Observations and insights from a study of RalGDS in cancer.
exchange factors are transducers of Ras activation. These exchange factors target the
small GTPases RalA and RalB. Four RalGEFs (RalGDS, Rgl 1, Rgl2/Rlf, and Rgl3) have been
identified with the ability to bind Ras through a conserved Ras binding domain. Other
Ral exchange (RalGPS1, RalGPS2, and Rgr) factors have also been identified which do not
have RBDs and are thought to be a... read morectivated by other signaling pathways In this thesis we
described three major findings that expand the knowledge and understanding of the Ral
exchange factor RalGDS. Our studies began with the investigation of structural
interactions within the protein. Without the benefit of crystal structure data it is
sometimes difficult to glean the relevance of protein interactions and modifications we
find in nature. Our characterization of RalGDS through binding assays allowed us to form
an understanding about the nature of the N-terminal REM domain's role in regulating the
catalytic activity of the Cdc25 domain of RalGDS. With our structural understanding we
were able to propose a mechanism for previous and new observations. Our second major
study identified and characterized the c-Met mediated phosphorylation of RalGDS at four
sites throughout the protein. This discovery marks the first confirmed and characterized
tyrosine phosphorylation of a RalGEF. We will also present the first functional evidence
of Ras effector uncoupling through direct phosphorylation of a Ras association domain.
In our final study we identify a novel interaction between 14-3-3σ and RalGDS in
response to H202 stimulation. The 14-3-3 family of proteins regulate a variety of
cellular processes and it is provocative that the two proteins have now been shown to
directly interact with each other. The elucidation of the biological consequence of this
interaction will likely offer interesting new insights into their combined functions
both in normal and cancer biology.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Biochemistry.
Advisors: Brian Schaffhausen, and Larry Feig.
Committee: Amy Yee, and Akiko Hata.
Keyword: Biochemistry.read less