Identification of Yeast Rho1p GTPase as a Regulatory Subunit of 1,3-β-Glucan Synthase

Qadota, Hiroshi; Python, Christophe Pierre; Inoue, Shunsuke B.; Arisawa, Mikio; Anraku, Yasuhiro; Zheng, Yi; Watanabe, T.; Levin, David E.; Ohya, Yoshikazu

doi:10.1126/science.272.5259.279

Cited by 436 publications

(426 citation statements)

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“…␤-1,3-Glucan is synthesized by ␤-1,3-glucan synthase (GS) localized on the plasma membrane (Qadota et al, 1996). GS is composed of a catalytic subunit encoded by the two homologous genes FKS1 and FKS2 (Inoue et al, 1995;Mazur et al, 1995), and a regulatory subunit, the small GTPase, Rho1p (Drgonova et al, 1996;Qadota et al, 1996).…”

Section: Discussionmentioning

confidence: 99%

Loss of Function ofKRE5Suppresses Temperature Sensitivity of Mutants Lacking Mitochondrial Anionic Lipids

Zhong

Gvozdenović-Jeremić

Webster

et al. 2005

MBoC

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Disruption of PGS1, which encodes the enzyme that catalyzes the committed step of cardiolipin (CL) synthesis, results in loss of the mitochondrial anionic phospholipids phosphatidylglycerol (PG) and CL. The pgs1⌬ mutant exhibits severe growth defects at 37°C. To understand the essential functions of mitochondrial anionic lipids at elevated temperatures, we isolated suppressors of pgs1⌬ that grew at 37°C. One of the suppressors has a loss of function mutation in KRE5, which is involved in cell wall biogenesis. The cell wall of pgs1⌬ contained markedly reduced ␤-1,3-glucan, which was restored in the suppressor. Stabilization of the cell wall with osmotic support alleviated the cell wall defects of pgs1⌬ and suppressed the temperature sensitivity of all CL-deficient mutants. Evidence is presented suggesting that the previously reported inability of pgs1⌬ to grow in the presence of ethidium bromide was due to defective cell wall integrity, not from "petite lethality." These findings demonstrated that mitochondrial anionic lipids are required for cellular functions that are essential in cell wall biogenesis, the maintenance of cell integrity, and survival at elevated temperature. INTRODUCTIONCardiolipin (CL), a unique anionic phospholipid with dimeric structure, is ubiquitous in eukaryotes and primarily found in the mitochondrial inner membrane . CL plays a key role in mitochondrial bioenergetics (Jiang et al., 2000; Greenberg, 2000, 2002;Schlame et al., 2000;Pfeiffer et al., 2003) and is also involved in mitochondrial biogenesis (Kawasaki et al., 1999;Jiang et al., 2000). Defective remodeling of CL is associated with Barth syndrome, a severe genetic disorder characterized by cardiomyopathy, neutropenia, skeletal myopathy, and respiratory chain defects (Vreken et al., 2000). The phenotype of Barth syndrome is dependent upon multiple factors that are not well understood (Barth et al., 1983(Barth et al., , 1996. Elucidation of the functions of CL will help to clarify the abnormalities associated with this disorder.The biosynthesis of CL is conserved in eukaryotic organisms. It occurs via three enzymatic reactions , including formation of phosphatidylglycerolphosphate (PGP) from CDP-DAG and glycerol-3-P, dephosphorylation of PGP to phosphatidylglycerol (PG), and condensation of CDP-DAG and PG to form CL. Disruption of PGS1, the structural gene encoding PGP synthase, results in the complete loss of both PG and CL (Janitor et al., 1996;Chang et al., 1998a). The crd1⌬ mutant, which lacks CL synthase, has no detectable CL but accumulates PG (Jiang et al., 1997;Chang et al., 1998b;Tuller et al., 1998;Jiang et al., 2000;Pfeiffer et al., 2003;Zhong et al., 2004). The human taffazin gene (TAZ1), which is associated with Barth syndrome, encodes a transacylase that may be involved in the remodeling of CL (Xu et al., 2003). Deletion of the yeast homolog of this gene, TAZ1, leads to decreased CL, aberrant CL acyl species, and accumulation of monolysocardiolipin . Mutants deficient in CL biosynthesis exhibit growth defects at elevat...

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Section: Discussionmentioning

confidence: 99%

Loss of Function ofKRE5Suppresses Temperature Sensitivity of Mutants Lacking Mitochondrial Anionic Lipids

Zhong

Gvozdenović-Jeremić

Webster

et al. 2005

MBoC

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“…The multi-enzyme complex 1,3-b-glucan synthase is composed of the catalytic subunit FKS1p/FLs2p and the regulatory subunit Rho1p GTPase. 31 The potent inhibitory effect of micafungin on the activity of 1,3-b-glucan synthase was determined in membrane preparations of both C. albicans and A. fumigatus by measuring incorporation of [ 14 C]UDP-glucose into a trichloroacetic-acid-insoluble precipitate. The short-term exposure of C. albicans to 0.1-0.5 mg ml À1 micafungin induced abnormal swelling and irregular shape of fungal cells, a reported feature resulting from inhibition of cell wall synthesis.…”

Section: Pre-clinical Study Of Fk463mentioning

confidence: 99%

Micafungin: a sulfated echinocandin

Hashimoto

2009

J Antibiot

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Micafungin is the second approved antifungal agent in the echinocandin series and is now used worldwide in chemotherapy for life-threatening fungal infections. It is water-soluble and is semi-synthesized from the acylated cyclic hexapeptide FR901379, a natural product from the fungus Coleophoma empetri F-11899, through enzymatic deacylation of FR901379, followed by chemical reacylation with the optimized N-acyl side chain. The water solubility of micafungin is ascribed to a sulfate moiety in the molecule. This feature differentiates micafungin from other echinocandin members. Micafungin is a potent inhibitor of 1,3-b-glucan synthase, an enzyme necessary for cell-wall synthesis of several fungal pathogens. The Journal of Antibiotics (2009) and Cryptococcus neoformans are a threat to human health. Incidences of these systemic fungal infections have increased significantly over the past few years. The major reasons for this dramatic increase are the extensive use of broad-spectrum antibiotics and the growing number of immunocompromised patients with acquired immunodeficiency syndrome (AIDS), cancer and transplants. 1,2 In the mid 1900s, few compounds, such as polyenes (for example, nystatin and amphotericin B) and flucytosine, were available for antifungal chemotherapy. Although the development of azole drugs started in the early 1970s, only a limited number of antifungal agents were available for treatment of life-threatening fungal infections. Moreover, the existing agents had disadvantages, such as the significant nephrotoxicity of amphotericin B 3 and the emergence of resistance to the azoles. 4 To overcome these defects, lipid formulations of polyenes were developed to reduce toxicity, and new triazoles (for example, voriconazole, ravuconazole and posaconazole) were developed to improve the antifungal spectra or susceptibility to azoleresistant isolates. 5 Despite a number of therapeutic advancements, there was a need to develop a new class of antifungal agents with novel mechanisms of action.

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“…In Saccharomyces cerevisiae, a complex surveillance system monitors cell wall integrity. This system includes (1!3)-b-D-glucan synthase FK506 sensitivity (FKS) genes, cell-surface proteins that act as mechanosensors of changes in wall shape and a signalling cascade [14,15]. If surveillance of cell wall integrity is conserved in plants, one would expect that biotrophic fungi will have evolved means to manipulate components of cell wall integrity in order to suppress SA-dependent resistance.…”

Section: Introductionmentioning

confidence: 99%

Knocking on the heaven’s wall: pathogenesis of and resistance to biotrophic fungi at the cell wall

Schulze‐Lefert

2004

Current Opinion in Plant Biology

124

101

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New findings challenge the traditional view of the plant cell wall as passive structural barrier to invasion by fungal microorganisms. A surveillance system for cell wall integrity appears to sense perturbation of the cell wall structure upon fungal attack and is interconnected with known plant defence signalling pathways. Biotrophic fungi might manipulate this surveillance system for the establishment of biotrophy. The attempts of fungi to invade also induce a sub-cellular polarisation in attacked cells, which activates an ancient vesicle-associated resistance response that possibly enables the focal transport of regulatory cargo and the secretion of toxic cargo. The underlying resistance machinery might have been subverted by biotrophic fungi for pathogenesis. IntroductionPenetration through the plant cell wall represents an Achilles heel in the pathogenesis of most biotrophic fungi and marks a lifestyle transition from extra-cellular to invasive growth. Modification of the plant cell wall was recognised for the first time as potential resistance mechanism almost 80 years ago following work in which 78 plant species and varieties were challenged with Alternaria spp. and other leaf-spotting fungi [1]. The termination of fungal pathogenesis at the cell wall was commonly associated with wall 'thickenings' and the formation of local additions or 'callosities' in the paramural space (i.e. the space between the cell wall and the plasma membrane). Formation of these cell wall appositions (CWAs) or papillae is usually accompanied by a co-localised accumulation of phenolics and reactive oxygen species [2][3][4][5][6]. The complex process of sub-cellular cell wall remodelling is tightly linked to the rapid disassembly and subsequent focal reassembly of the plant cytoskeleton at fungal entry sites, which is indicative of a pathogen-triggered cell polarisation [6][7][8][9]. There has been a long-standing controversy, however, over whether CWAs function in disease resistance or facilitate the entry of fungal pathogens into host cells by providing a structural collar for the intruder. New molecular genetic data from Arabidopsis and barley have indeed revealed that molecular processes at and in CWAs have Janus-faced functions, that is, functions for fungal pathogenesis and in resistance responses. Focal vesicle transport and vesicle fusion events that are dependent on SNAP (soluble N-ethylmaleimide-sensitive-factor-association protein) receptor (SNARE) proteins at the plasma membrane emerge as potential common underlying mechanisms that might be interconnected with a poorly understood cell wall integrity surveillance system. In this review, I discuss the seemingly paradoxical functions of these processes in establishing the biotrophic lifestyle and in disease resistance at the cell periphery.Linking cell wall structure to biotic stress signalling Callose, a (1!3)-b-D-glucan, has long been known to be synthesised and deposited rapidly at CWAs upon microbial attack. This polymer was thought to contribute to a physical barrie...

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Identification of Yeast Rho1p GTPase as a Regulatory Subunit of 1,3-β-Glucan Synthase

Cited by 436 publications

References 21 publications

Loss of Function ofKRE5Suppresses Temperature Sensitivity of Mutants Lacking Mitochondrial Anionic Lipids

Loss of Function ofKRE5Suppresses Temperature Sensitivity of Mutants Lacking Mitochondrial Anionic Lipids

Micafungin: a sulfated echinocandin

Knocking on the heaven’s wall: pathogenesis of and resistance to biotrophic fungi at the cell wall

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