# Cell Cycle Regulation of Membrane Trafficking

> **NIH NIH R01** · WAYNE STATE UNIVERSITY · 2021 · $238,959

## Abstract

Project Summary
 Cell division requires a carefully coordinated series of essential events that must be precisely regulated.
A central feature of cell division is the accurate segregation of chromosomes into daughter cells. Other
compartments of the cell must also be carefully packaged into daughter cells, and coordinated with
chromosome segregation. Membrane trafficking pathways are essential for the completion of cytokinesis at the
end of cell division. How cells trigger membrane trafficking during cytokinesis is not well understood. The large
protease separase is a central player in chromosome segregation due to its role in cohesin cleavage, which
allows chromosome separation at the onset of anaphase. After chromosome segregation, separase promotes
several events during anaphase. This proposal aims to understand a novel role of separase in the exocytosis
of RAB-11 vesicles required for cytokinesis. Separase also regulates exocytosis of large cortical granules
during anaphase of meiosis I to block polyspermy, which is an ideal context to analyze this regulatory pathway.
This proposal describes research aimed at understanding how separase promotes exocytosis in collaboration
with other closely related cell cycle regulators that have well characterized roles in chromosome segregation.
The dynamic localization of separase is regulated during cell division and only localizes to vesicles during
anaphase. Proposed research will investigate how chromosome segregation regulators control separase
activity and localization to vesicles. Overexpression of non-degradable securin will be used to determine how
this inhibitory chaperone controls the exocytic function of separase. Mutations of the PPH-5 phosphatase and
its activator HSP-90 were identified as suppressors of separation of function alleles of separase. The functions
of PPH-5 and HSP-90 will be characterized to determine whether they directly regulate separase during the
meiotic divisions. Separase phosphorylation sites will be mapped and phosphorylation mutants will be studied
to determine how they affect separase function. PPH-5 will be tested to determine if it directly
dephosphorylates separase in vitro. Finally, biochemical and genetic approaches will be employed to identify
substrates or targets of separase on vesicles to define the mechanism by which it promotes exocytosis. These
studies will be performed using the genetically tractable C. elegans embryo. This work will provide new insight
into how cells coordinate the essential process of chromosome segregation with exocytosis during cytokinesis,
which is relevant to understanding normal development and diseases such as infertility and cancer.

## Key facts

- **NIH application ID:** 10607265
- **Project number:** 7R01GM114471-08
- **Recipient organization:** WAYNE STATE UNIVERSITY
- **Principal Investigator:** Joshua Nathaniel Bembenek
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $238,959
- **Award type:** 7
- **Project period:** 2015-03-15 → 2025-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10607265

## Citation

> US National Institutes of Health, RePORTER application 10607265, Cell Cycle Regulation of Membrane Trafficking (7R01GM114471-08). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10607265. Licensed CC0.

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