Molecular Mechanisms of Calcium-Dependent Cell Regulation
Calcium is most commonly recognized as a primary mineral component of bone, but it also plays an essential role in the regulation of numerous cell processes. When calcium levels in cells increase in response to a variety of stimuli (see Figure), it binds to calcium regulatory proteins, which then trigger cascades of protein-protein interactions. The most important calcium regulatory protein is called calmodulin. It is highly conserved in all eukaryotic cells from slime mold to humans, and it plays a critical role in regulating essential cellular processes, including muscle contraction, neural transmission and cell division.
The Putkey lab has made hallmark contributions to the study of calmodulin, including isolating the first cDNA clone for vertebrate calmodulin, and the structural and biochemical characterization of recombinant calmodulin. Currently, the Putkey lab focuses on two small, intrinsically disordered proteins called PEP-19 and Ng that bind to calmodulin and modulate how it senses calcium signals. Using a combination of biophysical techniques and NMR solution structure determination, the Putkey lab has shown that PEP-19 modifies the calcium binding properties of calmodulin by electrostatically steering calcium to binding sites on calmodulin (see Figure). These studies have broad implication since PEP-19 expression is induced in response to a variety of normal and pathological conditions, including cancer. It is likely that PEP-19 serves to control the activities of calmodulin in the face of abnormal calcium levels associated with these conditions.
Development of Anti-Cancer Drugs
Rational drug design is a cutting-edge multi-step process that uses 3D structures to identify compounds that are predicted to bind to and alter the activity of target proteins involved in normal or pathological processes, including cancer. The small pluripotent G-protein signaling molecule called K-Ras is a prime target for cancer drugs since somatic mutations of K-Ras occur in about 25% of all human tumors. Compounds that bind to wild type and/or mutant forms of K-Ras would provide a powerful tool in the fight against numerous forms of cancer.
Dr. Putkey’s group, along with UTHealth colleague Dr. Gorfe, is pursuing an approach to design drugs that target K-Ras. Computational methods are first used to screen huge libraries of chemical compounds for those predicted to bind to unique pockets on the surface of K-Ras to exert an allosteric effect on the nucleotide binding site, or interactions between K-Ras and downstream proteins. NMR is then used to determine if these lead compounds bind to the predicted pockets on K-Ras. Biochemistry, biophysics, and cell biology are then used to better characterize the interactions of lead compounds with K-Ras, and to determine their effect on -Ras signaling pathways. Drs. Putkey and Gorfe have identified several promising lead compounds thus far (see Figure) and are proceeding with pre-clinical development of drugs targeting K-Ras.
Structural and molecular basis of calcium signaling in normal and disease states. Identifying drugs that bind to K-Ras and that have therapeutic benefits.