Gα13 Switch Region I Regulates Prostate Cancer Cell Migration
cancer is the third leading cause of cancer-related deaths in men in the United States.
While the survival rate is reasonably high when the tumor is diagnosed at an early and
localized stage, the mortality rate significantly increases upon metastatic progression
to the bone, liver, lymph nodes and lungs. To ameliorate disease progression, it is
therefore necessary to understand ... read morethe migratory and invasive mechanisms of prostate
cancer cells, and to ultimately develop a therapeutic approach to block the metastatic
cascade. The ubiquitous G protein, Gα13, is involved in activating oncogenic
targets involved in metastasis. Switch region I (SRI) is a motif located within the
conformationally-sensitive domain of Gα13 and is involved in G protein activation
as well as binding and activating a variety of Rho guanine nucleotide exchange factors
(RhoGEFs). RhoGEFs in turn activate GTPases such as RhoA, which promotes cellular
processes including cell migration, invasion, cell cycle maintenance, development,
adhesion, and cytoskeletal rearrangements. In this study, I investigated the role of
Gα13SRI in the migratory mechanism(s) of prostate cancer cells (PC3). I elucidated
the role of SRI by testing the effect of a novel, 13aa peptide derived from the
Gα13SRI sequence, which, in previous studies, has been shown to completely
abrogate RhoA activity. The novel peptide binds and occupies the RhoGEF binding site,
which prevents activation of RhoA by endogenous Gα13. Our data show a significant
reduction in the migration of PC3 cells following treatment with the SRI peptide in a
dose-dependent manner, with 100 μM of SRI peptide significantly inhibiting cell
migration in a wound-healing assay measured at 24-hours. A Transwell migration assay
yielded unexpected results, with more cells migrating following treatment with SRI
peptide compared to controls. This result prompted further investigation into the
adhesive properties of prostate cells following SRI peptide treatment. The migratory
mechanism was evaluated through a RhoA activation assay, demonstrating reduction of RhoA
activation in SRI peptide treated cells. Future studies investigating adhesion, invasive
properties, detachment-dependent cell death (Anoikis), and in vivo mouse models will
further clarify the mechanism of SRI function in prostate cancer cell migration. These
studies will help to better understand a key role of Gα13 in the regulation of
metastatic cascade, and can aid in the development of anti-metastatic therapeutics for
Thesis (M.S.)--Tufts University, 2017.
Submitted to the Dept. of Pharmacology & Experimental Therapeutics.
Advisor: Athar Chishti.
Committee: Ira Herman.
Keyword: Pharmacology.read less