Translationally controlled tumor protein key to organ growth

When amounts of a small protein called TCTP (translationally controlled tumor protein) are reduced in the cells of fruit flies, they are smaller than normal, indicating that the protein plays a major role in the growth and proliferation of cells, said researchers at Baylor College of Medicine in a report in current issue of the journal Nature.

Work in his laboratory shows that TCTP plays a role in regulating Rheb (Ras homologue enriched in brain), a protein controlling growth and differentiation, and may give clues to treatment of a particular benign disease called tuberous sclerosis that is associated with the control exerted through the same pathway, said Dr. Kwang-Wook Choi, associate professor of molecular and cellular biology at BCM and his colleagues.

When flies completely lack the protein, they do not live very long. However, when flies have only a little TCTP in their cells, they are very small, said Choi. Graduate student Ya-Chieh Hsu, through a series of studies that concentrated on the effect of the protein on the eyes and wings, elucidated the role of TCTP in the cell.

"She was able to show genetically and biochemically that TCTP is directly involved in regulating Rheb function so that it regulates cell size as well as cell numbers. We found that in the case of dysfunction, the eyes and wings get smaller," said Choi. "If you completely knock out this function in the eye, they have no eyes."

TCTP was of interest because it is over-expressed or overabundant in cancer cells.

"If you reduce the levels of TCTP, tumor cells revert to normal in the laboratory," said Choi. However, in their studies of fruit flies, Choi and his colleagues found when the protein is lacking, it has a profound effect on flies. However, too much does not cause tumor growth. Choi is also a faculty member of the BCM Graduate School of Biomedical Sciences.

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