A rat brain mRNA encoding a transcriptional activator homologous to the DNA binding domain of retroviral integrases

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The ␤-amyloid precursor protein (APP) 1 is an integral membrane protein from which the ␤-amyloid peptide is generated. The ␤-amyloid peptide forms the extracellular insoluble aggregates characteristic of Alzheimer's disease. The function of APP and the regulation of the proteolytic events generating the ␤-amyloid peptide are still unknown. APP was expected to be involved in signal transduction processes, because of its transmembrane topology. Three main isoforms of APP exist, generated by alternative splicing (APP 770 , APP 751 , and APP 695 ) and all possessing the same intracellular domain (reviewed in Ref.1). Although little is known about the putative extracellular ligand(s) for APP, several results describe the interaction of its intracellular domain with other proteins. These include the interaction with the heterotrimeric G protein Go (2), a 59-kDa ubiquitously expressed protein named APP-BP1 (3), the X11 protein (4), the neuron-abundant Fe65 protein, and an Fe65-like protein (4 -6). It was shown that intact APP binds to oligomeric Go protein and that the intracellular region of APP spanning residues 657-676 activates Go (2, 7). Furthermore, the interaction of APP with a monoclonal antibody directed against its extracellular domain mimics a ligand-receptor binding that triggers Go activation (7). APP-BP1 interacts both in vitro and in vivo with the carboxyl-terminal region of APP, which represents its intracellular domain. This protein is homologous to the product of the Arabidopsis auxin resistance gene AXR1 and to a Caenorabditis elegans protein of unknown function (3).The Fe65 gene is mainly expressed in the neurons of specific regions of the mammalian nervous system (8, 9) and encodes a protein containing two different types of protein-protein interaction domains: the WW domain (reviewed in Ref. 10) and the phosphotyrosine interaction/phosphotyrosine binding (PID/ PTB) domain (reviewed in Ref. 11). The latter was found in the oncoprotein Shc (12, 13), in its relatives , in other apparently unrelated proteins, such as Numb, X11, and Dab (15), and in insulin receptor substrate 1 (IRS-1) and 17). The PID/PTB domains interact with phosphotyrosine residues located in the intracellular domains of growth factor receptors, such as EGF-R, trkA, and plateletderived growth factor receptor in the case of Shc (13) and insulin receptor and interleukin 4 receptor in the case of IRS-1 (16). In contrast, the Fe65 region containing the two PID/PTB domains was demonstrated to interact with the intracellular domain of APP (5).All the PID/PTB domains present in the Shc family, IRS-1, and Fe65 interact with intracellular regions of membrane proteins containing the consensus motif ⌽XNPXY (where ⌽ is hydrophobic and X is any amino acid). However, Fe65 possesses at least two unique characteristics: (i) although all the known members of the PID/PTB family contain only one PID/ PTB element (13), Fe65 is an exception, because its sequence interacting with APP shows two consecutive PID/PTB domains; and (ii) although the Tyr prese...

Section: Methodsmentioning

confidence: 99%

Interaction of the Phosphotyrosine Interaction/Phosphotyrosine Binding-related Domains of Fe65 with Wild-type and Mutant Alzheimer's β-Amyloid Precursor Proteins

Zambrano

Buxbaum

Minopoli

et al. 1997

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“…The attempt to use the WW domain of Fe65 as bait to find its partners by the two-hybrid screening system failed because of the high background given by the GAL4-Fe65 fusion protein. This background is expected, considering the previous observation that the region of Fe65 containing the WW domain is per se able to strongly activate the transcription when fused to the GAL4 DNA binding domain (16). This means that the identification of the other ligands of the WW domain of Fe65, possibly responsible for its cytosol-nuclear trafficking, will require their purification and sequencing by classical biochemical procedures.…”

Section: Fe65 Nuclear Localizationmentioning

confidence: 97%

“…Three of these adaptor proteins belong to the Fe65 protein family; Fe65 was originally described as a protein highly expressed in neurons of specific areas of the mammalian nervous system and also possessing some characteristics of a transcription factor (15,16). It contains three protein-protein interaction domains, a WW and two PTB domains.…”

mentioning

confidence: 99%

The β-Amyloid Precursor Protein Functions as a Cytosolic Anchoring Site That Prevents Fe65 Nuclear Translocation

Minopoli

Candia

Bonetti

et al. 2001

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101

In this study we addressed the question of the intracellular localization of Fe65, an adaptor protein interacting with the ␤-amyloid precursor protein (APP) and with the transcription factor CP2/LSF/LBP1. By using tagged Fe65 expression vectors, we observed that a significant fraction of Fe65 is localized in the nucleus of transfected COS7 cells. Furthermore, the isolation of nuclei from untransfected PC12 cells allowed us to observe that a part of the endogenous Fe65 is present in the nuclear extract. The analysis of Fe65 mutant constructs demonstrated that the region of the protein required for its nuclear translocation includes the WW domain, and that, on the other hand, a small fragment of 100 residues, including this WW domain, contains enough structural information to target a reporter protein (green fluorescent protein ( The ␤-amyloid precursor protein (APP) 1 is a widely expressed integral membrane protein that is involved in the pathogenesis of Alzheimer's diseases. In fact, the main constituent of the Alzheimer's disease senile plaques, the ␤-amyloid peptide, derives from APP as a consequence of its proteolytic processing (for a recent review see Ref. 1). The overall structure of APP resembles that of a receptor or growth factor precursor, but only a small fraction of APP resides at the plasma membrane (2, 3). Part of the protein reaching the cell surface, through the secretory pathway, undergoes a juxtamembrane cleavage by the action of the ␣-secretase-ADAM10 protease (4) that results in the generation of a secreted, soluble form of APP. The rapid turnover of surface APP drives the protein to the endocytic compartment and then again to the endoplasmic reticulum-Golgi network (5, 6), where it undergoes cleavage by another proteolytic activity named ␤-secretase-BACE-1 (7-10), which generates a transmembrane 12-kDa fragment. This fragment is then cleaved by the ␥-secretase activity, which leads to the formation of ␤-amyloid peptide. Recent evidence strongly suggests the identity of ␥-secretase and presenilin dimer (11,12).The elucidation of the normal functions of APP could be important in understanding the molecular basis of Alzheimer's disease and in approaching its prevention and/or treatment, but such elucidation has been elusive up to now. One of the characteristics of this protein currently investigated is the complex network of protein-protein interactions that is centered at the short cytoplasmic tail of APP (13,14). Many proteins, in fact, interact with this C-terminal domain of APP, most of them possessing multiple protein-protein interaction domains, which in turn form complexes with other proteins, suggesting that these proteins function as adaptor proteins bridging APP to specific molecular pathways.Three of these adaptor proteins belong to the Fe65 protein family; Fe65 was originally described as a protein highly expressed in neurons of specific areas of the mammalian nervous system and also possessing some characteristics of a transcription factor (15, 16). It contains three protein-prot...

“…Fe65 is also predominantly expressed in the brain (26), suggesting that the physiological location and action of these two proteins resides in neurons. We therefore asked whether C60 protein was detectable when transfected into cultured primary neurons.…”

Section: Fe65 Binds To the C60 Protein And Markedly Enhances Itsmentioning

confidence: 99%

The Intracellular Domain of the β-Amyloid Precursor Protein Is Stabilized by Fe65 and Translocates to the Nucleus in a Notch-like Manner

Kimberly

Zheng

Guénette³

et al. 2001

416

328

The ␤-amyloid precursor protein (APP) is a ubiquitous receptor-like molecule without a known function. However, the recent recognition that APP and Notch undergo highly similar proteolytic processing has suggested a potential signaling function for APP. After ligand binding, Notch is cleaved by the ADAM-17 metalloprotease followed by an intramembrane cleavage mediated by ␥-secretase. The ␥-secretase cut releases the Notch intracellular domain (NICD), which enters the nucleus and modulates transcription. Because APP is processed similarly by ADAM-17 and ␥-secretase, we reasoned that the APP intracellular domain (AICD) has a role analogous to the NICD. We therefore generated a plasmid encoding the AICD sequence and studied the subcellular localization of the expressed protein (C60). Our results demonstrate that the cytoplasmic domain of APP is a highly labile fragment that is stabilized by forming complexes with Fe65 and can then enter the nucleus in neurons and non-neural cells. These findings strongly support the hypothesis that APP signals in the nucleus in a manner analogous to the function of Notch.The ␤-amyloid precursor protein (APP) 1 is a type I transmembrane protein that is proteolytically processed by three enzymatic activities (1). The large ectodomain is first cleaved at one of three sites close to the membrane by either ␣-or ␤-secretase to liberate a soluble APP extracellular piece (termed ␣-or ␤-APP s ). In doing so, ␣-secretase generates an 83-residue carboxyl-terminal fragment (CTF) C83, whereas ␤-secretase cuts at the other two sites to generate an 89-or 99-residue CTF (C89 and C99, respectively) (1, 2). These 3 CTFs are retained in the membrane and become substrates for an unusual intramembrane cleavage mediated by ␥-secretase, producing a heterogeneous set of products. The best characterized of these is the amyloid ␤-protein (A␤) derived from C99, which accumulates to high abundance in senile plaques and appears to play a central role in the etiology of Alzheimer's disease (AD) (1). Whereas the several A␤ species have been studied in great detail, the other products generated by ␥-secretase have received scant attention. One fragment of particular interest is the APP intracellular domain (AICD), the ϳ6-kDa extreme C terminus of APP that results from the ␥-secretase cleavage of the C83, C89, or C99 fragments.The potential importance of AICD has recently been emphasized by the recognition of similarities between APP and another type I transmembrane protein, Notch (3). Notch is a cell surface receptor that plays a critical role in many cell fate decisions during embryogenesis and adulthood (4). Following binding to its prototypical ligand Delta, Notch undergoes two cleavages, the first of which is performed by the metalloprotease ADAM-17, also called tumor necrosis factor-␣ converting enzyme (5, 6). It is subsequently cut by the presenilin-dependent ␥-secretase (7), releasing the Notch intracellular domain (NICD), a fragment analogous to AICD. After release from the membrane, the NICD fragment a...