scholarly journals Control of cellular morphogenesis by the Ip12/Bem2 GTPase-activating protein: possible role of protein phosphorylation.

1994 ◽  
Vol 127 (5) ◽  
pp. 1381-1394 ◽  
Author(s):  
Y J Kim ◽  
L Francisco ◽  
G C Chen ◽  
E Marcotte ◽  
C S Chan
Keyword(s):  
Cell Growth ◽  
Protein Phosphorylation ◽  
Protein Phosphatase ◽  
Gene Dosage ◽  
Protein Domain ◽  
Gtpase Activating Protein ◽  
Synthetic Lethal ◽  
Lethal Phenotype ◽  
Polarized Cell Growth ◽  
Mutant Phenotypes

The IPL2 gene is known to be required for normal polarized cell growth in the budding yeast Saccharomyces cerevisiae. We now show that IPL2 is identical to the previously identified BEM2 gene. bem2 mutants are defective in bud site selection at 26 degrees C and localized cell surface growth and organization of the actin cytoskeleton at 37 degrees C. BEM2 encodes a protein with a COOH-terminal domain homologous to sequences found in several GTPase-activating proteins, including human Bcr. The GTPase-activating protein-domain from the Bem2 protein (Bem2p) or human Bcr can functionally substitute for Bem2p. The Rho1 and Rho2 GTPases are the likely in vivo targets of Bem2p because bem2 mutant phenotypes can be partially suppressed by increasing the gene dosage of RHO1 or RHO2. CDC55 encodes the putative regulatory B subunit of protein phosphatase 2A, and mutations in BEM2 have previously been identified as suppressors of the cdc55-1 mutation. We show here that mutations in the previously identified GRR1 gene can suppress bem2 mutations. grr1 and cdc55 mutants are both elongated in shape and cold-sensitive for growth, and cells lacking both GRR1 and CDC55 exhibit a synthetic lethal phenotype. bem2 mutant phenotypes also can be suppressed by the SSD1-vl (also known as SRK1) mutation, which was shown previously to suppress mutations in the protein phosphatase-encoding SIT4 gene. Cells lacking both BEM2 and SIT4 exhibit a synthetic lethal phenotype even in the presence of the SSD1-v1 suppressor. These genetic interactions together suggest that protein phosphorylation and dephosphorylation play an important role in the BEM2-mediated process of polarized cell growth.

scholarly journals The Cdc42 GTPase activating protein Rga6 promotes the cortical localization of Septin

2021 ◽  
Author(s):  
Shengnan Zheng ◽  
Biyu Zheng ◽  
Zhenbang Liu ◽  
Wenfan Wei ◽  
Chuanhai Fu
Keyword(s):  
Cell Growth ◽  
Cell Polarity ◽  
Microscopic Analysis ◽  
Cell Cortex ◽  
Gtpase Activating Protein ◽  
Gtp Binding ◽  
Growing Cell ◽  
Polarized Cell Growth ◽  
Cortical Localization ◽  
Cortical Regions

Septins are a family of filament-forming GTP-binding proteins that regulate fundamental cellular activities such as cytokinesis, cell polarity, and membrane remodelling. In general, Septin filaments function as barriers and scaffolds on the cell cortex. However, little is known about the mechanism that governs the recruitment and localization of the Septin complex to the cell cortex. Here, we identified the Cdc42 GTPase activating protein Rga6 as a key protein involved in promoting the localization of the Septin complex to the cell cortex in the fission yeast Schizosaccharomyces pombe. Rga6 interacts with the Septin complex and colocalizes with the Septin complex on the cell cortex. Live-cell microscopic analysis further showed Septin enrichment at the cortical regions adjacent to the growing cell tip. The Septin enrichment likely plays a crucial role in confining active Cdc42 to the growing cell tip. Hence, our findings support a model that Rga6 regulates polarized cell growth partly through promoting targeted localization of the Septin complex on the cell cortex.

scholarly journals A Genetic Analysis of Interactions with Spc110p Reveals Distinct Functions of Spc97p and Spc98p, Components of the Yeast γ-Tubulin Complex

1998 ◽  
Vol 9 (8) ◽  
pp. 2201-2216 ◽  
Author(s):  
Thu Nguyen ◽  
Dani B.N. Vinh ◽  
Douglas K. Crawford ◽  
Trisha N. Davis
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Amino Terminus ◽  
Temperature Sensitive ◽  
Microtubule Organizing Center ◽  
Synthetic Lethal ◽  
Lethal Phenotype ◽  
Amino Terminal ◽  
N Terminus ◽  
Two Hybrid

The spindle pole body (SPB) in Saccharomyces cerevisiae functions as the microtubule-organizing center. Spc110p is an essential structural component of the SPB and spans between the central and inner plaques of this multilamellar organelle. The amino terminus of Spc110p faces the inner plaque, the substructure from which spindle microtubules radiate. We have undertaken a synthetic lethal screen to identify mutations that enhance the phenotype of the temperature-sensitive spc110–221 allele, which encodes mutations in the amino terminus. The screen identified mutations inSPC97 and SPC98, two genes encoding components of the Tub4p complex in yeast. The spc98–63allele is synthetic lethal only with spc110 alleles that encode mutations in the N terminus of Spc110p. In contrast, thespc97 alleles are synthetic lethal withspc110 alleles that encode mutations in either the N terminus or the C terminus. Using the two-hybrid assay, we show that the interactions of Spc110p with Spc97p and Spc98p are not equivalent. The N terminus of Spc110p displays a robust interaction with Spc98p in two different two-hybrid assays, while the interaction between Spc97p and Spc110p is not detectable in one strain and gives a weak signal in the other. Extra copies of SPC98 enhance the interaction between Spc97p and Spc110p, while extra copies of SPC97interfere with the interaction between Spc98p and Spc110p. By testing the interactions between mutant proteins, we show that the lethal phenotype in spc98–63 spc110–221 cells is caused by the failure of Spc98–63p to interact with Spc110–221p. In contrast, the lethal phenotype in spc97–62 spc110–221 cells can be attributed to a decreased interaction between Spc97–62p and Spc98p. Together, these studies provide evidence that Spc110p directly links the Tub4p complex to the SPB. Moreover, an interaction between Spc98p and the amino-terminal region of Spc110p is a critical component of the linkage, whereas the interaction between Spc97p and Spc110p is dependent on Spc98p.

scholarly journals The BNIP-2 and Cdc42GAP Homology (BCH) Domain of p50RhoGAP/Cdc42GAP Sequesters RhoA from Inactivation by the Adjacent GTPase-activating Protein Domain

2010 ◽  
Vol 21 (18) ◽  
pp. 3232-3246 ◽  
Author(s):  
Yi Ting Zhou ◽  
Li Li Chew ◽  
Sheng-cai Lin ◽  
Boon Chuan Low
Keyword(s):  
Rho Gtpases ◽  
Rho Gtpase ◽  
Intramolecular Interaction ◽  
Complete Loss ◽  
Protein Domain ◽  
Binding Motif ◽  
Gtpase Activating Protein ◽  
New Paradigm ◽  
Cell Rounding ◽  
In Cis

The BNIP-2 and Cdc42GAP homology (BCH) domain is a novel regulator for Rho GTPases, but its impact on p50-Rho GTPase-activating protein (p50RhoGAP or Cdc42GAP) in cells remains elusive. Here we show that deletion of the BCH domain from p50RhoGAP enhanced its GAP activity and caused drastic cell rounding. Introducing constitutively active RhoA or inactivating GAP domain blocked such effect, whereas replacing the BCH domain with endosome-targeting SNX3 excluded requirement of endosomal localization in regulating the GAP activity. Substitution with homologous BCH domain from Schizosaccharomyces pombe, which does not bind mammalian RhoA, also led to complete loss of suppression. Interestingly, the p50RhoGAP BCH domain only targeted RhoA, but not Cdc42 or Rac1, and it was unable to distinguish between GDP and the GTP-bound form of RhoA. Further mutagenesis revealed a RhoA-binding motif (residues 85-120), which when deleted, significantly reduced BCH inhibition on GAP-mediated cell rounding, whereas its full suppression also required an intramolecular interaction motif (residues 169-197). Therefore, BCH domain serves as a local modulator in cis to sequester RhoA from inactivation by the adjacent GAP domain, adding to a new paradigm for regulating p50RhoGAP signaling.

scholarly journals Contractile protein phosphorylation predicts human heart disease phenotypes

2013 ◽  
Vol 304 (12) ◽  
pp. H1644-H1650 ◽  
Author(s):  
Lori A. Walker ◽  
David A. Fullerton ◽  
Peter M. Buttrick
Keyword(s):  
Heart Failure ◽  
Heart Disease ◽  
Protein Phosphorylation ◽  
Protein Phosphatase ◽  
Human Heart ◽  
Troponin I ◽  
Systolic Function ◽  
Left Ventricular ◽  
Control Group ◽  
Lv Function

Human heart failure has been associated with a low level of thin-filament protein phosphorylation and an increase in calcium sensitivity of contraction relative to both “control” human heart tissue and tissue from small animal models. However, diverse strategies of human tissue procurement and the reliance on tissue obtained from subjects with end-stage heart failure suggest this may be an incomplete characterization. Therefore, we evaluated cardiac left ventricular (LV) biopsy samples from patients with aortic stenosis undergoing valve replacement who presented either with LV hypertrophy and preserved systolic function (Hyp) or with LV dilation and reduced ejection fraction (Dil). In Hyp, total troponin I (TnI) phosphorylation was markedly increased and myosin light chain 2 (MLC2) phosphorylation was unchanged relative to a control group of patients with normal LV function. Conversely, in Dil, total TnI phosphorylation was significantly reduced compared with control subjects and MLC2 phosphorylation was increased. Site-specific analysis of TnI phosphorylation revealed phenotype-specific differences such that Hyp samples demonstrated significant increases in phosphorylation at serine 22/23 and Dil samples had significant decreases at serine 43. The ratio of phosphorylation at the two sites was biased toward serine 22/23 in Hyp and toward serine 43/45 in Dil. Western blot analysis showed that protein phosphatase-1 was reduced in Hyp and protein phosphatase-2 was reduced in Dil. These data suggest that posttranslational modifications of sarcomeric proteins, both singly and in combination, are stage specific. Defining these changes in progressive heart disease may provide important diagnostic and treatment information.

scholarly journals Host-Polarized Cell Growth in Animal Symbionts

2018 ◽  
Vol 28 (7) ◽  
pp. 1039-1051.e5 ◽  
Author(s):  
Nika Pende ◽  
Jinglan Wang ◽  
Philipp M. Weber ◽  
Jolanda Verheul ◽  
Erkin Kuru ◽  
...  
Keyword(s):  
Cell Growth ◽  
Polarized Cell Growth

scholarly journals The EGP1 gene may be a positive regulator of protein phosphatase type 1 in the growth control of Saccharomyces cerevisiae.

1995 ◽  
Vol 15 (7) ◽  
pp. 3767-3776 ◽  
Author(s):  
N Hisamoto ◽  
D L Frederick ◽  
K Sugimoto ◽  
K Tatchell ◽  
K Matsumoto
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Growth ◽  
Protein Phosphatase ◽  
Double Mutant ◽  
Growth Control ◽  
Restrictive Temperature ◽  
Extra Copy ◽  
Additional Gene ◽  
Positive Modulator

The Saccharomyces cerevisiae GLC7 gene encodes the catalytic subunit of type 1 protein phosphatase (PP1) and is required for cell growth. A cold-sensitive glc7 mutant (glc7Y170) arrests in G2/M but remains viable at the restrictive temperature. In an effort to identify additional gene products that function in concert with PP1 to regulate growth, we isolated a mutation (gpp1) that exacerbated the growth phenotype of the glc7Y170 mutation, resulting in rapid death of the double mutant at the nonpermissive temperature. We identified an additional gene, EGP1, as an extra-copy suppressor of the glc7Y170 gpp1-1 double mutant. The nucleotide sequence of EGP1 predicts a leucine-rich repeat protein that is similar to Sds22, a protein from the fission yeast Schizosaccharomyces pombe that positively modulates PP1. EGP1 is essential for cell growth but becomes dispensable upon overexpression of the GLC7 gene. Egp1 and PP1 directly interact, as assayed by coimmunoprecipitation. These results suggest that Egp1 functions as a positive modulator of PP1 in the growth control of S. cerevisiae.

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