Neil A. Taylor

The cytokine tumor necrosis factor (TNF) is the primary trigger of inflammation. Like many extracellular signaling proteins, TNF is synthesized as a transmembrane protein; the active signal is its ectodomain, which is shed from cells after cleavage by an ADAM family metalloprotease, ADAM17 (TNFα-converting enzyme, TACE). We report that iRhom2 (RHBDF2), a proteolytically inactive member of the rhomboid family, is required for TNF release in mice. iRhom2 binds TACE and promotes its exit from the endoplasmic reticulum. The failure of TACE to exit the endoplasmic reticulum in the absence of iRhom2 prevents the furin-mediated maturation and trafficking of TACE to the cell surface, the site of TNF cleavage. Given the role of TNF in autoimmune and inflammatory diseases, iRhom2 may represent an attractive therapeutic target.

The proprotein convertases (PCs) are a seven-member family of endoproteases that activate proproteins by cleavage at basic motifs. Expression patterns for individual PCs vary widely, and all cells express several members. The list of substrates activated by PCs has grown to include neuropeptides, peptide hormones, growth and differentiation factors, receptors, enzymes, adhesion molecules, blood coagulation factors, plasma proteins, viral coat proteins, and bacterial toxins. It has become clear that the PC family plays a crucial role in a variety of physiological processes and is involved in the pathology of diseases such as cancer, viral infection, and Alzheimer's disease. Recent studies using PC inhibitors have demonstrated their potential as therapeutic targets. Despite the avalanche of in vitro data, the physiological role of individual PCs has remained largely elusive. Recently, however, knockout mouse models have been developed for furin, PC1, PC2, PC4, PC6B, LPC, and PACE4, and human patients with PC1 deficiency have been identified. The phenotypes range from undetectable to early embryonic lethality. The major lesson learned from these studies is that specific PC-substrate pairs do exist, but that there is substantial redundancy for the majority of substrates. To some extent, redundancy may be cell type and even species dependent.

The amyloid peptide is the main constituent of the amyloid plaques in brain of Alzheimer's disease patients. This peptide is generated from the amyloid precursor protein by two consecutive cleavages. Cleavage at the N terminus is performed by the recently discovered β-secretase (Bace). This aspartyl protease contains a propeptide that has to be removed to obtain mature Bace. Furin and other members of the furin family of prohormone convertases are involved in this process. Surprisingly, β-secretase activity, neither at the classical Asp1 position nor at the Glu11 position of amyloid precursor protein, seems to be controlled by this maturation step. Furthermore, we show that Glu11 cleavage is a function of the expression level of Bace, that it depends on the membrane anchorage of Bace, and that Asp1 cleavage can be followed by Glu11cleavage. Our data suggest that pro-Bace could be active as a β-secretase in the early biosynthetic compartments of the cell and could be involved in the generation of the intracellular pool of the amyloid peptide. We conclude that modulation of the conversion of pro-Bace to mature Bace is not a relevant drug target to treat Alzheimer's disease. The amyloid peptide is the main constituent of the amyloid plaques in brain of Alzheimer's disease patients. This peptide is generated from the amyloid precursor protein by two consecutive cleavages. Cleavage at the N terminus is performed by the recently discovered β-secretase (Bace). This aspartyl protease contains a propeptide that has to be removed to obtain mature Bace. Furin and other members of the furin family of prohormone convertases are involved in this process. Surprisingly, β-secretase activity, neither at the classical Asp1 position nor at the Glu11 position of amyloid precursor protein, seems to be controlled by this maturation step. Furthermore, we show that Glu11 cleavage is a function of the expression level of Bace, that it depends on the membrane anchorage of Bace, and that Asp1 cleavage can be followed by Glu11cleavage. Our data suggest that pro-Bace could be active as a β-secretase in the early biosynthetic compartments of the cell and could be involved in the generation of the intracellular pool of the amyloid peptide. We conclude that modulation of the conversion of pro-Bace to mature Bace is not a relevant drug target to treat Alzheimer's disease. Alzheimer's disease amyloid precursor protein isoelectric focusing beta-site APP-cleavingenzyme soluble Bace Bace in which the propeptide cleavage site RLPR↓ is mutated into ALPA (single letter amino acid code) proprotein convertases polyacrylamide gel electrophoresis α1-antitrypsin Portland amyloid β C-terminal fragments wild type Chinese hamster ovary The brain of patients suffering from Alzheimer's disease (AD)1 is characterized by the presence of amyloid plaques composed mainly of the 39–42 amino acid amyloid β (Aβ) peptide (1Glenner G.G. Wong C.W. Biochem. Biophys. Res. Commun. 1984; 120: 885-890Crossref PubMed Scopus (4170) Google Scholar, 2Masters C.L. Simms G. Weinman N.A. Multhaup G. McDonald B.L. Beyreuther K. Proc. Natl. Acad. Sci. U. S. A. 1985; 82: 4245-4249Crossref PubMed Scopus (3621) Google Scholar). Aβ derives from a type I single membrane-spanning protein termed amyloid precursor protein (APP) by post-translational proteolytic cleavage (3Haass C. Selkoe D.J. Cell. 1993; 75: 1039-1042Abstract Full Text PDF PubMed Scopus (737) Google Scholar). Two cleavages by β-and γ-secretases, respectively, are required to release Aβ from APP. Only recently the molecular identity of these enzymes has been elucidated. γ-Secretase is apparently a large complex, with presenilin being an essential component of it (4De Strooper B. Saftig P. Craessaerts K. Vanderstichele H. Guhde G. Annaert W. Von Figura K. Van Leuven F. Nature. 1998; 391: 387-390Crossref PubMed Scopus (1544) Google Scholar, 5Esler W.P. Kimberly W.T. Ostaszewski B.L. Diehl T.S. Moore C.L. Tsai J.Y. Rahmati T. Xia W. Selkoe D.J. Wolfe M.S. Nat. Cell. Biol. 2000; 2: 428-434Crossref PubMed Scopus (504) Google Scholar, 6Wolfe M.S. Xia W. Ostaszewski B.L. Diehl T.S. Kimberly W.T. Selkoe D.J. Nature. 1999; 398: 513-517Crossref PubMed Scopus (1679) Google Scholar, 7Li Y.M. Xu M. Lai M.T. Huang Q. Castro J.L. DiMuzio-Mower J. Harrison T. Lellis C. Nadin A. Neduvelil J.G. Register R.B. Sardana M.K. Shearman M.S. Smith A.L. Shi X.P. Yin K.C. Shafer J.A. Gardell S.J. Nature. 2000; 405: 689-694Crossref PubMed Scopus (861) Google Scholar). β-Secretase has been identified independently by 5 groups and was named Bace (beta-site APP cleavingenzyme), Asp-2, or memapsin 2 (membrane-anchored aspartic protease of the pepsin family) (8Hussain I. Powell D. Howlett D.R. Tew D.G. Meek T.D. Chapman C. Gloger I.S. Murphy K.E. Southan C.D. Ryan D.M. Smith T.S. Simmons D.L. Walsh F.S. Dingwall C. Christie G. Mol. Cell. Neurosci. 1999; 14: 419-427Crossref PubMed Scopus (997) Google Scholar, 9Vassar R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar, R. H. D.B. Nature. 1999; PubMed Scopus Google Scholar, G. S. D. A. J. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar). Bace is a type I membrane protein, with a aspartyl protease in Bace of the a has with expression in the brain (8Hussain I. Powell D. Howlett D.R. Tew D.G. Meek T.D. Chapman C. Gloger I.S. Murphy K.E. Southan C.D. Ryan D.M. Smith T.S. Simmons D.L. Walsh F.S. Dingwall C. Christie G. Mol. Cell. Neurosci. 1999; 14: 419-427Crossref PubMed Scopus (997) Google Scholar, 9Vassar R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar). mainly in and (8Hussain I. Powell D. Howlett D.R. Tew D.G. Meek T.D. Chapman C. Gloger I.S. Murphy K.E. Southan C.D. Ryan D.M. Smith T.S. Simmons D.L. Walsh F.S. Dingwall C. Christie G. Mol. Cell. Neurosci. 1999; 14: 419-427Crossref PubMed Scopus (997) Google R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar). Bace and of with to Bace β-secretase cleavage of APP (8Hussain I. Powell D. Howlett D.R. Tew D.G. Meek T.D. Chapman C. Gloger I.S. Murphy K.E. Southan C.D. Ryan D.M. Smith T.S. Simmons D.L. Walsh F.S. Dingwall C. Christie G. Mol. Cell. Neurosci. 1999; 14: 419-427Crossref PubMed Scopus (997) Google Scholar, 9Vassar R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar, R. H. D.B. Nature. 1999; PubMed Scopus Google Scholar, G. S. D. A. J. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar). Bace is a protein is with to the β-secretase cleavage site in APP. APP the APP R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar, R. H. D.B. Nature. 1999; PubMed Scopus Google Scholar, G. S. D. A. J. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar). The APP the β-secretase site R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar, R. H. D.B. Nature. 1999; PubMed Scopus Google Scholar, G. S. D. A. J. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar). Bace has an and is to the aspartic protease R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar). this is is on the cell of Bace. Bace is protein in a acid from which the amino to the peptide. of Bace from brain that the mature protein at acid that Bace is into the proprotein convertases and members of the are as that the of the propeptide to active M. Res. 1999; PubMed Scopus Google Scholar). has recently been that pro-Bace is in the and that propeptide cleavage in the C-terminal to the M. Denis P. Y. Mendiaz E.A. Fuller J. Bennett B.D. Kahn S. Ross S. Burgess T. Rogers G. R. Citron M. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, A. H. M. H. C. J. S. Multhaup G. C. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google the of members of the family in this process. are involved in the of peptide and and and M. Res. 1999; PubMed Scopus Google Scholar, Biol. 1998; 2: PubMed Scopus Google Scholar, K. Biochem. J. PubMed Scopus Google Scholar). are C-terminal to or and is amino acid and M. Res. 1999; PubMed Scopus Google Scholar). members been as and or enzymes a expression and not furin was in the of in R. D.J. J. D.G. G. Nat. Neurosci. 1999; 2: PubMed Scopus Google Scholar, R. B. A. S. T. G. J. Nature. 1999; PubMed Scopus Google Scholar). This to of the family could be involved in the of the of Bace. the to this is from a cell of we that in the of Bace could in We the maturation of Bace in in and we that mainly furin in to a other and could the Bace propeptide in in this step. We that Bace on APP is not by the of furin or by that pro-Bace can APP. We conclude that it is that the proteolytic maturation of pro-Bace is a Two on the of R. H. D.B. Nature. 1999; PubMed Scopus Google to and and The was into This was as to a C-terminal in Bace and The the of Bace the and The the by site the the followed by a and an site The with and in and in which the propeptide cleavage site RLPR↓ was mutated into to the and as that these the by was in a to the C-terminal to the to of the propeptide of Bace, has been A. H. M. H. C. J. S. Multhaup G. C. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). was to the Bace of the members of the proprotein family from The the APP terminus and the of APP been (4De Strooper B. Saftig P. Craessaerts K. Vanderstichele H. Guhde G. Annaert W. Von Figura K. Van Leuven F. Nature. 1998; 391: 387-390Crossref PubMed Scopus (1544) Google Scholar). and and respectively, and from the and was by G. Teplow D.B. R. B. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). from and with a in at followed by to the Craessaerts K. I. G. D. P. B. P. Strooper B. J. Biol. 1999; PubMed Scopus Google Scholar). with and 2 at and to at was on a to a and by and and the of from Chinese hamster ovary and the Mol. PubMed Scopus Google and in with with 2 of and of and the and or 2 and in and in the and with the in the of was to the and was of Bace and in of and and performed as M. W. W. Van J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, N.A. B.D. Van J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). of Bace and Bace with or not The which was APP with Bace and as in the and or and and APP and C-terminal fragments from the cell Aβ and APP from the as (4De Strooper B. Saftig P. Craessaerts K. Vanderstichele H. Guhde G. Annaert W. Von Figura K. Van Leuven F. Nature. 1998; 391: 387-390Crossref PubMed Scopus (1544) Google Scholar, Strooper B. Craessaerts K. Van Leuven F. Van H. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). from from the by was performed with or of Bace in isoelectric focusing was performed as in Science. Scholar). a gel and was at a of and a of to with as We to the intracellular of Bace in of Bace, and in the of Bace and the is Bace in the of Bace in Bace from (8Hussain I. Powell D. Howlett D.R. Tew D.G. Meek T.D. Chapman C. Gloger I.S. Murphy K.E. Southan C.D. Ryan D.M. Smith T.S. Simmons D.L. Walsh F.S. Dingwall C. Christie G. Mol. Cell. Neurosci. 1999; 14: 419-427Crossref PubMed Scopus (997) Google Scholar, 9Vassar R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, G. S. D. A. J. Proc. Natl. Acad. Sci. U. S. A. 2000; PubMed Scopus Google Scholar, M. Denis P. Y. Mendiaz E.A. Fuller J. Bennett B.D. Kahn S. Ross S. Burgess T. Rogers G. R. Citron M. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, A. H. M. H. C. J. S. Multhaup G. C. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). Our data these at the of expression and that Bace to the relevant the of expression of Bace are not to the maturation and the of Bace was performed in We and the Bace from a and identity to the by R. H. D.B. Nature. 1999; PubMed Scopus Google Scholar). the and maturation of Bace, and 2 the protein as a with an of and two at and with M. Denis P. Y. Mendiaz E.A. Fuller J. Bennett B.D. Kahn S. Ross S. Burgess T. Rogers G. R. Citron M. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, A. H. M. H. C. J. S. Multhaup G. C. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). The protein the the of protein and the the 2 of and with 2 that the protein not the protein in a single of This that the protein the The protein is the Bace the protein is Bace and the is the The large in molecular that the of Bace are is M. Denis P. Y. Mendiaz E.A. Fuller J. Bennett B.D. Kahn S. Ross S. Burgess T. Rogers G. R. Citron M. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). of the N terminus of Bace a propeptide of amino in the are and by M. Res. 1999; PubMed Scopus Google Scholar, Biol. 1998; 2: PubMed Scopus Google Scholar, K. Biochem. J. PubMed Scopus Google Scholar). Bace from brain or at R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar, R. H. D.B. Nature. 1999; PubMed Scopus Google it is that Bace is by a of this the are essential by M. Res. 1999; PubMed Scopus Google we the at the and in the We this protein expression in is apparently and in a from 2 We generated the soluble of and and the and with soluble Bace is and and can be from the 2 The soluble and are and an precursor can be in the not This that the in a to the protein, it as a Cleavage of the propeptide the molecular of pro-Bace by the it is that this pro-Bace and Bace is to in the gel electrophoresis We that the propeptide of Bace contains and the mature Bace protein is in We to isoelectric focusing to from Bace. We the cell Mol. PubMed Scopus Google to the of furin in the of Bace and We by the the of protein to be is that wild type Bace of with furin in of the protein the at the of the gel that the propeptide been removed by This was the which not with mature and in to the generated in the presence of furin The of the to mature is with other in in Science. Scholar). This can be by the in the of with the to aspartic conversion that the to with Bace. furin of pro-Bace was to the mature Bace and The in could be by mature Bace not by the propeptide This that this Bace. We that a of pro-Bace was to furin as on the in from which it is that a large of Bace of we conclude that this Bace. this pool is in the early compartments of the it is not which is active in the The of protein that is in on the other the protein that has the and is to furin and are in and is not by the in to Bace Furthermore, protease that this cleavage is performed by a protease not is that the ALPA a site that by a of the identity of this protease and the site of it is that this is recently a single amino acid into the cleavage site of Bace to a This is not in with that the Bace is by a of the the ALPA an cleavage the that Bace and are in with the of the cleavage furin that furin is involved in pro-Bace maturation in other members of the could the cleavage of be other that and and in and Bace of the enzymes was 5 it is that furin was to Furthermore, on was in not in and could be by expression of furin and by expression of the is a protease from the α1-antitrypsin and has been to furin and to a and F. K. G. Y. G. Proc. Natl. Acad. Sci. U. S. A. 1998; PubMed Scopus Google Scholar, S. D. A. M. M. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). The was performed with Bace of furin in of other of pro-Bace to a as This is to be a cell in the cell the other the data with suggest that furin has a in pro-Bace in of Bace by and with Bace or with furin or or followed by of with or and on or and pro-Bace to the and The an protein of by and with or with furin or and was with and on The position of and is the cleavage and membrane anchorage of Bace β-secretase activity, with Bace, and furin or as in of APP was by in and of C-terminal fragments APP and Aβ or by to and generated by and in of APP in cleavage of APP mainly at the as by the of at the site and by the that of the APP to and on the other which is with data in other cell that β-secretase is and APP is mainly by the in M. Strooper B. Multhaup G. Beyreuther K. J. Neurosci. PubMed Google Scholar). of Bace cleavage of APP at the 2 β-secretase and Glu11 R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google with the in and β-secretase the APP has been R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google Scholar, 10Sinha S. Anderson J.P. Barbour R. Basi G.S. Caccavello R. Davis D. Doan M. Dovey H.F. Frigon N. Hong J. Jacobson-Croak K. Jewett N. Keim P. Knops J. Lieberburg I. Power M. Tan H. Tatsuno G. Tung J. Schenk D. Seubert P. S. D. J. Nature. 1999; PubMed Scopus Google Scholar, R. H. D.B. Nature. 1999; PubMed Scopus Google Scholar, C. Citron M. Selkoe D.J. J. Biol. 1993; Full Text PDF PubMed Google Scholar, S. B.D. R. J. Neurosci. 1998; PubMed Google Scholar, P. Proc. Natl. Acad. Sci. U. S. A. 1993; PubMed Scopus Google Scholar). is that and at position Glu11 are at Asp1 the The is not with and We that Asp1 is the β-secretase site that the amino that is generated by Asp1 cleavage can be by Bace to the Glu11 C-terminal APP this is was by two Bace at into the with an that the generated in Bace in the of APP that contains this the of Glu11 cleavage in is a of the of Bace Bace expression in a Asp1 This in we of with of Bace in of Bace protein expression of into the that at of Bace protein of of the Aβ at with Bace expression are in the of the peptide at Asp1 and in was a the of Bace expression and the of in the and of by in the of two these show that the cleavage at Glu11 is a function of the expression level of Bace. The Glu11 position is to be a cleavage site of Bace R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google at this position are by of and are in plaques of patients M. Strooper B. Multhaup G. Beyreuther K. J. Neurosci. PubMed Google and We the Glu11 cleavage as a of the Bace in we the of which cleavage of APP at Our to the proteolytic of Bace at position Glu11 as as at position Asp1 and to propeptide is Bace or this of APP was in the of that pro-Bace is an active and or mature Bace is 5 other at can pro-Bace could that mature Bace is in that the of APP. we this we this as of that other in to in in β-secretase cleavage as with Bace or Bace furin in in we that Bace is in the by of a it is of APP This as not propeptide cleavage in the and this protein of Bace expression level on Asp1 and Glu11 cleavage of APP. with of and the of was with 2 of was to this and the and Bace of the was by to and β two of the in the and to the position of the Aβ The as as active as Bace in APP and of cleavage of APP mainly at position Asp1 and The that not at Glu11 in that is in the APP or at the Glu11 which is to the cell membrane the Asp1 site R. Bennett B.D. Babu-Khan S. Kahn S. Mendiaz E.A. Denis P. Teplow D.B. Ross S. Amarante P. Loeloff R. Luo Y. Fisher S. Fuller J. Edenson S. Lile J. Jarosinski M.A. Biere A.L. Curran E. Burgess T. Louis J.C. Collins F. Treanor J. Rogers G. Citron M. Science. 1999; 286: 735-741Crossref PubMed Scopus (3271) Google and that the of Bace is to cleavage at the Glu11 we and that the and maturation of Bace in the M. Denis P. Y. Mendiaz E.A. Fuller J. Bennett B.D. Kahn S. Ross S. Burgess T. Rogers G. R. Citron M. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google A. H. M. H. C. J. S. Multhaup G. C. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). We in that pro-Bace is by furin to mature is in the proteolytic maturation of Bace, other members of the family can of furin We that this maturation is not essential the β-secretase of Bace on APP. We conclude that the maturation of pro-Bace has as a target Alzheimer's disease. other from proteolytic of the been in and intracellular the propeptide of Bace is or intracellular of it is that APP is not the of Bace and that cleavage of other Bace is on of the that pro-Bace is to APP that it could be active as a β-secretase in early biosynthetic cell in and early it is that pro-Bace is involved in the generation of the intracellular amyloid peptide pool as T. B. N. D. C.L. K. Beyreuther K. Nat. PubMed Scopus Google Scholar, N. E. M. A. Multhaup G. C.L. Beyreuther K. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar, C. T. A. U. H. Y. C. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, B.D. D.G. J. Biol. PubMed Scopus Google Scholar). This pool is by as the in Alzheimer's disease. this was a by B. Denis P. M. Teplow D.B. Kahn S. Louis J.C. Citron M. R. J. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google that furin is the proteolytic of the propeptide from Bace. We with and the the terminus of

ADAM17 (where ADAM is 'a disintegrin and metalloproteinase') can rapidly modulate cell-surface signalling events by the proteolytic release of soluble forms of proligands for cellular receptors. Many regulatory pathways affect the ADAM17 sheddase activity, but the mechanisms for the activation are still not clear. We have utilized a cell-based ADAM17 assay to show that thiol isomerases, specifically PDI (protein disulfide isomerase), could be responsible for maintaining ADAM17 in an inactive form. Down-regulation of thiol isomerases, by changes in the redox environment (for instance as elicited by phorbol ester modulation of mitochondrial reactive oxygen species) markedly enhanced ADAM17 activation. On the basis of ELISA binding studies with novel fragment antibodies against ADAM17 we propose that isomerization of the disulfide bonds in ADAM17, and the subsequent conformational changes, form the basis for the modulation of ADAM17 activity. The shuffling of disulfide bond patterns in ADAMs has been suggested by a number of recent adamalysin crystal structures, with distinct disulfide bond patterns altering the relative orientations of the domains. Such a mechanism is rapid and reversible, and the role of thiol isomerases should be investigated further as a potential factor in the redox regulation of ADAM17.

Furin is an endoprotease of the family of mammalian proprotein convertases and is involved in the activation of a large variety of regulatory proteins by cleavage at basic motifs. A large number of substrates have been attributed to furin on the basis of in vitro and ex vivo data. However, no physiological substrates have been confirmed directly in a mammalian model system, and early embryonic lethality of a furin knock-out mouse model has precluded in vivo verification of most candidate substrates. Here, we report the generation and characterization of an interferon inducible Mx-Cre/loxP furin knock-out mouse model. Induction resulted in near-complete ablation of the floxed fur exon in liver. In sharp contrast with the general furin knock-out mouse model, no obvious adverse effects were observed in the transgenic mice after induction. Histological analysis of the liver did not reveal any overt deviations from normal morphology. Analysis of candidate substrates in liver revealed complete redundancy for the processing of the insulin receptor. Variable degrees of redundancy were observed for the processing of albumin, alpha(5) integrin, lipoprotein receptor-related protein, vitronectin and alpha(1)-microglobulin/bikunin. None of the tested substrates displayed a complete block of processing. The absence of a severe phenotype raises the possibility of using furin as a local therapeutic target in the treatment of pathologies like cancer and viral infections, although the observed redundancy may require combination therapy or the development of a more broad spectrum convertase inhibitor.