title: Regulation of osteoblast development by Bcl-2-associated athanogene-1 (BAG-1).
abstract: BCL-2-associated athanogene-1 (BAG-1) is expressed by osteoblast-lineage cells; early embryonic lethality in Bag-1 null mice, however, has limited the investigation of BAG-1 function in osteoblast development. In the present study, bone morphogenetic protein-2/BMP-2-directed osteogenic differentiation of bone marrow stromal cells (BMSCs) of Bag-1(+/-) (heterozygous) female mice was decreased significantly. Genes crucial for osteogenic differentiation, bone matrix formation and mineralisation were expressed at significantly lower levels in cultures of Bag-1(+/-) BMSCs supplemented with BMP-2, while genes with roles in inhibition of BMP-2-directed osteoblastogenesis were significantly upregulated. 17-β-estradiol (E2) enhanced responsiveness of BMSCs of wild-type and Bag-1(+/-) mice to BMP-2, and promoted robust BMP-2-stimulated osteogenic differentiation of BMSCs. BAG-1 can modulate cellular responses to E2 by regulating the establishment of functional estrogen receptors (ERs), crucially, via its interaction with heat shock proteins (HSC70/HSP70). Inhibition of BAG-1 binding to HSC70 by the small-molecule chemical inhibitor, Thioflavin-S, and a short peptide derived from the C-terminal BAG domain, which mediates binding with the ATPase domain of HSC70, resulted in significant downregulation of E2/ER-facilitated BMP-2-directed osteogenic differentiation of BMSCs. These studies demonstrate for the first time the significance of BAG-1-mediated protein-protein interactions, specifically, BAG-1-regulated activation of ER by HSC70, in modulation of E2-facilitated BMP-2-directed osteoblast development.
authors.affiliation: Centre for Human Development, Stem Cells and Regeneration, Institute of Developmental Sciences, University of Southampton, Southampton SO16 6YD, United Kingdom.
authors.forename: Joanna
authors.initials: J
authors.lastname: Greenhough
authors.affiliation: Cancer Research UK Centre Cancer Sciences Unit, Somers Building, University of Southampton, Southampton SO16 6YD, United Kingdom.
authors.forename: Emmanouil S
authors.initials: ES
authors.lastname: Papadakis
authors.affiliation: Cancer Research UK Centre Cancer Sciences Unit, Somers Building, University of Southampton, Southampton SO16 6YD, United Kingdom.
authors.forename: Ramsey I
authors.initials: RI
authors.lastname: Cutress
authors.affiliation: Institute of Cancer Sciences, Manchester Cancer Research Centre, University of Manchester, Manchester M13 9WL, United Kingdom.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Townsend
authors.affiliation: Centre for Human Development, Stem Cells and Regeneration, Institute of Developmental Sciences, University of Southampton, Southampton SO16 6YD, United Kingdom.
authors.forename: Richard O C
authors.initials: ROC
authors.lastname: Oreffo
authors.affiliation: Centre for Human Development, Stem Cells and Regeneration, Institute of Developmental Sciences, University of Southampton, Southampton SO16 6YD, United Kingdom.
authors.forename: Rahul S
authors.initials: RS
authors.lastname: Tare
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D052160:Benzothiazoles; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D057895:Haploinsufficiency / Q000187:drug effects; D006579:Heterozygote; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D010455:Peptides / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: C091732:BCL2-associated athanogene 1 protein; D052160:Benzothiazoles; D055396:Bone Morphogenetic Protein 2; D004268:DNA-Binding Proteins; D004967:Estrogens; D050883:HSC70 Heat-Shock Proteins; D010455:Peptides; D011960:Receptors, Estrogen; D013844:Thiazoles; D014157:Transcription Factors; C009462:thioflavin T; D004247:DNA