# Novel Functions for Ras family GTPases

> **NIH VA I01** · RALPH H JOHNSON VA MEDICAL CENTER · 2020 · —

## Abstract

Project Summary:
Ras proteins play a central role in many aspects of biology. These monomeric GTPases cycle between an
inactivate GDP-bound state and an active GTP-bound state. Mutational activation of Ras occurs in
approximately 30% of human tumors with some cancers such as pancreatic cancer having Ras mutations in
>90% of tumors. These cancer associated mutations trap Ras in the GTP-bound state, leading to chronic
activation of Ras-regulated signaling pathways and oncogenic transformation. Thus, RasGTP has been
considered the only biologically important form of the molecule. However, we have discovered a novel role for
nucleotide-free Ras (nfRas) in the negative regulation of cell signaling. This form of Ras, formed as an
intermediate in the transition from RasGDP to RasGTP, negatively regulates phosphatidylinositol 3-kinase,
class 2beta (PI3KC2β). These finding have profound implications for the understanding of Ras-mediated
signaling and transformation. We propose that nfRas binds targets, e.g., PI3KC2β, leading to the mutual
inhibition of both Ras and the associated target. Our model predicts that oncogenic activation of Ras leads to
loss of repression of these targets resulting in their activation without binding RasGTP. Thus, our findings point
to a new class of molecules important for Ras-driven tumorigenesis yet do not bind activated Ras. To better
understand the role of nfRas in cell signaling, we have generated high affinity, high specificity monobody
reagents that selectively bind different states of Ras. Using these reagents we demonstrate that nfRas
represents a significant pool of total cellular Ras. In addition, one of our Ras monobodies which binds to all
three forms of Ras (GTP, GDP, and nucleotide free) acts as a highly potent inhibitor of oncogenic Ras-
mediated signaling. Using these reagents we will characterize the regulation of nfRas in vivo and determine the
role of nfRas in regulating specific targets. Finally, we will utilize these novel monobody reagents to perturb
Ras function in vivo using a novel chemical-genetic approach to interfere with pancreatic cancer development
and progression. Given the prevalence of Ras mutations in human cancers, it is critical to understand the
mechanisms through which Ras contributes to tumorigenesis. Our work represents an entirely new concept
in Ras biology that defines a new class of targets that participate in Ras-mediated signaling and
transformation. These studies will provide new insights into the mechanisms of Ras-mediated tumorigenesis
and are therefore of high translational significance. This work will be beneficial to Veterans as well as the
general population, both of which suffer from cancer. However, the incidence for certain cancers, such as lung
and pancreatic cancer the latter of which has a high incidence of Ras mutations (<90%), has been reported to
be up to 5-7x higher in Veteran populations making these studies particularly relevant to Veterans. Additionally,
the go...

## Key facts

- **NIH application ID:** 9859302
- **Project number:** 5I01BX002095-07
- **Recipient organization:** RALPH H JOHNSON VA MEDICAL CENTER
- **Principal Investigator:** John P O'Bryan
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2013-10-01 → 2020-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9859302

## Citation

> US National Institutes of Health, RePORTER application 9859302, Novel Functions for Ras family GTPases (5I01BX002095-07). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9859302. Licensed CC0.

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