Project Summary/Abstract
G protein coupled receptors (GPCRs) constitute a family of signaling receptors that regulate essentially every
physiological process. Recent studies have begun to recognize the roles of G proteins and GPCRs in tumor
biology. In particular, signaling by the ß2-adrenergic receptor (ß2-AR) and mutations in its cognate G protein,
GNAS, have been associated with pancreatic ductal adenocarcinoma (PDAC) progression. Understanding the
basic molecular mechanisms of GPCR signaling will be imperative for realizing their potential as novel
therapeutic targets. Studies of ligand-dependent GPCR signaling have traditionally focused on receptor
activation at the plasma membrane. However, the recent discovery that intracellular compartments also function
as active signaling sites that elicit different signaling outcomes raises a critical biological question: how does
GPCR trafficking dictate unique signals, and do these unique signals lead to unique cellular outcomes? The
proposed work addresses this question by focusing on the role of endosomal GPCR activation in shaping cAMP-
dependent transcriptional responses. First, starting in an established HEK293 cell model, the proposed studies
will assess the mechanisms by which trafficking encodes the amount and timing of cAMP generation. Through
manipulations of receptors and trafficking machinery, the relationship between endosomal residence time and
cAMP signaling profiles will be tested to determine whether trafficking is sufficient to shape cAMP output or
whether other factors, such as posttranslational modifications or interacting proteins, are required. Next, the
proposed work will define how these distinct cAMP profiles are decoded to elicit a specific downstream response.
Defined steps in the signaling cascade will be probed in order to ascertain whether the transcriptional response
is sensitive to variations in cAMP generation or whether cells have evolved a uniform response to cAMP stimulus.
Finally, the proposed studies will explore whether the principles delineated in the HEK293 system are relevant
to our understanding of oncogenic signaling by ß2-AR and GNAS in PDAC. The timing, location, and duration of
cAMP generation in pancreatic ductal epithelial cells will be evaluated to determine if these cAMP signatures are
regulated and consequential and how PDAC-associated mutations affect this relationship. These studies will
advance an exciting area of fundamental cell biology—the spatiotemporal control of receptor-mediated signaling.
The proposed research will also provide new insights into the mechanisms of oncogenic signaling by ß2-AR and
GNAS in PDAC and, more broadly, the paradigm of GPCR-induced cAMP signaling in cancer. This project will
be carried out at the University of California, San Francisco under the mentorship of Dr. Mark von Zastrow, a
leader in the field of GPCR trafficking and signaling, in collaboration with two experts in the fields of pancreatic
cancer (Dr. Eric Collisson, UCSF) and oncogenic signaling by GPCRs (Dr. J. Silvio Gutkind, UCSD). In addition
to the conceptual and experimental training from those labs, UCSF also offers a vibrant research community
with expertise and facilities that will enable the successful realization of the proposed studies.