07/21/05 and 07/22/05 (Forbes Lectures)

Thursday, 07/21/05 Lecture:
Breeding Marine Fluorescent Proteins to Spy on Cells

Roger Y. Tsien, University of California, San Diego; Howard Hughes Medical Institute

Introduction by Janis C. Weeks, University of Oregon


Lecture Abstract:
Genetically encoded tags and indicators are molecular spies that reveal specific gene products and biochemical processes in living cells and organisms. Fluorescent proteins from jellyfish and corals have been bred to eliminate multimerization and cover the entire visible spectrum. Somatic hypermutation in B lymphoma cells harnesses the immune system to produce a powerful new way to evolve protein properties. Indicators constructed from fluorescent proteins can report local dynamic signals such as redox potential, protein-protein interactions, and kinase vs. phosphatase activities. Improved reporters for protein kinase A activity reveal that insulin and cAMP signals interact in adipocytes in novel ways relevant to obesity. Analogous reporters show localized activation of protein kinase A and Src in cells undergoing directed locomotion or mechanical deformation. New genetically encoded calcium indicators offer promise for monitoring neuronal activity and are helping to elucidate the complex way that calcium in various compartments helps control programmed cell death. Indicators for glutamate are beginning to uncover dynamics of glutamate release and reuptake during synaptic modulation and neuronal excitotoxicity.

Friday, 07/22/05 Lecture:
Building Synthetic Molecules to Spy on Cells and Tumors

Roger Y. Tsien, University of California, San Diego; Howard Hughes Medical Institute

Introduction by Felix E. Schweizer, University of California, Los Angeles

Lecture Abstract:

Although fluorescent proteins are powerful tools, they cannot be reduced below ~220 amino acids, and their only useful readout is fluorescence. Much shorter peptide sequences combine genetic encoding with the greater range of spectroscopic properties available by organic synthesis. Tetracysteine motifs of 6-12 amino acids can be labeled in live cells with membrane-permeant biarsenical dyes. Unique applica-tions include green vs. red pulse-chase labeling of old vs. new copies of the same protein, electron-microscopic localization, chromophore-assisted light inactiva-tion of a chosen protein without the problems of antibody penetration, and measurement of local Ca2+ within nanometers of proteins such as Ca2+ channels.   For clinical applications one would prefer not to have to introduce genes or be limited to optical detection. Arginine-rich sequences are known to mediate uptake of a wide variety of contrast agents into cells and tissues in vivo. We find that such uptake can be pre-vented by appending certain polyanionic sequences and selectively re-activated by cleavage of the linker. This new mechanism offers the exciting possibility that radio-active, magnetic, and infrared contrast agents and therapeutic drugs may be concen-trated in diseased tissues expressing particular extracellular proteases.

Roger Tsien is a Professor of Pharmacology and Chemistry at the University of California, San Diego (UCSD), and an Investigator at the Howard Hughes Medical Institute. He received his A.B. in Chemistry and Physics from Harvard College in 1972, and his Ph.D. in Physiology from the University of Cambridge in 1977. He was a postdoctoral fellow with with Dr. T.J. Rink at Cambridge, joined the faculty at the University of California, Berkeley in 1981, and moved to UCSD in 1989. Dr. Tsien is a member of the National Academy of Sciences and the recipient of several honors and awards, most importantly the Passano, Artois-Baillet-Latour, Gairdner, Heineken, Wolf, Keio, and Perl Prizes.

Janis C. Weeks received her B.S. in Life Sciences from Massachusetts Institute of Technology. She received her Ph.D. from the University of California, San Diego and was a postdoctoral research associate at the the University of Washington. Dr. Weeks joined the faculty of the University of Oregon in 1989, has held the rank of professor since 1995, and served as the Head of the Department of Biology from 1998 to 2001. Dr. Weeks started out at the MBL as a teaching assistant in 1978, becoming an instructor of the MBL's Neural Systems and Behavior Course in 1985 and Co-Director from 1996-2000. She has served on MBL's Science Council and became a trustee of the Grass Foundation in 2003.

Felix Erich Schweizer is an Associate Professor in the Department of Neurobiology at the University of California, Los Angeles (UCLA). He received his Ph.D. in Biochemistry from the University of Basel in 1989. From 1990 to 1994, he was a post-doctoral fellow in the Department of Molecular and Cellular Physiology at Stanford University in the laboratory of Professor Richard Tsien. From 1994 to 1998, he was postdoctoral fellow in the Department of Neurobiology at Duke University in the laboratory of Professor George Augustine. Dr. Schweizer is a member of the Society for Neuroscience, the Society for General Physiologists, and the Association of Swiss Societies for Experimental Biology. He has received numerous awards including the Stein-Oppenheimer grant at UCLA, and a grant from the Whitehall Foundation. Dr. Schweizer is an alumnus of the MBL’s Neurobiology course. He was a Grass Fellow at the MBL in 1994, served as Associate Director of the Grass Laboratory in 1997, and was a faculty member of the MBL’s Neurobiology course from 1998 to 2003.


About the Forbes Lecture:
Since 1959, the special two-part Forbes Lecture has been supported by The Grass Foundation, a private foundation which supports research and education in neuroscience. The lectures are given in honor of pioneering neurobiologist Alexander Forbes. Traditionally, the Forbes lecturer also spends several weeks at the MBL, working alongside the Grass Fellowship Program.