title: Bone Morphogenetic Protein-2 (BMP-2) Activates NFATc1 Transcription Factor via an Autoregulatory Loop Involving Smad/Akt/Ca2+ Signaling.
abstract: Bone remodeling is controlled by dual actions of osteoclasts (OCs) and osteoblasts (OBs). The calcium-sensitive nuclear factor of activated T cells (NFAT) c1 transcription factor, as an OC signature gene, regulates differentiation of OCs downstream of bone morphogenetic protein-2 (BMP-2)-stimulated osteoblast-coded factors. To analyze a functional link between BMP-2 and NFATc1, we analyzed bones from OB-specific BMP-2 knock-out mice for NFATc1 expression by immunohistochemical staining and found significant reduction in NFATc1 expression. This indicated a requirement of BMP-2 for NFATc1 expression in OBs. We showed that BMP-2, via the receptor-specific Smad pathway, regulates expression of NFATc1 in OBs. Phosphatidylinositol 3-kinase/Akt signaling acting downstream of BMP-2 also drives NFATc1 expression and transcriptional activation. Under the basal condition, NFATc1 is phosphorylated. Activation of NFAT requires dephosphorylation by the calcium-dependent serine/threonine phosphatase calcineurin. We examined the role of calcium in BMP-2-stimulated regulation of NFATc1 in osteoblasts. 1,2Bis(2aminophenoxy)ethaneN,N,N',N'-tetraacetic acid acetoxymethyl ester, an inhibitor of intracellular calcium abundance, blocked BMP-2-induced transcription of NFATc1. Interestingly, BMP-2 induced calcium release from intracellular stores and increased calcineurin phosphatase activity, resulting in NFATc1 nuclear translocation. Cyclosporin A, which inhibits calcineurin upstream of NFATc1, blocked BMP-2-induced NFATc1 mRNA and protein expression. Expression of NFATc1 directly increased its transcription and VIVIT peptide, an inhibitor of NFATc1, suppressed BMP-2-stimulated NFATc1 transcription, confirming its autoregulation. Together, these data show a role of NFATc1 downstream of BMP-2 in mouse bone development and provide novel evidence for the presence of a cross-talk among Smad, phosphatidylinositol 3-kinase/Akt, and Ca(2+) signaling for BMP-2-induced NFATc1 expression through an autoregulatory loop.
authors.affiliation: Departments of Pathology.
authors.forename: Chandi C
authors.initials: CC
authors.lastname: Mandal
authors.affiliation: Medicine, and.
authors.forename: Falguni
authors.initials: F
authors.lastname: Das
authors.affiliation: Departments of Pathology.
authors.forename: Suthakar
authors.initials: S
authors.lastname: Ganapathy
authors.affiliation: Periodontics, University of Texas Health Science Center, San Antonio, Texas 78229.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Harris
authors.affiliation: Medicine, and From Veterans Affairs Research and Geriatric Research Education and Clinical Center, South Texas Veterans Health Care System and.
authors.forename: Goutam Ghosh
authors.initials: GG
authors.lastname: Choudhury
authors.affiliation: Departments of Pathology, From Veterans Affairs Research and choudhury@uthscsa.edu.
authors.forename: Nandini
authors.initials: N
authors.lastname: Ghosh-Choudhury
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism*; D019703:Calcineurin / Q000737:chemistry / Q000378:metabolism; D065096:Calcium Chelating Agents / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D050778:NFATC Transcription Factors / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051902:Smad5 Protein / Q000819:agonists / Q000235:genetics / Q000378:metabolism
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D065096:Calcium Chelating Agents; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D011994:Recombinant Proteins; D051902:Smad5 Protein; C497798:Smad5 protein, mouse; D058539:Phosphatidylinositol 3-Kinase; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D019703:Calcineurin
keywords: BMP-2; NFAT transcription factor; NFATc1; SMAD transcription factor; Smad signaling; bone morphogenetic protein (BMP); calcineurin; calcium-calcineurin signaling; osteoblast; phosphatidylinositol 3-kinase (PI 3-kinase)