# Regulation of Arf GTPase activation at the Golgi complex

> **NIH NIH R01** · CORNELL UNIVERSITY · 2020 · $309,643

## Abstract

Project Summary/Abstract
 The Golgi complex is the central sorting station for nearly a third of all proteins in eukaryotic cells, but
how cells regulate the complex flow of material through this organelle remains largely unknown. Protein and
membrane traffic at the Golgi is controlled by Arf GTPases that function by recruiting effectors to make
outgoing vesicles and tether incoming vesicles. The master regulators that activate Arf GTPase pathways are
Arf-GEFs (guanine nucleotide exchange factors). In order to understand the molecular logic of Golgi
trafficking, we must understand how the Golgi Arf-GEFs are regulated to make the molecular decision of
where and when to activate their substrate Arf proteins. We have uncovered regulatory mechanisms that
govern the function of the trans-Golgi network (TGN)-localized Arf-GEF, Sec7. We discovered that Sec7 can
switch between autoinhibited and activated states, and is regulated by direct interactions with the activated
forms of four different Golgi GTPases: Ypt31/32 (Rab11), Ypt1 (Rab1), Arl1, and Arf1. This collection of
interactions represents a previously unappreciated level of crosstalk between these prominent Golgi GTPase
pathways. Key questions remain regarding the biochemical basis for Sec7 regulation and the cell biology
underpinning these interactions. Furthermore, we have determined that Gea1 and Gea2, the Arf-GEFs that
localize to early Golgi compartments, are regulated through mechanisms that are distinct from those of Sec7.
Our long-term goal is to determine how cells regulate trafficking at the Golgi complex. In order to both
broaden and deepen our mechanistic understanding of the regulation of Arf activation at the Golgi, we
propose the following Aims for this project: 1) Investigate the intra-molecular and inter-molecular
interactions that regulate Sec7. We will use our established in vitro assays to characterize a newly identified
functional link between distinct Sec7 regulatory domains. Using a new assay for measuring Sec7 activity in
vivo, we will explore the possibilities that Sec7 integrates multiple GTPase signals and can sense and respond
to changes in Golgi cargo load. We will perform an intragenic suppressor screen to identify new functional
connections between Sec7 regulatory domains. Finally, we will seek additional structural information
regarding the Sec7 C-terminal regulatory domains. 2) Determine the mechanisms regulating localization and
activity of the early-Golgi Arf-GEFs Gea1/2. In order to understand how trafficking is regulated at the early-
Golgi, we will perform a comprehensive investigation of the mechanisms regulating Gea1/2 membrane
localization and activity. We will utilize chimeras and temperature sensitive-mutants to identify and
characterize the regions of Gea1/2 regulating localization and activity. We will combine in vitro and in vivo
approaches to characterize the roles of Gea1/2 binding partners. Finally, we will seek structural information to
explain th...

## Key facts

- **NIH application ID:** 9857016
- **Project number:** 5R01GM098621-09
- **Recipient organization:** CORNELL UNIVERSITY
- **Principal Investigator:** J Christopher Fromme
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $309,643
- **Award type:** 5
- **Project period:** 2012-02-01 → 2021-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9857016

## Citation

> US National Institutes of Health, RePORTER application 9857016, Regulation of Arf GTPase activation at the Golgi complex (5R01GM098621-09). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9857016. Licensed CC0.

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