Dr. Castle has devoted his scientific career to elucidating the mechanism of secretion from exocrine cells, in particular salivary glands, and throughout his career he has made many novel and important contributions that have had a highly significant impact on our understanding of the molecular mechanisms of exocytosis. These include analysis of secretory granules and their membrane components; demonstration of a proton pump in secretion granules, the role of pH in aggregation of protein in the granules as well as removal of other ions in condensation of granule content, and salivary-gland-specific proline-rich proteins that play a role for their sorting into secretion granules. These studies have led to the more general conclusion that there is no common module in secreted proteins that ensure their sorting into secretion granules, and that this process therefore is of a passive nature.
In recent years, there has been intense interest in membrane trafficking in the cell and the process whereby the fusion of secretion granules and cell membranes occurs, and proteins such as v-SNAREs and t-SNAREs have been identified. Dr. Castle has contributed significantly to this field with his discovery of a new family of proteins--named SCAMPs--occurring widespread in different mammalian tissues that may be important in a late step in exocytosis.
Dr. Castle is also responsible for demonstrating a total of four pathways of secretion in parotid cells--the constitutive, the constitutive-like, the minor regulated, and the major regulated pathways--and for demonstrating that granule exocytosis is reserved for massive protein export during meals. These are only some highlights to illustrate Dr. Castle's many significant contributions. His work is characterized by being meticulously and rigorously performed. His papers are a joy to read because of the completeness of his studies. As a result, the majority of his work has appeared in journals of the highest and first rank, including Cell, Journal of Biological Chemistry, Biochemistry, Journal of Cell Biology, and Proceedings of the National Academy of Science.
Publication in these journals reflects not only the high quality of his work, but also the more widespread implications of his studies. Broad recognition of Dr. Castle's work can also be found in articles and book chapters he has been asked to write, and his many invitations to speak at national and international symposia and meetings, most recently as Chair of the Gordon Conference on Salivary Glands and Exocrine Secretion.
The IADR Salivary Research Award, supported by the William Wrigley, Jr. Company, consists of a cash prize and a plaque and is one of 15 Distinguished Scientist Awards conferred annually by the IADR, representing the highest honor the Association can bestow. Dr. Castle received his award today during the Opening Ceremonies of the IADR's 83rd General Session.