title: Nongenomic STAT5-dependent effects on Golgi apparatus and endoplasmic reticulum structure and function.
abstract: We report unexpected nongenomic functions of signal transducer and activator of transcription (STAT) 5 species in the cytoplasm aimed at preserving the structure and function of the Golgi apparatus and rough endoplasmic reticulum (ER) in vascular cells. Immunoimaging and green fluorescent protein-tagged-STAT5a protein localization studies showed the constitutive association of nonphosphorylated STAT5a, and to a lesser extent STAT5b, with the Golgi apparatus and of STAT5a with centrosomes in human pulmonary arterial endothelial and smooth muscle cells. Acute knockdown of STAT5a/b species using small interfering RNAs (siRNAs), including in the presence of an mRNA synthesis inhibitor (5,6-dichloro-1-β-d-ribofuranosylbenzimidazole), produced a dramatic phenotype within 1 day, consisting of dilatation and fragmentation of Golgi cisternae, a marked tubule-to-cyst change in the ER, increased accumulation of reticulon-4 (RTN4)/Nogo-B and atlastin-3 (ATL3) at cyst-zone boundaries, cystic separation of the outer and inner nuclear membranes, accompanied by scalloped/lunate distortion of the nucleus, with accumulation of RTN4 on convex sides of distorted nuclei. These cells showed inhibition of vesicular stomatitis virus G protein glycoprotein trafficking, mitochondrial fragmentation, and reduced mitochondrial function. STAT5a/b(-/-) mouse embryo fibroblasts also showed altered ER/Golgi dynamics. RTN4 knockdown using siRNA did not affect development of the cystic phenotype; ATL3 siRNA led to effacement of cyst-zone boundaries. In magnetic-bead cross-immunopanning assays, ATL3 bound both STAT5a and STAT5b. Remarkably, this novel cystic ER/lunate nucleus phenotype was characteristic of vascular cells in arterial lesions of idiopathic pulmonary hypertension, an unrelentingly fatal human disease. These data provide evidence of a STAT-family protein regulating the structure of a cytoplasmic organelle and implicate this mechanism in the pathogenesis of a human disease.
authors.affiliation: Dept. of Cell Biology & Anatomy, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Lee
authors.forename: Yang-Ming
authors.initials: YM
authors.lastname: Yang
authors.forename: Feng-Xia
authors.initials: FX
authors.lastname: Liang
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Gough
authors.forename: David E
authors.initials: DE
authors.lastname: Levy
authors.forename: Pravin B
authors.initials: PB
authors.lastname: Sehgal
mesh_terms: D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D018385:Centrosome / Q000378:metabolism / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D004004:Dichlororibofuranosylbenzimidazole / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure*; D042783:Endothelial Cells; D065627:Familial Primary Pulmonary Hypertension; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000378:metabolism; D008562:Membrane Glycoproteins; D051379:Mice; D008854:Microscopy, Electron; D009185:Myelin Proteins / Q000378:metabolism; D032389:Myocytes, Smooth Muscle; D000070798:Nogo Proteins; D021381:Protein Transport; D011651:Pulmonary Artery / Q000166:cytology; D034741:RNA, Small Interfering; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D014759:Viral Envelope Proteins
chemical_list: C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; D009185:Myelin Proteins; D000070798:Nogo Proteins; D034741:RNA, Small Interfering; C000603199:RTN4 protein, human; C000603201:Rtn4 protein, mouse; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; C494095:STAT5B protein, human; D025521:Tumor Suppressor Proteins; D014759:Viral Envelope Proteins; D004004:Dichlororibofuranosylbenzimidazole