Predominant intracellular localization of the type I transforming growth factor-beta receptor and increased nuclear accumulation after growth arrest.
Transforming growth factor-beta (TGF-beta) signaling requires the functional interaction of two distinct receptors, type I (RI) and type II (RII), at the cell surface. Exposure of cells to TGF-beta results in receptor internalization and down-regulation (Zwaagstra et al., 1999, Exp. Cell Res. 252, 352362); however, little is known about the subsequent fate of RI or RII. In this study the cellular distribution of RI was examined in cells before and after treatment with ligand. RI was localized by immunocytochemistry and confocal microscopy using two polyclonal antisera directed against two different epitopes, one in the C-terminal region and one in the N-terminal region of the cytoplasmic domain. The majority of RI molecules in untreated MvlLu and A549 cells were found to be intracellular. Treatment of MvlLu and A549 cells with 100 pM TGF-beta1 for 24 h at 37 degrees C caused a redistribution of surface RI on MvlLu cells, as evidenced by surface RI aggregation. Unexpectedly, this TGF-beta1 treatment also caused redistribution and accumulation of intracellular RI in and around the nucleus for both MvlLu and A549 cells. Nuclear accumulation of RI was also promoted independently of ligand receptor activation by treatment of MvlLu cells with olomoucine, an agent that results in growth arrest. The capacity of RI to localize in the nucleus was confirmed by microscopic examination of 293 cells transiently expressing RI fused to green fluorescent protein (RI-GFP). Olomoucine treatment of these cells resulted in the movement of RI-GFP into the nucleus. Our results indicate that growth arrest alters intracellular transport/routing of RI and may indicate that RI functions not only at the cell surface but inside the cell as well.
Cell Surface Recognition Group, Biotechnology Research Institute, National Research Council Canada, Montreal, Quebec.
J C
JC
Zwaagstra
A
A
Guimond
M D
MD
O'Connor-McCourt
D030201:Activin Receptors, Type I; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D002467:Cell Nucleus / Q000502:physiology*; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D004721:Endoplasmic Reticulum / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006056:Golgi Apparatus / Q000502:physiology; D049452:Green Fluorescent Proteins; D006801:Humans; D007701:Kinetin; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D008175:Lung Neoplasms; D008907:Mink; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D011687:Purines / Q000494:pharmacology; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D020545:Respiratory Mucosa; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D008164:Luminescent Proteins; D011687:Purines; D018125:Receptors, Transforming Growth Factor beta; D011993:Recombinant Fusion Proteins; D016212:Transforming Growth Factor beta; D049452:Green Fluorescent Proteins; C090046:olomoucine; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D007701:Kinetin