title: MxA Is a Novel Regulator of Endosome-Associated Transcriptional Signaling by Bone Morphogenetic Proteins 4 and 9 (BMP4 and BMP9).
abstract: There is confusion about the role that IFN-α plays in the pathogenesis of pulmonary arterial hypertension (PAH) with different investigators reporting a causative or a protective role. There is now clear evidence in PAH pathogenesis for the involvement of BMP4 and BMP9 signaling, and its disruption by mutations in BMPR2. In the present study, we investigated MxA, an IFN-α-inducible cytoplasmic dynamin-family GTPase for effects on BMP4/9 signaling, including in the presence of PAH-disease-associated mutants of BMPR2. In human pulmonary arterial endothelial cells (HPAECs), IFN-α-induced endogenous as well as exogenously expressed MxA was associated with endosomes that aligned alongside microtubules and tubules of the endoplasmic reticulum (ER). Moreover, IFN-α and MxA stimulated basal and BMP4/9 signaling to a Smad1/5/8-responsive pBRE-Luc reporter. In HEK293T cells, immunoelectron microscopy confirmed the association of MxA with endosomes, and immunofluorescence methods showed these to be positive for early endosome markers (early endosomal antigen 1, clathrin light chain and Rab5) and RSmad1/5/8. Functionally, using different genetic and inhibitor approaches, we observed that clathrin-mediated endocytosis enhanced and caveolin-mediated endocytosis inhibited the transcriptional response to BMP4 and BMP9. MxA produced a further 3-4-fold enhancement of the BMP-induced response in a clathrin-endocytosis dependent manner. The microtubule inhibitor nocodazole and stabilizer paclitaxel respectively attenuated and enhanced the effect of MxA, implicating microtubule integrity in this process. MxA enhanced BMP-induced signaling in the presence of wild-type BMPR2, and partially rescued signaling from some PAH-disease-associated BMPR2 mutants. Taken together, the data identify MxA as a novel stimulator of BMP4 and BMP9 transcriptional signaling, and suggest it to be a candidate IFN-α-inducible mechanism that might have a protective role against development of PAH and other vascular diseases.
authors.affiliation: Department of. Cell Biology & Anatomy, New York Medical College, Valhalla, New York, United States of America.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Department of. Cell Biology & Anatomy, and Department of Medicine, New York Medical College, Valhalla, New York, United States of America.
authors.forename: Pravin B
authors.initials: PB
authors.lastname: Sehgal
mesh_terms: D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism*; D002966:Clathrin / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics; D011992:Endosomes / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D055427:Growth Differentiation Factor 2; D055412:Growth Differentiation Factors / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000378:metabolism*; D016898:Interferon-alpha / Q000235:genetics / Q000378:metabolism; D064547:Myxovirus Resistance Proteins / Q000235:genetics / Q000378:metabolism*; D011651:Pulmonary Artery / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D051898:Smad1 Protein / Q000235:genetics / Q000378:metabolism; D051902:Smad5 Protein / Q000235:genetics / Q000378:metabolism; D051904:Smad8 Protein / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D033921:Vesicular Transport Proteins; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; D002966:Clathrin; C525887:GDF2 protein, human; D055427:Growth Differentiation Factor 2; D055412:Growth Differentiation Factors; D016898:Interferon-alpha; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; C497399:SMAD1 protein, human; C497797:SMAD5 protein, human; C107514:SMAD9 protein, human; D051898:Smad1 Protein; D051902:Smad5 Protein; D051904:Smad8 Protein; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; C427755:RAB5C protein, human; D020696:rab5 GTP-Binding Proteins