, a key kinetochore component, is regulated in budding yeast and metazoan meiosis. The past decades of kinetochore research have established the Ndc80 complex to be a key microtubule interactor and a central hub for regulating chromosome segregation. Recent studies further demonstrate that Ndc80 is the limiting kinetochore subunit that dictates the timing of kinetochore activation in budding yeast meiosis. Here, we discuss the molecular circuits that regulate Ndc80 protein synthesis and degradation in budding yeast meiosis and compare the findings with those from metazoans. We envision the regulatory principles discovered in budding yeast to be conserved in metazoans, thereby providing guidance into future investigations on kinetochore regulation in human health and disease.

Traffic to the endocytic compartment of plants

1989 ◽  
Vol 47 ◽  
pp. 754-755
Author(s):  
L. R. Griffing ◽  
R. D. Record ◽  
H. H. Mollenhauer
Keyword(s):  
Plasma Membrane ◽  
Golgi Complex ◽  
Fluid Phase ◽  
Multivesicular Body ◽  
Endocytic Pathway ◽  
Cationized Ferritin ◽  
Plant Protoplasts ◽  
Whole Cells ◽  
Membrane Bound ◽  
And Function

The endocytic pathway of plants has been identified and partially characterized using nonspecific membrane-bound and fluid phase probes . The function of endocytosis in plants is, however, unknown. We shall describe how ultrastructural histochemistry, immunocytochemical analyses and fluorescence imaging have been used to explore the physiology and function of the endocytic pathway in plant protoplasts and whole cells.Cationized ferritin (CF) can be used as a marker of plasma membrane uptake in plant protoplasts. Several different organelles become labeled upon exposure of protoplasts to CF: clathrin-coated vesicles (CV), the partially coated reticulum (PCR), the Golgi complex (GC), the multivesicular body (MVB), and the vacuole (V). These organelles also participate in the pathways of secretion and delivery of protein to the lysosome (vacuole). What are the sites of overlap/divergence among the secretory, endocytic and lysosomal pathways in these cells?

Functional Organization of the Porosome Complex and Associated Structures Facilitating Cellular Secretion

Physiology ◽  
2009 ◽  
Vol 24 (6) ◽  
pp. 367-376 ◽  
Author(s):  
Bhanu P. Jena
Keyword(s):  
Plasma Membrane ◽  
Functional Organization ◽  
Secretory Activity ◽  
Human Platelets ◽  
Frog Neuromuscular Junction ◽  
Cell Secretion ◽  
Cell Plasma Membrane ◽  
Cell Plasma ◽  
Membrane Bound ◽  
Cellular Secretion

Porosomes, the universal secretory machinery at the cell plasma membrane, are cup-shaped supramolecular lipoprotein structures, where membrane-bound vesicles transiently dock and fuse to release intravesicular contents during cell secretion. In this review, the discovery of the porosome and its structure, dynamics, composition, and functional reconstitution are outlined. Furthermore, the architecture of porosome-like structures such as the “canaliculi system” in human platelets and various associated structures such as the T-bars at the Drosophila synapse or the “beams,” “ribs,” and “pegs” at the frog neuromuscular junction, each organized to facilitate a certain specialized secretory activity, are briefly discussed.

scholarly journals Soluble and Membrane-Bound TGF-β-Mediated Regulation of Intratumoral T Cell Differentiation and Function in B-Cell Non-Hodgkin Lymphoma

PLoS ONE ◽  
2013 ◽  
Vol 8 (3) ◽  
pp. e59456 ◽  
Author(s):  
Zhi-Zhang Yang ◽  
Deanna M. Grote ◽  
Steven C. Ziesmer ◽  
Bing Xiu ◽  
Nicole R. Yates ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
B Cell ◽  
Hodgkin Lymphoma ◽  
T Cell Differentiation ◽  
Non Hodgkin Lymphoma ◽  
Membrane Bound ◽  
And Function

scholarly journals Phosphatidylinositol 4,5-bisphosphate regulates cilium transition zone maturation in Drosophila melanogaster

2018 ◽  
Author(s):  
Alind Gupta ◽  
Lacramioara Fabian ◽  
Julie A. Brill
Keyword(s):  
Drosophila Melanogaster ◽  
Plasma Membrane ◽  
Transition Zone ◽  
Genetic Disorders ◽  
Ectopic Expression ◽  
Membrane Lipid ◽  
Type I ◽  
Male Germline ◽  
Membrane Tethering ◽  
And Function

AbstractCilia are cellular antennae that are essential for human development and physiology. A large number of genetic disorders linked to cilium dysfunction are associated with proteins that localize to the ciliary transition zone (TZ), a structure at the base of cilia that regulates trafficking in and out of the cilium. Despite substantial effort to identify TZ proteins and their roles in cilium assembly and function, processes underlying maturation of TZs are not well understood. Here, we report a role for the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) in TZ maturation in the Drosophila melanogaster male germline. We show that reduction of cellular PIP2 levels by ectopic expression of a phosphoinositide phosphatase or mutation of the type I phosphatidylinositol phosphate kinase Skittles induces formation of longer than normal TZs. These hyperelongated TZs exhibit functional defects, including loss of plasma membrane tethering. We also report that the onion rings (onr) allele of Drosophila exo84 decouples TZ hyperelongation from loss of cilium-plasma membrane tethering. Our results reveal a requirement for PIP2 in supporting ciliogenesis by promoting proper TZ maturation.Brief summary statementThe authors show that the membrane phospholipid PIP2, and the kinase that produces PIP2 called Skittles, are needed for normal ciliary transition zone morphology and function in the Drosophila male germline.

scholarly journals RAS Nanoclusters: Dynamic Signaling Platforms Amenable to Therapeutic Intervention

Biomolecules ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 377
Author(s):  
Que N. Van ◽  
Priyanka Prakash ◽  
Rebika Shrestha ◽  
Trent E. Balius ◽  
Thomas J. Turbyville ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Plasma Membrane ◽  
Molecular Switches ◽  
Ras Proteins ◽  
Input Signals ◽  
Membrane Bound ◽  
Intracellular Signal ◽  
Lipid Environment ◽  
And Function ◽  
Clustering Behavior

RAS proteins are mutated in approximately 20% of all cancers and are generally associated with poor clinical outcomes. RAS proteins are localized to the plasma membrane and function as molecular switches, turned on by partners that receive extracellular mitogenic signals. In the on-state, they activate intracellular signal transduction cascades. Membrane-bound RAS molecules segregate into multimers, known as nanoclusters. These nanoclusters, held together through weak protein–protein and protein–lipid associations, are highly dynamic and respond to cellular input signals and fluctuations in the local lipid environment. Disruption of RAS nanoclusters results in downregulation of RAS-mediated mitogenic signaling. In this review, we discuss the propensity of RAS proteins to display clustering behavior and the interfaces that are associated with these assemblies. Strategies to therapeutically disrupt nanocluster formation or the stabilization of signaling incompetent RAS complexes are discussed.

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