Intracellular proteolytic processing of precursor polypeptides is an essential step in the maturation of many proteins, including plasma proteins, hormones, neuropeptides, and growth factors. Most frequently, propeptide cleavage occurs after paired basic amino acid residues. To date, no mammalian propeptide processing enzyme with such specificity has been purified or cloned and functionally characterized. We report the isolation and functional expression of a cDNA encoding a propeptide-cleaving enzyme from a human liver cell line. The encoded protein, called PACE (paired basic amino acid cleaving enzyme), has structural homology to the well-characterized subtilisin-like protease Kex2 from yeast.The functional specificity of PACE for mediating propeptide cleavage at paired basic amino acid residues was demonstrated by the enhancement of propeptide processing of human von Willebrand factor when coexpressed with PACE in COS-1 cells.

In plasma, antihemophilic factor (factor VIII) exists as a 200-kilodalton heavy-chain polypeptide in a metal ion association with an 80-kilodalton light-chain polypeptide. This complex is bound by hydrophobic and hydrophilic interactions to a large multimeric glycoprotein, von Willebrand factor (vWF). Accumulation of secreted human factor VIII activity expressed in Chinese hamster ovary cells requires the addition of serum in the growth medium, which provides vWF. Here we report that coexpression of vWF with factor VIII in Chinese hamster ovary cells resulted in increased stable accumulation of factor VIII activity in the absence of serum in the growth medium. In the coexpressing cells, the vWF cDNA transcription unit was transcribed to yield mRNA which was efficiently translated. vWF was properly processed and secreted to yield disulfide-bonded high-molecular-weight multimers similar to those observed in vWF secreted from human endothelial cells. Nuclear run-on assays showed that the factor VIII gene was transcribed at a level similar to that of the vWF gene, but the mRNA did not accumulate to high levels in the cytoplasm. In addition, although the translation efficiency of the factor VIII mRNA was similar to that of vWF, the processing and secretion of the factor VIII primary translation product was dramatically reduced compared with vWF. These results demonstrate that in Chinese hamster ovary cells both factor VIII mRNA accumulation and the processing and secretion of the primary factor VIII translation product are inefficient processes.The factor VIII complex has two distinct biologic functions: coagulant activity and a role in primary hemostasis (for reviews, see references 32 and 43). The analysis of factor VIII deficiency diseases, classic hemophilia and von Willebrand's disease, have contributed to the understanding that factor VIII is a complex of two components: the factor VIII procoagulant protein (antihemophilic factor) and the factor VIII-related antigen (von Willebrand factor [vWF]).The factor VIII molecule is an important regulatory protein in the blood coagulation cascade. After activation by thrombin, it accelerates the rate of factor X activation by factor IXa, eventually leading to the formation of the fibrin clot (18,28,39,49,50). Factor VIII is synthesized as a large precursor which is cleaved to generate an amino-terminalderived heavy chain of 200 kilodaltons (kDa) in a metal ion-stabilized complex with the carboxy-terminal-derived light chain of 80 kDa (9,13,41,51). Factor VIII has binding sites for factor IXa, factor X, Ca2 , phospholipid, and vWF.

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The von Willebrand factor (vWF) mediates platelet adhesion to the vascular subendothelium by binding to collagen, other matrix constituents, and the platelet receptor glycoproteins Ib/IX and IIb/IIIa. Although substantial progress has been made in defining vWF structure-function relationships, there are conflicting data regarding the location of its collagen-binding site(s). Possible collagen-binding sites have been localized in the A1 and A3 domains of vWF. To study the proposed binding sites, we have expressed cDNA sequences encoding the A1 and A3 domains of vWF in Escherichia coli and purified the resulting proteins from bacterial inclusion bodies. In addition, a chimeric molecule containing residues 465-598 of the vWF A1 domain polypeptide (vWF-A1) fused in frame to residues 1018-1114 of the vWF A3 domain polypeptide (vWF-A3) was also expressed. Each of the three recombinant proteins purified as a monomer and contained a single disulfide bond. As previously reported (Cruz, M. A., Handin, R. I., and Wise, R. J. (1993) J. Biol. Chem. 268, 21238-21245), recombinant vWF-A1 inhibited ristocetin-induced platelet agglutination, but did not compete with vWF multimers for collagen binding. In contrast, vWF-A3 inhibited the binding of multimeric vWF to immobilized collagen, but did not inhibit ristocetin-induced platelet agglutination. Metabolically labeled vWF-A3 bound to immobilized collagen in a saturable and reversible manner with a Kd of 1.8 x 10(-6) M. The vWF-A1/A3 chimera was bifunctional. It inhibited vWF binding to platelet glycoprotein Ib/IX with an IC50 of 0.6 x 10(-6) M and inhibited vWF binding to collagen with an IC50 of 0.5-1.0 x 10(-6) M. These results, taken together, provide firm evidence that the major collagen-binding site in vWF resides in the A3 domain.

Definitive cure of an animal model of a human disease by gene transfer into hematopoietic stem cells has not yet been accomplished in the absence of spontaneous in vivo selection for transduced cells. Erythropoietic protoporphyria is a genetic disease in which ferrochelatase is defective. Protoporphyrin accumulates in erythrocytes, leaks into the plasma and results in severe skin photosensitivity. Using a mouse model of erythropoietic protoporphyria, we demonstrate here that ex vivo preselection of hematopoietic stem cells transduced with a polycistronic retrovirus expressing both human ferrochelatase and green fluorescent protein results in complete and long-term correction of skin photosensitivity in all transplanted mice.

The purpose of this investigation was to determine if a structured, home-based exercise program was beneficial to reduce symptoms of chemotherapy-induced peripheral neuropathy and improve quality of life (QOL). A total of 50 women who are breast cancer survivors and are listed in the Breast Cancer Registry of Greater Cincinnati database were recruited by mail. Participants were initially asked to complete the McGill QOL questionnaire and the Leeds Assessment of Neuropathic Symptoms and Signs, before beginning a 10-week home-based exercise program. At the completion of the exercise program, subjects were asked again to complete the same two questionnaires. Pre- and post-intervention data were analyzed using a repeated measures ANOVA, at a significance level of α<0.05. Six individuals completed the investigation. Prior to the 10-week exercise program, participants described their pain as unpleasant skin sensations (Pre-HBEx, N=6), abnormally sensitive to touch (Pre-HBEx, N=6), and coming on suddenly in bursts for no apparent reason (Pre-HBEx, N=5). Following 10-weeks of exercise, participants reported experiencing less of these symptoms (Post-HBEx, N=3, 1, and 4 respectively; P=0.05). It was also determined that troublesome symptoms were significantly reduced after 10-weeks of home-based exercise (P=0.05).

As part of a systematic study of platelet interaction with adhesive proteins under flow conditions, we studied platelet adhesion to multimeric and dimeric von Willebrand factor (vWF) coated to glass. vWF-dependent adhesion to collagen type III was studied for comparison. Adhesion to glass-coated vWF and vWF-mediated adhesion to collagen type III were in many respects similar. Both showed no decrease at increasing shear rates and a decline to 50% of maximum with a low-molecular-weight multimeric fraction. Adhesion to glass-coated vWF was partially inhibited by heparin and completely inhibited by prostaglandin I(2) and anti-glycoprotein (GP) Ib and anti-GPIIb-IIIa antibodies. vWF-dependent adhesion to collagen was not inhibited by heparin, was partially inhibited by anti-GPIIb-IIIa, and was completely inhibited by prostaglandin I(2) and anti-GPIb. Recombinant dimeric vWF was made by deletion of the propeptide and expression in Chinese hamster ovary cells. Adhesion was 50% of that with plasma vWF, and larger concentrations of dimeric vWF were required. Adhesion to dimeric vWF was optimal at 1500 s(-1), with a gradual decrease at higher shear rates. We conclude that adhesion to collagen type III is strongly but not completely determined by the adhesive properties of vWF.