Fysiologföreningen: Ludwig Wagner
Current status of knowledge about the third hexa-EF-hand calcium binding protein Secretagogin
Professor Ludwig Wagner
Department of Medicine III Medical, University of Vienna
The hexa-EF-hand calcium binding protein Secretagogin (SCGN) was identified in 1994 by a monoclonal antibody, D24. Its primary and genomic structure was elucidated much later by immunoscreening of a human pancreatic beta cell library based on the lambda-gt11 bacterophage. Its tissue expression initially seemed restricted to the islet of Langerhans and intestinal neuroendocrine cells, the thyroid gland and testis. Later it was found in human cerebellum and the hippocampus as well as in the pituitary and further discrete neuron groups in the brain. The expression in various CNS and in neuroendocrine tumors has become important for diagnostic purposes in clinical settings. Its physicochemical properties were classified as those of a typical calcium sensor protein, changing its tertiary structure upon exposure to calcium. Several interaction partners have been identified, among them SNAP25 and -23, both participating in the SNARE complex. The protein is detected in the serum/plasma as it is secreted from cell lines, especially upon stimulation. However, the levels are much lower than those of insulin. Its physiological property, although still elusive, is currently thought to represent an important role in transducing the intracellular calcium signal into motoric and mechanistic processes such as cellular secretion in endocrine cells as well as at the synaptic cleft, but there might be additional tasks.
Host: Tibor Harkany