scholarly journals Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1

2019 ◽  
Author(s):  
Kristi E. Miller ◽  
Hay-Oak Park
Keyword(s):  
Cell Polarity ◽  
Bound States ◽  
Bound State ◽  
Scaffold Protein ◽  
Cell Polarization ◽  
Temporal Regulation ◽  
Ras Gtpase ◽  
Px Domain ◽  
Associated Proteins ◽  
Bud Site

AbstractEstablishing cell polarity is critical for growth and development of most organisms. The Cdc42 GTPase plays a central role in polarity development in species ranging from yeast to humans. In budding yeast, a specific growth site (i.e. bud site) is selected in the G1 phase, which determines the axis of cell polarization. Rsr1, a Ras GTPase, interacts with Cdc42 and its associated proteins to promote polarized growth at the proper bud site. Yet the mechanism underlying spatial cue-directed cell polarization is not fully understood. Here, we show that Rsr1 associates with Bem1, a scaffold protein, preferentially in its GDP-bound state in early G1. This interaction involves a part of the Bem1 Phox homology (PX) domain, which overlaps with a region previously shown to interact with Exo70, an exocyst component. Furthermore, overexpression of the constitutively GDP-bound Rsr1 interferes with Bem1’s association with Exo70 and inhibits Bem1-dependent Exo70 polarization. We propose that Rsr1 plays a delicate role in coordination of spatial and temporal regulation of polarity establishment via its GTP- and GDP-bound states.

scholarly journals Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1

2019 ◽  
Vol 30 (20) ◽  
pp. 2543-2557 ◽  
Author(s):  
Kristi E. Miller ◽  
Wing-Cheong Lo ◽  
Ching-Shan Chou ◽  
Hay-Oak Park
Keyword(s):  
Bound States ◽  
Scaffold Protein ◽  
Cell Polarization ◽  
Temporal Regulation ◽  
Ras Gtpase ◽  
Polarized Secretion ◽  
Associated Proteins ◽  
Guanosine Triphosphatase ◽  
Bud Site

The Cdc42 guanosine triphosphatase (GTPase) plays a central role in polarity development in species ranging from yeast to humans. In budding yeast, a specific growth site is selected in the G1 phase. Rsr1, a Ras GTPase, interacts with Cdc42 and its associated proteins to promote polarized growth at the proper bud site. Yet how Rsr1 regulates cell polarization is not fully understood. Here, we show that Rsr1-GDP interacts with the scaffold protein Bem1 in early G1, likely hindering the role of Bem1 in Cdc42 polarization and polarized secretion. Consistent with these in vivo observations, mathematical modeling predicts that Bem1 is unable to promote Cdc42 polarization in early G1 in the presence of Rsr1-GDP. We find that a part of the Bem1 Phox homology domain, which overlaps with a region interacting with the exocyst component Exo70, is necessary for the association of Bem1 with Rsr1-GDP. Overexpression of the GDP-locked Rsr1 interferes with Bem1-dependent Exo70 polarization. We thus propose that Rsr1 functions in spatial and temporal regulation of polarity establishment by associating with distinct polarity factors in its GTP- and GDP-bound states.

scholarly journals A Role for the Rap GTPase YlRsr1 in Cellular Morphogenesis and the Involvement of YlRsr1 and the Ras GTPase YlRas2 in Bud Site Selection in the Dimorphic Yeast Yarrowia lipolytica

2014 ◽  
Vol 13 (5) ◽  
pp. 580-590 ◽  
Author(s):  
Yun-Qing Li ◽  
Min Li ◽  
Xiao-Feng Zhao ◽  
Xiang-Dong Gao
Keyword(s):  
Yarrowia Lipolytica ◽  
Site Selection ◽  
Bound States ◽  
Selection Process ◽  
Content Type ◽  
Yeast Form ◽  
Ras Gtpase ◽  
Cellular Morphogenesis ◽  
Dimorphic Yeast ◽  
Bud Site

ABSTRACT Yarrowia lipolytica is a dimorphic yeast species that can grow in the ovoid yeast form or in the elongated pseudohyphal or hyphal form depending on the growth conditions. Here, we show that the Rap GTPase Rsr1 of Y. lipolytica (YlRsr1) plays an important role in cellular morphogenesis in this microorganism. Cells deleted for Yl RSR1 exhibited impaired polarized growth during yeast-form growth. Pseudohyphal and hyphal development were also abnormal. YlRsr1 is also important for cell growth, since the deletion of Yl RSR1 in cells lacking the Ras GTPase YlRas2 caused lethality. Y. lipolytica cells bud in a bipolar pattern in which the cells produce the new buds at the two poles. YlRsr1 plays a prominent role in this bud site selection process. YlRsr1's function in bud site selection absolutely requires the cycling of YlRsr1 between the GTP- and GDP-bound states but its function in cellular morphogenesis does not, suggesting that the two processes are differentially regulated. Interestingly, the Ras GTPase YlRas2 is also involved in the control of bud site selection, as Yl ras2 Δ cells were severely impaired in bipolar bud site selection. The GTP/GDP cycling and the plasma membrane localization of YlRas2 are important for YlRas2's function in bud site selection. However, they are not essential for this process, suggesting that the mechanism by which YlRas2 acts is different from that of YlRsr1. Our results suggest that YlRsr1 is regulated by the GTPase-activating protein (GAP) YlBud2 and partially by YlCdc25, the potential guanine nucleotide exchange factor (GEF) for YlRas2.

scholarly journals Bound states of a Klein–Gordon particle in the presence of a smooth potential well

2020 ◽  
Vol 35 (23) ◽  
pp. 2050140
Author(s):  
Eduardo López ◽  
Clara Rojas
Keyword(s):  
Bound States ◽  
Gordon Equation ◽  
Bound State ◽  
Potential Well ◽  
One Dimensional ◽  
Smooth Potential ◽  
Klein Gordon ◽  
The One ◽  
Potential Parameters ◽  
Klein Gordon Equation

We solve the one-dimensional time-independent Klein–Gordon equation in the presence of a smooth potential well. The bound state solutions are given in terms of the Whittaker [Formula: see text] function, and the antiparticle bound state is discussed in terms of potential parameters.

RETARDATION EFFECTS IN COVARIANT THREE-DIMENSIONAL BOUND STATE WAVE FUNCTIONS

2005 ◽  
Vol 14 (06) ◽  
pp. 931-947 ◽  
Author(s):  
F. PILOTTO ◽  
M. DILLIG
Keyword(s):  
Bound States ◽  
Three Dimensional ◽  
Bound State ◽  
Relative Energy ◽  
Wave Functions ◽  
Three Dimensions ◽  
State Wave ◽  
Scalar Diquark ◽  
Bound State Wave Function ◽  
Retardation Effects

We investigate the influence of retardation effects on covariant 3-dimensional wave functions for bound hadrons. Within a quark-(scalar) diquark representation of a baryon, the four-dimensional Bethe–Salpeter equation is solved for a 1-rank separable kernel which simulates Coulombic attraction and confinement. We project the manifestly covariant bound state wave function into three dimensions upon integrating out the non-static energy dependence and compare it with solutions of three-dimensional quasi-potential equations obtained from different kinematical projections on the relative energy variable. We find that for long-range interactions, as characteristic in QCD, retardation effects in bound states are of crucial importance.

THE NEXT STEP IN LEPTONIC DECAYS OF ETA AND KL BOUND STATES

1992 ◽  
Vol 07 (09) ◽  
pp. 1935-1951 ◽  
Author(s):  
G.A. KOZLOV
Keyword(s):  
Field Theory ◽  
Transition Form Factor ◽  
Bound States ◽  
Three Dimensional ◽  
Bound State ◽  
Quantum Field ◽  
Relative Momentum ◽  
Transition Form ◽  
Structure Transition ◽  
Leptonic Decays

A systematic discussion of the probability of eta and KL bound-state decays—[Formula: see text] and [Formula: see text](l=e, μ)—within a three-dimensional reduction to the two-body quantum field theory is presented. The bound-state vertex function depends on the relative momentum of constituent-like particles. A structure-transition form factor is defined by a confinement-type quark-antiquark wave function. The phenomenology of this kind of decays is analyzed.

Cdc28-Clb mitotic kinase negatively regulates bud site assembly in the budding yeast

2001 ◽  
Vol 114 (1) ◽  
pp. 207-218 ◽  
Author(s):  
C.G. Padmashree ◽  
U. Surana
Keyword(s):  
Kinase Activity ◽  
Budding Yeast ◽  
Critical Role ◽  
The Other ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Formation ◽  
Temporal Regulation ◽  
Mitotic Kinase ◽  
Cortical Localization ◽  
Bud Site

In the budding yeast Saccharomyces cerevisiae, a prospective mother normally commences the formation of a daughter (the bud) only in the G(1) phase of the cell division cycle. This suggests a strict temporal regulation of the processes that initiate the formation of a new bud. Using cortical localization of bud site components Spa2 and Bni1 as an indicator of bud site assembly, we show that cells assemble a bud site following inactivation of the Cdc28-Clb mitotic kinase but prior to START. Interestingly, an untimely inactivation of the mitotic kinase is sufficient to drive cells to assemble a new bud site inappropriately in G(2) or M phases. The induction of Cdc28/Clb kinase activity in G(1), on the other hand, dramatically reduces a cell's ability to construct an incipient bud site. Our findings strongly suggest that the Cdc28-Clb kinase plays a critical role in the mechanism that restricts the timing of bud formation to the G(1) phase of the cell cycle.

Cell polarity and tissue patterning in plants

Development ◽  
1991 ◽  
Vol 113 (Supplement_1) ◽  
pp. 83-93 ◽  
Author(s):  
Tsvi Sachs
Keyword(s):  
Cell Polarity ◽  
Cell Shape ◽  
Auxin Transport ◽  
Developmental Stages ◽  
Important Determinant ◽  
Genetic System ◽  
Cell Patterning ◽  
Cell Polarization ◽  
Sources And Sinks ◽  
Tissue Patterning

Cell polarization is the specialization of developmental events along one orientation or one direction. Such polarization must be an early, essential stage of tissue patterning. The specification of orientation could not occur only at the level of the genetic system and it must express a coordination of events in many cells. There is a positive feedback relation between cell polarization and the transport of the known hormone auxin: polarity determines oriented auxin transport while transport itself induces both new and continued polarization. Since cell polarization increases gradually, this feedback leads to the canalization of transport – and of the associated cell differentiation – along defined strands of specialized cells. Recent work has shown that the same canalized flow can also be an important determinant of cell shape. In primordial, embryonic regions cell growth is oriented along the flow of auxin from the shoot towards the root. In later developmental stages the cells respond to the same flow by growing in girth, presumably adjusting the capacity of the tissues to the flow of signals. Finally, disrupted flow near wounds results in the development of relatively unorganized callus. Continued callus development appears to require the participation of the cells, as sources and sinks of auxin and other signals. The overall picture to emerge suggests that cell patterning can result from competition between cells acting as preferred channels, sources and sinks for developmental signals.

scholarly journals Structural insights into the mechanism of the DEAH-box RNA helicase Prp43

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Marcel J Tauchert ◽  
Jean-Baptiste Fourmann ◽  
Reinhard Lührmann ◽  
Ralf Ficner
Keyword(s):  
Conformational Changes ◽  
Bound States ◽  
Rna Binding ◽  
Atp Hydrolysis ◽  
Bound State ◽  
Rna Helicases ◽  
Large Rearrangements ◽  
Rna Complex ◽  
Structural Insights ◽  
Terminal Domains

The DEAH-box helicase Prp43 is a key player in pre-mRNA splicing as well as the maturation of rRNAs. The exact modus operandi of Prp43 and of all other spliceosomal DEAH-box RNA helicases is still elusive. Here, we report crystal structures of Prp43 complexes in different functional states and the analysis of structure-based mutants providing insights into the unwinding and loading mechanism of RNAs. The Prp43•ATP-analog•RNA complex shows the localization of the RNA inside a tunnel formed by the two RecA-like and C-terminal domains. In the ATP-bound state this tunnel can be transformed into a groove prone for RNA binding by large rearrangements of the C-terminal domains. Several conformational changes between the ATP- and ADP-bound states explain the coupling of ATP hydrolysis to RNA translocation, mainly mediated by a β-turn of the RecA1 domain containing the newly identified RF motif. This mechanism is clearly different to those of other RNA helicases.

THE BETHE–SALPETER EQUATION APPROACH TO BOUND STATE: SCALAR–FERMION CASE AND SCALAR–SCALAR CASE

2007 ◽  
Vol 22 (39) ◽  
pp. 2979-2992 ◽  
Author(s):  
JIAO-KAI CHEN ◽  
ZHENG-XIN TANG ◽  
QING-DONG CHEN
Keyword(s):  
Bound States ◽  
Bound State ◽  
Wave Functions ◽  
Scalar Case ◽  
Equation Approach

The general form of the Bethe–Salpeter wave functions for bound states comprising one scalar constituent and one fermion, or two scalars is presented. Using the reduced Salpeter equation obtained, we can work out the effective nonrelativistic potentials. And one new version of reduced Bethe–Salpeter equation is proposed by extending Gross approximation.

scholarly journals Instability of charged massive scalar fields in bound states around Kerr–Sen black holes

2015 ◽  
Vol 24 (14) ◽  
pp. 1550102 ◽  
Author(s):  
Haryanto M. Siahaan
Keyword(s):  
Black Holes ◽  
Bound States ◽  
Gordon Equation ◽  
Scalar Fields ◽  
Bound State ◽  
Imaginary Component ◽  
Scalar Perturbation ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Klein Gordon

In this paper, we show the instability of a charged massive scalar field in bound states around Kerr–Sen black holes. By matching the near and far region solutions of the radial part in the corresponding Klein–Gordon equation, one can show that the frequency of bound state scalar fields contains an imaginary component which gives rise to an amplification factor for the fields. Hence, the unstable modes for a charged and massive scalar perturbation in Kerr–Sen background can be shown.

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