Newborn daughters get a fresh start through PI(3,5)P2-mediated vacuolar acidification.

Huda et al. (https://doi.org/10.

Structure of yeast RAVE bound to a partial V complex.

Vacuolar-type ATPases (V-ATPases) are membrane-embedded proton pumps that acidify intracellular compartments in almost all eukaryotic cells. Homologous with ATP synthases, these multisubunit enzymes consist of a soluble catalytic V subcomplex and a membrane-embedded proton-translocating V subcomplex. The V and V subcomplexes can undergo reversible dissociation to regulate proton pumping, with reassociation of V and V requiring the protein complex known as RAVE (regulator of the ATPase of vacuoles and endosomes).

V-ATPase Disassembly at the Yeast Lysosome-Like Vacuole Is a Phenotypic Driver of Lysosome Dysfunction in Replicative Aging.

Declines in lysosomal acidification and function with aging are observed in organisms ranging from yeast to humans. V-ATPases play a central role in organelle acidification and V-ATPase activity is regulated by reversible disassembly in many different settings. Using the yeast as a replicative aging model, we demonstrate that V-ATPases disassemble into their V and V subcomplexes in aging cells, with release of V subunit C (Vma5) from the lysosome-like vacuole into the cytosol.

Structure of yeast RAVE bound to a partial V complex.

Vacuolar-type ATPases (V-ATPases) are membrane-embedded proton pumps that acidify intracellular compartments in almost all eukaryotic cells. Homologous with ATP synthases, these multi-subunit enzymes consist of a soluble catalytic V subcomplex and a membrane-embedded proton-translocating V subcomplex. The V and V subcomplexes can undergo reversible dissociation to regulate proton pumping, with reassociation of V and V requiring the protein complex known as RAVE (regulator of the A TPase of v acuoles and e ndosomes).

Human V-ATPase a-subunit isoforms bind specifically to distinct phosphoinositide phospholipids.

Vacuolar H-ATPases (V-ATPases) are highly conserved multisubunit enzymes that maintain the distinct pH of eukaryotic organelles. The integral membrane a-subunit is encoded by tissue- and organelle-specific isoforms, and its cytosolic N-terminal domain (aNT) modulates organelle-specific regulation and targeting of V-ATPases. Organelle membranes have specific phosphatidylinositol phosphate (PIP) lipid enrichment linked to maintenance of organelle pH.

The cytosolic N-terminal domain of V-ATPase a-subunits is a regulatory hub targeted by multiple signals.

Vacuolar H-ATPases (V-ATPases) acidify several organelles in all eukaryotic cells and export protons across the plasma membrane in a subset of cell types. V-ATPases are multisubunit enzymes consisting of a peripheral subcomplex, V, that is exposed to the cytosol and an integral membrane subcomplex, V, that contains the proton pore. The V a-subunit is the largest membrane subunit and consists of two domains.

Human V-ATPase a-subunit isoforms bind specifically to distinct phosphoinositide phospholipids.

V-ATPases are highly conserved multi-subunit enzymes that maintain the distinct pH of eukaryotic organelles. The integral membrane a-subunit is encoded by tissue and organelle specific isoforms, and its cytosolic N-terminal domain (aNT) modulates organelle specific regulation and targeting of V-ATPases. Organelle membranes have specific phosphatidylinositol phosphate (PIP) lipid enrichment linked to maintenance of organelle pH.

Inpatient Transition From Intravenous to Inhaled Treprostinil in a Pediatric Patient.

We report a case of a 7-year old male with idiopathic pulmonary arterial hypertension, successfully transitioned from an intravenous infusion to inhaled treprostinil during inpatient admission, after his intentional removal of multiple central venous catheters. He had no clinical, echocardiographic, or serum biomarker evidence of loss of control of pulmonary arterial hypertension during the 4-day transition. The patient was discharged home without complications, and 3 weeks after discharge the patient's pulmonary hypertension remained well controlled per clinical and echocardiographic evidence, including a significantly improved 6-minute walk distance test.

Chimeric a-subunit isoforms generate functional yeast V-ATPases with altered regulatory properties in vitro and in vivo.

V-ATPases are highly regulated proton pumps that acidify organelles. The V-ATPase a-subunit is a two-domain protein containing a C-terminal transmembrane domain responsible for proton transport and an N-terminal cytosolic domain (aNT) that is a regulatory hub, integrating environmental inputs to regulate assembly, localization, and V-ATPase activity. The yeast encodes only two organelle-specific a-isoforms, Stv1 in the Golgi and Vph1 in the vacuole.

A dual action small molecule enhances azoles and overcomes resistance through co-targeting Pdr5 and Vma1.

Fungal infection threatens human health worldwide due to the limited arsenal of antifungals and the rapid emergence of resistance. Epidermal growth factor receptor (EGFR) is demonstrated to mediate epithelial cell endocytosis of the leading human fungal pathogen, Candida albicans. However, whether EGFR inhibitors act on fungal cells remains unknown.

Adaptive laboratory evolution in S. cerevisiae highlights role of transcription factors in fungal xenobiotic resistance.

In vitro evolution and whole genome analysis were used to comprehensively identify the genetic determinants of chemical resistance in Saccharomyces cerevisiae. Sequence analysis identified many genes contributing to the resistance phenotype as well as numerous amino acids in potential targets that may play a role in compound binding. Our work shows that compound-target pairs can be conserved across multiple species.

Valproate activates the Snf1 kinase in Saccharomyces cerevisiae by decreasing the cytosolic pH.

Valproate (VPA) is a widely used mood stabilizer, but its therapeutic mechanism of action is not understood. This knowledge gap hinders the development of more effective drugs with fewer side effects. Using the yeast model to elucidate the effects of VPA on cellular metabolism, we determined that the drug upregulated expression of genes normally repressed during logarithmic growth on glucose medium and increased levels of activated (phosphorylated) Snf1 kinase, the major metabolic regulator of these genes.

RAVE and Rabconnectin-3 Complexes as Signal Dependent Regulators of Organelle Acidification.

The yeast RAVE (Regulator of H-ATPase of Vacuolar and Endosomal membranes) complex and Rabconnectin-3 complexes of higher eukaryotes regulate acidification of organelles such as lysosomes and endosomes by catalyzing V-ATPase assembly. V-ATPases are highly conserved proton pumps consisting of a peripheral V subcomplex that contains the sites of ATP hydrolysis, attached to an integral membrane V subcomplex that forms the transmembrane proton pore. Reversible disassembly of the V-ATPase is a conserved regulatory mechanism that occurs in response to multiple signals, serving to tune ATPase activity and compartment acidification to changing extracellular conditions.

Defining steps in RAVE-catalyzed V-ATPase assembly using purified RAVE and V-ATPase subcomplexes.

The vacuolar H-ATPase (V-ATPase) is a highly conserved proton pump responsible for the acidification of intracellular organelles in virtually all eukaryotic cells. V-ATPases are regulated by the rapid and reversible disassembly of the peripheral V domain from the integral membrane V domain, accompanied by release of the V C subunit from both domains. Efficient reassembly of V-ATPases requires the Regulator of the H-ATPase of Vacuoles and Endosomes (RAVE) complex in yeast.

Regulation of V-ATPase Activity and Organelle pH by Phosphatidylinositol Phosphate Lipids.

Luminal pH and the distinctive distribution of phosphatidylinositol phosphate (PIP) lipids are central identifying features of organelles in all eukaryotic cells that are also critical for organelle function. V-ATPases are conserved proton pumps that populate and acidify multiple organelles of the secretory and the endocytic pathway. Complete loss of V-ATPase activity causes embryonic lethality in higher animals and conditional lethality in yeast, while partial loss of V-ATPase function is associated with multiple disease states.

Whole exome sequencing identified ATP6V1C2 as a novel candidate gene for recessive distal renal tubular acidosis.

Distal renal tubular acidosis is a rare renal tubular disorder characterized by hyperchloremic metabolic acidosis and impaired urinary acidification. Mutations in three genes (ATP6V0A4, ATP6V1B1 and SLC4A1) constitute a monogenic causation in 58-70% of familial cases of distal renal tubular acidosis. Recently, mutations in FOXI1 have been identified as an additional cause.

Interaction between the yeast RAVE complex and Vph1-containing V sectors is a central glucose-sensitive interaction required for V-ATPase reassembly.

The yeast vacuolar H-ATPase (V-ATPase) of budding yeast () is regulated by reversible disassembly. Disassembly inhibits V-ATPase activity under low-glucose conditions by releasing peripheral V subcomplexes from membrane-bound V subcomplexes. V-ATPase reassembly and reactivation requires intervention of the conserved regulator of H-ATPase of vacuoles and endosomes (RAVE) complex, which binds to cytosolic V subcomplexes and assists reassembly with integral membrane V complexes.

Recognition and management of food allergy in children.

Incidence of food allergy has been increasing and is more commonly seen in children. Allergic reactions can vary, with symptoms ranging from mild to severe. This article aims to explore the immunological mechanisms involved in food allergy, as well as distinguishing between immunoglobulin E (IgE) mediated and non-IgE-mediated reactions.

Interaction of the late endo-lysosomal lipid PI(3,5)P2 with the Vph1 isoform of yeast V-ATPase increases its activity and cellular stress tolerance.

The low-level endo-lysosomal signaling lipid, phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), is required for full assembly and activity of vacuolar H-ATPases (V-ATPases) containing the vacuolar a-subunit isoform Vph1 in yeast. The cytosolic N-terminal domain of Vph1 is also recruited to membranes in a PI(3,5)P2-dependent manner, but it is not known if its interaction with PI(3,5)P2 is direct. Here, using biochemical characterization of isolated yeast vacuolar vesicles, we demonstrate that addition of exogenous short-chain PI(3,5)P2 to Vph1-containing vacuolar vesicles activates V-ATPase activity and proton pumping.

Some assembly required: Contributions of Tom Stevens' lab to the V-ATPase field.

Tom Stevens' lab has explored the subunit composition and assembly of the yeast V-ATPase for more than 30 years. Early studies helped establish yeast as the predominant model system for study of V-ATPase proton pumps and led to the discovery of protein splicing of the V-ATPase catalytic subunit. The Vma phenotype, characteristic of loss-of-V-ATPase activity in yeast was key in determining the enzyme's subunit composition via yeast genetics.

Compensatory Internalization of Pma1 in V-ATPase Mutants in Requires Calcium- and Glucose-Sensitive Phosphatases.

Loss of V-ATPase activity in organelles, whether through V-ATPase inhibition or V-ATPase () mutations, triggers a compensatory downregulation of the essential plasma membrane proton pump Pma1 in We have previously determined that the α-arrestin Rim8 and ubiquitin ligase Rsp5 are essential for Pma1 ubiquination and endocytosis in response to loss of V-ATPase activity. Here, we show that Pma1 endocytosis in V-ATPase mutants does not require Rim101 pathway components upstream and downstream of Rim8, indicating that Rim8 is acting independently in Pma1 internalization. We find that two phosphatases, the calcium-responsive phosphatase calcineurin and the glucose-sensitive phosphatase Glc7 (PP1), and one of the Glc7 regulatory subunits Reg1, exhibit negative synthetic genetic interactions with mutants, and demonstrate that both phosphatases are essential for ubiquitination and endocytic downregulation of Pma1 in these mutants.