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2 edition of Regulation and function of mammalian septins during cell division. found in the catalog.

Regulation and function of mammalian septins during cell division.

Mark Christopher Surka

Regulation and function of mammalian septins during cell division.

by Mark Christopher Surka

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Published .
Written in English


About the Edition

Septins are required for cell division in a number of organisms ranging from Saccharomyces cerevisiae to humans. In addition, these proteins appear to play a role in several other processes such as secretion, neuronal guidance, and neurite outgrowth. Given the breadth of their possible functions, septins must be carefully regulated. In this thesis I show that during cell division, septins may be regulated by phosphorylation. I show that one particular animal septin, Sept2, is phosphorylated in vitro by three kinases, Casein Kinase II, CAMP-dependent kinase, and Protein Kinase C. Moreover, phosphorylation by CAMP-dependent kinase results in disruption of Sept2"s ability to bind phospholipids. In vivo, Sept2 is phosphorylated on a Casein Kinase II site, and the in vivo phosphorylation increases during cell division, suggesting that septin phosphorylation may play a role in regulating different aspects of mitosis. Septin phosphorylation may affect protein-protein interactions between septin molecules or other proteins. In order to better understand the significance of septin phosphorylation, septin-interacting proteins were identified. I show that Sept2 associates in one or more complexes with several other septins. One of these septins, Sept9, associates with both the actin and microtubule networks, while Sept2 predominately associates with the actin cytoskeleton. This difference in localization not only occurs in interphase cells, but also throughout cell division. Like other septins studied to date, I show that Sept9 is required for cell division in tissue culture cells. Besides having a role in cell division, Sept9 also plays a role in regulating both the actin and microtubule cytoskeletons. Depletion of Sept9 through siRNA-transfection results in the loss of actin stress fibers and in an increase in acetylated tubulin levels. The loss of actin stress fibers results from a loss of ROCK signaling to myosin. In addition, I also found that Sept9 immunoprecipitates contain not only septin proteins, but also myosin heavy chain Ha, providing evidence to support a role for septins in regulating ROCK phosphorylation of myosin II. Finally I devise a model in which septin function during cell division is proposed along with a role for its regulation through changes in its phosphorylation status.

The Physical Object
Pagination227 leaves.
Number of Pages227
ID Numbers
Open LibraryOL19886892M
ISBN 100612942465

Microtubules (MTs) are polar polymers of α/β tubulin heterodimers that, besides forming the mitotic spindle during cell division, have diverse cell type–specific functions. that there is an additional level of control of MAP4 activity by regulation of MT stability through binding of mammalian septins to Regulation of the. Septins are conserved GTPases that form filaments and are required for cell division. During interphase, septin filaments associate with cellular membrane and cytoskeleton networks, yet the functional significance of these associations have, to our knowledge, remained unknown. We recently discovered that different septins, SEPT2 and SEPT11, regulate the InlB-mediated entry of Listeria.

1 UMEÅ UNIVERSITY MEDICAL DISSERTATIONS New series nr: ISSN: ISBN: Cytoskeletal Filament Systems Assembly, Regulation, and Interplay in Mammalian Cells. The murine septin4 gene (Sept4) has been implicated in diverse cellular functions, including cytokinesis, apoptosis, and tumor suppression. Here, we investigated the function of Sept4 proteins during mouse development by creating a targeted deletion of the Sept4 genomic locus. Sept4 mutant mice are viable but male sterile due to immotile and structurally defective sperm.

not be necessary for septin function is supported by studies on the role of the Gin4p kinase in septin organization Gin4p binds directly to the septins and colocalizes with them for most of the cell cycle (see Fig. 5a,a 9), suggesting that it plays an important role in septin funct In Dgin4cells, the septins. Given the proposed role of septins in cell membrane dynamics, we investigated the function of septins during FcγR-mediated phagocytosis. We show that several septins are expressed in RAW and J mouse macrophage cell lines and that SEPT2 and SEPT11 are colocalized with submembranous actin-rich structures during the early stages of FcγR.


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Regulation and function of mammalian septins during cell division by Mark Christopher Surka Download PDF EPUB FB2

Function and Regulation of Septins During Mammalian Cell Division Mathew Paul Estey Doctor of Philosophy Department of Biochemistry University of Toronto Abstract Septins are a family of GTP-binding proteins implicated in mammalian cell division.

Since theseAuthor: Mathew Estey. Introduction. Septins are a conserved family of cytoskeletal GTP-binding proteins that function in cytokinesis, cell polarity, and membrane remodeling in many eukaryotic cell types (1, 2).To contribute to these diverse process, septins polymerize into filaments and higher-order structures that organize the cell cortex into domains that are tightly controlled in time and/or space ().Cited by: Functions for mammalian septins have been described for two distinct steps in cell division: first during chromosome segregation, and, later, during cytokinesis (Kinoshita et al., ; Spiliotis et al., ).

Depletion of septins by RNAi induces defects in both of these processes, although with rather low penetrance, and in neither case has Cited by: In mammalian cells, septins colo-calize with both the actin and microtubule cytoskeletons and cell membranes, and they are thought to serve multiple functions ().

The septin protein Nedd5/Septin-2 colocalizes with actin, microtubules, and exocyst components in a variety of cell types (, ). Indeed, septins have been shown in vitro to bind the actin-binding protein anil and anillin recruits septins to the actomyosin ring during cell division Moreover, septins have been Cited by: The role of septins in cell division provides a paradigm for how these proteins might coordinate intracellular membrane traffic and the cytoskeleton during interphase in mammalian cells.

As noted above, septins associate with both actin and microtubule cytoskeletons, and regulate the localization of cytoskeleton-binding and motor proteins, and.

There are seven different septins in Saccharomyces of those are involved in mitosis, while two (Spr3 and Spr28) are specific to sporulation. Mitotic septins (Cdc3, Cdc10, Cdc11, Cdc12, Shs1) form a ring structure at the bud neck during cell division. They are involved in the selection of the bud-site, the positioning of the mitotic spindle, polarized growth, and cytokinesis.

Septins are a major component of the mammalian cytoskeleton. Septins associate with filamentous actin (F-actin) and microtubules, but the nature and significance of these interactions are not well.

A diffusion barrier has also been described at the division site in mammalian cells, and mammalian septins are important for various stages of cytokinesis.

This raises the possibility that mammalian septins also form a membrane diffusion barrier during cytokinesis, although this hypothesis remains to be tested. Additionally, septins function in the mitotic exit checkpoint as a scaffold for a microtubule sensor (Castillon et al.,Kusch et al., ).

Thus, septins may coordinate microtubule and actin functions during cell division and DNA damage-induced arrest in yeast.

Mammalian septins may also coordinate microtubule and actin dynamics. Asymmetric furrowing was initially documented in embryonic cell division in a variety of species (Rappaport, ), in polarized cultured mammalian epithelial cells (Reinsch and Karsenti, ), as well as in the C.

elegans one-cell embryo (Maddox et al., ). In this latter model system, septins were shown to break the symmetry of actomyosin. Introduction. Originally identified in Saccharomyces cerevisiae as required for septum formation and cell division, septins form a family of GTPases among fungi and animals sharing a conserved role in cytokinesis ().In mammals, septins are recognized for a variety of other essential cellular functions including roles in secretion, membrane remodeling, and cytoskeleton dynamics ().

In this section, we will provide a more integrated overview on the involvement of septins in cell division in S. ceresiviae and mammalian cells. Cell division in budding yeast. Budding yeast undergo asymmetric division, resulting in two cells with distinct sizes.

The daughter cell is approximately two-thirds of its mother in size. In cells, higher-order septin ring-like structures are found at the base of cilia, flagella, dendritic spines and yeast buds, where they associate tightly with the plasma membrane and recruit other molecules (the 'septin ring' paradigm, shown in Fig 1).Thereby septins mediate the formation of a lateral diffusion barrier in the membrane with which they have contact, and compartmentalize the.

The various isoforms seem to determine the function and regulation of the septin complex. Septins self-assemble into higher-order structures, including filaments and rings in orders, which are typical for different cell types.

Misregulation of septins leads to human diseases such as neurodegenerative and bleeding disorders. The pioneering cell division cycle screens carried out by Hartwell in first identified septins as genes that are essential for yeast cytokinesis ([Hartwell, ][1]).

However, significant characterization of the evolutionarily conserved proteins they encode did not begin until the late s.

Previously, our laboratory has demonstrated two major defects in cell division in HeLa cells associated with depleting mammalian septins: binucleation and an increase in the presence of cells connected by midbodies (Estey et al., ).

Cells lacking SEPT2, SEPT7, or SEPT11 were binucleate after imprecise furrow ingression or contractile ring. Septins are cytoskeleton components widely recognized for their role in eukaryotic cell division. Krokowski et al. discover that septins recognize dividing bacterial cells for entrapment and delivery to lysosomes.

These results reveal a fundamental danger signal used by the host cell to recognize intracellular bacterial pathogens for cellular immunity. Septins are widely recognized as a component of the cytoskeleton that is essential for cell division, and new work has shown that septins can recognise cell shape by assembling into filaments on membrane regions that display micrometer-scale curvature (e.g.

at the cytokinetic furrow). Moreover, infection biology studies have illuminated important roles for septins in mediating the outcome of. It may be that targeting of septins to membrane domains is relevant to some of their functions including the potential to act as a diffusion barrier in both yeast and mammalian cells.

Anillin is a conserved protein implicated in cytoskeletal dynamics during cellularization and ANLN gene in humans and the scraps gene in Drosophila encode Anillin.

Inanillin was first isolated in embryos of Drosophila was identified as an F-actin binding protein. Six years later, the anillin gene was cloned from cDNA originating from a Drosophila ovary. In addition, septin localization during cytokinesis of mammalian cells may also be facilitated by an analogous mechanism, namely cooperative binding at the plasma membrane and a septin adaptor such as anillin, which appears to interact with both septins and actin bundles at the contractile ring (Oegema et al., ; Kinoshita et al., ).Ultimately, the septin ring separates and remains after the completion of the division marking the membrane region where cell division has occurred.

Mammalian septin domain organization.