My immediate goal is to acquire the necessary skills and expertise to make a successful transition to independence in the academic field of basic cell and cancer biology. The long-term goals of this work are to advance our knowledge on the molecular mechanisms that regulate the interaction of K-Ras with the plasma membrane (PM). The Ras GTPases comprising three main isoforms H-, N- and K-Ras operate at the PM as molecular switches in essential signaling pathways. Oncogenic mutant K-Ras is highly prevalent in multiple human tumors. Despite significant efforts to directly target Ras activity, no anti-Ras drugs have been developed and taken into the clinic. Since Ras proteins must be anchored to the inner leaflet of the PM for full biological activity, I propose that inhibition of K-Ras PM interaction is a valid therapeutic approach to abrogate oncogenic K-Ras activity. Recently, we performed a high content cell-based screen (HCS) of chemical and human siRNA libraries to identify both exogenous and endogenous regulators of the K-Ras PM interaction. We identified three classes of compounds and a set of proteins that induce K-Ras dissociation from the PM. The mechanisms, which reduced K-Ras signaling were: 1) increased K-Ras phosphorylation by AMPK/eNOS/PKG pathway, and 2) perturbation of cellular phosphatidylserine (PS) distribution.
Specific Aim 1 will characterize cGMP-activated protein kinase (PKG) as a novel K-Ras kinase regulated by the AMPK/eNOS/PKG pathway.
Specific Aim 2 will develop novel strategies to abrogate K-Ras PM binding and signal output by reducing PS PM levels and inducing K-Ras phosphorylation.
Specific Aim 3 will characterize a set of proteins that regulate cellular PS distribution.
These aims will be addressed by combining my experience in molecular and cell biology to the techniques available in the mentor's laboratory, and will set the path to future investigations aiming to the abrogation of oncogenic K-Ras signal output. Collectively, the overall theme of this proposal is to characterize these novel mechanisms, whereby K-Ras interaction with the PM can be regulated, and be a tractable therapeutic approach to target K-Ras-driven cancer cells.
Approximately 15% of all human carcinomas have activating point mutations in ras genes. Mutations in K-ras are most frequent, accounting for about 85% of the total, followed by N- and H-ras with about 15% and less than 1%, respectively. Oncogenic K-Ras mutants are found in 90% of pancreatic, 45% of colorectal and 35% of lung cancers. To date, no anti-Ras drugs have been successfully developed and taken into the clinic. Ras must be at the plasma membrane for its biological activity, and blocking of Ras binding to the plasma membrane abrogates Ras signal output. I will investigate molecular mechanisms of K-Ras interaction with the plasma membrane, and will identify compounds and proteins that regulate K-Ras PM interaction. Such compounds and/or proteins may be a starting point to develop novel anti-cancer therapies that specifically target K-Ras-driven cancers.
|Salim, A A; Tan, L; Huang, X-C et al. (2016) Oligomycins as inhibitors of K-Ras plasma membrane localisation. Org Biomol Chem 14:711-5|
|Cho, Kwang-Jin; Casteel, Darren E; Prakash, Priyanka et al. (2016) AMPK and Endothelial Nitric Oxide Synthase Signaling Regulates K-Ras Plasma Membrane Interactions via Cyclic GMP-Dependent Protein Kinase 2. Mol Cell Biol 36:3086-3099|
|Cho, Kwang-Jin; van der Hoeven, Dharini; Zhou, Yong et al. (2015) Inhibition of Acid Sphingomyelinase Depletes Cellular Phosphatidylserine and Mislocalizes K-Ras from the Plasma Membrane. Mol Cell Biol 36:363-74|
|Salim, Angela A; Xiao, Xue; Cho, Kwang-Jin et al. (2014) Rare Streptomyces sp. polyketides as modulators of K-Ras localisation. Org Biomol Chem 12:4872-8|
|Salim, Angela A; Cho, Kwang-Jin; Tan, Lingxiao et al. (2014) Rare Streptomyces N-formyl amino-salicylamides inhibit oncogenic K-Ras. Org Lett 16:5036-9|