Multi-cancer V-ATPase molecular signatures: A distinctive balance of subunit C isoforms in esophageal carcinoma.

BACKGROUND: V-ATPases are hetero-oligomeric enzymes consisting of 13 subunits and playing key roles in ion homeostasis and signaling. Differential expression of these proton pumps has been implicated in carcinogenesis and metastasis. To elucidate putative molecular signatures underlying these phenomena, we evaluated the expression of V-ATPase genes in esophageal squamous cell carcinoma (ESCC) and extended the analysis to other cancers. METHODS: Expression of all V-ATPase genes were analyzed in ESCC by a microarray data and in different types of tumors available from public databases. Expression of C isoforms was validated by qRT-PCR in paired ESCC samples. FINDINGS: A differential expression pattern of V-ATPase genes was found in different tumors, with combinations in up- and down-regulation leading to an imbalance in the expression ratios of their isoforms. Particularly, a high C1 and low C2 expression pattern accurately discriminated ESCC from normal tissues. Structural modeling of C2a isoform uncovered motifs for oncogenic kinases in an additional peptide stretch, and an actin-biding domain downstream to this sequence. INTERPRETATION: Altogether these data revealed that the expression ratios of subunits/isoforms could form a conformational code that controls the H+ pump regulation and interactions related to tumorigenesis. This study establishes a paradigm change by uncovering multi-cancer molecular signatures present in the V-ATPase structure, from which future studies must address the complexity of the onco-related V-ATPase assemblies as a whole, rather than targeting changes in specific subunit isoforms. FUNDING: This work was supported by grants from CNPq and FAPERJ-Brazil.

Expression of ATP6V1C1 during oral carcinogenesis.

We investigated the gene and protein expressions of V-type ATPase protein subunit C1 (ATP6V1C1) in cases of oral squamous cell carcinoma (OSCC) and contralateral normal mucosa in smokers, nonsmokers and former smokers. Subjects were separated into five groups of 15: group 1, smokers with OSCC; group 2, normal contralateral mucosa of OSCC patients; group 3, chronic smokers; group 4, former smokers who had stopped smoking 1 year earlier; group 5, individuals who had never smoked. Exfoliative cytology specimens from oral mucosa of smokers, former smokers and nonsmokers showed normal gene and protein expression. We found significantly greater gene expression in the OSCC group than in the nonsmoker groups. No difference in gene expression was observed between normal contralateral mucosa and nonsmoker groups, smoker and nonsmoker groups or former smoker and nonsmoker groups. We observed intense immunostaining for ATP6V1C1 protein in all cases of OSCC and weak or no staining in smoker, former smoker and nonsmoker groups. Significantly greater expression of ATP6V1C1 protein was observed in the OSCC group compared to the other groups, which supports the role of ATP6V1C1 in effecting changes associated with oral cancer. Analysis of the mucosae of chronic smokers, former smokers and the normal contralateral mucosa of patients with OSCC showed unaltered ATP6V1C1 gene and protein expression. Early stages of carcinogenesis, represented by altered epithelium of chronic smokers, had neither gene nor protein alterations as seen in OSCC. Therefore, we infer that the changes in ATP6V1C1 occur during later stages of carcinogenesis. Our preliminary study provides a basis for future studies of using ATP6V1C1 levels for detecting early stage OSCC.

An update in the structure, function, and regulation of V-ATPases: the role of the C subunit / Uma atualização na estrutura, função e regulação das V-ATPases: o papel das subunidades C

Vacuolar ATPases (V-ATPases) are present in specialized proton secretory cells in which they pump protons across the membranes of various intracellular organelles and across the plasma membrane. The proton transport mechanism is electrogenic and establishes an acidic pH and a positive transmembrane potential in these intracellular and extracellular compartments. V-ATPases have been found to be practically identical in terms of the composition of their subunits in all eukaryotic cells. They have two distinct structures: a peripheral catalytic sector (V1) and a hydrophobic membrane sector (V0) responsible for driving protons. V-ATPase activity is regulated by three different mechanisms, which control pump density, association/dissociation of the V1 and V0 domains, and secretory activity. The C subunit is a 40-kDa protein located in the V1 domain of V-ATPase. The protein is encoded by the ATP6V1C gene and is located at position 22 of the long arm of chromosome 8 (8q22.3). The C subunit has very important functions in terms of controlling the regulation of the reversible dissociation of V-ATPases.

As Vacuolar ATPases (V-ATPases) estão presentes nas células especializadas em secreção de protões, nas quais eles são bombeados através das membranas de vários organelos intracelulares e da membrana plasmática. O mecanismo de transporte de protões é eletrogênico e estabelece um pH ácido e um potencial transmembrana positivo nestes compartimentos intracelulares e extracelulares. As V-ATPases foram encontradas em todas as células eucarióticas, praticamente idênticas em termos de composição das suas subunidades. Elas têm duas estruturas distintas: um setor periférico catalítico (V1) e uma membrana hidrofóbica (V0), responsável pela condução de protões. A atividade das V-ATPases é regulada por três mecanismos diferentes, os quais controlam a densidade de bomba, associação/dissociação de domínios V1 e V0, e a atividade secretora. A subunidade C é uma proteína de 40-kDa, localizada no domínio V1 da V-ATPase. Essa proteína é codificada pelo gene ATP6V1C e está localizada na posição 22 do braço longo do cromossomo 8 (8q22.3). A subunidade C tem funções muito importantes em termos de controle do regulamento da dissociação reversível da V-ATPase.

An update in the structure, function, and regulation of V-ATPases: the role of the C subunit

Vacuolar ATPases (V-ATPases) are present in specialized proton secretory cells in which they pump protons across the membranes of various intracellular organelles and across the plasma membrane. The proton transport mechanism is electrogenic and establishes an acidic pH and a positive transmembrane potential in these intracellular and extracellular compartments. V-ATPases have been found to be practically identical in terms of the composition of their subunits in all eukaryotic cells. They have two distinct structures: a peripheral catalytic sector (V1) and a hydrophobic membrane sector (V0) responsible for driving protons. V-ATPase activity is regulated by three different mechanisms, which control pump density, association/dissociation of the V1 and V0 domains, and secretory activity. The C subunit is a 40-kDa protein located in the V1 domain of V-ATPase. The protein is encoded by the ATP6V1C gene and is located at position 22 of the long arm of chromosome 8 (8q22.3). The C subunit has very important functions in terms of controlling the regulation of the reversible dissociation of V-ATPases.

As Vacuolar ATPases (V-ATPases) estão presentes nas células especializadas em secreção de protões, nas quais eles são bombeados através das membranas de vários organelos intracelulares e da membrana plasmática. O mecanismo de transporte de protões é eletrogênico e estabelece um pH ácido e um potencial transmembrana positivo nestes compartimentos intracelulares e extracelulares. As V-ATPases foram encontradas em todas as células eucarióticas, praticamente idênticas em termos de composição das suas subunidades. Elas têm duas estruturas distintas: um setor periférico catalítico (V1) e uma membrana hidrofóbica (V0), responsável pela condução de protões. A atividade das V-ATPases é regulada por três mecanismos diferentes, os quais controlam a densidade de bomba, associação/dissociação de domínios V1 e V0, e a atividade secretora. A subunidade C é uma proteína de 40-kDa, localizada no domínio V1 da V-ATPase. Essa proteína é codificada pelo gene ATP6V1C e está localizada na posição 22 do braço longo do cromossomo 8 (8q22.3). A subunidade C tem funções muito importantes em termos de controle do regulamento da dissociação reversível da V-ATPase.