Intracellular phosphorylation of target proteins by protein kinases acts as a chemical switch that allows the cell to transmit stimuli from the plasma membrane to the nucleus in a highly regulated manner. Identification of the direct substrates of protein kinases could lead to an understanding of the complex interplay between kinases and the activation and recruitment of downstream effector proteins. This goal has proven elusive to genetic methods because of the tremendous redundancy and overlapping substrate specificities among protein kinases. Similarly, it is enormously challenging to find highly specific inhibitors for kinases because of the conserved nature of kinase active sites. A chemical-genetic method has been developed recently to address this issue. Proteins involved in signal transduction most often bind small molecules as co-factors in well conserved binding pockets. In light of this fact, genetic engineering and chemistry can be brought together to design specific protein/ligand pairs. A functionally-silent mutation was introduced in the active site of a protein kinase to allow for the specific use of a labeled ATP analog. We have successfully applied this method to the study of several kinases, uncovering previously unknown substrates and relationships. These tools have allowed us to probe the roles of multiple kinases involved in cancer and neurodegenerative diseases.

Another project in the laboratory is aimed towards developing specific activators and inhibitors of any G protein of interest. Involved in almost all aspects of cellular function, G proteins are a large family of proteins comprising approximately 0.5% of mammalian genomes. A wide variety of diseases have their roots in deregulated G protein activities or have harmful signals conveyed through them. Despite their great potential as drug targets, no active site inhibitors are known to date. Traditionally, the surprising affinity of G proteins for their substrates and the high intracellular concentration of GTP have been blamed for this failure. The lack of such tools to allow specific and temporal control over the activities of G proteins has significantly impeded the elucidation of their pathways. We used H-Ras to develop a system answering this need. Convergent engineering of the nucleotide and of its binding pocket resulted in the production of two complementary small molecule/mutant protein pairs leading to the highly specific inhibition or activation of this G protein. This system allows for the highly selective identification of effectors of G proteins to help elucidate their signaling pathways.

Education

Recognitions

• Editor, Current Protocols in Chemical Biology , 2008-Present
• Honorary Editorial Board Member, Cell Biology Insights , 2008-Present

Selected Publications

• Kumar D, Patel G, Johnson, E, Shah, K, Synthesis and anticancer activities of novel 3,5-disubstituted-1,2,4-oxadiazoles. Bioorg Med Chem Lett 2009 , 19(20), 2739-41.
• Sun KH, Lee HG, Smith MA, Shah K, Direct and indirect roles of cyclin-dependent kinase 5 as an upstream regulator in the c-Jun NH2-terminal kinase cascade: relevance to neurotoxic insults in Alzheimer's disease. Mol Biol Cell 2009 , 20(21), 4611-19.
• Kumar D, Sundaree S, Johnson, E, Shah, K, An efficient synthesis and biological study of novel indolyl-1,3,4-oxadiazoles as potent anticancer agents. Bioorg Med Chem Lett. 2009 , 19(15), 4492-4.
• Das M, Wiley DJ, Chen X, Shah K, Verde F., The conserved NDR kinase Orb6 controls polarized cell growth by spatial regulation of the small GTPase Cdc42. Curr Biol 2009 , 19(15), 1314-19.