title: Diversity of proton pumps in osteoclasts: V-ATPase with a3 and d2 isoforms is a major form in osteoclasts.
abstract: Osteoclasts acidify bone resorption lacunae through proton translocation by plasma membrane V-ATPase (vacuolar-type ATPase) which has an a3 isoform, one of the four isoforms of the trans-membrane a subunit (Toyomura et al., J. Biol. Chem., 278, 22023-22030, 2003). d2, a kidney- and epididymis-specific isoform of the d subunit, was also induced in osteoclast-like cells derived from the RAW264.7 line, and formed V-ATPase with a3. The amount of d2 in osteoclasts was 4-fold higher than that of d1, a ubiquitous isoform. These results indicate that V-ATPase with d2/a3 is a major osteoclast proton pump. Essentially the same results were obtained with osteoclasts derived from mouse spleen macrophages. Macrophages from a3-knock-out mice could differentiate into multi-nuclear cells with osteoclast-specific enzymes. In these cells, the d2 isoform was also induced and assembled in V-ATPase with the a1 or a2 isoform. However, they did not absorb calcium phosphate, indicating that V-ATPase with d2/a1 or d2/a2 could not perform the function of that with d2/a3.
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Matsumoto
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Daido
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Doshisha Women's College, Kyotanabe, Kyoto 610-0395, Japan.
authors.forename: Ge-Hong
authors.initials: GH
authors.lastname: Sun-Wada
authors.affiliation: Division of Biological Science, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Yoh
authors.initials: Y
authors.lastname: Wada
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694, Japan.
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Futai
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Yahaba, Iwate 028-3694, Japan. Electronic address: nakanim@iwate-med.ac.jp.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Nakanishi-Matsui
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000201:enzymology; D051379:Mice; D018345:Mice, Knockout; D010010:Osteoclasts / Q000201:enzymology / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D017494:Proton Pumps / Q000378:metabolism*; D013154:Spleen / Q000166:cytology / Q000201:enzymology; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D017494:Proton Pumps; D025262:Vacuolar Proton-Translocating ATPases
keywords: Isoform; Osteoclast; Vacuolar-type ATPase; a3 knock out mouse