Yno1p/Aim14p, a NADPH-oxidase ortholog, controls extramitochondrial reactive oxygen species generation, apoptosis, and actin cable formation in yeast

Abstract

The large protein superfamily of NADPH oxidases (NOX enzymes) is found in members of all eukaryotic kingdoms: animals, plants, fungi, and protists. The physiological functions of these NOX enzymes range from defense to specialized oxidative biosynthesis and to signaling. In filamentous fungi, NOX enzymes are involved in signaling cell differentiation, in particular in the formation of fruiting bodies. On the basis of bioinformatics analysis, until now it was believed that the genomes of unicellular fungi like Saccharomyces cerevisiae and Schizosaccharomyces pombe do not harbor genes coding for NOX enzymes. Nevertheless, the genome of S. cerevisiae contains nine ORFs showing sequence similarity to the catalytic subunits of mammalian NOX enzymes, only some of which have been functionally assigned as ferric reductases involved in iron ion transport. Here we show that one of the nine ORFs (YGL160W, AIM14) encodes a genuine NADPH oxidase, which is located in the endoplasmic reticulum (ER) and produces superoxide in a NADPH-dependent fashion. We renamed this ORF YNO1 (yeast NADPH oxidase 1). Overexpression of YNO1 causes YCA1-dependent apoptosis, whereas deletion of the gene makes cells less sensitive to apoptotic stimuli. Several independent lines of evidence point to regulation of the actin cytoskeleton by reactive oxygen species (ROS) produced by Yno1p.cell cycle | integral membrane reductase | wiskostatin | latrunculin R eactive oxygen species (ROS) have multiple roles in physiology and pathophysiology, in particular during aging and induction of programmed cell death. This includes also nonmitochondrial sources, besides the long-studied mitochondrially generated ROS. These findings can be viewed as important additions to the classical "free radical theory of aging" (1) and theories developed thereafter (2, 3).In higher organisms, among others, at least two major sources of superoxide other than mitochondria are known. On the one hand, xanthine oxidase, an enzyme in the catabolism of purines, which catalyses the oxidation of hypoxanthine to xanthine and to uric acid, produces superoxide (4). On the other hand, NADPH oxidases (NOX) catalyze the production of superoxide from oxygen and NADPH (5).The NADPH oxidase superfamily of membrane-located enzymes of higher cells has been known for a decade (for review, ref. 5). Whereas the human NOX2 was discovered early on, other NOX (Nox1/3/4/5) as well as dual oxidase (DUOX) (Duox1/2) enzymes (displaying two domains: a NADPH oxidase domain and a peroxidase domain) have been found relatively recently in human cells. The human NOX2 was discovered as a defense enzyme of neutrophils and macrophages, which produce a burst of superoxide (O 2 · − ) as a first line of defense against invading microorganisms. Although X-ray or NMR structure determinations are not available, we know from indirect evidence and bioinformatics that the catalytic subunit of the macrophage enzyme contains six transmembrane helices, is located in the plasma membrane, and produces superoxide in a vectorial ...

NADPH oxidases regulate septin-mediated cytoskeletal remodeling during plant infection by the rice blast fungus

“…When considered together, our results are consistent with a model whereby the M. oryzae Nox2/NoxR complex is essential for septin-mediated Factin assembly at the appressorium pore, which is a prerequisite for penetration peg formation and rice infection. In Saccharomyces cerevisiae, a recently identified Nox-encoding gene, YNO1, has also been implicated in actin cable formation (30), suggesting that regulation of F-actin dynamics may be one of the key underlying mechanisms by which Nox exert their diverse roles in cellular differentiation. In M. oryzae, Nox2 is regulated as part of a complex involving NoxR and is also known to interact with Rac1 (31), a small GTPase involved in polarized cell growth and also implicated in F-actin dynamics.…”

New Insights Into the Roles of NADPH Oxidases in Sexual Development and Ascospore Germination in Sordaria macrospora

“…These authors showed that Δnox1 still initated penetration peg formation but was unable to proliferate in the infected plant tissue. Furthermore, Yno1p, the NOX enzyme from yeast, has a regulatory role in actin remodeling (Rinnerthaler et al 2012). Interestingly, F-actin remodeling is also crucial for CAT fusion in N. crassa (Roca et al 2010).…”

Redox regulation of the yeast voltage-gated Ca2+ channel homolog Cch1p by glutathionylation of specific cysteine residues

“…The current study reveals that Cch1p responds to both fast activation (high pH and H 2 O 2 ) and slow activation stress (tunicamycin and mating pheromones) in a similar manner that parallels the redox changes observed in the cell. Indeed, these various stress responses and triggers in yeast cells have been reported to result in oxidative stress (Pozniakovsky et al, 2005;Rinnerthaler et al, 2012;Viladevall et al, 2004;Zhang et al, 2006), underlining the possibility that activation of Cch1p is a conserved redox-dependent mechanism.…”

“…Slow activation mechanisms, like mating pheromone exposure, have also been shown to produce reactive oxygen species (ROS) in S. cerevisiae cells (Pozniakovsky et al, 2005;Zhang et al, 2006). Similarly, tunicamycin has also been shown to generate ROS in WT yeast cells (Rinnerthaler et al, 2012). Thus, it was of interest to determine whether an alteration in the redox environment of the cytosol might be causing these slow and fast activation effects, and the oxidizing state might be the common activation mechanism.…”