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Summary Septins, a conserved family of filament-forming proteins, contribute to eukaryotic cell division, polarity, and membrane trafficking. Septins scaffold other proteins to cellular membranes, but it is not fully understood how septins associate with membranes. We identified and characterized an isoform ofCaenorhabditis elegansseptin UNC-61 that was predicted to contain a transmembrane domain (TMD). The TMD isoform is expressed in a subset of tissues where the known septins were known to act, and TMD function was required for tissue integrity of the egg-laying apparatus. We found predicted TMD-containing septins across much of opisthokont phylogeny and demonstrated that the TMD-containing sequence of a primate TMD-septin is sufficient for localization to cellular membranes. Together, our findings reveal a novel mechanism of septin-membrane association with profound implications for septin dynamics and regulation.
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Simultaneous co‐overexpression of Saccharomyces cerevisiae septins Cdc3 and Cdc10 drives pervasive, phospholipid‐, and tag‐dependent plasma membrane localization
Abstract Septin proteins contribute to many eukaryotic processes involving cellular membranes. In the budding yeast Saccharomyces cerevisiae , septin hetero‐oligomers interact with the plasma membrane (PM) almost exclusively at the future site of cytokinesis. While multiple mechanisms of membrane recruitment have been identified, including direct interactions with specific phospholipids and curvature‐sensitive interactions via amphipathic helices, these do not fully explain why yeast septins do not localize all over the inner leaflet of the PM. While engineering an inducible split‐yellow fluorescent protein (YFP) system to measure the kinetics of yeast septin complex assembly, we found that ectopic co‐overexpression of two tagged septins, Cdc3 and Cdc10, resulted in nearly uniform PM localization, as well as perturbation of endogenous septin function. Septin localization and function in gametogenesis were also perturbed. PM localization required the C‐terminal YFP fragment fused to the C terminus of Cdc3, the septin‐associated kinases Cla4 and Gin4, and phosphotidylinositol‐4,5‐bis‐phosphate (PI[4,5]P 2 ), but not the putative PI(4,5)P 2 ‐binding residues in Cdc3. Endogenous Cdc10 was recruited to the PM, likely contributing to the functional interference. PM‐localized septins did not exchange with the cytosolic pool, indicative of stable polymers. These findings provide new clues as to what normally restricts septin localization to specific membranes.
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- Award ID(s):
- 1928900
- PAR ID:
- 10464187
- Date Published:
- Journal Name:
- Cytoskeleton
- Volume:
- 80
- Issue:
- 7-8
- ISSN:
- 1949-3584
- Page Range / eLocation ID:
- 199 to 214
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/cm.21762
