Exocrine meets endocrine: pancreatic stone protein and regenerating protein--two sides of the same coin.
BACKGROUND
Regenerating protein (reg) and pancreatic stone protein (PSP) have been discovered independently in the fields of diabetes and pancreatitis.


METHODS
These proteins are identical; however, because of the gap between the endocrine and exocrine field, there was never a consensus and the nomenclature has not been rectified. Since the time of the initial discovery, more isoforms have been unified. Historically, PSP was discovered long before reg, yet, in many areas outside of the pancreatitis research field, reg is being used.


RESULTS
For PSP/reg, a role in proliferation and regeneration of islet cells has been postulated. A hitherto insufficiently understood phenomenon is the massive up-regulation of PSP/reg in pancreatic tissue and juice under conditions of stress. Similarly, PAP (pancreatitis-associated protein)/reg III has been attributed various functional roles. Structurally, the ability to form fibrils after tryptic cleavage is a striking common features of both proteins. However, this biochemical transformation is in itself not enough to gain functional insight. Thus, physiological and genetic approaches are required to further characterize the role of these proteins in the pancreas. Recently, more evidence has been presented in support of the theory that PSP/reg plays a key role in islet neogenesis/regeneration.


CONCLUSIONS
In this review we discuss the debate on the localization and functional roles of PSP/reg and PAP/regIII. Therefore, we have summarized hypotheses and experimental results supporting such hypotheses.
Graf
Rolf
R
Pancreatitis Research Laboratory, Department of Visceral and Transplantation Surgery, University Hospital Zurich, Zurich, Switzerland. Rolf.graf@usz.ch
Schiesser
Marc
M
Reding
Theresia
T
Appenzeller
Philippe
P
Sun
Li-Kang
LK
Fortunato
Franco
F
Perren
Aurel
A
Bimmler
Daniel
D
D000818:Animals; D006801:Humans; D007515:Islets of Langerhans / Q000502:physiology*; D051847:Lithostathine / Q000502:physiology*; D046790:Pancreas, Exocrine / Q000502:physiology*; D010195:Pancreatitis / Q000503:physiopathology*; D000073718:Pancreatitis-Associated Proteins; D009626:Terminology as Topic
D051847:Lithostathine; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human