title: Pin1 down-regulates transforming growth factor-beta (TGF-beta) signaling by inducing degradation of Smad proteins.
abstract: Transforming growth factor-beta (TGF-beta) is crucial in numerous cellular processes, such as proliferation, differentiation, migration, and apoptosis. TGF-beta signaling is transduced by intracellular Smad proteins that are regulated by the ubiquitin-proteasome system. Smad ubiquitin regulatory factor 2 (Smurf2) prevents TGF-beta and bone morphogenetic protein signaling by interacting with Smads and inducing their ubiquitin-mediated degradation. Here we identified Pin1, a peptidylprolyl cis-trans isomerase, as a novel protein binding Smads. Pin1 interacted with Smad2 and Smad3 but not Smad4; this interaction was enhanced by the phosphorylation of (S/T)P motifs in the Smad linker region. (S/T)P motif phosphorylation also enhanced the interaction of Smad2/3 with Smurf2. Pin1 reduced Smad2/3 protein levels in a manner dependent on its peptidyl-prolyl cis-trans isomerase activity. Knockdown of Pin1 increased the protein levels of endogenous Smad2/3. In addition, Pin1 both enhanced the interaction of Smurf2 with Smads and enhanced Smad ubiquitination. Pin1 inhibited TGF-beta-induced transcription and gene expression, suggesting that Pin1 negatively regulates TGF-beta signaling by down-regulating Smad2/3 protein levels via induction of Smurf2-mediated ubiquitin-proteasomal degradation.
authors.affiliation: Division of Biochemistry, the Cancer Institute of the Japanese Foundation for Cancer Research (JFCR), Tokyo 135-8550, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Nakano
authors.forename: Daizo
authors.initials: D
authors.lastname: Koinuma
authors.forename: Keiji
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Takafumi
authors.initials: T
authors.lastname: Uchida
authors.forename: Masao
authors.initials: M
authors.lastname: Saitoh
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kawabata
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Hanai
authors.forename: Hirotada
authors.initials: H
authors.lastname: Akiyama
authors.forename: Masahiro
authors.initials: M
authors.lastname: Abe
authors.forename: Kohei
authors.initials: K
authors.lastname: Miyazono
authors.forename: Toshio
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Imamura
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000502:physiology*; D055785:Gene Knockdown Techniques / Q000379:methods; D006801:Humans; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D025801:Ubiquitin; C471641:SMURF2 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase