Actin and Endocytosis in Budding Yeast

Goode, Bruce L.; Eskin, Julian A.; Wendland, Beverly

doi:10.1534/genetics.112.145540

Cited by 216 publications

(249 citation statements)

References 428 publications

(650 reference statements)

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“…Kymograph analysis revealed that cell elongation in LatA-treated sty1Δ and wis1Δ cells gradually declines over time (Figure 2B). This could be explained as follows: (1) in the initial period after LatA treatment, tip-localized active Cdc42 can drive cell elongation through positive regulation of exocytosis [29]; (2) however, after LatA treatment, membrane proteins involved in exocytosis would no longer be recycled by endocytic retrieval from the plasma membrane, because endocytosis in yeasts depends on the actin cytoskeleton [30]; and therefore (3) such proteins will eventually be depleted from cytoplasmic pools, ultimately leading to cessation of elongation.…”

Section: Resultsmentioning

confidence: 99%

Remodeling of the Fission Yeast Cdc42 Cell-Polarity Module via the Sty1 p38 Stress-Activated Protein Kinase Pathway

2016

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SummaryThe Rho family GTPase Cdc42 is a key regulator of eukaryotic cellular organization and cell polarity [1]. In the fission yeast Schizosaccharomyces pombe, active Cdc42 and associated effectors and regulators (the “Cdc42 polarity module”) coordinate polarized growth at cell tips by controlling the actin cytoskeleton and exocytosis [2, 3, 4]. Localization of the Cdc42 polarity module to cell tips is thus critical for its function. Here we show that the fission yeast stress-activated protein kinase Sty1, a homolog of mammalian p38 MAP kinase, regulates localization of the Cdc42 polarity module. In wild-type cells, treatment with latrunculin A, a drug that leads to actin depolymerization, induces dispersal of the Cdc42 module from cell tips and cessation of polarized growth [5, 6]. We show that latrunculin A treatment also activates the Sty1 MAP kinase pathway and, strikingly, we find that loss of Sty1 MAP kinase signaling prevents latrunculin A-induced dispersal of the Cdc42 module, allowing polarized growth even in complete absence of the actin cytoskeleton. Regulation of the Cdc42 module by Sty1 is independent of Sty1’s role in stress-induced gene expression. We also describe a system for activation of Sty1 kinase “on demand” in the absence of any external stress, and use this to show that Sty1 activation alone is sufficient to disperse the Cdc42 module from cell tips in otherwise unperturbed cells. During nitrogen-starvation-induced quiescence, inhibition of Sty1 converts non-growing, depolarized cells into growing, polarized cells. Our results place MAP kinase Sty1 as an important physiological regulator of the Cdc42 polarity module.

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Section: Resultsmentioning

confidence: 99%

Remodeling of the Fission Yeast Cdc42 Cell-Polarity Module via the Sty1 p38 Stress-Activated Protein Kinase Pathway

2016

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“…albicans strains lacking ARP2 or ARP3 have dramatic actin cytoskeleton defects and delayed rates of endocytosis [17]. A common feature of cells with endocytic defects and depolarized actin patches is hyperactivity of cell wall stress pathways [19]. We assessed whether the mutants in our study also exhibited endocytic defects accompanying the activation of cell wall stress.…”

Section: Resultsmentioning

confidence: 99%

Functional Genomic Analysis of Candida albicans Adherence Reveals a Key Role for the Arp2/3 Complex in Cell Wall Remodelling and Biofilm Formation

et al. 2016

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Fungal biofilms are complex, structured communities that can form on surfaces such as catheters and other indwelling medical devices. Biofilms are of particular concern with Candida albicans, one of the leading opportunistic fungal pathogens of humans. C. albicans biofilms include yeast and filamentous cells that are surrounded by an extracellular matrix, and they are intrinsically resistant to antifungal drugs such that resolving biofilm infections often requires surgery to remove the contaminated device. C. albicans biofilms form through a regulated process of adhesion to surfaces, filamentation, maturation, and ultimately dispersion. To uncover new strategies to block the initial stages of biofilm formation, we utilized a functional genomic approach to identify genes that modulate C. albicans adherence. We screened a library of 1,481 double barcoded doxycycline-repressible conditional gene expression strains covering ~25% of the C. albicans genome. We identified five genes for which transcriptional repression impaired adherence, including: ARC18, PMT1, MNN9, SPT7, and orf19.831. The most severe adherence defect was observed upon transcriptional repression of ARC18, which encodes a member of the Arp2/3 complex that is involved in regulation of the actin cytoskeleton and endocytosis. Depletion of components of the Arp2/3 complex not only impaired adherence, but also caused reduced biofilm formation, increased cell surface hydrophobicity, and increased exposure of cell wall chitin and β-glucans. Reduced function of the Arp2/3 complex led to impaired cell wall integrity and activation of Rho1-mediated cell wall stress responses, thereby causing cell wall remodelling and reduced adherence. Thus, we identify important functional relationships between cell wall stress responses and a novel mechanism that controls adherence and biofilm formation, thereby illuminating novel strategies to cripple a leading fungal pathogen of humans.

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“…Such clarification should have significance far beyond the understanding of Chlamydomonas itself, as this alga can now serve as an experimentally tractable representative not only of the plant superkingdom (where genetic studies of actin function are challenging because of the multitude of actin genes) but also of at least some fraction (Rogozin et al 2009) of the vast majority of the eukaryotic world that lies outside of the opisthokonts (animals, fungi, and their close relatives), where most studies of actin function have been done. For example, is the role of actin in endocytosis, well documented in the opisthokonts (Goode et al 2015), universal (and thus presumably ancestral) in eukaryotes more generally? Does the formation of cleavage furrows (which is nearly universal in eukaryotes other than higher plants) always involve actin (Balasubramanian et al 2012), even though type-II myosin (a component of the opisthokont actomyosin ring) is not present in groups other than the opisthokonts and their "close" relatives the amoebozoa (Richards and Cavalier-Smith 2005)?…”

Section: Discussionmentioning

confidence: 99%

Evidence That an Unconventional Actin Can Provide Essential F-Actin Function and That a Surveillance System Monitors F-Actin Integrity inChlamydomonas

2015

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Actin is one of the most conserved eukaryotic proteins. It is thought to have multiple essential cellular roles and to function primarily or exclusively as filaments ("F-actin"). Chlamydomonas has been an enigma, because a null mutation (ida5-1) in its single gene for conventional actin does not affect growth. A highly divergent actin gene, NAP1, is upregulated in ida5-1 cells, but it has been unclear whether NAP1 can form filaments or provide actin function. Here, we used the actin-depolymerizing drug latrunculin B (LatB), the F-actin-specific probe Lifeact-Venus, and genetic and molecular methods to resolve these issues. LatB-treated wild-type cells continue to proliferate; they initially lose Lifeact-stained structures but recover them concomitant with upregulation of NAP1. Thirty-nine LatB-sensitive mutants fell into four genes (NAP1 and LAT1-LAT3) in which we identified the causative mutations using a novel combinatorial pool-sequencing strategy. LAT1-LAT3 are required for NAP1 upregulation upon LatB treatment, and ectopic expression of NAP1 largely rescues the LatB sensitivity of the lat1-lat3 mutants, suggesting that the LAT gene products comprise a regulatory hierarchy with NAP1 expression as the major functional output. Selection of LatB-resistant revertants of a nap1 mutant yielded dominant IDA5 mutations that presumably render F-IDA5 resistant to LatB, and nap1 and lat mutations are synthetically lethal with ida5-1 in the absence of LatB. We conclude that both IDA5 and the divergent NAP1 can form filaments and redundantly provide essential F-actin functions and that a novel surveillance system, probably responding to a loss of F-actin, triggers NAP1 expression and perhaps other compensatory responses.

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Actin and Endocytosis in Budding Yeast

Cited by 216 publications

References 428 publications

Remodeling of the Fission Yeast Cdc42 Cell-Polarity Module via the Sty1 p38 Stress-Activated Protein Kinase Pathway

Remodeling of the Fission Yeast Cdc42 Cell-Polarity Module via the Sty1 p38 Stress-Activated Protein Kinase Pathway

Functional Genomic Analysis of Candida albicans Adherence Reveals a Key Role for the Arp2/3 Complex in Cell Wall Remodelling and Biofilm Formation

Evidence That an Unconventional Actin Can Provide Essential F-Actin Function and That a Surveillance System Monitors F-Actin Integrity inChlamydomonas

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