Lewis C. Cantley joined the faculty of Harvard Medical School in 1992, when he was also appointed Chief of the Division of Signal Transduction in the Department of Medicine at Beth Israel Hospital. He graduated summa cum laude from Wesleyan College and earned his Ph.D. from Cornell University in 1975. His postdoctoral research and first faculty appointment were in the Department of Biochemistry and Molecular Biology at Harvard University. Prior to joining Harvard Medical School, Dr. Cantley was Professor of Physiology at Tufts University School of Medicine.

Research Summary

The major research objective of this laboratory is to understand the biochemical pathways that regulate normal mammalian cell growth and the defects that cause cell transformation. More than 10 years ago this laboratory discovered phosphoinositide 3-kinase (PI 3-kinase) because of its association with various oncoproteins. Subsequent research from this laboratory and other laboratories showed that PI 3-kinase activation is critical for oncogene-mediated cell transformation, as well as for insulin-dependent stimulation of glucose uptake and metabolism. Recent work from this laboratory and other laboratories revealed that one of the products of PI 3-kinase directly activates the AKT/PKT protein kinase to provide a cell survival signal. A variety of proteins have evolved domains that specifically interact with lipid products of the PI 3-kinase as a mechanism of regulated recruitment to cell membranes. The roles of these proteins in cell growth, cell migration and cell survival are under investigation. In addition, this laboratory has knocked out genes for subunits of PI 3-kinase in the mouse in order to better understand the importance of this enzyme in development, immunity and cancers (Fruman et al. 1999). Another major focus of this laboratory is the structural basis for specificity in protein/protein interactions in signal transduction cascades. In particular, this laboratory has focused on the mechanism by which protein phosphorylation can control the assembly of signaling complexes. A novel oriented peptide library technique was developed o determine optimal phosphopeptides for binding to various protein. This technique was subsequent modified to determine optimal substrates for protein kinases. Through collaborations with other laboratories, it has been possible to determine structures of protein-peptide complexes and thus explain how specificity in signaling is maintained. These studies have also allowed predictions of intracellular targets of signaling proteins using a bioinformatics approach.

A crystal structure of the pleckstrin homology domain of the Bruton's Tyrosine Kinase bound to the head group of the lipid phosphatidylinositol-3,4,5-trisphosphate. The yellow stick figures indicate the diacylgylcerol component of the the lipid anchoring into the inner leaflet of the 'green' plasma membrane. From Baraldi et al., 1999 Structure Fold Des. 7:449-60.; Fruman et al., (1999) Cell 97, 817. Enlarge

Projects

1) Phosphatidylinositol (PI) Signal Transduction.

Growth factors and oncogene products affect enzymes in the phosphatidylinositol (PI) signal transduction pathways. The middle T protein of a DNA tumor virus, polyoma virus, forms a complex with a cellular PI kinase. This enzyme is also activated by almost all growth factors that act through receptor protein-tyrosine kinases (several of which are proto-oncogenes). Activation of this pathway is essential for the ability of cells to grow in response to several growth factors. These results strongly implicate this enzyme in growth and transformation pathways.

We discovered that the oncoprotein-associated PI kinase is in a pathway distinct from the conventional hormone-responsive turnover of PI in response to hormones. In conventional turnover PI is phosphorylated in the D-4 position of the inositol ring to produce PI-4-phosphate, followed by a second phosphorylation to form PI-4,5-biphosphate, the precursor for the two second messengers: inositol-1,4,5-trisphosphate and diacylglycerol. In contrast, the newly discovered oncoprotein-associated PI kinase phosphorylates the D-3 position on the inositol ring to produce PI-3-phosphate. This subtle difference previously went undetected because of the failure of existing techniques to separate PI-3-phosphate from PI-4-phosphate. However, PI-3-phosphate production is the first step in a novel pathway. Mutational data strongly suggest that this pathway provides a signal for growth and that certain oncogenes accomplish cell transformation by overstimulating this pathway.

We have purified the PI 3-kinase to homogeneity and found that it consists of two proteins of molecular weight 85,000 and 110,000 Da. Both subunits are members of multigene families. The 85,000 Da subunit is regulatory and contains two Src-homology 2 (SH2) domains. SH2 domains are small, conserved protein structures that bind directly to phosphotyrosine moieties and thereby mediate specific and reversible assembly of signaling protein complexes in vivo. The 85,000 Da subunit also has a region of homology to BCR and rac-GAP and an SH3 domain, suggesting complex regulation. We are using genetic and biochemical approaches to understand the function and mechanism of regulation of this pathway.

2) SH2 and SH3 Peptide Libraries.

A second focus of the laboratory is the use of partially degenerate peptide libraries to ascertain the optimal sequence motifs for protein kinases and for Src-homology domains (SH2 and SH3). We have recently discovered that a degenerate peptide library with a single phosphotyrosine moiety at position 4 in the sequence can be used to screen for the optimal motif for individual SH2 domains. With this technique we have been able to predict, solely on the basis of primary sequence, which SH2 domains will interact with which downstream signaling molecules. Many of these predictions have already been confirmed by us and others.

Even more recently, we have adapted this technique to determine the optimal sequence for individual protein kinases. This procedure allows us to determine from a mixture of more than 2.5 billion peptides the optimal 9 amino acid substrate for a particular protein kinase. By scanning the protein data base for the occurrence of this sequence, we can predict likely in vivo substrates. In addition, we have been able to design peptide substrates and inhibitors on the basis of these findings.

3) Peptide libraries to discover structural basis of protein protein interactions.

4) Structural basis for regulation of protein kinases.

Selected References

Yaffe, M. B., Rittinger, K., Volinia, S., Caron, P. R., Aitken, A., Leffers, H., Gamblin, S. J., Smerdon, S. J. and Cantley, L. C. (1997) The Structural Basis for 14-3-3: Phosphopeptide Binding Specificity.  Cell 91, 961-971.

Rameh, L. E., Tolias, K. F., Duckworth, B. C. and Cantley, L. C. (1997) A new pathway for phosphatidylinositol-4,5-bisphosphate synthesis.  Nature 390, 192-195.

Songyang, Z., Fanning, A. S., Fu, C., Xu, J., Marfatia, S. M., Chishti, A. H., Crompton, A., Chan, A. C., Anderson, J. M. and Cantley, L. C. (1997)  Recognition of Unique Carboxyl-terminal Motifs by Distinct PDZ Domains.  Science 275, 73-77.

Cantley LC, Neel BG (1999) New insights into tumor suppression: PTEN suppresses tumor formation by restraining the phosphoinositide 3-kinase/AKT pathway. Proc Natl Acad Sci U S A 96, 4240-5

Fruman DA, Rameh LE, Cantley LC (1999) Phosphoinositide binding domains: embracing 3-phosphate. Cell 97, 817-20

Fruman, D. A., Snapper, S. B, Yballe, C., Davidson, L., Yu, J. Y., Alt, F. W. and Cantley, L. C. (1999) Impaired B cell development and proliferation in absence of phosphoinositide 3-kinase p85a.  Science 283, 393-397.

Yaffe, M.B and Cantley, L.C. (1999)  Grabbing Phosphoproteins.  Nature 402, 30-31.

Fruman, D. A., Mauvais-Jarvis, F., Pollard, D. A., Yballe, C. M., Brazil, D., Bronson, R. T., Kahn, C. R. and Cantley, L. C. (2000) Hepatocellular necrosis, chylous ascites and altered glucose homeostasis in mice lacking all isoforms of phosphoinositide 3-kinase p85alpha Nature Genetics 26, 379-382.

Obata T, Yaffe MB, Leparc GG, Piro ET, Maegawa H, Kashiwagi A, Kikkawa R, Cantley LC (2000) Use of peptide and protein library screening to define optimal substrate motifs for AKT/PKB. J. Biol. Chem. 275, 36108-36115.

Yaffe, M. B., Leparc, G. G., Lai, J., Obata, T., Volinia, S. and Cantley, L. C. (2001) A motif-based profile scanning approach for genome wide prediction of signaling pathways. Nature Biotechnology 19:348-53.

Manning, BD, Tee, AR, Logsdon, MN, Blenis, J, and Cantley, LC (2002) Identification of the Tuberous Sclerosis Complex-2 Tumor Suppressor Gene Product Tuberin as a Target of the Phosphoinositide 3-Kinase/Akt Pathway. Molecular Cell 10: 151-162.

Ueki K, Yballe C.M., Brachmann, S.M., Vicent D., Kahn C.R. and Cantley L.C. (2002) Increased Insulin Sensitivity in Mice Lacking the p85beta Subunit of Phosphoinositide 3-Kinase Proc. Natl. Acad. Sci. USA 99(1):419-424.

Cantley LC. (2002) The phosphoinositide 3-kinase pathway. Science;296(5573):1655-7.

Elia AE, Cantley LC, Yaffe MB. (2003) Proteomic screen finds pSer/pThr-binding domain localizing Plk1 to mitotic substrates. Science. 299(5610):1228-31.