Lloyd A. Greene, PhD

The basic interests of this laboratory concern the mechanisms of neuronal differentiation and degeneration and the regulation thereof by external growth factors. A major model employed is a cell line (designated PC12) developed by this laboratory which, in response to the neurotrophic factor NGF, acquires a neuronal phenotype characterized by generation of neurites and the specific induction of neuronal genes. As in the case of neurons, NGF can also promote the survival of PC12 cells. Thus this system provides a convenient means to assess at the molecular level the mechanisms by which growth factors regulate neuronal differentiation as well as survival and death. This system is complemented with studies of cultured CNS and peripheral neurons.

Current studies are aimed at some of the following issues: 1) What are the intracellular signaling pathways that are stimulated by NGF? NGF sets in motion a number of signaling elements and we are involved in both dissecting these and defining the neuronal properties they regulate. 2) How do receptors for NGF activate intracellular signaling pathways? The surface receptor for NGF is a tyrosine kinase designated Trk. Mutational and structural analysis are being used to define the molecular mechanisms by which Trk signaling is activated by NGF. 3) What are the NGF-regulated genes that mediate neuronal differentiation? The SAGE (Serial Analysis of Gene Expression) technique is being employed to address this issue at high resolution and to maximally exploit current and upcoming genomic sequence information. 4) How do factors such as NGF prevent neuronal death, both during development and in the mature nervous system? Conversely, why do neurons die in neurodegenerative disorders and trauma and can this be prevented by exploiting our understanding of the molecular mechanisms governing neuronal survival and death?

Selected Publications:

• Cunningham, M.E., Stephens, R.M., Kaplan, D.R. and Greene, L.A. Autophosphorylation of activation loop tyrosines regulates signaling by the Trk NGF receptor. J. Biol. Chem. 272: 10957-10967 (1997).

• Stefanis, L., Burke, R.E. and Greene, L.A. Apoptosis in neurodegenerative disorders. Curr. Opinion in Neurol. 10: 288-305 (1997).

• Park, D., Levine, B., Ferrari, G., and Greene, L.A. Cyclin dependent kinase inhibitors and dominant negative cyclin dependent kinase 4 and 6 promote survival of NGF-deprived sympathetic neurons. J. Neurosci. 17: 8975-8983 (1997).

• Angelastro, J,M., Ho, C.-L., Frappier, T.. Liem. R.K.H. and Greene, L.A. Peripherin is tyrosine phosphorylated at its carboxyl terminal tyrosine. J. Neurochem. 70: 540-549 (1998).

• Park, D.S., Morris, D.J., Stefanis, L., Troy, C.M., Shelanski, M.L., Geller, H.M. and Greene, L.A. Multiple pathways of neuronal death induced by DNA damaging agents, NGF deprivation and oxidative stress. J. Neurosci. 18: 830-840 (1998).

• Yan, C.Y.I and Greene, L.A. Prevention of neuronal death by N-acetylcysteine requires activation of the Ras pathway. J. Neurosci. 18: 4042-4049 (1998).

• Anderson, B.L., Boldogh, I., Evangelista, M., Boone, C., Greene, L.A. and Pon, L.A. The SH3 domain of a yeast type I myosin, Myo5p, binds to verprolin and is required for targeting to sites of actin polarization. J. Cell Biol. 141: 1357-1370 (1998).

• Greene, L.A., Farenelli, S.E., Cunningham, M.E. and Park, D.S. Culture and experimental use of the PC12 rat pheochromocytoma cell line. In: Culturing Nerve Cells, 2nd Edition (G. Banker and K. Goslin, eds) MIT Press, Cambridge, MA. pp161-187 (1998).

• Park, D.S., Morris, E.J., Padmanabhan, J., Shelanski, M.L., Geller, H.M., and Greene, L.A. Cyclin dependent kinases participate in death of neurons evoked by DNA damaging agents. J. Cell Biol. (in press, 1998).