title: Human septin-septin interactions as a prerequisite for targeting septin complexes in the cytosol.
abstract: Septins are a cytosolic GTP-binding protein family first characterized in yeast, but gaining increasing recognition as critical protagonists in higher eukaryotic cellular events. Mammalian septins have been associated with cytokinesis and exocytosis, along with contributing to the development of neurological disorders. Ten different septins, divided into four groups, have been identified in mammals, and individual septins are capable of interacting with each other to form macromolecular complexes. The present study characterizes the structural requirements for human septin-septin interactions using a yeast two-hybrid system. We focus on three septins that are highly expressed in platelets and neurons, SEPT4 [previously designated H5, CDCrel-2 (cell-division-control-related-2), PNUTL2], SEPT5 (CDCrel-1, PNUTL1) and SEPT8 (KIAA0202). Each of these three septins contains a characteristic domain structure consisting of unique N- and C-termini, and a central core domain conserved among the family of proteins. The yeast two-hybrid system yielded data consistent with a model where each of the three septins can interact with itself (homotypic assembly) or with one of the other septins (heterotypic assembly). For SEPT5 and SEPT8, the results illustrate a model whereby heterotypic septin assembly is dependent on the conserved central core domain and homotypic interactions require the N- and C-termini of each protein. We also characterized a model in which the proper cellular localization of SEPT5 and SEPT8 requires concomitant expression of both proteins. Co-transfection of SEPT5 and SEPT8 results in both proteins targeted to a vesicular-like location. Therefore the cellular repertoire of human septins has an impact on function by targeting septin macromolecular complexes to specific cellular locations.
authors.affiliation: The Roon Research Center for Arteriosclerosis and Thrombosis, Division of Experimental Hemostasis and Thrombosis, Department of Molecular and Experimental Medicine The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Constantino
authors.initials: C
authors.lastname: Martínez
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Sanjuan
authors.forename: Judith A
authors.initials: JA
authors.lastname: Dent
authors.forename: Lars
authors.initials: L
authors.lastname: Karlsson
authors.forename: Jerry
authors.initials: J
authors.lastname: Ware
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002522:Chlorocebus aethiops; D016384:Consensus Sequence; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D058112:Septins
chemical_list: D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C492027:SEPTIN4 protein, human; C109366:SEPTIN5 protein, human; C464445:SEPTIN8 protein, human; D058112:Septins