title: Versatile roles of V-ATPases accessory subunit Ac45 in osteoclast formation and function.
abstract: Vacuolar-type H(+)-ATPases (V-ATPases) are macromolecular proton pumps that acidify intracellular cargos and deliver protons across the plasma membrane of a variety of specialized cells, including bone-resorbing osteoclasts. Extracellular acidification is crucial for osteoclastic bone resorption, a process that initiates the dissolution of mineralized bone matrix. While the importance of V-ATPases in osteoclastic resorptive function is well-defined, whether V-ATPases facilitate additional aspects of osteoclast function and/or formation remains largely obscure. Here we report that the V-ATPase accessory subunit Ac45 participates in both osteoclast formation and function. Using a siRNA-based approach, we show that targeted suppression of Ac45 impairs intracellular acidification and endocytosis, both are prerequisite for osteoclastic bone resorptive function in vitro. Interestingly, we find that knockdown of Ac45 also attenuates osteoclastogenesis owing to a reduced fusion capacity of osteoclastic precursor cells. Finally, in an effort to gain more detailed insights into the functional role of Ac45 in osteoclasts, we attempted to generate osteoclast-specific Ac45 conditional knockout mice using a Cathepsin K-Cre-LoxP system. Surprisingly, however, insertion of the neomycin cassette in the Ac45-Flox(Neo) mice resulted in marked disturbances in CNS development and ensuing embryonic lethality thus precluding functional assessment of Ac45 in osteoclasts and peripheral bone tissues. Based on these unexpected findings we propose that, in addition to its canonical function in V-ATPase-mediated acidification, Ac45 plays versatile roles during osteoclast formation and function.
authors.affiliation: Shanghai Key Laboratory of Orthopaedic Implant, Department of Orthopaedics, Shanghai Jiao Tong University School of Medicine, Ninth People's Hospital, Shanghai, The People's Republic of China.
authors.forename: An
authors.initials: A
authors.lastname: Qin
authors.forename: Tak S
authors.initials: TS
authors.lastname: Cheng
authors.forename: Zhen
authors.initials: Z
authors.lastname: Lin
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Pavlos
authors.forename: Qing
authors.initials: Q
authors.lastname: Jiang
authors.forename: Jiake
authors.initials: J
authors.lastname: Xu
authors.forename: Ke R
authors.initials: KR
authors.lastname: Dai
authors.forename: Ming H
authors.initials: MH
authors.lastname: Zheng
mesh_terms: D000818:Animals; D001862:Bone Resorption; D004705:Endocytosis; D006863:Hydrogen-Ion Concentration; D051379:Mice; D010010:Osteoclasts / Q000166:cytology* / Q000502:physiology*; D021122:Protein Subunits; D013234:Stem Cells / Q000166:cytology; D025262:Vacuolar Proton-Translocating ATPases / Q000502:physiology*
chemical_list: C484226:Atp6ap1 protein, mouse; D021122:Protein Subunits; D025262:Vacuolar Proton-Translocating ATPases
references.citation: J Biol Chem. 1994 Sep 30;269(39):24102-6
references.pmid: 7929063
references.citation: Nat Genet. 2000 Sep;26(1):71-5
references.pmid: 10973252
references.citation: J Clin Invest. 2000 Jul;106(2):309-18
references.pmid: 10903347
references.citation: Biochemistry. 2010 Jun 15;49(23):4715-23
references.pmid: 20450191
references.citation: J Bone Miner Res. 2000 Nov;15(11):2178-86
references.pmid: 11092398
references.citation: Nature. 2001 Feb 1;409(6820):581-8
references.pmid: 11214310
references.citation: J Biol Chem. 2009 May 22;284(21):14667-76
references.pmid: 19321441
references.citation: Biochem J. 2009 Jan 1;417(1):195-203
references.pmid: 18657050
references.citation: Anat Rec. 1989 Jun;224(2):317-24
references.pmid: 2549811
references.citation: Nat Rev Mol Cell Biol. 2007 Nov;8(11):917-29
references.pmid: 17912264
references.citation: Hum Mutat. 2003 Feb;21(2):151-7
references.pmid: 12552563
references.citation: Nat Med. 2006 Dec;12(12):1403-9
references.pmid: 17128270
references.citation: Proc Natl Acad Sci U S A. 1982 Jul;79(14):4327-31
references.pmid: 6289300
references.citation: Science. 1989 Aug 25;245(4920):855-7
references.pmid: 2528207
references.citation: J Cell Sci. 2000 Feb;113 ( Pt 3):377-81
references.pmid: 10639325
references.citation: J Biol Chem. 2001 Nov 23;276(47):44064-8
references.pmid: 11533034
references.citation: J Cell Biochem. 2003 Apr 15;88(6):1256-64
references.pmid: 12647307
references.citation: J Cell Sci. 1998 Oct;111 ( Pt 20):2999-3006
references.pmid: 9739073
references.citation: Nat Genet. 2000 Jul;25(3):343-6
references.pmid: 10888887
references.citation: Nat Rev Genet. 2001 Oct;2(10):743-55
references.pmid: 11584291
references.citation: Biochim Biophys Acta. 2008 Dec;1783(12):2301-10
references.pmid: 18657579
references.citation: Nat Genet. 1998 Feb;18(2):136-41
references.pmid: 9462741
references.citation: J Neurochem. 2011 May;117(4):603-12
references.pmid: 21375531
references.citation: Science. 1997 Apr 11;276(5310):270-3
references.pmid: 9092479
references.citation: Annu Rev Cell Dev Biol. 1997;13:779-808
references.pmid: 9442887
references.citation: Neurosci Lett. 1996 Nov 15;219(1):13-6
references.pmid: 8961292
references.citation: J Bone Miner Res. 1994 Oct;9(10):1575-82
references.pmid: 7817803
references.citation: J Bone Miner Res. 2011 Jan;26(1):169-81
references.pmid: 20683884
references.citation: Eur J Biochem. 1999 Jun;262(2):484-91
references.pmid: 10336633
references.citation: Am J Physiol. 1993 Oct;265(4 Pt 1):C1015-29
references.pmid: 8238296
references.citation: Nat Genet. 1999 Dec;23(4):447-51
references.pmid: 10581033
references.citation: J Cell Sci. 1999 Nov;112 ( Pt 21):3657-66
references.pmid: 10523502
references.citation: Biochem Biophys Res Commun. 1990 Apr 16;168(1):309-13
references.pmid: 2139331
references.citation: J Cell Biol. 2003 Jul 21;162(2):211-22
references.pmid: 12876274
references.citation: J Bone Miner Res. 2011 Jul;26(7):1484-93
references.pmid: 21305608
references.citation: J Biol Chem. 2005 Jan 14;280(2):1070-6
references.pmid: 15525650
references.citation: J Biol Chem. 2008 May 9;283(19):13194-204
references.pmid: 18227071
references.citation: Proc Natl Acad Sci U S A. 2008 Aug 26;105(34):12319-24
references.pmid: 18713856
references.citation: Am J Pathol. 2003 Jan;162(1):57-68
references.pmid: 12507890
references.citation: J Histochem Cytochem. 2002 Jan;50(1):33-42
references.pmid: 11748292
references.citation: J Mol Biol. 2009 Mar 6;386(4):989-99
references.pmid: 19244615
references.citation: Exp Hematol. 1999 Aug;27(8):1229-41
references.pmid: 10428500
references.citation: Mol Cell Biol. 2011 Apr;31(7):1551-64
references.pmid: 21262767
references.citation: Methods. 2001 Dec;25(4):402-8
references.pmid: 11846609
references.citation: Anal Biochem. 1991 Feb 1;192(2):316-21
references.pmid: 1827963
references.citation: Mol Biol Cell. 2010 Oct 1;21(19):3330-9
references.pmid: 20702583
references.citation: Mol Membr Biol. 2002 Jan-Mar;19(1):67-71
references.pmid: 11989824
references.citation: Science. 1994 Jul 1;265(5168):103-6
references.pmid: 8016642
references.citation: Science. 1997 Apr 11;276(5310):266-9
references.pmid: 9092478
references.citation: Toxicol Pathol. 2010 Oct;38(6):872-906
references.pmid: 20805319
references.citation: J Exp Biol. 2000 Jan;203(Pt 1):71-80
references.pmid: 10600675
references.citation: J Neurochem. 2006 Jan;96(2):324-34
references.pmid: 16336635
references.citation: J Biol Chem. 2003 May 16;278(20):18499-505
references.pmid: 12606563
references.citation: J Clin Invest. 1994 Jun;93(6):2311-8
references.pmid: 8200964
references.citation: J Exp Biol. 1997 Jan;200(Pt 1):1-8
references.pmid: 9023991
references.citation: FEBS Lett. 2005 Sep 12;579(22):4937-42
references.pmid: 16115623
references.citation: J Bone Miner Res. 2009 May;24(5):871-85
references.pmid: 19113919
references.citation: J Exp Med. 2005 Aug 1;202(3):345-51
references.pmid: 16061724
references.citation: Hum Mol Genet. 2001 Aug 15;10(17):1767-73
references.pmid: 11532986