Correspondence to Sanjay W. Pimplikar: sanjay.pimplikar{at}case.edu
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Introduction |
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The generation of AICD peptide follows the general steps of "regulated intramembrane proteolysis" which results in the release of a membrane-tethered transcriptional regulator in response to an external signal (Brown et al., 2000). We and other investigators have shown that cleaved AICD enters the nucleus and regulates gene expression in vitro (Cao and Sudhof, 2001; Gao and Pimplikar, 2001; Baek et al., 2002). The AICD target genes are not firmly known, and a majority of support for its transcriptional role comes from the use of an artificial reporter gene. Although additional in vitro studies showed that AICD also alters cell signaling (Leissring et al., 2002) and induces apoptosis (Passer et al., 2000; Kinoshita et al., 2002), the physiologic relevance of AICD has been uncertain because its steady-state levels are reported to be low (Cupers et al., 2001; Kimberly et al., 2001). To examine the in vivo role of AICD, we generated transgenic mice that express AICD and Fe65 in the forebrain and hippocampal regions of the postnatal brain. We report that the transgenic mice show two- to threefold higher levels of AICD than control mice, and display robust activation of glycogen synthase kinase-3ß (GSK-3ß) and increased phosphorylation of a downstream substrate, CRMP2, a key component of the axonal guidance signaling pathway. We also demonstrate the presence of endogenous AICD in the membrane fractions from control mice, which suggests that the steady-state levels of AICD are higher than previously believed. Together, our in vivo findings support a biologic role for AICD in regulating gene expression and cell signaling.
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Results |
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We cloned myc-tagged Fe65 or AICD in plasmid NN265 that contained intron and SV40 polyadenylation sequences (Abel et al., 1997). A fragment that contained the intron, the transgene open reading frame, and polyA signal was excised and cloned into MM403, downstream of the 8-kb CaMKII promoter (Fig. 1 A). We mixed AICD and Fe65 expressing plasmids in 1:1 proportion, and co-injected the linearized plasmids into oocytes of C57BL/6 mice. Injected oocytes were implanted in pseudopregnant C57BL/6 mice; by PCR on tail DNA, 9 out of 49 pups obtained were found to have incorporated both transgenes. All 9 founder mice were mated with C57BL/6 mice. Germline transmission was observed in five lines, of which four of the founder lines transmitted both transgenes to F1 pups (unpublished data). In the current study, we present data from two of these four independent lines (named FeC
.12 and FeC
.25). The fifth line, called Fe.27, did not transmit the AICD transgene to pups (Fig. 1 B), and thereby, fortuitously created a Fe65 single transgenic line. The expression levels of Fe65 transgene were determined by Western blot analysis. Total brain homogenates (40 µg protein each) from two animals from each transgenic line or two nontransgenic littermates was separated by SDS-PAGE on a 10% gel, transferred to a nitrocellulose membrane, and probed using anti-myc antibodies to detect the transgene or anti-Fe65 3H6 antibody to detect total Fe65 (endogenous + transgene). The myc-Fe65 signal was apparent in mice from all three transgenic lines, but was absent in nontransgenic littermates (Fig. 1 C, top panel). The total levels of Fe65 in the three transgenic lines (Fig. 1 D; top panel) were comparable, and were approximately twice as high as the nontransgenic control animals, when normalized for the levels of tubulin (Fig. 1 E). The Fe65 levels in Fe.27 mice were not significantly different from those in FeC
.12 or FeC
.25 mice (P = 0.04 by Bonferroni/Dunn test).
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To understand why the membrane-associated AICD was not detected in previous studies, we separated membrane proteins from R1.40 brains in duplicate lanes on the same gel, and electrophoretically transferred them onto a nitrocellulose membrane. The membrane was cut lengthwise in two. One part received the antigen retrieval treatment (see "Materials and Methods"), whereas the other part was kept in PBS at room temperature. Both blots were blocked in 10% calf serum and processed identically. Fig. 2 D shows that although the AICD band is detected clearly upon antigen retrieval (arrow, lanes 4 and 5), it is not detected in the absence of the treatment, even though APP-CTFs are clearly visible (lanes 2 and 3). We verified these results further by comparing brain membranes from R1.40 mice with control C57BL/6 mice. R1.40 mice, which produce increased amounts of Aß peptides (Lamb et al., 1997), also should give rise to increased amounts of AICD. AICD was present in greater amounts in R1.40 mice (Fig. 2 E, lanes 4 and 5) compared with controls (lanes 2 and 3), and was absent in APP-KO mice (lanes 6 and 7).
Together, these results show that the endogenous AICD can be detected in the membrane, but not the cytosolic fractions, of wild-type C57BL/6 animals (Fig. 2 B, also compare Fig. 2 E with Fig. 2 A). More importantly, the AICD transgenic mice express AICD at greater levels than do nontransgenic control mice, and similar to those levels observed in APP transgenic mice with familial Alzheimer's disease (FAD) mutation (Fig. 2 C). This lends strong support to the validity of our transgenic model.
Validation of AICD transgenic mice
Although no bona fide target genes of AICD have been identified genetically, a chromatin immunoprecipitation assay was used recently to show that AICD is recruited to KAI1 gene promoter and stimulates its transcription (Baek et al., 2002; Von Rotz et al., 2004). We sought to validate our animal model by examining the expression of KAI1 gene in the AICD transgenic mice. We probed the membrane fractions from nontransgenic littermate controls, two FeC transgenic lines, and Fe.27 animals with anti-KAI1 antibody (Fig. 3 A, top panel). A doublet of KAI1 protein band was visible in FeC
.12 and FeC
.25 mice (lanes 36), but not in nontransgenic controls (lanes 1 and 2) nor in Fe65 transgenic Fe.27 mice (lanes 7 and 8). When normalized for protein loading (Fig. 3 A, bottom panel), FeC
.25 seem to express higher levels of KAI1 compared with FeC
.12. These data confirm and extend in vivo the previous observations that AICD activates KAI1 gene expression (Baek et al., 2002; Von Rotz et al., 2004). These findings also validate the supposition that the
-secretase cleaved, 59-residue long AICD exhibits biologic effects that are observed when APP is cleaved in vivo to generate AICD (Cao and Sudhof, 2001; Baek et al., 2002).
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Elevated levels of active glycogen synthase kinase3 in transgenic mice expressing AICD
Glycogen synthase kinase (GSK)3ß is a proline-directed Ser/Thr kinase that is implicated in AD pathogenesis (Jope and Johnson, 2004). In vitro observations suggest that ectopic expression of AICD results in a significant increase in the mRNA and protein levels of GSK-3ß (Kim et al., 2003; Von Rotz et al., 2004). To examine whether AICD activates GSK-3ß in vivo, we determined the status of GSK-3 by using antibodies that recognize the activated or inhibited forms of the enzyme. Phosphorylation of GSK-3ß at Y216 stimulates its kinase activity (active form), whereas phosphorylation at S9 potently represses (inactive form) the kinase activity (Jope and Johnson, 2004). Brain cytosolic fractions were immunoblotted with antibody anti-pY216/279 that recognizes the phospho-Y216 on GSK-3ß and the equivalent Y279 residue on GSK-3. Fig. 4 A shows that activated forms of GSK-3
and -3ß were elevated in FeC
.12 and FeC
.25 mice (top panel, lanes 36) when compared with nontransgenic controls (lanes 1 and 2) or Fe.27 mice (lanes 7 and 8). Densitometric analysis revealed (Fig. 4 B) an
1.7-fold increase in pGSK-3ß levels in FeC
animals (GSK-3
showed similar changes). We also analyzed the total GSK-3ß levels by stripping the blots and reprobing with antibodies that recognize GSK-3ß and observed no significant changes in the protein levels in transgenic mice compared with the control animals (Fig. 4 A, bottom panel).
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In addition to the GSK-3 pathway, the extracellular signal-regulated kinase (ERK) pathway also is activated in AD brains (Zhu et al., 2003). To determine the selectivity of the AICD effect, we examined the levels of phosho-ERK1 and -ERK2 in the transgenic animals. Brain homogenates from FeC, Fe.27, and nontransgenic littermate animals were immunoblotted using pERK antibodies that recognize activated ERK1 and ERK2. We observed no significant differences in the levels of activated ERK1 or ERK2 (Fig. 4 E) in control or transgenic mice. Thus, these findings show that the ERK is not activated in 812-wk old FeC
mice, and that AICD does not cause ERK activation. The lack of AICD on ERK activation is consistent with the reports the ERK activation occurs by way of Aß peptides (Bell et al., 2004). However, the possibility cannot be ruled out that AICD modulates some other signaling pathways.
GSK-3ß mRNA levels are not increased in transgenic mice
In contrast to the in vitro observations that AICD causes an increase in the GSK-3ß protein levels in tissue culture cells, we did not observe an increase in the GSK-3ß protein levels in the transgenic mice (Fig. 4, A and C). To examine this discrepancy in detail, we measured the mRNA levels in brain extracts by real-time PCR. Total RNA was extracted from brain tissue, subjected to reverse transcriptase reaction, and real-time PCR was performed. We used primers for GSK-3ß and KAI1, and normalized the values by using ß-actin. FeC.12 mice showed a 1.8-fold increase in KAI1 message when compared with nontransgenic or Fe.27 mice (Fig. 5 A). By contrast, we detected no change in GSK-3ß transcripts when compared with nontransgenic or Fe.27 mice (Fig. 5 B). These observations suggest that GSK-3ß activation in FeC
transgenic mice is not due to increased transcription or translation of GSK-3ß gene. Because GSK-3ß kinase activity is regulated largely at the posttranslational level by upstream kinases and phosphatases (Jope and Johnson, 2004), it is possible that AICD activates GSK-3ß by modulating upstream regulators. However, because the transgenes are expressed only in certain neuronal cells, we cannot rule out the possibility that a slight increase in GSK-3ß mRNA or protein was undetected in whole brain extracts.
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Discussion |
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The finding that an AICD59co-migrating peptide is present in the membrane fraction of the normal, wild-type C57BL/6 animals is novel and unanticipated because it was not detected in previous studies. We provide compelling data, by using various controls, that the membrane-associated, AICD59co-migrating band is a product of APP. These include APP KO mice, which do not show the presence of AICD, and APP transgenic mice with FAD mutation, which show elevated AICD levels compared with control animals. The AICD peptide is not detected by Western blotting in the absence of antigen-retrieval treatment; this may explain why previous studies failed to detect AICD. Antigen-retrieval techniques have been used routinely in immunohistochemical detection of antigens in tissue sections, and our present findings indicate that such techniques also can be useful in Western blotting. The absence of AICD in the cytosol and its association with the membrane suggest that the AICD peptide is hydrophobic in nature. Studies that reported the "-cleavage" of APP-CTF found the resultant AICD peptide (AICD50) to be soluble and to fractionate in the cytosolic, but not in the membrane, fraction (Gu et al., 2001; Yu et al., 2001). These considerations make the AICDco-migrating band that was identified in the present study more likely to be AICD59/57 than AICD50. The possibility that the endogenous band represents AICD57, rather than AICD59, cannot be ruled out. Future studies are required to establish unequivocally the length of the endogenous, membrane-associated AICD. In any case, our findings show that the steady-state levels of endogenously produced AICD peptides are higher than previously believed.
The FeC double transgenic mice that were generated in the current study showed robust stimulation of GSK-3ß activity, without any significant changes in the mRNA or GSK-3ß protein levels. These changes are caused primarily by AICD, because the Fe.27 mice express similar levels of Fe65 (Fig. 1 E) but do not exhibit altered GSK-3 signaling. However, it is possible that AICD may not be able to activate GSK-3 without Fe65. We do not know how AICD stimulates the GSK-3ß activity in mice. Because the levels of mRNA transcripts and total protein of GSK-3ß are not changed in the transgenic mice, our findings suggest a posttranscriptional signaling role for AICD in GSK-3 activation. Recently, Cao and Sudhof (2004) suggested that AICD acts catalytically in the context of membrane to "activate" Fe65, and bring about its biologic effects without necessarily being present in the nucleus. We detected AICD in the membrane and nuclear fractions in transgenic and control mice (Fig. 2 B). The presence of AICD in the membrane fraction is consistent with the above hypothesis. Nonetheless, the presence of AICD in the nuclear, but not in the cytosolic fraction of control mice shows that AICD accumulates in the nucleus and likely performs its function. Incidentally, our transgenic mice demonstrate the biologic relevance of the "
-cleaved" AICD because they show that AICD59 peptide in vivo replicates the known activities of AICD (expression of KAI1 gene and activation of GSK-3ß). Future studies on AICD50 transgenic mice will be required to determine the biologic effects of the "
-cleaved" AICD peptide, which is not likely to remain associated with membranes.
The finding that AICD stimulates GSK-3 activity in vivo could be relevant to AD pathology. GSK-3ß activity is elevated in AD brains (Pei et al., 1997; Kaytor and Orr, 2002; Bhat et al., 2004) and in the "Swedish mutation" mouse model, Tg2576, of AD (Tomidokoro et al., 2001). Higher GSK-3 activity in AD brains is responsible for phosphorylating the microtubule-binding protein, tau (Augustinack et al., 2002). Hyperphosphorylated tau aggregates into paired helical filaments and forms NFTs, a hallmark of AD pathology (Pei et al., 1999; Ishizawa et al., 2003). Significantly, the spatiotemporal distribution of active GSK-3ß in AD brains coincides with the progression of NFTs and neurodegeneration, but not with the amyloid deposition (Pei et al., 1997; Pei et al., 1999). Thus, activated GSK-3ß found in AD brains is one of the critical factors in the formation of NFTs. It is not clear what induces GSK-3ß activation in AD brains, and our transgenic mice suggest that AICD could be a contributing factor. We observed elevated AICD levels in R1.40 transgenic mice that carry the "Swedish mutation" (Fig. 2), and our preliminary findings show that GSK-3 also is activated in these animals (unpublished data); however, R1.40 mice also show increased Aß load. Because some in vitro studies suggest that Aß can activate GSK-3ß, it will be crucial to determine the contribution of these two APP-derived fragments toward GSK-3 activation in AD. We have initiated analysis of phospho-tau, a known substrate of GSK-3 in FeC transgenic mice. In the young animals that we examined so far (812 weeks old), we did not detect any significant changes in tau phosphorylation as detected by antibodies AT-8, AT-100, and TG-3 (not shown). It is not an uncommon observation that abnormal tau phosphorylation is detected in older animals, but not in young animals (Andorfer et al., 2003).
The FeC transgenic mice described here recapitulated the known in vitro effects of AICD, and revealed a new observation that AICD induces phosphorylation of CRMP2 on the residues that are crucially involved in growth cone collapse and axonal guidance. The phosphorylation of T509/S522 in CRMP2 plays a crucial role in mediating the repulsive action of Sema3a (Uchida et al., 2005). Sema3a is an extracellular matrix protein that binds Plexin/Neuropilin receptors in growth cones, activates GSK-3ß, and phosphorylates CRMP2 on T509 and S522. These two residues are crucial in axonal guidance, because mutation of either residue abolishes the action of Sema3a and eliminates 3F4-reactivity (incidentally, 3F4-reactive phospho-CRMP2 is known to accumulate in the NFTs in AD brains [Yoshida et al., 1998; Gu et al., 2000; Cole et al., 2004]). Thus, increased phosphorylation of CRMP2 in the transgenic mice suggests an AICD-mediated signaling role for APP in axonal guidance or elongation (Fig. 6 E). The identity of an upstream ligand that binds APP and initiates the signaling cascade is unknown. F-spondin, a contact-repellent protein that is present in floor plate and hippocampus, may be a candidate because it binds APP and inhibits AICD production (Ho and Sudhof, 2004). The proposed role of AICD in mediating APP signaling and axonal elongation is consistent with the cortical dysplasia that is observed in mice lacking all three members of the APP family (Herms et al., 2004), or Fe65 and Fe65L1 proteins (Guenette et al., 2003).
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Materials and methods |
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Tissue preparation
The data presented here are from multiple 812-wk old, mixed gender animals from two double transgenic lines (FeC.12 and FeC
.25) and a single Fe65 transgenic line (Fe.27). We used nontransgenic littermates as controls. Mice were killed by cervical dislocation and their brains were removed, divided sagittally (after removing cerebellum), and quick frozen. Tissues were homogenized in 10 volumes of Tris-buffered saline (50 mM Tris, pH 7.4, 150 mM NaCl, 1 mM EDTA) with freshly added 1 mM PMSF and protease and phosphatase inhibitor cocktail (Sigma-Aldrich). Total homogenates were centrifuged briefly to remove nuclei and unbroken tissue, and centrifuged at 150,000 g for 60 min to obtain cytosol (supernatant) and crude membrane (pellet) fractions. The nuclear extracts were prepared using the NE-PER kit (Pierce Chemical Co.). Protein determination was performed using a Bio-Rad Laboratories kit. Equal amounts of proteins (usually 1025 µg per lane) were loaded on the gel.
Western blotting
Immunoblotting was performed as described before (Zheng et al., 1998; Gao and Pimplikar, 2001) using a 10% SDS-PAGE gel, except for AICD detection, which was performed as described by Pinnix et al. (2001), with some modifications. In brief, the proteins were separated using NuPAGE Novex Bris-Tris 412% gel (Invitrogen) and transferred on to nitrocellulose membrane. The membranes were incubated with boiling PBS for 5 min (antigen-retrieval treatment) before blocking in TBS containing 10% newborn calf serum for 2 h at room temperature. The blots were incubated with up to 1:10,000 dilution of antibody 0443 (gift of K. Sambamurti, Medical University of South Carolina, Charleston, SC) overnight at 4°C, and the blots were visualized using ECL. Other antibodies used are as follows: antibody 369 (gift of S. Gandy) to probe AICD; anti-myc antibody 9E10 (CLONTECH Laboratories, Inc.) to detect myc-Fe65 transgene; and antibody 3H6 (Upstate Biotechnology) to detect total Fe65 (this antibody detects mouse and rat Fe65). Anti-pS9GSK-3ß antibody to detect inhibited kinase was from Cell Signaling; anti-pY279/216 to detect activated GSK-3 (Cell Signaling) was a gift of M. Smith (Case Western Reserve University, Cleveland OH); and SERCA2 antibody, MA3-919, was from Affinity BioReagents, Inc. Antibody 3F4 recognizes CRMP2 phosphorylated at S522 and T509, and antibody C4G binds unphosphorylated CRMP2 (both antibodies were the gifts of Y. Ihara and Y. Morishima, University of Tokyo, Tokyo, Japan). Antibody that recognizes pT514 CRMP2 was a gift of K. Kaibuchi. Anti-pERK1/2 antibody was from Cell Signaling. Protein bands were visualized by ECL using Pierce SuperSignal system. Protein levels were quantified by scanning the films in Photoshop (Adobe), and measuring the band pixel densities in NIH Image J software (National Institutes of Health). The results were analyzed by ANOVA with Fisher's protected least significance difference (PLSD) test using StatView software (Abacus Concepts). The data presented here are from multiple animals from FeC.12 and FeC
.25 lines and were repeated in the FeC
.22 transgenic line.
Quantitative real-time PCR
Animals were killed by cervical dislocation, brains were dissected, cerebellum was discarded, and total RNA was isolated from the brain tissue with RNeasy kit (QIAGEN). First-strand cDNA synthesis was performed using 4 µg RNA with the Superscript First-Strand Synthesis system for RT-PCR (Invitrogen) according to the manufacturer's protocol. The cDNA mixture was diluted 1:20; 5 µl of the cDNA product was used for real-time PCR performed on the iCycler (Bio-Rad Laboratories), and detected by using iQ SYBR Green Supermix. The amplification cycle was 95°C for 10 s, 65°C for 15 s, and 72°C for 15 s. Primers were designed by using Primer 3 software to amplify the 3' region of the ORF. Primer sequences were: ß-actin (forward: TACAGCTTCACCACCACAGC; reverse: ATGCCACAGGATTCCATACC), KAI1 (forward: TCTGTGGGAGACAGGGTAGG; reverse: CTGCCAAGAAACACCAGTCC), and GSK-3ß (forward: TCCATTCCTTTGGAATCTGC; reverse: CAATTCAGCCAACACACACAGC). Melting curve analysis confirmed that only one product was amplified. Specificity was confirmed by electrophoresis of PCR products through 1.5% agarose gels (stained with ethidium bromide). Only one product was observed with each primer set, and the product size matched that predicted from published cDNA sequences. Expression was normalized to ß-actin.
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Acknowledgments |
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This work was supported by a grant from the Alzheimer's Association to S.W. Pimplikar (IIRG-3894) and by a grant from the National Institute on Aging to UAC/CWRU ADRC (P50-AG08012).
Submitted: 13 May 2005
Accepted: 16 September 2005
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References |
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Abel, T., P.V. Nguyen, M. Barad, T.A. Deuel, E.R. Kandel, and R. Bourtchouladze. 1997. Genetic demonstration of a role for PKA in the late phase of LTP and in hippocampus-based long-term memory. Cell. 88:615626.[CrossRef][Medline]
Andorfer, C., Y. Kress, M. Espinoza, R. de Silva, K.L. Tucker, Y.A. Barde, K. Duff, and P. Davies. 2003. Hyperphosphorylation and aggregation of tau in mice expressing normal human tau isoforms. J. Neurochem. 86:582590.[CrossRef][Medline]
Annaert, W., and B. De Strooper. 2002. A cell biological perspective on Alzheimer's disease. Annu. Rev. Cell Dev. Biol. 18:2551.[CrossRef][Medline]
Augustinack, J.C., A. Schneider, E.M. Mandelkow, and B.T. Hyman. 2002. Specific tau phosphorylation sites correlate with severity of neuronal cytopathology in Alzheimer's disease. Acta Neuropathol. (Berl.). 103:2635.[CrossRef][Medline]
Baek, S.H., K.A. Ohgi, D.W. Rose, E.H. Koo, C.K. Glass, and M.G. Rosenfeld. 2002. Exchange of N-CoR corepressor and Tip60 coactivator complexes links gene expression by NF-kappaB and beta-amyloid precursor protein. Cell. 110:5567.[CrossRef][Medline]
Bell, K.A., K.J. O'Riordan, J.D. Sweatt, and K.T. Dineley. 2004. MAPK recruitment by beta-amyloid in organotypic hippocampal slice cultures depends on physical state and exposure time. J. Neurochem. 91:349361.[CrossRef][Medline]
Bhat, R.V., S.L. Budd Haeberlein, and J. Avila. 2004. Glycogen synthase kinase 3: a drug target for CNS therapies. J. Neurochem. 89:13131317.[CrossRef][Medline]
Borg, J.P., J. Ooi, E. Levy, and B. Margolis. 1996. The phosphotyrosine interaction domains of X11 and FE65 bind to distinct sites on the YENPTY motif of amyloid precursor protein. Mol. Cell. Biol. 16:62296241.[Abstract]
Brown, M.S., J. Ye, R.B. Rawson, and J.L. Goldstein. 2000. Regulated intramembrane proteolysis: a control mechanism conserved from bacteria to humans. Cell. 100:391398.[CrossRef][Medline]
Cao, X., and T.C. Sudhof. 2001. A transcriptionally [correction of transcriptively] active complex of APP with Fe65 and histone acetyltransferase Tip60. Science. 293:115120.
Cao, X., and T.C. Sudhof. 2004. Dissection of amyloid-beta precursor protein-dependent transcriptional transactivation. J. Biol. Chem. 279:2460124611.
Cole, A.R., A. Knebel, N.A. Morrice, L.A. Robertson, A.J. Irving, C.N. Connolly, and C. Sutherland. 2004. GSK-3 phosphorylation of the Alzheimer epitope within collapsin response mediator proteins regulates axon elongation in primary neurons. J. Biol. Chem. 279:5017650180.
Cupers, P., I. Orlans, K. Craessaerts, W. Annaert, and B. De Strooper. 2001. The amyloid precursor protein (APP)-cytoplasmic fragment generated by gamma-secretase is rapidly degraded but distributes partially in a nuclear fraction of neurones in culture. J. Neurochem. 78:11681178.[CrossRef][Medline]
De Strooper, B., and W. Annaert. 2000. Proteolytic processing and cell biological functions of the amyloid precursor protein. J. Cell Sci. 113:18571870.
Fukata, Y., T.J. Itoh, T. Kimura, C. Menager, T. Nishimura, T. Shiromizu, H. Watanabe, N. Inagaki, A. Iwamatsu, H. Hotani, and K. Kaibuchi. 2002. CRMP-2 binds to tubulin heterodimers to promote microtubule assembly. Nat. Cell Biol. 4:583591.[Medline]
Gao, Y., and S.W. Pimplikar. 2001. The gamma-secretasecleaved C-terminal fragment of amyloid precursor protein mediates signaling to the nucleus. Proc. Natl. Acad. Sci. USA. 98:1497914984.
Gu, Y., N. Hamajima, and Y. Ihara. 2000. Neurofibrillary tangle-associated collapsin response mediator protein-2 (CRMP-2) is highly phosphorylated on Thr-509, Ser-518, and Ser-522. Biochemistry. 39:42674275.[CrossRef][Medline]
Gu, Y., H. Misonou, T. Sato, N. Dohmae, K. Takio, and Y. Ihara. 2001. Distinct intramembrane cleavage of the beta-amyloid precursor protein family resembling gamma-secretaselike cleavage of Notch. J. Biol. Chem. 276:3523535238.
Guenette, S.Y., Y. Chang, T. Hiesberger, J.A. Richardson, and J. Herz. 2003. Mice deficient for the Fe65 and Fe65L1 proteins have neurological defects. Society for Neuroscience Abstract. 336:10.
Herms, J., B. Anliker, S. Heber, S. Ring, M. Fuhrmann, H. Kretzschmar, S. Sisodia, and U. Muller. 2004. Cortical dysplasia resembling human type 2 lissencephaly in mice lacking all three APP family members. EMBO J. 23:41064115.
Ho, A., and T.C. Sudhof. 2004. Binding of F-spondin to amyloid-beta precursor protein: a candidate amyloid-beta precursor protein ligand that modulates amyloid-beta precursor protein cleavage. Proc. Natl. Acad. Sci. USA. 101:25482553.
Ishizawa, T., N. Sahara, K. Ishiguro, J. Kersh, E. McGowan, J. Lewis, M. Hutton, D.W. Dickson, and S.H. Yen. 2003. Co-localization of glycogen synthase kinase-3 with neurofibrillary tangles and granulovacuolar degeneration in transgenic mice. Am. J. Pathol. 163:10571067.
Jope, R.S., and G.V. Johnson. 2004. The glamour and gloom of glycogen synthase kinase-3. Trends Biochem. Sci. 29:95102.[CrossRef][Medline]
Kaytor, M.D., and H.T. Orr. 2002. The GSK3 beta signaling cascade and neurodegenerative disease. Curr. Opin. Neurobiol. 12:275278.[CrossRef][Medline]
Kim, H.S., E.M. Kim, J.P. Lee, C.H. Park, S. Kim, J.H. Seo, K.A. Chang, E. Yu, S.J. Jeong, Y.H. Chong, and Y.H. Suh. 2003. C-terminal fragments of amyloid precursor protein exert neurotoxicity by inducing glycogen synthase kinase-3beta expression. FASEB J. 17:19511953.
Kimberly, W.T., J.B. Zheng, S.Y. Guenette, and D.J. Selkoe. 2001. The intracellular domain of the beta-amyloid precursor protein is stabilized by Fe65 and translocates to the nucleus in a notch-like manner. J. Biol. Chem. 276:4028840292.
Kinoshita, A., C.M. Whelan, O. Berezovska, and B.T. Hyman. 2002. The gamma secretase-generated carboxyl-terminal domain of the amyloid precursor protein induces apoptosis via Tip60 in H4 cells. J. Biol. Chem. 277:2853028536.
Lamb, B.T., L.M. Call, H.H. Slunt, K.A. Bardel, A.M. Lawler, C.B. Eckman, S.G. Younkin, G. Holtz, S.L. Wagner, D.L. Price, et al. 1997. Altered metabolism of familial Alzheimer's disease-linked amyloid precursor protein variants in yeast artificial chromosome transgenic mice. Hum. Mol. Genet. 6:15351541.
Leissring, M.A., M.P. Murphy, T.R. Mead, Y. Akbari, M.C. Sugarman, M. Jannatipour, B. Anliker, U. Muller, P. Saftig, B. De Strooper, et al. 2002. A physiologic signaling role for the gamma-secretasederived intracellular fragment of APP. Proc. Natl. Acad. Sci. USA. 99:46974702.
Mueller, T., D. Koegel, J.H.M. Prehn, and R. Egensperger. 2004. Role of the ß-amyloid precursor protein intracellular domain (AICD) and Fe65 in regulation of gene expression and calcium dependent neuronal cell death. Society for Neuroscience Abstract. 335:9.
Passer, B., L. Pellegrini, C. Russo, R.M. Siegel, M.J. Lenardo, G. Schettini, M. Bachmann, M. Tabaton, and L. D'Adamio. 2000. Generation of an apoptotic intracellular peptide by gamma-secretase cleavage of Alzheimer's amyloid beta protein precursor. J. Alzheimers Dis. 2:289301.[Medline]
Pei, J.J., E. Braak, H. Braak, I. Grundke-Iqbal, K. Iqbal, B. Winblad, and R.F. Cowburn. 1999. Distribution of active glycogen synthase kinase 3beta (GSK-3beta) in brains staged for Alzheimer disease neurofibrillary changes. J. Neuropathol. Exp. Neurol. 58:10101019.[Medline]
Pei, J.J., T. Tanaka, Y.C. Tung, E. Braak, K. Iqbal, and I. Grundke-Iqbal. 1997. Distribution, levels, and activity of glycogen synthase kinase-3 in the Alzheimer disease brain. J. Neuropathol. Exp. Neurol. 56:7078.[Medline]
Pinnix, I., U. Musunuru, H. Tun, A. Sridharan, T. Golde, C. Eckman, C. Ziani-Cherif, L. Onstead, and K. Sambamurti. 2001. A novel gamma-secretase assay based on detection of the putative C-terminal fragment-gamma of amyloid beta protein precursor. J. Biol. Chem. 276:481487.
Price, D.L., R.E. Tanzi, D.R. Borchelt, and S.S. Sisodia. 1998. Alzheimer's disease: genetic studies and transgenic models. Annu. Rev. Genet. 32:461493.[CrossRef][Medline]
Sabo, S.L., A.F. Ikin, J.D. Buxbaum, and P. Greengard. 2001. The Alzheimer amyloid precursor protein (APP) and FE65, an APP-binding protein, regulate cell movement. J. Cell Biol. 153:14031414.
Sabo, S.L., A.F. Ikin, J.D. Buxbaum, and P. Greengard. 2003. The amyloid precursor protein and its regulatory protein, FE65, in growth cones and synapses in vitro and in vivo. J. Neurosci. 23:54075415.
Selkoe, D.J. 2005. Defining molecular targets to prevent Alzheimer disease. Arch. Neurol. 62:192195.
Tomidokoro, Y., K. Ishiguro, Y. Harigaya, E. Matsubara, M. Ikeda, J.M. Park, K. Yasutake, T. Kawarabayashi, K. Okamoto, and M. Shoji. 2001. Abeta amyloidosis induces the initial stage of tau accumulation in APP(Sw) mice. Neurosci. Lett. 299:169172.[CrossRef][Medline]
Uchida, Y., T. Ohshima, Y. Sasaki, H. Suzuki, S. Yanai, N. Yamashita, F. Nakamura, K. Takei, Y. Ihara, K. Mikoshiba, et al. 2005. Semaphorin3A signalling is mediated via sequential Cdk5 and GSK3beta phosphorylation of CRMP2: implication of common phosphorylating mechanism underlying axon guidance and Alzheimer's disease. Genes Cells. 10:165179.
Von Rotz, R.C., B.M. Kohli, J. Bosset, M. Meier, T. Suzuki, R.M. Nitsch, and U. Konietzko. 2004. The APP intracellular domain forms nuclear multiprotein complexes and regulates the transcription of its own precursor. J. Cell Sci. 117:44354448.
Yoshida, H., A. Watanabe, and Y. Ihara. 1998. Collapsin response mediator protein-2 is associated with neurofibrillary tangles in Alzheimer's disease. J. Biol. Chem. 273:97619768.
Yoshimura, T., Y. Kawano, N. Arimura, S. Kawabata, A. Kikuchi, and K. Kaibuchi. 2005. GSK-3beta regulates phosphorylation of CRMP-2 and neuronal polarity. Cell. 120:137149.[CrossRef][Medline]
Yu, C., S.H. Kim, T. Ikeuchi, H. Xu, L. Gasparini, R. Wang, and S.S. Sisodia. 2001. Characterization of a presenilin-mediated amyloid precursor protein carboxyl-terminal fragment gamma. Evidence for distinct mechanisms involved in gamma -secretase processing of the APP and Notch1 transmembrane domains. J. Biol. Chem. 276:4375643760.
Zheng, P., J. Eastman, S. Vande Pol, and S.W. Pimplikar. 1998. PAT1, a microtubule-interacting protein, recognizes the basolateral sorting signal of amyloid precursor protein. Proc. Natl. Acad. Sci. USA. 95:1474514750.
Zhu, X., Z. Sun, H.G. Lee, S.L. Siedlak, G. Perry, and M.A. Smith. 2003. Distribution, levels, and activation of MEK1 in Alzheimer's disease. J. Neurochem. 86:136142.[CrossRef][Medline]
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