The Mammalian Septin Interactome

Neubauer, Katharina; Zieger, Barbara

doi:10.3389/fcell.2017.00003

Cited by 94 publications

(92 citation statements)

References 101 publications

(151 reference statements)

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“…This choice was made based on two criteria. First, previous experiments have shown the existence of such a complex in platelets where it associates with microtubules and plays an important role in granule trafficking (Martínez et al, ; Neubauer & Zieger, ). Second, it is a conservative choice as it represents a minimal alteration when compared to the canonical SEPT2–SEPT6–SEPT7 complex.…”

Section: Introductionmentioning

confidence: 99%

A revised order of subunits in mammalian septin complexes

Mendonça¹,

Macêdo

Guimarães³

et al. 2019

Cytoskeleton

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Septins are GTP binding proteins considered to be novel components of the cytoskeleton. They polymerize into filaments based on hexameric or octameric core particles in which two copies of either three or four different septins, respectively, assemble into a specific sequence. Viable combinations of the 13 human septins are believed to obey substitution rules in which the different septins involved must come from distinct subgroups. The hexameric assembly, for example, has been reported to be SEPT7–SEPT6–SEPT2–SEPT2–SEPT6–SEPT7. Here, we have replaced SEPT2 by SEPT5 according to the substitution rules and used transmission electron microscopy to demonstrate that the resulting recombinant complex assembles into hexameric particles which are inverted with respect that predicted previously. MBP‐SEPT5 constructs and immunostaining show that SEPT5 occupies the terminal positions of the hexamer. We further show that this is also true for the assembly including SEPT2, in direct contradiction with that reported previously. Consequently, both complexes expose an NC interface, as reported for yeast, which we show to be more susceptible to high salt concentrations. The correct assembly for the canonical combination of septins 2‐6‐7 is therefore established to be SEPT2–SEPT6–SEPT7–SEPT7–SEPT6–SEPT2, implying the need for revision of the mechanisms involved in filament assembly.

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Section: Introductionmentioning

confidence: 99%

A revised order of subunits in mammalian septin complexes

Mendonça¹,

Macêdo

Guimarães³

et al. 2019

Cytoskeleton

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“…where it associates with microtubules and plays an important role in granule trafficking [23,24]. Secondly it is a conservative choice as it represents a minimal alteration when compared to the canonical SEPT2-SEPT6-SEPT7 complex.…”

Section: Firstly Previous Experiments Have Shown the Existence Of Sumentioning

confidence: 99%

Repositioning septins within the core particle

Mendonça

Macêdo

Itri³

et al. 2019

Preprint

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Abbreviations (Define non-standard or uncommon abbreviations). AbstractSeptins are GTP binding proteins considered to be a novel component of the cytoskeleton. They polymerize into filaments based on hetero-oligomeric core particles which, in humans, are either hexamers or octamers composed of two copies each of either three or four different septins from the 13 available. Not all combinations are possible as it is believed that these must obey substitution rules which determine that different septins must be derived from four distinct and well-established sub-groups. Here, we have purified and characterized one such combinations, SEPT5-SEPT6-SEPT7, and used TEM to derive the first structural information concerning its assembly. The full complex was purified using an affinity tag attached to only one of its components (SEPT7) and was able to bind to and perturb lipid bilayers. Although the complex assembled into elongated hexameric particles, the position of SEPT5 was incompatible with that predicted by the reported structure of SEPT2-SEPT6-SEPT7 based on the substitution rules. MBP-fusion constructs for SEPT5 and SEPT2 and immuno-staining clearly show that these septins occupy the terminal positions of the SEPT5-SEPT6-SEPT7 and SEPT2-SEPT6-SEPT7 hexamers, respectively. In so doing they expose a so-called NC interface which we show to be more susceptible to perturbation at high salt concentrations. Our results show that the true structure of the hexamer is inverted with respect to that described previously and, as such, is more compatible with that reported for yeast. Taken together, our results suggest that the mechanisms involved in spontaneous self-assembly of septin core particles and their filaments deserve further reflection.

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“…Protein hits were cross-checked against the Biological General Repository for Interaction Datasets (BioGRID; https://thebiogrid.org), septin interactomes (49,54) and reviews of septin interactions (22), which were used for in litero verification of interactions (asterisks in Figure 2…”

Section: Bioinformatic Analyses and Data Graphingmentioning

confidence: 99%

“…While the precise identity and diversity of septin complexes eludes our knowledge, septin-septin interactions are influenced by GTP binding and hydrolysis, the relative abundance of septin paralogs and isoforms, which can vary between cell types, and the presence of domains (e.g., N-terminal extensions) that may interfere with the Gdomain binding interface (9,(16)(17)(18)(19). Importantly, the localization and function of septin complexes appear to depend on the properties and binding partners of their individual subunits (20)(21)(22). Septin 9 (SEPT9) is a ubiquitously expressed septin, which is essential for embryonic development; SEPT9 knock-out mice die early in gestation (23).…”

Section: Introductionmentioning

confidence: 99%

Proteomic profiling of the oncogenic septin 9 reveals isoform-specific interactions in breast cancer cells

Devlin

Perkins

Bowen

et al. 2019

Preprint

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Septins are a family of multimeric GTP-binding proteins, which are abnormally expressed in cancer. Septin 9 (SEPT9) is an essential and ubiquitously expressed septin with multiple isoforms, which have differential expression patterns and effects in breast cancer cells. It is unknown, however, if SEPT9 isoforms associate with different molecular networks and functions. Here, we performed a proteomic screen in MCF-7 breast cancer cells to identify the interactome of GFP-SEPT9 isoforms 1, 4 and 5, which vary significantly in their N-terminal extensions. While all three isoforms associated with SEPT2 and SEPT7, the truncated SEPT9_i4 and SEPT9_i5 interacted with septins of the SEPT6 group more promiscuously than SEPT9_i1, which bound predominately SEPT8. Spatial mapping and functional clustering of non-septin partners showed isoform-specific differences in interactions with proteins of distinct subcellular organelles (e.g., nuclei, centrosomes, cilia) and functions such as cell signaling and ubiquitination. Notably, the interactome of the full length SEPT9_i1 was more enriched in cytoskeletal regulators, while the truncated SEPT9_i4 and SEPT9_i5 exhibited preferential and isoform-specific interactions with nuclear, signaling and ubiquitinating proteins. These data provide evidence for isoform-specific interactions, which arise from truncations in the N-terminal extensions of SEPT9, and point to novel roles in the pathogenesis of breast cancer. L.D. performed experiments, analyzed data, made figures and co-wrote manuscript with E.T.S.; G.P. contributed technically and intellectually to ESI/LC-MS/MS experimentation and softwarebased peptide identification; J.R.B. performed microscopy imaging; C.M. created MCF-7 cell lines and contributed to the manuscript; E.T.S. conceived and directed the project (experiments and analyses), drafted manuscript and edited figures.

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The Mammalian Septin Interactome

Cited by 94 publications

References 101 publications

A revised order of subunits in mammalian septin complexes

A revised order of subunits in mammalian septin complexes

Repositioning septins within the core particle

Proteomic profiling of the oncogenic septin 9 reveals isoform-specific interactions in breast cancer cells

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