# Septin Filaments: Architecture, Assembly and Regulation

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA BERKELEY · 2020 · $333,131

## Abstract

PROJECT SUMMARY
Septins are a family of conserved GTP-binding proteins that assemble into hetero-oligomeric complexes and
polymerize into filaments and other supramolecular arrangements. Septin structures associate with the plasma
membrane by interacting with a specific phosphoinositide, and are involved in cell compartmentation, in cell
division, and other membrane remodeling events. In budding yeast, septins establish a diffusion barrier at the
neck between a mother and daughter cell, promote membrane curvature, and act as a scaffold to recruit other
proteins to the site of cytokinesis. In humans, septin structures serve very similar functions; they are localized
at the cleavage furrow, at the root of the primary cilium, at the base of every dendritic spine, and within the
annulus in spermatozoa. Marked alterations of septin gene expression are found in solid tumors of certain
tissues and septin gene translocations in mixed lineage leukemias. SEPT9 mutations are one apparent cause
of hereditary neuralgic amyotrophy. Substitution mutations preventing GTP binding to SEPT12 disrupt the
sperm annulus and cause male infertiity. In-depth structural and functional analysis of septins is necessary to
understand the molecular mechanisms governing septin organization and function and obtain new insights to
illuminate their pathophysiology. This project aims to apply novel tools and the experimental advantages of
yeast to interrogate septin-based structures and eludicate fundamental properties of their organization,
regulation and function that should be applicable to the highly homologous septin-based structures in human
cells. Our specific aims include experimental tests of the following hypotheses. (1) Post-translational
modifications (PTMs) of septins and septin-associated proteins drive the dramatic changes in septin structural
organization that occur during passage through the cell division cycle. Therefore, comprehensive analysis by
mass spectrometry of PTMs (especially phosphorylation and SUMOylation) that septins undergo during cell
cycle progression, and subsequent genetic analysis of the physiological importance of those modifications by
site-directed mutagenesis in vivo and a FRET-based method in vitro, will be conducted. (2) Sequential
recruitment of septin-binding proteins exert and order the spatio-temporal changes in septin organization and
function that impose proper cell morphology. Hence, comprehensive analysis of the in vivo septin interactome
using a tripartite split-GFP method will be carried out. In addition, a novel clonable tag for in vivo labeling and
protein localization at the ultrastructural level, which will be applied to dynamic analysis of the septin
interactome using correlated light (fluorescence) and electron microscopy (CLEM), will be developed; and, (3)
Association with PtdIns4,5P2 is obligatory for septin recruitment to the plasma membrane. Thus, to gain
unprecedented insight as to how septins associate with a PtdIns4...

## Key facts

- **NIH application ID:** 9839562
- **Project number:** 5R01GM101314-07
- **Recipient organization:** UNIVERSITY OF CALIFORNIA BERKELEY
- **Principal Investigator:** Jeremy W. Thorner
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $333,131
- **Award type:** 5
- **Project period:** 2013-01-01 → 2021-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9839562

## Citation

> US National Institutes of Health, RePORTER application 9839562, Septin Filaments: Architecture, Assembly and Regulation (5R01GM101314-07). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/9839562. Licensed CC0.

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