title: Live-cell single-molecule imaging reveals clathrin and caveolin-1 dependent docking of SMAD4 at the cell membrane.
abstract: Transforming growth factor β (TGF-β) signaling is important for many biological processes. Although the sequential events of this cascade are known, the dynamics remain speculative. Here, live-cell single-molecule total internal reflection fluorescence microscopy was used to monitor the dynamics of SMAD4, a TGF-β downstream effector, in MDA-MB-231 breast cancer cells. Contrary to previous belief, SMAD4 was detectable at the cytoplasmic membrane, displaying two subpopulations with different membrane docking behaviors. These subpopulations were regulated by clathrin and caveolin-1, and had opposing roles in the nuclear shuttling of SMAD4 and the subsequent transcriptional regulation of genes associated with cell migration. The notion that membrane-docking behaviors of downstream molecules could predict the cellular response to growth factors may revolutionize the way we view cell signaling.
authors.affiliation: Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030, USA. Electronic address: yyang@tmhs.org.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yang
authors.forename: Joy
authors.initials: J
authors.lastname: Wolfram
authors.forename: Jianliang
authors.initials: J
authors.lastname: Shen
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Fang
authors.forename: Haifa
authors.initials: H
authors.lastname: Shen
authors.forename: Mauro
authors.initials: M
authors.lastname: Ferrari
mesh_terms: D051242:Caveolin 1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002966:Clathrin / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D062105:Molecular Docking Simulation / Q000379:methods; D057054:Molecular Imaging / Q000379:methods; D011485:Protein Binding / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D059010:Single-Cell Analysis / Q000379:methods; D051901:Smad4 Protein / Q000737:chemistry / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology / Q000502:physiology; D014407:Tumor Cells, Cultured
chemical_list: D051242:Caveolin 1; D002966:Clathrin; D034741:RNA, Small Interfering; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta
keywords: Caveolin-1; Clathrin; Membrane docking; SMAD4; Single-molecule fluorescence imaging