We found that when a site-specific binding protein interacts with the "handle" region of the prorenin prosegment, the prorenin molecule undergoes a conformational change to its enzymatically active state. This nonproteolytic activation is completely blocked by a decoy peptide with the handle region structure, which competitively binds to such a binding protein. Given increased plasma prorenin in diabetes, we examined the hypothesis that the nonproteolytic activation of prorenin plays a significant role in diabetic organ damage. Streptozotocin-induced diabetic rats were treated with subcutaneous administration of handle region peptide. Metabolic and renal histological changes and the renin-Ang system components in the plasma and kidneys were determined at 8, 16, and 24 weeks following streptozotocin treatment. Kidneys of diabetic rats contained increased Ang I and II without any changes in renin, Ang-converting enzyme, or angiotensinogen synthesis. Treatment with the handle region peptide decreased the renal content of Ang I and II, however, and completely inhibited the development of diabetic nephropathy without affecting hyperglycemia. We propose that the nonproteolytic activation of prorenin may be a significant mechanism of diabetic nephropathy. The mechanism and substances causing nonproteolytic activation of prorenin may serve as important therapeutic targets for the prevention of diabetic organ damage.

Prorenin is the inactive precursor of renin (EC 3.4.23.15), which is a key enzyme in the regulation of blood pressure and electrolyte balance. Prorenin has a prosegment with 43 residues attached to the N terminus of mature renin with 339 -341 residues (1-4). The prosegment has been considered to associate with mature renin to prevent interaction with angiotensinogen, its macromolecular renin substrate (5-7). Prorenin does not proteolytically self-activate like pepsinogen, and its blood circulating level is 10 times higher than that of mature renin (8, 9). Some investigators have recently proposed that prorenin is a useful marker of diabetic microvascular complications and Wilms' tumor (11-13). However, much information regarding prorenin is unclear or lacking. The intrinsic activation enzyme, the activation mechanism in vivo, and its physiological role and source in the circulation remain unknown.Prorenin has reportedly been activated in vitro by endopeptidases such as trypsin and cathepsin B (3, 14, 15) and has also been non-proteolytically activated under acidic pH and/or low temperature (17)(18)(19)(20)(21)(22). We recently showed that specific antibodies to the prosegment (L 1P PTDTTTFKRIFLKR 15P ) activated human prorenin non-proteolytically (23). More recently, a renin/prorenin receptor was found in several tissues with nonproteolytically activated renin as well as prorenin (24). These non-proteolytic activations have generally been thought to arise from a conformational change of the prorenin molecule in vivo.The inactivation mechanism for prorenin has been reported using recombinant prorenins mutated at single to triple residues in the prosegment that formed ionic bonds (25-27) or a hydrophobic bond (27) between the prosegment and mature renin. Advanced research on the role of the prosegment in the non-proteolytic activation of prorenin may provide clues to solving those problems. Recently, we found that the acid activation rate of rat prorenin was less than one-fifth of that of human prorenin (4), and the speed of this process was only dependent on the amino acid sequence in the prosegment with 43 amino acid residues (28). These results led to our working hypothesis that there was an essential region in the N-terminal side of the prosegment for non-proteolytic activation of prorenin. In this study, we propose a hypothesis that there are two key regions, "gate" and "handle," in prorenin non-proteolytic activation using several kinds of prorenin-specific antibodies. EXPERIMENTAL PROCEDURESDesignation of Antigen Peptides-Antigen peptides in several regions of the prorenin prosegment were designed on the basis of the primary structure of the prosegment and the stereo structure of human prorenin predicted by the homology modeling method, as shown in Fig.

Transfusion of blood products is associated with increased recurrence rate and worse survival after elective hepatic resection for patients with hepatocellular carcinoma.

Our data suggest that combined preoperative CEA and CA 19-9 levels are suitable for assessing expected curability and resectability in patients with pancreatic cancer.

Patients were discharged without any complications. The umbilical wounds were almost invisible 1 month after surgery. We believe that SILS, with some technical refinements, can be safely applied for distal pancreatectomy. Although the cosmetic benefits of single-incision laparoscopic distal pancreatectomy are obvious, several issues such as the extent of invasiveness, cost, indications, and learning curve need to be investigated.