title: Microtubules support a disk-like septin arrangement at the plasma membrane of mammalian cells.
abstract: Septin family proteins oligomerize through guanosine 5'-triphosphate-binding domains into core heteromers, which in turn polymerize at the cleavage furrow of dividing fungal and animal cells. Septin assemblies during the interphase of animal cells remain poorly defined and are the topic of this report. In this study, we developed protocols for visualization of authentic higher-order assemblies using tagged septins to effectively replace the endogenous gene product within septin core heteromers in human cells. Our analysis revealed that septins assemble into microtubule-supported, disk-like structures at the plasma membrane. In the absence of cell substrate adhesion, this is the predominant higher-order arrangement in interphase cells and each of the seven to eight septin family members expressed by the two analyzed cell types appears equally represented. However, studies of myeloid and lymphoid cell model systems revealed cell type-specific alterations of higher-order septin arrangements in response to substrate adhesion. Live-cell observations suggested that all higher-order septin assemblies are mutually exclusive with plasma membrane regions undergoing remodeling. The combined data point to a mechanism by which densely arranged cortical microtubules, which are typical for nonadhered spherical cells, support plasma membrane-bound, disk-like septin assemblies.
authors: Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden. mikael.sellin@molbiol.umu.se
authors: Mikael E
authors: ME
authors: Sellin
authors: Per
authors: P
authors: Holmfeldt
authors: Sonja
authors: S
authors: Stenmark
authors: Martin
authors: M
authors: Gullberg
mesh_terms: D002448:Cell Adhesion; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D020014:K562 Cells; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology; D008870:Microtubules / Q000378:metabolism*; D010539:Permeability; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D058112:Septins / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D018797:Cell Cycle Proteins; D011994:Recombinant Proteins; C485192:green fluorescent protein, Aequorea victoria; D049452:Green Fluorescent Proteins; C113158:SEPTIN7 protein, human; C474315:SEPTIN9 protein, human; D058112:Septins