Biochemical and cell biological analyses of a mammalian septin complex, Sept7/9b/11.
Septins are members of a conserved family of cytoskeletal GTPases present in organisms as diverse as yeast and mammals. Unlike lower eukaryotic cells, the physiological significance of mammalian septin complexes is largely unknown. Using specific antibodies, we found at least five septins, Sept2, Sept7, Sept8, Sept9b, and Sept11, in septin complexes affinity-purified with anti-Sept7 antibody-conjugated column from rat embryonic fibroblast REF52 cells. Immunofluorescence studies revealed co-localization of Sept7, Sept9b, and Sept11 along stress fibers in REF52 cells. Biochemical and immunoprecipitation analyses revealed that the three septins directly bind with each other through their N- or C-terminal divergent regions. These septins per se formed distinct and characteristic filament structures when transiently expressed in COS7 cells. When two of the three septins were co-expressed in COS7 cells, combination-dependent filament elongation, bundling, or disruption was observed. Taken together, our results suggest that septin filament structures may be affected by interactions with other septins included in the complex.
Nagata
Koh-ichi
K
Department of Molecular Neurobiology, the Institute for Developmental Research, Aichi Human Service Center, 713-8 Kamiya-Cho, Kasugai, Aichi 480-0392, Japan. knagata@inst-hsc.jp
Asano
Tomiko
T
Nozawa
Yoshinori
Y
Inagaki
Masaki
M
D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000502:physiology*; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000502:physiology*; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D058112:Septins
D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D011994:Recombinant Proteins; D005982:Glutathione Transferase; D020558:GTP Phosphohydrolases; C496549:SEPTIN11 protein, human; C113158:SEPTIN7 protein, human; C474315:SEPTIN9 protein, human; D058112:Septins