HCO3(-) reabsorption in the renal tubules plays a critically important role in maintaining the global acid-base balance. Loss of HCO3(-) causes metabolic acidosis. Proximal renal tubule is the major site for HCO3(-) reabsorption, accounting for more than 80% of total HCO3(-) reabsorption along the nephron. Over the past more than half centuries, tremendous progresses have been made on understanding the molecular mechanisms underlying the HCO3(-) reabsorption in proximal tubules. The transepithelial movement of HCO3(-) involves the coordinated operation of machineries on both the apical and the basolateral membranes of the epithelial cells. On the apical domain, Na(+)-H(+) exchanger NHE3 and the vacuolar H(+)-ATPase are two major pathways mediating the apical uptake of HCO3(-)-related species. Taken together, NHE3 and H(+)-ATPase are responsible for about 80% of HCO3(-) reabsorption in the proximal tubule. The remaining 20% is likely mediated by pathways yet to be characterized. On the basolateral membrane, NBCe1 represents the only major known pathway mediating the extrusion of HCO3(-) coupled with Na(+) into the interstitial space. In the present article, we provide a historical view about the studies on the mechanisms of HCO3(-) reabsorption since 1940s. Moreover, we summarize the latest progresses emerging over the past decade in the physiological as well as pathological roles of acid-base transporters underlying the HCO3(-) reabsorption in proximal tubules.
Acidosis ; physiopathology ; Animals ; Bicarbonates ; metabolism ; Humans ; Kidney Tubules, Proximal ; physiopathology ; Sodium-Hydrogen Exchangers ; physiology ; Vacuolar Proton-Translocating ATPases ; physiology

Objective: To investigate the clinical presentation and genetic characteristics of malignant infantile osteopetrosis. Methods: This was a retrospective case study. Thirty-seven children with malignant infantile osteopetrosis admitted into Beijing Children's Hospital from January 2013 to September 2022 were enrolled in this study. According to the gene mutations, the patients were divided into the CLCN7 group and the TCIRG1 group. Clinical characteristics, laboratory tests, and prognosis were compared between two groups. Wilcoxon test or Fisher exact test were used in inter-group comparison. The survival rate was estimated with the Kaplan-Meier method and the Log-Rank test was used to compare the difference in survival between groups. Results: Among the 37 cases, there were 22 males and 15 females. The age of diagnosis was 0.5 (0.2, 1.0) year. There were 13 patients (35%) and 24 patients (65%) with mutations in CLCN7 and TCIRGI gene respectively. Patients in the CLCN7 group had an older age of diagnosis than those in the TCIRGI group (1.2 (0.4, 3.6) vs. 0.4 (0.2, 0.6) years, Z=-2.60, P=0.008). The levels of serum phosphorus (1.7 (1.3, 1.8) vs. 1.1 (0.8, 1.6) mmol/L, Z=-2.59, P=0.010), creatine kinase isoenzyme (CK-MB) (457 (143, 610) vs. 56 (37, 82) U/L, Z=-3.38, P=0.001) and the level of neutrophils (14.0 (9.9, 18.1) vs. 9.2 (6.7, 11.1) ×10⁹/L, Z=-2.07, P=0.039) at diagnosis were higher in the CLCN7 group than that in the TCIRG1 group. However, the level of D-dimer in the CLCN7 group was lower than that in the TCIRGI group (2.7 (1.0, 3.1) vs. 6.3 (2.5, 9.7) μg/L, Z=2.83, P=0.005). After hematopoietic stem cell transplantation, there was no significant difference in 5-year overall survival rate between the two groups (92.3%±7.4% vs. 83.3%±7.6%, χ²=0.56, P=0.456). Conclusions: TCIRGI gene mutations are more common in children with osteopetrosis. Children with TCIRGI gene mutations have younger age, lower levels of phosphorus, CK-MB, and neutrophils and higher level of D-dimer at the onset. After hematopoietic stem cell transplantation, patients with CLCN7 or TCIRGI gene mutations have similar prognosis.
Child ; Male ; Female ; Humans ; Osteopetrosis/therapy* ; Retrospective Studies ; Prognosis ; Genes, Recessive ; Phosphorus ; Chloride Channels/genetics* ; Vacuolar Proton-Translocating ATPases/genetics*

Aquaporin-6 (AQP6) is a water channel protein located in intracellular vesicles of the proximal tubules and in intercalated cells (ICs) in the collecting duct (CD) of the rat kidney. The function of AQP6 is unknown. However, it colocalizes with vacuolar H+-ATPase in type-A ICs, indicating that it may be important for the function of proton pumps in these cells. The aims of this study were to compare the expression of AQP6 between rat and mouse kidneys, and to establish which types of IC express AQP6. Kidneys of adult male rats and mice were processed for immunohistochemistry using antibodies against AQP6, H+-ATPase, and anion exchanger 1 (AE1). AQP6 was expressed in the S1, S2, and S3 segments of the proximal tubule and in ICs of the CD and connecting tubule (CNT) in both rats and mice. In the rat proximal tubule, AQP6 immunoreactivity was present in intracellular vesicles, whereas in the mouse proximal tubule it was present in the brush border as well as in intracellular vesicles. Triple immunostaining for AQP6, AE1, and H+-ATPase revealed that AQP6 was expressed only in type-A ICs in the CDs and CNTs of both rats and mice, and that the staining was diffuse throughout. There was no AQP6 labeling of type-B ICs, non-A-non-B ICs, or principal cells. The functional significance of the expression of AQP6 in proximal tubule cells and type-A ICs remains to be established. We propose that AQP6 is involved in the retrieval and maintenance of H+-ATPasecontaining vesicles in acid-secreting epithelial cells in the kidney.
Adult ; Animals ; Antibodies ; Aquaporin 6 ; Epithelial Cells ; Humans ; Immunohistochemistry ; Kidney ; Male ; Mice ; Microvilli ; Proton Pumps ; Rats ; Vacuolar Proton-Translocating ATPases ; Water

Vacuolar-type ATPase (V-ATPase), located in the membrane and organelle membrane, is one of important H⁺-transporting proteins. It keeps the proton balance by transporting H⁺ into vacuole, vesicle, or extracellular using the energy from ATP hydrolysis. The subunit B of the vacuolar-type ATPase (BmV-ATPase B) contains the ATP catalytic site, and plays an important role in this process. To study the function of V-ATPase B in Bombyx mori (BmV-ATPase B), we cloned its coding gene from the midgut of the 5th instar silkworm larvae. Then we constructed prokaryotic expression vector and produced the recombinant protein in E. coli. The recombinant protein was identified as BmV-ATPase B by mass spectrometry and purified using Ni-NTA affinity chromatography. This purified protein was used to immunize rabbit to generate polyclonal antibodies of BmV-ATPase B. Finally, the expression patterns of BmV-ATPase B in the silk gland were analyzed by western blotting and immunofluorescence. The full length CDS sequence of BmV-ATPase B was 1 473 bp. BmV-ATPase B was 55 kDa with a PI of 5.3. We analyzed the expression patterns of BmV-ATPase B in different sections of silk gland from the silkworm on the 3rd day of 5th instar and 1st day of wander stage by western blotting. BmV-ATPase B was expressed in all sections of the silk gland and it was abundant in the anterior silk gland (ASG) both in these two developmental stages. Furthermore, immunofluorescence indicated that BmV-ATPase B was located in the silk gland cells. Laser confocal scanning microscopy analysis revealed that BmV-ATPase B was mainly expressed in the cytomembrane of silk gland cells. These data elucidated the expression patterns of BmV-ATPase B in the silk gland of silkworm, which provides a good basis for further studies on the function of V-ATPase B in silk fiber formation.
Animals ; Bombyx ; enzymology ; Cloning, Molecular ; Escherichia coli ; metabolism ; Insect Proteins ; genetics ; metabolism ; Larva ; Recombinant Proteins ; genetics ; metabolism ; Silk ; Vacuolar Proton-Translocating ATPases ; genetics ; metabolism

OBJECTIVETo observe the ultracytochemical localization of H(+)-adenosine triphosphatase (H(+)-ATPase) in the cell organelles.

METHODSThe localization of H(+)-ATPase in the cell organelles was observed in the hepatocytes and renal cells of Wistar rats using routine ultracytochemical methods.

RESULTSH(+)-ATPase activities were observed on the lysosomal membrane and nuclear envelope of the hepatocytes and proximal tubule epithelial cells of the nephron in Wistar rats.

CONCLUSIONThis finding supports the hypothesis that H(+)-ATPase (V-ATPase) is present on the plasma membrane and in the endomembrane system.

Animals ; Cell Membrane ; enzymology ; Hepatocytes ; cytology ; enzymology ; ultrastructure ; Histocytochemistry ; methods ; Kidney ; cytology ; enzymology ; ultrastructure ; Lysosomes ; enzymology ; Male ; Organelles ; enzymology ; Rats ; Rats, Wistar ; Vacuolar Proton-Translocating ATPases ; metabolism

OBJECTIVETo investigate the synergistic effect between the N-terminus domain of the a2 isoform of vacuolar ATPase (a2NTD) and macrophage colony-stimulating factor (M-CSF) on modulating macrophage polarization and the impact of polarized macrophages on proliferation of gastric cancer cells.

METHODSPeripheral blood mononuclear cells were derived from healthy donor and induced into macrophages. Then macrophages were randomly divided into four groups: the control group (RPMI 1640), the experimental group I (M-CSF 100 μg/L), the experimental group II (a2NTD 500 μg/L) and the experimental group III (a2NTD 500 μg/L plus M-CSF 100 μg/L). After stimulation for 48 hours, double color immunofluorescence cytochemistry was adopted to detect the expression of cell membrane molecules on macrophages; ELISA was used to measure the secretion of cytokines IL-10 and IL-12; CCK-8 assay was used to evaluate the impact of macrophages on proliferation ability of gastric cancer cell strain SGC-7901.

RESULTSThe expression of CD68, also known as macrophage surface antigen, was detected on macrophage membrane in all four groups (+). The mean absorbance (A) was 0.092 ± 0.005 in control group, 0.095 ± 0.006 in group I, 0.094 ± 0.005 in group II, 0.094 ± 0.005 in group III, and no significant differences were observed among 4 groups (all P>0.05). Meanwhile, the expression of CD206, which mainly exists on M2 macrophage membrane, was hard to detect in control group (-) with A 0.025 ± 0.004; it was normal in groupI and group II (+) with A 0.191 ± 0.012 in group I and 0.197 ± 0.136 in group II (P=0.212), and it was up-regulated significantly in group III (+++) with A 0.285 ± 0.011. There were significant differences between either two groups except group I and group II (all P<0.01). Secretion of IL-10 in group I and group II [(85.65 ± 13.64) ng/L and (87.77 ± 14.25) ng/L] was significantly higher compared with control group [(71.67 ± 7.56) ng/L, P<0.01]. Secretion of IL-12 in group I and group II [(9.91 ± 1.50) ng/L and (10.15 ± 1.80) ng/L] was significantly lower compared with control group [(16.87 ± 1.10) ng/L, P<0.01]. Secretion of IL-10 in group III [(116.98 ± 14.27) ng/L] was the highest, and secretion of IL-12 [(5.31 ± 0.88) ng/L] was the lowest (all P<0.01). There was a synergistic effect between a2NTD and M-CSF on the secretion of both IL-10 and IL-12. Elevated proliferation of gastric cancer cell strain SGC-7901 was detected in all four groups, in which group III showed the greatest impact compared with other 3 groups (P<0.01).

CONCLUSIONSa2NTD and M-CSF show a synergistic effect in modulating macrophage phenotype and the secretion of IL-10 and IL-12. The polarized macrophage can significantly enhance proliferation of gastric cancer cell strain SGC-7901.

Cell Proliferation ; Humans ; Interleukin-10 ; metabolism ; Interleukin-12 ; metabolism ; Macrophage Colony-Stimulating Factor ; pharmacology ; Macrophages ; cytology ; Phenotype ; Stomach Neoplasms ; pathology ; Tumor Cells, Cultured ; Vacuolar Proton-Translocating ATPases ; pharmacology

By using differential display, we identified one of the genes encoding the multi-subunit complex protein V-ATPase, c subunit gene (ATP6L), and showed alterations of the gene expression by oxidative stresses. Expression of the ATP6L gene in Neuro-2A cells was increased by the treatment with H2O2 and incubation in hypoxic chamber, implying that the expression of the ATP6L gene is regulated by oxidative stresses. To examine mechanisms involved in the regulation of the gene expression by oxidative stresses, the transcriptional activity of the rat ATP6L promoter was studied. Transcription initiation site was determined by primer extension analysis and DNA sequencing, and promoter of the rat ATP6L and its deletion clones were constructed in reporter assay vector. Significant changes of the promoter activities in Neuro-2A cells were observed in two regions within the proximal 1 kbp promoter, and one containing a suppressor was in -195 to -220, which contains GC box that is activated by binding of Sp1 protein. The suppression of promoter activity was lost in mutants of the GC box. We confirmed by electrophoretic mobility shift and supershift assays that Sp1 protein specifically binds to the GC box. The promoter activity was not changed by the H2O2 treatment and incubation in hypoxic chamber, however, H2O2 increased the stability of ATP6L mRNA. These data suggest that the expression of the ATP6L gene by oxidative stresses is regulated at posttranscriptional level, whereas the GC box is important in basal activities of the promoter.
Animals ; Clone Cells ; Gene Expression* ; Hydrogen Peroxide ; Oxidative Stress* ; Rats ; RNA, Messenger ; Sequence Analysis, DNA ; Transcription Initiation Site ; Vacuolar Proton-Translocating ATPases*

OBJECTIVETo explore the application of preimplantation genetic diagnosis (PGD) for infantile malignant osteopetrosis (IMO).

METHODSFor a family affected with IMO, PGD was provided using combined parental mutation detection and haplotype constructions with microsatellite markers spanning the TCIRG1 gene. Prenatal diagnosis was performed on the chorionic villus and amniocentesis samples by direct sequencing.

RESULTSPrenatal diagnosis showed that the fetus by the third pregnancy has carried the parental mutations [c.242delC (p.Pro81Argfs*85) and c.1114C>T (p.Gln372*)], and the pregnancy was terminated. PGD was subsequently performed through mutations detection and haplotype analyses following whole genome amplification (WGA) of each of 13 cells. The results showed that 6 of the 13 embryos were unaffected, 3 were carriers and 4 were affected. Well developed unaffected/carrier embryos were selected and transferred into the uterus. A single pregnancy was confirmed. Subsequently pre- and post-natal diagnoses have confirmed development of a healthy child.

CONCLUSIONThe study demonstrated the advantage of PGD over prenatal diagnosis when natural pregnancies have repeatedly produced IMO children/fetuses.

Adult ; Base Sequence ; Female ; Fertilization in Vitro ; Fetus ; Genetic Carrier Screening ; Humans ; Infant ; Male ; Microsatellite Repeats ; Molecular Sequence Data ; Osteopetrosis ; diagnosis ; embryology ; genetics ; prevention & control ; Pedigree ; Point Mutation ; Pregnancy ; Preimplantation Diagnosis ; Vacuolar Proton-Translocating ATPases ; genetics

OBJECTIVETo detect potential mutation of the TCIRG1 gene in a boy with infantile malignant osteopetrosis.

METHODSTarget sequence capture and next-generation sequencing were applied for the proband and his parents to identify the causative mutation, and Sanger sequencing was used to verify the suspected mutation.

RESULTSThe proband manifested at 4 months of age with symptoms including anemia, thrombocytopenia, hepatosplenomegaly, and cephalus quadratus. X-ray revealed generalized increased bone density. A novel compound heterozygous mutation, c.796G to T (p.E266X) and c.1372G to A (p.G458S), were identified in the boy. His father and grandmother also carried the c.796G to T (p.E266X) mutation, and his mother carried the c.1372G to A (p.G458S) mutation. Neither mutation was found in the PubMed and ClinVar databases.

CONCLUSIONThe novel compound heterozygous mutation c.796G to T (p.E266X) and c.1372G to A (p.G458S) probably underlies the disease in the proband. Above results may enrich the mutation spectrum of the TCIRG1 gene and provide new evidence for the molecular basis of infantile malignant osteopetrosis.

Adult ; Asian Continental Ancestry Group ; Base Sequence ; Humans ; Infant ; Infant, Newborn ; Infant, Newborn, Diseases ; genetics ; Male ; Middle Aged ; Molecular Sequence Data ; Mutation ; Osteopetrosis ; genetics ; Pedigree ; Vacuolar Proton-Translocating ATPases ; genetics

Homo sapiens longevity assurance homologue 2 (LASS2) is a novel gene isolated from a human liver cDNA library by our laboratory, and it is a human homologue of the yeast longevity assurance gene LAG1 (Saccharomyces cerevisiae longevity assurance gene). According to our previous results, LASS2 could interact with subunit c of vacuolar type H(+)-ATPase (V-ATPase), and the overexpression of LASS2 could inhibit the cell growth of a human hepatocellular carcinoma (HCC) cell line, SMMC-7721. In order to understand the role of the interaction between LASS2 and V-ATPase in HCC cell growth, we transiently transfected plasmid pCMV-HA2-LASS2 into HCCLM3, a HCC cell line without the significant expression of endogenous LASS2. The pH-sensitive fluorescence probes, BCECF and BCECF-AM, were used to measure the intracellular and extracellular H(+) concentrations of HCCLM3 cells respectively. The effect of LASS2 gene on apoptosis was evaluated with Annexin-V/FITC and propidium iodide (PI) by flow cytometry. Western blot was used to detect cytochrome c (Cyt c) in the cytosol and mitochondria, as well as pro-caspase-3 in cytosol. The results showed that the cell growth of LASS2-transfected HCCLM3 cells was significantly inhibited compared with that of the mock control. LASS2 transfection increased intracellular H(+) concentration of HCCLM3 cells, while decreased extracellular H(+) concentration. Moreover, LASS2 transfection significantly enhanced the apoptosis of HCCLM3 cells. In LASS2-transfected cells, the amounts of Cyt c increased in the cytosol, while decreased in the mitochondria. Meanwhile, the expression of pro-caspase-3 in the cytosolic extracts was decreased. These results implicate that LASS2 gene might increase intracellular H(+) of HCC cells via the interaction with V-ATPase, thereby inducing cell apoptosis through mitochondrial pathway.
Apoptosis ; Carcinoma, Hepatocellular ; pathology ; Caspase 3 ; metabolism ; Cell Line, Tumor ; Cell Proliferation ; Humans ; Liver Neoplasms ; pathology ; Membrane Proteins ; metabolism ; RNA, Small Interfering ; Sphingosine N-Acyltransferase ; metabolism ; Transfection ; Tumor Suppressor Proteins ; metabolism ; Vacuolar Proton-Translocating ATPases ; metabolism