Affiliations

Director, Molecular Pharmacology GPB Home Area

Distinguished Research Professor, Biological Chemistry

Ralph and Marjorie Crump Distinguished Professor Emeritus, Molecular & Medical Pharmacology

Vice Chair, Molecular & Medical Pharmacology

Member, CTSI, Crump Institute for Molecular Imaging, I3T Theme, JCCC Cancer Molecular Imaging, Molecular Biology Institute

Identification and Characterization of Genes that Modulate Mitogenesis and Inflammatory Responses. We study how extracellular stimuli elicit changes in cell growth and differentiation, as a result of induced transcription of quiescent primary response genes. We cloned seven "TIS" genes whose transcription is rapidly induced by mitogens in growth-arrested fibroblasts. The TIS genes are all induced by activation of pre-existing transcription factors. The TIS10 gene, now called COX-2, encodes a second form of cyclooxygenase (COX), the rate-limiting enzyme responsible for production of prostaglandins in acute inflammation. COX-2 is the molecular target for Vioxx and Celebrex, the largest selling group of compounds ever to enter the pharmaceutical industry. We study (i) cis-acting promoter sequences and transacting factors regulating COX-2 expression in response to growth factors, inflammatory agents, and cytokines and (ii) the biological role of COX-2 in ligand-induced proliferation,inflammation and cancer. Identification and Charactizattion of Genes Regulating Neuronal Differentiation and Function: We have identified genes that are expressed in neurons either (i) in a neuron-specific manner, following depolarization, or (ii) in neuronal precursor cells in response to neurotrophins such as nerve growth factor. We identified synaptotagmin IV as a gene induced by depolarization in hippocampal neurons, but not by growth factors, hormones, etc. Syt IV, like other synaptotagmins, is found in synaptic vesicles after its induction. Synaptotagmins mediate stimulus-initiated, calcium-dependent fusion of synaptic vesicles to presynaptic membrane. Syt4 appears to be a molecule which, as a result of neuronal stimulation, alters the composition of the synaptic machinery. Syt IV knockout mice, created in our laboratory, are viable but show defects in learning hippocampal dependent tasks. We are now studying the regulation of Syt IV expression by depolarization, the biochemical properties of Syt IV, and the role of Syt IV in memory and learning. We have isolated a number of additional depolarization-induced genes whose roles in memory and learning we will also study. Non-invasive, Repetitive and Quantitatitve Imaging of Reporter Gene Expression in Living Animals. The use of reporter genes such as luciferase, beta-galactosidase and green flourescent protein has opened new areas in cell biology. We have recently developed reporter gene systems that can be used to image gene expression in living vertebrates. We use reporter genes whose protein products can trap positron labeled substrates in tissues, and then image the reporter gene dependent trapping of the positron labeled reporter probes with by positron emission tomography. We have developed two PET reporter gene systems; (1) an enzyme based system that uses the Herpes Simplex Virus thmidine kinase as the reporter gene and positron labelled substrates as a reporter probe and (2) a receptor based system that uses the Dopamine D2 Receptor as the reporter gene and positron labeled ligand as the reporter probe. More recently, we have begun to use optical reporter systems that allow us to monitor gene expression with luciferase in living animals with sensitive CCD cameras. We are currently applying these techniques to transgenic mouse models of disease and to development of gene therapy vectors whose location and expression can be monitored in living subjects.