Scientists viewing journal articles about growth hormone (GH) online were especially interested in a University of Texas Health Science Center at San Antonio research project published in the second half of last year, according to results recently made available by the digital library ScienceDirect.
“Spatio-temporal kinetics of growth hormone receptor signaling in single cells using FRET microscopy,” published in the August 2006 issue (Volume 16, Issue 4) of Growth Hormone & IGF Research, was one of the 10 most downloaded articles from the journal on ScienceDirect between October and December 2006.
Venkata Krishnan Ramanujan, Ph.D., instructor/research in the Health Science Center’s department of cellular and structural biology, and Brian Herman, Ph.D., vice president for research and professor of cellular and structural biology, co-authored the article. Eva Biener-Ramanujan and Arieh Gertler, from the Institute of Biochemistry, Food Science and Nutrition in the Faculty of Agricultural, Food and Environmental Quality Sciences at the Hebrew University of Jerusalem, also were co-authors. Dr. Biener-Ramanujan was a graduate student in the laboratory of Dr. Brian Herman when these studies were conducted.
Growth hormone: activity and study Growth hormone stimulates activity by binding to specific receptors in the plasma membrane of cells. The binding of GH to its receptors then triggers the activation of other molecules inside cells, which ultimately results in cell growth. The Health Science Center researchers asked two questions about this activity:
- Does GH bind to individual receptors in the plasma membrane that then begin to cluster, or does it bind to preexisting receptor clusters?
- After this binding occurs, do GH receptor clusters have to be brought inside cells to activate other molecules to stimulate growth?
New discoveries “This study provided new data demonstrating that growth hormone can bind to preexisting receptor clusters rather than binding to individual receptors that then undergo clustering,” Dr. Herman said. “Thus, activation of the growth hormone receptor signaling pathway involves a change in conformation of existing growth hormone receptor clusters rather than growth hormone-induced formation of receptor clusters.”
Regarding the second question, he said: “The data in this paper demonstrate that activated growth hormone receptor clusters remain on the plasma membrane and activate downstream molecules without having to be internalized into the cell.”
Steps toward therapiesThe findings, although complex to the lay public, have definite long-range implications for development of new therapies. “These studies, by explaining the mechanism by which growth hormone signals its biological activity, will allow us to design therapeutic modalities that can either mimic GH action when GH is deficient or inhibit GH action when GH is over-expressed,” Dr. Herman said. “While this naturally relates to the normal growth and development of humans, it may also have some relevance to slowing some of the changes in muscle mass that occur during aging.”
Journal focusThe journal,
Growth Hormone & IGF Research, is a forum for research on the regulation of growth and metabolism in humans, animals, tissues and cells. It publishes articles on all aspects of growth-promoting and growth-inhibiting hormones and factors, with particular emphasis on insulin-like growth factors (IGFs) and growth hormone.
