ABSTRACT
Interstitial pulmonary fibrosis is caused by the excess production of extracellular matrix (ECM) by Fb in response to TGF-ß1. Here, we show that the peptidyl-prolyl isomerase Pin1 modulates the production of many pro- and antifibrogenic cytokines and ECM. After acute, bleomycin injury, Pin1(-/-) mice showed reduced, pulmonary expression of collagens, tissue inhibitors of metalloproteinases, and fibrogenic cytokines but increased matrix metalloproteinases, compared with WT mice, despite similar levels of inflammation. In primary fibroblasts, Pin1 was required for TGF-ß-induced phosphorylation, nuclear translocation, and transcriptional activity of Smad3. In Pin1(-/-) cells, inhibitory Smad6 was found in the cytoplasm rather than nucleus. Smad6 knockdown in Pin1(-/-) fibroblasts restored TGF-ß-induced Smad3 activation, translocation, and target gene expression. Therefore, Pin1 is essential for normal Smad6 function and ECM production in response to injury or TGF-ß and thus may be an attractive therapeutic target to prevent excess scarring in diverse lung diseases.
Subject(s)
Peptidylprolyl Isomerase/metabolism , Pulmonary Fibrosis/metabolism , Signal Transduction , Smad3 Protein/metabolism , Smad6 Protein/metabolism , Active Transport, Cell Nucleus/drug effects , Animals , Bleomycin , Cell Nucleus/metabolism , Cells, Cultured , Cytoplasm/metabolism , Fibroblasts/cytology , Fibroblasts/drug effects , Fibroblasts/metabolism , Immunoblotting , Immunoprecipitation , Mice , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Confocal , Mutation , NIMA-Interacting Peptidylprolyl Isomerase , Peptidylprolyl Isomerase/genetics , Phosphorylation/drug effects , Protein Binding/drug effects , Pulmonary Fibrosis/chemically induced , Pulmonary Fibrosis/genetics , RNA Interference , Smad3 Protein/genetics , Smad6 Protein/genetics , Transforming Growth Factor beta1/metabolism , Transforming Growth Factor beta1/pharmacologyABSTRACT
Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and the leading known genetic cause of autism. Fragile X mental retardation protein (FMRP), which is absent or expressed at substantially reduced levels in FXS, binds to and controls the postsynaptic translation of amyloid ß-protein precursor (AßPP) mRNA. Cleavage of AßPP can produce ß-amyloid (Aß), a 39-43 amino acid peptide mis-expressed in Alzheimer's disease (AD) and Down syndrome (DS). Aß is over-expressed in the brain of Fmr1(KO) mice, suggesting a pathogenic role in FXS. To determine if genetic reduction of AßPP/Aß rescues characteristic FXS phenotypes, we assessed audiogenic seizures (AGS), anxiety, the ratio of mature versus immature dendritic spines and metabotropic glutamate receptor (mGluR)-mediated long-term depression (LTD) in Fmr1(KO) mice after removal of one App allele. All of these phenotypes were partially or completely reverted to normal. Plasma Aß(1-42) was significantly reduced in full-mutation FXS males compared to age-matched controls while cortical and hippocampal levels were somewhat increased, suggesting that Aß is sequestered in the brain. Evolving therapies directed at reducing Aß in AD may be applicable to FXS and Aß may serve as a plasma-based biomarker to facilitate disease diagnosis or assess therapeutic efficacy.