title: Autocrine motility factor receptor is a marker for a distinct membranous tubular organelle.
abstract: Autocrine motility factor (AMF) is secreted by tumor cells and is capable of stimulating the motility of the secreting cells. In addition to being expressed on the cell surface, its receptor, AMF-R, is found within a Triton X-100 extractable intracellular tubular compartment. AMF-R tubules can be distinguished by double immunofluorescence microscopy from endosomes labeled with the transferrin receptor, lysosomes labeled with LAMP-2, and the Golgi apparatus labeled with beta-COP. AMF-R can also be separated from a LAMP-2 containing lysosomal fraction by differential centrifugation of MDCK cells and is found within a 100,000 g membrane pellet. By electron microscopic immunocytochemistry, AMF-R is localized predominantly to smooth vesicular and tubular membranous organelles as well as to a lesser extent to the plasma membrane and rough endoplasmic reticulum. AMF-R tubules have a variable diameter of 50-250 nm and can acquire an elaborate branched morphology. By immunofluorescence microscopy, AMF-R tubules are clearly distinguished from the calnexin labeled rough endoplasmic reticulum and AMF-R tubule expression is stable to extended cycloheximide treatment. The AMF-R tubule is therefore not a biosynthetic subcompartment of the endoplasmic reticulum. The tubular morphology of the AMF-R tubule is modulated by both the actin and microtubule cytoskeletons. In a similar fashion to that described previously for the tubular lysosome and endoplasmic reticulum, the linear extension and peripheral cellular orientation of the AMF-R tubule are dependent on the integrity of the microtubule cytoskeleton. The AMF-R tubule may thus form part of a family of microtubule-associated tubular organelles.
authors.affiliation: Département de Pathologie, Université de Montréal, Québec, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Benlimame
authors.forename: D
authors.initials: D
authors.lastname: Simard
authors.forename: I R
authors.initials: IR
authors.lastname: Nabi
mesh_terms: D000818:Animals; D015703:Antigens, CD; D015415:Biomarkers; D020126:Brefeldin A; D002135:Calcium-Binding Proteins / Q000032:analysis; D037281:Calnexin; D002458:Cell Fractionation / Q000379:methods; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry*; D020756:Coatomer Protein; D003513:Cycloheximide / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000737:chemistry; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins / Q000032:analysis; D008565:Membrane Proteins / Q000032:analysis; D008861:Microsomes / Q000737:chemistry; D008869:Microtubule-Associated Proteins / Q000032:analysis; D008870:Microtubules / Q000187:drug effects / Q000502:physiology; D015739:Nocodazole / Q000494:pharmacology; D015388:Organelles / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D060285:Receptors, Autocrine Motility Factor; D018121:Receptors, Cytokine / Q000032:analysis* / Q000096:biosynthesis; D011990:Receptors, Transferrin / Q000032:analysis; D044767:Ubiquitin-Protein Ligases
chemical_list: D015703:Antigens, CD; D015415:Biomarkers; D002135:Calcium-Binding Proteins; D020756:Coatomer Protein; D003517:Cyclopentanes; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D011500:Protein Synthesis Inhibitors; D018121:Receptors, Cytokine; D011990:Receptors, Transferrin; D037281:Calnexin; D020126:Brefeldin A; D003571:Cytochalasin B; D003513:Cycloheximide; D060285:Receptors, Autocrine Motility Factor; D044767:Ubiquitin-Protein Ligases; D015739:Nocodazole