Signal Transduction by Tyrosine Kinases: Current Projects
Regulation of nonreceptor tyrosine kinases
Nonreceptor tyrosine kinases (NRTKs) never exist as isolated catalytic domains. A long-standing goal of our lab has been to understand the roles of the noncatalytic regions in enzyme function. For Src-family tyrosine kinases, we worked together with Dr. John Kuriyan’s lab to show how the SH3 and SH2 domains maintain an inactive conformation. We identified several cellular proteins that activate Src by engaging the enzyme’s SH3 domain. This mode of activation has proven to be widespread among Src family kinases. Nature 385, 650-653 (1997); Science 289, 1938-1942 (2000); Molecular Cell 8, 269-280 (2001); J. Biol. Chem. 277, 28238-28246 (2002); J. Biol. Chem. 290, 15934-15947 (2015).
In current projects, we are investigating the noncatalytic regions of other NRTKs, such as the ACK1 family. FEBS Lett. 596, 2808-2820 (2022); J. Biol. Chem. 298, 102664 (2022); Nature Comm. 13, 6929 (2022); Kinases Phosphatases 1:167-180 (2023).
Disease-associated mutations in tyrosine kinases
Because of their potent ability to promote cell growth, tyrosine kinases are under stringent control in human cells. For several families of tyrosine kinases, our laboratory has shown that cancer-associated mutations disrupt important intramolecular interactions to hyperactivate the enzymes. In other cases, we have shown that loss-of-function mutations intefere with the normal physiological functions of tyrosine kinases. J. Biol. Chem. 285, 10605-10615 (2010); Biochemistry 54, 3173-3182 (2015); Biochemistry 62, 1124-1137 (2023); J. Biol. Chem. 299, 105115 (2023); Biochemistry 63, 407-418 (2024); medRxiv 2024.02.15.24302255 (2024).
Structure and autoregulation of insulin-like growth factor I receptors
In collaboration with Dr. Stevan Hubbard, we are studying the insulin and insulin-like growth factor 1 (IGF1) receptor tyrosine kinases. We characterized the structure and regulation of the IGF1 receptor kinase domain. We also determined the co-crystal structure of IGF1R kinase and a small-molecule inhibitor, which, in addition to revealing the basis of inhibitor specificity, afforded a view of the initial trans-autophosphorylation event. Current work on IR/IGF1R is focused on the mechanism of holoreceptor signaling. Nature Struct. Biol. 8, 1058-1063 (2001); J. Biol. Chem. 281, 23785-23791 (2006); EMBO Journal. 27, 1985-1994 (2008); Nature Comm. 6, 6406 (2015).
In collaboration with Erwin London (Stony Brook), we are studying the membrane components that are required for IR/IGF1R signaling. Analytical Biochem. 536, 69-77 (2017); BBA Biomembranes 1861, 819-826 (2019); J. Biol. Chem. 297, 101010 (2021).
Evolution of tyrosine kinase signaling
The pTyr-based signaling system (consisting of tyrosine kinases, tyrosine phosphatases, and pTyr-binding modules) was originally thought to be unique to metazoans. Recent genomic studies show that the unicellular choanoflagellate M. brevicollis has even more tyrosine kinases than humans. Strikingly, many of these kinases contain domain combinations that are not seen in metazoan kinases. Genome analyses of additional primitive eukaryotes have reinforced the idea that phosphotyrosine signaling evolved before the split between unicellular and multicellular eukaryotes (≈ 600 million years ago). Our laboratory is comparing these ancestral kinases (and their signaling pathways) with mammalian kinase signaling systems. We have cloned and characterized numerous tyrosine kinases from choanoflagellates and other single-celled organisms. Our data suggest that kinase regulation arose recently in metazoan evolution. Understanding the molecular basis of this development can shed light on regions of present-day proto-oncogenic kinases that are involved in allosteric regulation.
Current work also focuses on the evolution of the IR/IGF1R signaling pathway. Nature 451, 783-788 (2008); J. Biol. Chem. 283, 15491-15501 (2008); Proc. Natl. Acad. Sci. USA. 105, 9674-9679 (2008); Biochemistry 53, 1320-29 (2014); Sci. Rep. 8, 5362 (2018); Biochem. Biophys. Rep. 23, 100775 (2020); FASEB J. 38, e23355 (2024).