Oklahoma Medical Research Foundation

University of Illinois

Xinli Lin

Jordan J N Tang

Lin Hong

Gerald Koelsch

Arun K Ghosh

Jordan J Tang

Gerald Keolsch

Methods for the production of purified, catalytically active, recombinant memapsin 2 have been developed. The substrate and subsite specificity of the catalytically active enzyme have been determined. The substrate and subsite specificity information was used to design substrate analogs of the natural memapsin 2 substrate that can inhibit the function of memapsin 2. The substrate analogs are based on peptide sequences, shown to be related to the natural peptide substrates for memapsin 2. The substrate analogs contain at least one analog of an amide bond which is not capable of being cleaved by memapsin 2. Processes for the synthesis of two substrate analogues including isosteres at the sites of the critical amino acid residues were developed and the substrate analogues, OMR99-1 and OM99-2, were synthesized. OM99-2 is based on an octapeptide Glu-Val-Asn-Leu-Ala-Ala-Glu-Phe (SEQ ID NO:28) with the Leu-Ala peptide bond substituted by a transition-state isostere hydroxyethylene group (FIG.). The inhibition constant of OM99-2 is 1.6&#xd7;10M against recombinant pro-memapsin 2. Crystallography of memapsin 2 bond to this inhibitor was used to determine the three dimensional structure of the protein, as well as the importance of the various residues in binding. This information can be used by those skilled in the art to design new inhibitors, using commercially available software programs and techniques familiar to those in organic chemistry and enzymology, to design new inhibitors to memapsin 2, useful in diagnostics and for the treatment and/or prevention of Alzheimer's disease.

Catalytically active recombinant memapsin and methods of use thereof

A universal folding method that has been demonstrated to be effective in refolding a variety of very different proteins expressed in bacteria as inclusion bodies has been developed. Representative proteins that can be dissolved and refolded in biologically active form, with the native structure, are shown in Table I. The method has two key steps to unfold and then refold the proteins expressed in the inclusion bodies. The first step is to raise the pH of the protein solution in the presence of denaturing agents to pH greater than 9, preferably 10. The protein solution may be maintained at the elevated pH for a period of up to about 24 hours, or the pH immediately decreased slowly, in increments of about 0.2 pH units/24 hours, until the solution reaches a pH of about 8.0, or both steps used. In the preferred embodiment, purified inclusion bodies are dissolved in 8 M urea, 0.1 M Tris, 1 mM glycine, 1 mM EDTA, 10 mM beta-mercaptoethanol, 10 mM dithiothreitol (DTT), 1 mM reduced glutathione (GSH), 0.1 mM oxidized glutathione (GSSG), pH 10. The absorbance at 280 nm (OD280) of the protein solution is 5.0. This solution is rapidly diluted into 20 volumes of 20 mM Tris base. The resulting solution is adjusted to pH 9.0 with 1 M HCl and is kept at 4&#xb0; C. for 24 hr. The pH is adjusted to pH 8.8 and the solution is kept at 4&#xb0; C. for another 24 hrs. This process is repeated until the pH is adjusted to 8.0. After 24 hr at pH 8.0, the refolded proteins can be concentrated by ultrafiltration and applied to a gel filtration column for purification.

Universal procedure for refolding recombinant proteins

A universal folding method that has been demonstrated to be effective in refolding a variety of very different proteins expressed in bacteria as inclusion bodies has been developed. Representative proteins that can be dissolved and refolded in biologically active form, with the native structure, are shown in Table I. The method has two key steps to unfold and then refold the proteins expressed in the inclusion bodies. The first step is to raise the pH of the protein solution in the presence of denaturing agents to pH greater than 9, preferably 10. The protein solution may be maintained at the elevated pH for a period of up to about 24 hours, or the pH immediately decreased slowly, in increments of about 0.2 pH units/24 hours, until the solution reaches a pH of about 8.0, or both steps used. In the preferred embodiment, purified inclusion bodies are dissolved in 8 M urea, 0.1 M Tris, 1 mM glycine, 1 mM EDTA, 10 mM beta-mercaptoethanol, 10 mM dithiothreitol (DTT), 1 mM redued glutathion (GSH), 0.1 mM oxidized glutathion (GSSG), pH 10. The absorbance at 280 nm (OD280) of the protein solution is 5.0. This solution is rapidly diluted into 20 volumes of 20 mM Tris base. The resulting solutin is adjusted to pH 9.0 with 1 M HCl and is kept at 4&deg; C. for 24 hr. The pH is adjusted to pH 8.8 and the solution is kept at 4&deg; C. for another 24 hrs. This process is repeated until the pH is adjusted to 8.0. After 24 hr at pH 8.0, the refolded proteins can be concentrated by ultrafiltration and applied to a gel filtration column for purification.

Methods for the production of purified, catalytically active, recombinant memapsin 2 have been developed. The substrate and subsite specificity of the catalytically active enzyme have been determined. The substrate and subsite specificity information was used to design substrate analogs of the natural memapsin 2 substrate that can inhibit the function of memapsin 2. The substrate analogs are based on peptide sequences, shown to be related to the natural peptide substrates for memapsin 2. The substrate analogs contain at least one analog of an amide bond which is not capable of being cleaved by memapsin 2. Processes for the synthesis of two substrate analogues including isosteres at the sites of the critical amino acid residues were developed and the substrate analogues, OMR99-1 and OM99-2, were synthesized. OM99-2 is based on an octapeptide Glu-Val-Asn-Leu-Ala-Ala-Glu-Phe (SEQ ID NO:28) with the Leu-Ala peptide bond substituted by a transition-state isostere hydroxyethylene group (FIG. ). The inhibition constant of OM99-2 is 1.6&times;10 M against recombinant pro-memapsin 2. Crystallography of memapsin 2 bound to this inhibitor was used to determine the three dimensional structure of the protein, as well as the importance of the various residues in binding. This information can be used by those skilled in the art to design new inhibitors, using commercially available software programs and techniques familiar to those in organic chemistry and enzymology, to design new inhibitors to memapsin 2, useful in diagnostics and for the treatment and/or prevention of Alzheimer's disease.

A combination of adenoviral and retroviral vectors used to construct second generation packaging cells that deliver marker genes to target cells is described. A vector based upon Moloney murine leukemia virus (MLV) was used to deliver marker genes, and an adenovirus-based delivery system was used to deliver MLV structural genes (gagpol and env) to cultured cells. The procedure transformed the cells into new retroviral producer cells, which generate replication-incompetent retroviral particles in the culture supernatant for transferring marker genes to target cells. The titer of the retroviral-containing supernatant generated from the second generation producer cells reached above 105 cfu/ml which is comparable to the MLV-based producer cell lines currently used in human gene therapy trials. The vector and procedures are adaptable for experimental human gene therapy in which the new producer cells are transplanted into patients for continuous gene transfer.

Construction of retroviral producer cells from adenoviral and retroviral vectors

A previously unknown aspartic protease capable of cleavage of proteins by hydrolysis, referred to herein as &ldquo;napsin&rdquo;, has been cloned from a human liver library. Two cDNA clones have been cloned, sequenced and expressed. These encode isozymes of the protease, referred to as &ldquo;napsin A&rdquo; and &ldquo;napsin B&rdquo;. The gene has also be obtained and partially sequenced. A process for rapid purification of the enzyme using immobilized petpstatin has also been developed, and enzyme isolated from human kidney tissue. Polyclonal antibodies to the enzymes have been made which are also useful for isolation and detection of the enzyme. Similarities to other aspartic proteases, especially cathepsin D, establish the usefulness of the enzyme in diagnostic assays as well as as a protease. Either or both the amount or type of napsin expressed in a particular tissue can be determined using labelled antibodies or nucleotide probes to the napsin.

Growing community of inventors

Edmond, OK, United States of America

Xinli Lin