Interaction of Apolipoprotein J-Amyloid β-Peptide Complex with Low Density Lipoprotein Receptor-related Protein-2/Megalin

Apolipoprotein J (apoJ) has been shown to be the predominant amyloid β-peptide (Aβ)-binding protein in cerebrospinal fluid. We have previously demonstrated that the endocytic receptor low density lipoprotein receptor-related protein-2/megalin (LRP-2), which is expressed by choroid plexus epithelium and ependymal cells lining the brain ventricles and neural tube, binds and mediates cellular uptake of apoJ (Kounnas, M. Z., Loukinova, E. B., Stefansson, S., Harmony, J. A., Brewer, B., Strickland, D. K., and Argraves, W. S. (1995) J. Biol. Chem. 270, 13070–13075). In the present study, we evaluated the ability of apoJ to mediate binding of Aβ1–40-apoJ complex to LRP-2 in vitro. Immunoblot analysis showed that incubation of apoJ with Aβ1–40 resulted in the formation of Aβ1–40-apoJ complex and the inhibition of the formation of Aβ1–40 aggregates. Using an enzyme-linked immunosorbent assay, an estimated dissociation constant (K d) of 4.8 nm was derived for the interaction between Aβ1–40 and apoJ. Enzyme-linked immunosorbent assay was also used to study the interaction of the Aβ1–40-apoJ complex with LRP-2. The results showed that Aβ alone did not bind directly to LRP-2; however, when Aβ1–40 was combined with apoJ to form a complex, binding to LRP-2 took place. The binding interaction could be blocked by inclusion of the receptor-associated protein, an antagonist of apoJ binding to LRP-2. When LRP-2-expressing cells were given125I-Aβ1–40, cellular uptake of the radiolabeled peptide was promoted by co-incubation with apoJ. When the cells were provided purified125I-Aβ1–40-apoJ complex, the complex was internalized and degraded, and both processes were inhibited with polyclonal LRP-2 antibodies. Furthermore, chloroquine treatment inhibited the cellular degradation of the complex. The data indicate that apoJ facilitates Aβ1–40 binding to LRP-2 and that the receptor mediates cellular clearance of Aβ1–40-apoJ complex leading to lysosomal degradation of Aβ1–40. The findings support the possibility that LRP-2 can act in vivoto mediate clearance of the complex from biological fluids such as cerebrospinal fluid and thereby play a role in the regulation of Aβ accumulation. Apolipoprotein J (apoJ) has been shown to be the predominant amyloid β-peptide (Aβ)-binding protein in cerebrospinal fluid. We have previously demonstrated that the endocytic receptor low density lipoprotein receptor-related protein-2/megalin (LRP-2), which is expressed by choroid plexus epithelium and ependymal cells lining the brain ventricles and neural tube, binds and mediates cellular uptake of apoJ (Kounnas, M. Z., Loukinova, E. B., Stefansson, S., Harmony, J. A., Brewer, B., Strickland, D. K., and Argraves, W. S. (1995) J. Biol. Chem. 270, 13070–13075). In the present study, we evaluated the ability of apoJ to mediate binding of Aβ1–40-apoJ complex to LRP-2 in vitro. Immunoblot analysis showed that incubation of apoJ with Aβ1–40 resulted in the formation of Aβ1–40-apoJ complex and the inhibition of the formation of Aβ1–40 aggregates. Using an enzyme-linked immunosorbent assay, an estimated dissociation constant (K d) of 4.8 nm was derived for the interaction between Aβ1–40 and apoJ. Enzyme-linked immunosorbent assay was also used to study the interaction of the Aβ1–40-apoJ complex with LRP-2. The results showed that Aβ alone did not bind directly to LRP-2; however, when Aβ1–40 was combined with apoJ to form a complex, binding to LRP-2 took place. The binding interaction could be blocked by inclusion of the receptor-associated protein, an antagonist of apoJ binding to LRP-2. When LRP-2-expressing cells were given125I-Aβ1–40, cellular uptake of the radiolabeled peptide was promoted by co-incubation with apoJ. When the cells were provided purified125I-Aβ1–40-apoJ complex, the complex was internalized and degraded, and both processes were inhibited with polyclonal LRP-2 antibodies. Furthermore, chloroquine treatment inhibited the cellular degradation of the complex. The data indicate that apoJ facilitates Aβ1–40 binding to LRP-2 and that the receptor mediates cellular clearance of Aβ1–40-apoJ complex leading to lysosomal degradation of Aβ1–40. The findings support the possibility that LRP-2 can act in vivoto mediate clearance of the complex from biological fluids such as cerebrospinal fluid and thereby play a role in the regulation of Aβ accumulation. A hallmark feature of Alzheimer's disease is the accelerated cerebral accumulation of amyloid β-protein (Aβ), 1The abbreviations used are: Aβ, amyloid β-peptide; apoJ, apolipoprotein J/clusterin; LRP-2, low density lipoprotein receptor-related protein-2/megalin; RAP, receptor-associated protein; BSA, bovine serum albumin; TBS, Tris-buffered saline; mAb, monoclonal antibody; PBS, phosphate-buffered saline; dPBS, Dulbecco's PBS; PAGE, polyacrylamide gel electrophoresis; OG,N-octyl-β-d-glucopyranoside; Tricine,N-2-hydroxy-1,1-bis(hydroxymethyl)ethylglycine; RA, retinoic acid; Bt2cAMP, dibutyryl cyclic AMP; DMEM, Dulbecco's modified Eagle's medium; ELISA, enzyme-linked immunosorbent assays; SS, serum substitute. a small 39–42-residue proteolytically derived fragment of amyloid β-precursor protein (1Kang J. Lemaire H.G. Unterbeck A. Salbaum J.M. Masters C.L. Grzeschik K.H. Multhaup G. Beyreuther K. Muller-Hill B. Nature. 1987; 325: 733-736Crossref PubMed Scopus (3957) Google Scholar,2Selkoe D.J. Annu. Rev. Cell Biol. 1994; 10: 373-403Crossref PubMed Scopus (747) Google Scholar). The accumulation takes the form of spherical extracellular deposits of Aβ fibrils in the vicinity of morphologically abnormal axons and dendrites. Associated with these so-called plaques are microglia and astrocytes. The mechanisms that lead to accumulation of Aβ are still obscure but represent an area of intense investigation. Whereas much emphasis is currently placed on trying to determine the mechanism(s) of Aβ biosynthesis from amyloid β-precursor protein processing (3Haass C. Hung A.Y. Schlossmacher M.G. Teplow D.B. Selkoe D.J. J. Biol. Chem. 1993; 268: 3021-3024Abstract Full Text PDF PubMed Google Scholar, 4Haass C. Koo E.H. Teplow D.B. Selkoe D.J. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 1564-1568Crossref PubMed Scopus (94) Google Scholar), little is being done on determining possible mechanisms that mediate the catabolism of Aβ. Catabolic processes may prevent the extracellular accumulation of Aβ that is expressed under normal physiological conditions yet does not accumulate to the extent seen in Alzheimer's disease or Down's syndrome. Aβ can be found in cerebrospinal fluid and blood in complex with apolipoprotein J (apoJ) or apolipoprotein E (apoE) (5Ghiso J. Matsubara E. Koudinov A. Choi-Miura N.H. Tomita M. Wisniewski T. Frangione B. Biochem. J. 1993; 293: 27-30Crossref PubMed Scopus (264) Google Scholar, 6Matsubara E. Frangione B. Ghiso J. J. Biol. Chem. 1995; 270: 7563-7567Abstract Full Text Full Text PDF PubMed Scopus (182) Google Scholar). Whereas apoE has been reported to promote Aβ fibrilogenesis (7Ma J. Yee A. Brewer Jr., H.B. Das S. Potter H. Nature. 1994; 372: 92-94Crossref PubMed Scopus (862) Google Scholar, 8Soto C. Castano E.M. Prelli F. Kumar R.A. Baumann M. FEBS Lett. 1995; 371: 110-114Crossref PubMed Scopus (52) Google Scholar, 9Wisniewski T. Castano E.M. Golabek A. Vogel T. Frangione B. Am. J. Pathol. 1994; 145: 1030-1035PubMed Google Scholar), apoJ has been shown to slow the formation of Aβ aggregates and may therefore act to maintain Aβ in a soluble form and prevent it from forming pathological fibrils (10Oda T. Pasinetti G.M. Osterburg H.H. Anderson C. Johnson S.A. Finch C.E. Biochem. Biophys. Res. Commun. 1994; 204: 1131-1136Crossref PubMed Scopus (100) Google Scholar). Our discoveries that LRP-2 2LRP-2 is synonymous with glycoprotein 330 (gp330), brushin, and megalin. is an endocytic receptor for apoJ (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar) and LRP-2 is expressed by cells that are in contact with cerebrospinal fluid (choroid plexus and ependymal cells) (12Kounnas M.Z. Haudenschild C.C. Strickland D.K. Argraves W.S. In Vivo ( Athens ). 1994; 8: 343-351PubMed Google Scholar) prompted us to hypothesize that LRP-2 may mediate clearance of Aβ complexed with apoJ, thereby controlling the accumulation of Aβ. In the present study, we used in vitro solid phase binding assays as well as cellular internalization and degradation assays to evaluate the roles of apoJ and LRP-2 in mediating cellular clearance of Aβ. Human apoJ was purchased from Quidel (San Diego, CA). Synthetic Aβ fragment 1–40 and ovalbumin were obtained from Sigma. Bovine serum albumin was purchased from U. S. Biochemical Corp. Human RAP was expressed as a glutathione S-transferase fusion protein in bacteria and prepared free of glutathioneS-transferase as described by Williams et al. (13Williams S.E. Ashcom J.D. Argraves W.S. Strickland D.K. J. Biol. Chem. 1992; 267: 9035-9040Abstract Full Text PDF PubMed Google Scholar). LRP-2 was purified from extracts of porcine kidney by affinity chromatography using a column of RAP coupled to Sepharose as described previously (36Kounnas M.Z. Stefansson S. Loukinova E. Argraves K.M. Strickland D.K. Argraves W.S. Ann. N. Y. Acad. Sci. 1994; 737: 114-123Crossref PubMed Scopus (44) Google Scholar). The mouse monoclonal antibody to LRP-2 designated 1H2 was provided by Dr. Robert McCluskey (Massachusetts General Hospital, Boston, MA). Mouse monoclonal antibody to human apoJ (mAb 1D11) was obtained from Dr. Judith Harmony (University of Cincinnati College of Medicine, Cincinnati, OH). Mouse monoclonal antibody to human Aβ (mAb 4G8) was purchased from Senetek (Maryland Heights, MO). Rabbit anti-LRP-2 IgGs (rabbit 6286) were isolated by immunoaffinity chromatography on a column of porcine LRP-2 coupled to CNBr-activated Sepharose (Pharmacia Biotech Inc.) with minor modification to a previously described procedure (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar). IgG was sequentially eluted using 100 mm glycine, pH 2.3, followed by 100 mm triethylamine, pH 11.5, and the combined eluates were dialyzed against 50 mm Tris, pH 7.4, 150 mm NaCl. The polyclonal anti-LRP-2 IgG preparation was absorbed on a column of RAP-Sepharose followed by selection on a column of protein G-Sepharose. Control rabbit IgG was isolated from the preimmune serum of rabbit 6286 by protein G-Sepharose chromatography. ApoJ was combined with synthetic Aβ1–40 at a 1:15 molar ratio in PBS as described previously (14Zlokovic B.V. Martel C.L. Matsubara E. McComb J.G. Zheng G. McCluskey R.T. Frangione B. Ghiso J. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 4229-4234Crossref PubMed Scopus (380) Google Scholar) and incubated for 24 h at 37 °C. Typically, a 1:15 molar ratio was maintained for preparing complexes of unlabeled Aβ1–40 and apoJ, although the total protein concentration varied according to the assay. For SDS-PAGE and immunoblotting analyses the concentration of apoJ was 0.95 μm and Aβ1–40 was 15 μm, whereas for solid phase binding assays, apoJ was 0.095 μmand Aβ1–40 was 1.5 μm. As a control, ovalbumin was substituted for apoJ. Aβ1–40 peptide (300 μg in Dulbecco's PBS (dPBS)) was radioiodinated by the IODO-GEN (Pierce) method using 2 mCi of Na125I (Amersham Life Science, Inc.). Unincorporated 125Iiodine was removed by Sepharose G-15 chromatography using a 0.7 × 18-cm column equilibrated with dPBS. Radioiodinated Aβ1–40 peptide (100 μg) was combined with apoJ (50 μg in dPBS) at a 30:1 molar ratio and incubated for 36 h at 37 °C. Following the incubation, radiolabeled Aβ-apoJ complex was separated from free 125I-labeled Aβ by gel filtration chromatography using a model 650E Waters protein purification system (Waters, Milford, MA) and a Superdex-200HR column (Pharmacia) equilibrated with dPBS. The integrity of the complex was evaluated by electrophoresis under non-denaturating conditions on 4–12% polyacrylamide, Tris/glycine-containing gels (Novex, San Diego, CA) followed by autoradiography. Microtiter wells were coated with LRP-2, Aβ, or BSA (each at 3 μg/ml) in 150 mm NaCl, 50 mm Tris, pH 8.0 (TBS) containing 5 mm CaCl2 for 18 h at 4 °C. Unoccupied sites were either blocked with TBS containing 3% nonfat milk or treated with PBS containing 0.1%N-octyl-β-d-glucopyranoside For wells that were blocked with TBS containing 3% nonfat were in TBS containing 3% nonfat milk For wells treated with PBS containing were in PBS containing were using mouse monoclonal (Amersham and the in mm pH data from were using a form of the binding as described by Ashcom et al. J.D. S.E. K. Argraves W.S. Strickland D.K. J. Cell Biol. PubMed Scopus Google Scholar). Aβ-apoJ complexes by were on gels in the of The separated were to in for 2 h at the were incubated with nonfat milk in TBS The were incubated with monoclonal Aβ or apoJ followed by in nonfat TBS, the were incubated with and to evaluate the of apoJ on the internalization mouse cells were treated for with retinoic and dibutyryl cyclic as described previously S. Argraves K.M. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar), by and of × in Dulbecco's modified Eagle's Life Inc.) containing bovine serum mm pH 7.4, 100 100 Inc.) and The cells were for 18 h at 37 with containing and in DMEM, BSA, serum containing of apoJ was to the cells and incubated for 5 h at 37 The of radiolabeled Aβ that was internalized by cells was as the of that with the treatment (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google S. Argraves K.M. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar). evaluate the role of LRP-2 in the cellular internalization and degradation of complex, mouse cells were as described to the complex, the was removed and the cells were treated with containing either anti-LRP-2 IgG rabbit IgG or chloroquine complex in or in containing anti-LRP-2 IgG rabbit IgG or chloroquine was and incubated with the cells for 5 or 18 h at 37 The of radiolabeled complex that was internalized was as described the that was soluble in was to represent degradation were for degradation by the of degradation that when the radiolabeled complex was incubated in wells were used to determine synthetic Aβ1–40 peptide was of binding directly to purified LRP-2. As shown in LRP-2 did not bind to wells coated with Aβ1–40. Aβ1–40 to did not bind to wells In assays, shown to bind to apoJ in a either when Aβ1–40 was coated wells and apoJ was in phase or when apoJ was coated and Aβ1–40 was in phase The data for apoJ binding to Aβ1–40 were using a K. H. S. Strickland D.K. Argraves W.S. J. Biol. Chem. 1992; 267: Full Text PDF PubMed Google Scholar), and the of binding d) was to be 4.8 is in with the of nm reported by Matsubara et al. E. Frangione B. Ghiso J. J. Biol. Chem. 1995; 270: 7563-7567Abstract Full Text Full Text PDF PubMed Scopus (182) Google Scholar). the binding of Aβ1–40 to apoJ was not binding can be that the ability to E. G. J. J. Biol. 1995; PubMed Scopus Google Scholar). The results indicate that Aβ1–40 does not bind to LRP-2 but does bind with affinity to apoJ. Aβ-apoJ complex, Aβ1–40 was incubated with apoJ for 24 h at 37 and complex formation was evaluated by SDS-PAGE and As shown in incubation resulted in the formation of an with monoclonal Aβ antibody 2 The a to the apoJ 4 and of Aβ with ovalbumin did not a a 2 showed that in the containing Aβ, which been incubated alone for 24 h at 37 was a a to 2 with of analysis of using monoclonal Aβ antibody of and and a that the to Aβ and the and were not by were with Aβ of for the of these was also present in the of the Aβ incubated with the Aβ was in containing Aβ incubated with apoJ The data that incubation of apoJ with Aβ under the conditions that we described resulted in the formation of a complex of Aβ and apoJ that is in The conditions of SDS-PAGE were to of the Aβ-apoJ complex as a apoJ. The results also showed that apoJ inhibited the formation of Aβ not the formation of Aβ and evaluate the ability of Aβ-apoJ complex to with LRP-2, wells coated with LRP-2 were incubated with of Aβ and apoJ or Aβ and ovalbumin that been for 24 h at 37 °C. As shown in 3 Aβ binding to LRP-2, as by Aβ monoclonal when Aβ was with apoJ but not with showed that of the Aβ and apoJ or Aβ and to wells coated with BSA When monoclonal antibody to apoJ was used to apoJ binding to LRP-2, the of binding of apoJ to LRP-2 was not modified by the inclusion of Aβ The results indicate that apoJ mediates binding of Aβ to LRP-2 and that the affinity of the Aβ-apoJ complex for LRP-2 does not to be from that of apoJ RAP has been shown to the binding of apoJ to LRP-2 (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar). As shown in incubation of Aβ-apoJ complex with RAP blocked the binding of the complex to LRP-2. with the that apoJ can to the interaction of Aβ with LRP-2. determine apoJ cellular internalization of Aβ, was to LRP-2-expressing cells in the of of apoJ. As shown in apoJ promoted the internalization of in a We the cellular clearance of Aβ-apoJ complex and evaluated the role of LRP-2 in the Radioiodinated Aβ was combined with unlabeled apoJ, and the complex was purified by gel filtration chromatography. A the of the and the gel analysis of the is shown in the of A. The results that the chromatography procedure of complex from the of the however, free radiolabeled peptide did with the complex. of were to LRP-2-expressing and the of internalization of was As shown in was a complex internalized as In the internalized was by the inclusion of a molar of unlabeled peptide not internalization was also in the of LRP-2 or As shown in anti-LRP-2 IgG complex internalization by as with treatment with rabbit The results indicate that Aβ-apoJ complex is internalized by LRP-2-expressing cells to a extent Aβ alone and that the internalization of the complex can be inhibited by LRP-2 LRP-2 in the clearance We also evaluated the internalized complex was as is the for LRP-2 apoJ (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar). As shown in of complex to LRP-2-expressing cells resulted in the internalization and degradation of the complex. was by the of in the that could be blocked by treatment with an of lysosomal internalization and degradation of the complex were also inhibited with the findings indicate that LRP-2 mediates of Aβ-apoJ complex leading to degradation in In study, we the ability of the Aβ-apoJ complex to bind to the endocytic receptor LRP-2 in both and the physiological of interaction to be we have previously that it is of a in which LRP-2-expressing such as of the choroid plexus and can the Aβ-apoJ complex from the cerebrospinal fluid (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google Scholar). In support of such a is the that both apoJ and LRP-2 are expressed at in the choroid plexus epithelium as well as ependymal cells that the ventricles of the brain and neural (12Kounnas M.Z. Haudenschild C.C. Strickland D.K. Argraves W.S. In Vivo ( Athens ). 1994; 8: 343-351PubMed Google Scholar, M. Biochem. Biol. 1994; PubMed Scopus Google Scholar, Harmony J.A. Proc. Natl. Acad. Sci. U. S. A. 1993; PubMed Scopus Google Scholar) and are therefore in contact with cerebrospinal fluid. In to LRP-2 a possible role in clearance of Aβ-apoJ complex from the cerebrospinal is that LRP-2 may have a role in uptake of the complex from the blood by cells of the cerebral (14Zlokovic B.V. Martel C.L. Matsubara E. McComb J.G. Zheng G. McCluskey R.T. Frangione B. Ghiso J. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 4229-4234Crossref PubMed Scopus (380) Google Scholar, B.V. Martel C.L. Matsubara E. Wisniewski T. McComb J.G. Frangione B. Ghiso J. Biochem. Biophys. Res. Commun. 1994; PubMed Scopus Google Scholar). Following on the of LRP-2 as the receptor for apoJ, et al. (14Zlokovic B.V. Martel C.L. Matsubara E. McComb J.G. Zheng G. McCluskey R.T. Frangione B. Ghiso J. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 4229-4234Crossref PubMed Scopus (380) Google Scholar) radiolabeled Aβ-apoJ complex brain and that RAP or monoclonal antibody to LRP-2 the brain uptake of the radiolabeled complex. Whereas these findings LRP-2 as being for the is to that LRP-2 is expressed by brain the results in the present study that LRP-2 is a receptor for the Aβ-apoJ complex, that it could to mediate Aβ-apoJ in LRP-2-expressing Our results also indicate that apoJ the formation of aggregates of Aβ1–40 is with using a assay (10Oda T. Pasinetti G.M. Osterburg H.H. Anderson C. Johnson S.A. Finch C.E. Biochem. Biophys. Res. Commun. 1994; 204: 1131-1136Crossref PubMed Scopus (100) Google Scholar) and with the that apoJ to maintain Aβ in a soluble it from forming amyloid are the hallmark of the found in brain and in the of with Alzheimer's disease Biochem. Biophys. Res. Commun. PubMed Scopus Google Scholar, Biochem. Biophys. Res. Commun. PubMed Scopus Google Scholar). In the Aβ-apoJ interaction may have a that the form of Aβ has been shown to be to cells D. J. 1993; PubMed Google Scholar). to the and of apoJ, apoE has been shown to promote the formation of Aβ fibrils (7Ma J. Yee A. Brewer Jr., H.B. Das S. Potter H. Nature. 1994; 372: 92-94Crossref PubMed Scopus (862) Google Scholar, 9Wisniewski T. Castano E.M. Golabek A. Vogel T. Frangione B. Am. J. Pathol. 1994; 145: 1030-1035PubMed Google Scholar). are to the that the in interaction of Aβ with apoJ or is possible that under normal physiological the interaction between apoJ and Aβ is that of apoE to prevent clearance of by endocytic apoE such as and LRP-2 may also to the extracellular of complex as we have for the Aβ-apoJ complex. In the endocytic of and the described low density lipoprotein receptor H. K. J. H. H. H. S. T. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar) may be to clearance of complex from brain LRP-2 and have in the H. K. J. H. H. H. S. T. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar, Strickland D.K. 1993; Full Text PDF PubMed Scopus Google Scholar, G. J.M. J. Biol. Chem. 1994; Full Text PDF PubMed Google Scholar, Strickland D.K. Ann. 1995; PubMed Scopus Google Scholar), whereas LRP-2 in the brain is to cells of the choroid plexus and (12Kounnas M.Z. Haudenschild C.C. Strickland D.K. Argraves W.S. In Vivo ( Athens ). 1994; 8: 343-351PubMed Google G. Strickland D.K. D. G. McCluskey R.T. J. 1994; PubMed Scopus Google Scholar, Scopus Google Scholar). is that of of Aβ-apoJ is that Aβ is for lysosomal is the for LRP-2 and complex, low density and apoJ (11Kounnas M.Z. Loukinova E.B. Stefansson S. Harmony J.A. Brewer B.H. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: 13070-13075Abstract Full Text Full Text PDF PubMed Scopus (204) Google S. Argraves K.M. Strickland D.K. Argraves W.S. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar, S. M.Z. J. Strickland D.K. Argraves W.S. J. Cell Sci. 1995; PubMed Google Scholar, S. Argraves W.S. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google however, that Aβ could be in that a of indicate that it can be in as a of processing of amyloid β-precursor protein S. Selkoe D.J. 1992; PubMed Scopus Google Scholar, K. Y. N. N. Res. 1994; PubMed Scopus Google Scholar). is possible that the lysosomal of Aβ in the form of a complex with apoJ may it to is to that LRP-2 is not the by which extracellular Aβ can be For LRP-2 can B. D. J. Proc. Natl. Acad. Sci. U. S. A. 1992; PubMed Scopus Google Scholar). internalization was shown to lead to accumulation of Aβ in the form of aggregates that are to lysosomal internalization may by both formation and lysosomal degradation of Aβ.