title: Phospho-Smad1 modulation by nedd4 E3 ligase in BMP/TGF-β signaling.
abstract: A considerable number of studies have focused on the regulation of mothers against decapentaplegic homologue (Smad)-dependent or -independent pathways in the signaling by each transforming growth factor β (TGF-β) superfamily member in diverse biologic contexts. The sophisticated regulation of the actions of these molecules and the underlying molecular mechanisms still remain elusive. Here we show new mechanisms of ambilateral R (receptor-regulated)-Smad regulation of bone morphogenetic protein 2 (BMP-2)/TGF-β1 signals. In a specific context, both signals regulate the nonclassic Smads pathway reciprocally, BMP-2 to Smad2/3 and TGF-β1 to Smad1/5/8, as well as their own classic linear Smad pathway. Interestingly, in this study, we found that C-terminal phosphorylated forms of each pathway Smad degraded rapidly 3 hours after stimulation of nonclassic signals but are dramatically restored by treatment with via proteasomal inhibition. Furthermore, an E3 ligase, neural precursor cell expressed, developmentally down-regulated 4 (Nedd4), also was found as one of the important modulators of the p-Smad1 in both BMP-2 and TGF-β1 action. Overexpressed Nedd4 suppressed the BMP-induced osteoblast transdifferentiation process of premyoblast C2C12 cells or alkaline phosphatase (ALP) level of human osteosarcoma cells and promoted TGF-β1-induced degradation of p-Smad1 via physical interaction and polyubiquitination. Conversely, siNedd4 potentiated BMP signals through upregulation of p-Smad1 and ALP activity, the effect of which led to an increased the rate of P(i) -induced calcification of human vascular smooth muscle cells. These new insights about proteasomal degradation-mediated phosphorylated nonclassic Smad regulation of BMP-2/TGF-β1 could, in part, help to unravel the complex mechanisms of abnormal nonosseous calcification by the aberrant activity of BMP/TGF-β/Smads.
authors.affiliation: Department of Biochemistry, School of Dentistry, Kyungpook National University, and Second BK21 Program, Daegu 700-422, Korea.
authors.forename: Byung-Gyu
authors.initials: BG
authors.lastname: Kim
authors.forename: Ji-Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Jiro
authors.initials: J
authors.lastname: Yasuda
authors.forename: Hyun-Mo
authors.initials: HM
authors.lastname: Ryoo
authors.forename: Je-Yoel
authors.initials: JY
authors.lastname: Cho
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D002113:Calcification, Physiologic / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D000075702:Nedd4 Ubiquitin Protein Ligases; D010766:Phosphorylation / Q000187:drug effects; D025821:Polyubiquitin / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D051898:Smad1 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D055396:Bone Morphogenetic Protein 2; D056827:Endosomal Sorting Complexes Required for Transport; D061988:Proteasome Inhibitors; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D016212:Transforming Growth Factor beta; D025821:Polyubiquitin; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex