by
(reprinted with permission from Current
Biology, March 1997, Vol. 7, p. R125.)
(Issue 6 ? posted April 18, 1997; archived May 2, 1997)
Tom Pollard is the new president of the prestigious Salk Institute for Biological Studies in La Jolla, California. Until recently, it seemed unlikely that Pollard, who has spent his research career studying how cells move, would make a move himself. He seemed settled at Johns Hopkins University School of Medicine, where he has been for the past nineteen years. But Pollard says it was time for a change, and that the chance of working at the Salk Institute - which is renowned for the high quality of its research, yet small enough to allow its president to continue his pioneering work on cellular motility - was too tempting to refuse.
Pollard's interest in cell motility arose from an undergraduate summer job during which he watched many hours of time-lapse film of moving cells. At this time, it was known that movement in muscle tissue was the result of actin and myosin filaments sliding over each other, but nothing was known about the biochemistry of motility in non-muscle cells.
Eager to maintain his interest in research as a medical student at Harvard Medical School, Pollard worked in the laboratory of Sus Ito. Pollard recalls the extreme generosity of Ito in training him in electron microscopy and other techniques, despite the fact that he was doing research quite unrelated to the main interest of Ito's laboratory. During this time, Pollard purchased some amoebae to use in an experiment that was proving difficult. Although the amoebae did not solve the experimental problem, their motility caught Pollard's interest.
The real breakthrough came when he heard about some experiments done by Lewis Wolpert, who had isolated cellular extracts that 'moved' when the chemical ATP was added. Fortunately, because he was a newcomer in the cell motility field, Pollard was not exposed to the scepticism of other workers about Wolpert's work, and after several attempts he managed to repeat the in vitro motility experiment. This provided a crucial cell-free system that would allow dissection of the cellular machinery involved in cell motility. In the electron microscope, Pollard saw thick and thin filaments similar to those found in muscle tissue in these cell extracts, suggesting that cellular movement may involve the same components used in contractile tissues.
After an internship, Pollard worked as a postdoctoral fellow with Ed Korn at the National Institutes for Health, where they did some of the early work on cytoplasmic actin and the association of actin filaments with the plasma membrane. They also discovered the first unconventional myosin, which they called myosin-I. The concept of a myosin different from the two-headed myosin in muscle was so unexpected that their discovery was not generally accepted for more than 10 years.
Pollard returned to the Department of Anatomy at Harvard, where he continued his research on the molecular interactions involved in cell motility. He also began teaching both at Harvard Medical School and, during the summers, at Woods Hole Marine Biological Laboratory. During this time, it became clear that actin and myosin are used by a variety of cells for movement, although the architectural arrangement of these proteins is considerably more complex than in muscle tissue.
In 1977, Pollard moved to Johns Hopkins where, in addition to running his research laboratory, he directed the Department of Cell Biology and Anatomy. He earned a reputation for being an exceptional teacher, if one with a regrettable taste in colourful ties. He is held in great affection by his students and postdocs, despite his expectation that they should devote their Saturdays to lab work. As he discovered the regulation of myosin-I by a cofactor protein (later shown to be a kinase) on a Saturday, he considers it a good day for doing science; one wonders if he will continue this tradition at the Salk.
The Pollard family in the Himalayas
After surviving a potentially fatal cancer, Pollard fulfilled a lifelong dream by taking his family trekking in the Himalayas in 1988. The brush with mortality also gave him an additional impetus in a new activity - scientific public policy. Inspired both by his wife Patty, who is active in nonpartisan politics, and by a number of scientific colleagues, he began lobbying the US government for better support for biomedical research. He has gone on to chair the Commission for Life Sciences at the National Academy of Sciences, which directs studies on scientific issues of public importance such as whether environmental electromagnetic radiation affects human health (there is still no solid evidence on this).
In his new position at the Salk Institute, Tom Pollard will be moving between his administrative duties - in which he will doubtless keep as firm a grip on the purse strings as ever - and the laboratory. He is determined to publish as sole author on his own experimental work within the next three years. Whether or not he achieves this goal, there is little doubt that he will continue to be upwardly motile.
Matthijs Smith is currently a postdoctoral research fellow at the Royal Children's Hospital in Melbourne, Australia.
