Biomedical subjects

Luciano D'Adamio

Publications and source records attributed to Luciano D'Adamio.

At least 19 recordsLinked to original sources

PubMed2006

Mitochondrial rhomboid PARL regulates cytochrome c release during apoptosis via OPA1-dependent cristae remodeling.

Rhomboids, evolutionarily conserved integral membrane proteases, participate in crucial signaling pathways. Presenilin-associated rhomboid-like (PARL) is an inner mitochondrial membrane rhomboid of unknown function, whose yeast ortholog is involved in mitochondrial fusion. Parl-/- mice display normal intrauterine development but from the fourth postnatal week undergo progressive multisystemic atrophy leading to cachectic death. Atrophy is sustained by increased apoptosis, both in and ex vivo. Parl-/- cells display normal mitochondrial morphology and function but are no longer protected against intrinsic apoptotic death stimuli by the dynamin-related mitochondrial protein OPA1. Parl-/- mitochondria display reduced levels of a soluble, intermembrane space (IMS) form of OPA1, and OPA1 specifically targeted to IMS complements Parl-/- cells, substantiating the importance of PARL in OPA1 processing. Parl-/- mitochondria undergo faster apoptotic cristae remodeling and cytochrome c release. These findings implicate regulated intramembrane proteolysis in controlling apoptosis.

Animals↗

PubMed2005

Central role of the scaffold protein tumor necrosis factor receptor-associated factor 2 in regulating endoplasmic reticulum stress-induced apoptosis.

The endoplasmic reticulum represents the quality control site of the cell for folding and assembly of cargo proteins. A variety of conditions can alter the ability of the endoplasmic reticulum (ER) to properly fold proteins, thus resulting in ER stress. Cells respond to ER stress by activating different signal transduction pathways leading to increased transcription of chaperone genes, decreased protein synthesis, and eventually to apoptosis. In the present paper we analyzed the role that the adaptor protein tumor necrosis factor-receptor associated factor 2 (TRAF2) plays in regulating cellular responses to apoptotic stimuli from the endoplasmic reticulum. Mouse embryonic fibroblasts derived from TRAF2-/- mice were more susceptible to apoptosis induced by ER stress than the wild type counterpart. This increased susceptibility to ER stress-induced apoptosis was because of an increased accumulation of reactive oxygen species following ER stress, and was abolished by the use of antioxidant. In addition, we demonstrated that the NF-kappaB pathway protects cells from ER stress-induced apoptosis, controlling ROS accumulation. Our results underscore the involvement of TRAF2 in regulating ER stress responses and the role of NF-kappaB in protecting cells from ER stress-induced apoptosis.

Animals↗

PubMed2005

Hyperphosphorylation of JNK-interacting protein 1, a protein associated with Alzheimer disease.

The c-Jun N-terminal kinase (JNK) group of mitogen-activated protein (MAP) kinases are activated by pleiotropic signals including environmental stresses, growth factors, and hormones. JNK-interacting protein 1 (JIP1) is a scaffold protein that assembles and facilitates the activation of the mixed lineage kinase-dependent JNK module and also establishes an interaction with beta-amyloid precursor protein that has been partially characterized. Here we show that, similarly to other proteins involved in various neurological diseases, JIP1 becomes hyperphosphorylated following activation of stress-activated and MAP kinases. By immobilized metal affinity chromatography and a combined microcapillary LC/MALDI-TOF/ESI-ion trap mass spectrometry approach, we identified 35 sites of mitotic phosphorylation within JIP1, among which eight were present within (Ser/Thr)-Pro sequence. This motif is modified by various kinases in aggregates of the microtubule-associated protein tau, which generates typical intraneuronal lesions occurring in Alzheimer disease. Most of the post-translational modifications found were located within the JNK, MAP kinase kinase, and RAC-alpha Ser/Thr protein kinase binding regions; no modifications occurred in protein Src homology 3 and phosphotyrosine interaction domains, which are essential for binding to kinesin, beta-amyloid precursor protein, and MAP kinase kinase kinase. Protein phosphorylation is known to affect stability and protein-protein interactions. Thus, the findings that JIP1 is extensively phosphorylated after activation of stress-activated and MAP kinases indicate that these signaling pathways might modulate JIP1 signaling by regulating its stability and association with some, but not all, interacting proteins.

Adaptor Proteins, Signal Transducing↗

PubMed2005

The familial dementia BRI2 gene binds the Alzheimer gene amyloid-beta precursor protein and inhibits amyloid-beta production.

Alzheimer disease (AD), the most common senile dementia, is characterized by amyloid plaques, vascular amyloid, neurofibrillary tangles, and progressive neurodegeneration. Amyloid is mainly composed by amyloid-beta (A(beta)) peptides, which are derive from processing of the beta-amyloid precursor protein (APP), better named amyloid-beta precursor protein (A(beta)PP), by secretases. The A(beta)PP intracellular domain (AID), which is released together with A(beta), has signaling function, since it modulates apoptosis and transcription. Despite its biological and pathological importance, the mechanisms regulating A(beta)PP processing are poorly understood. As cleavage of other gamma-secretase substrates is regulated by membrane bound proteins, we have postulated the existence of integral membrane proteins that bind A(beta)PP and regulate its processing. Here, we show that BRI2, a type II membrane protein, interacts with A(beta)PP. Interestingly, 17 amino acids corresponding to the NH2-terminal portion of A(beta) are necessary for this interaction. Moreover, BRI2 expression regulates A(beta)PP processing resulting in reduced A(beta) and AID levels. Altogether, these findings characterize the BRI2-A(beta)PP interaction as a regulatory mechanism of A(beta)PP processing that inhibits A(beta) production. Notably, BRI2 mutations cause familial British (FBD) and Danish dementias (FDD) that are clinically and pathologically similar to AD. Finding that BRI2 pathogenic mutations alter the regulatory function of BRI2 on A(beta)PP processing would define dysregulation of A(beta)PP cleavage as a pathogenic mechanism common to AD, FDD, and FBD.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Presenilin-dependent transcriptional control of the Abeta-degrading enzyme neprilysin by intracellular domains of betaAPP and APLP.

Amyloid beta-peptide (Abeta), which plays a central role in Alzheimer's disease, is generated by presenilin-dependent gamma-secretase cleavage of beta-amyloid precursor protein (betaAPP). We report that the presenilins (PS1 and PS2) also regulate Abeta degradation. Presenilin-deficient cells fail to degrade Abeta and have drastic reductions in the transcription, expression, and activity of neprilysin, a key Abeta-degrading enzyme. Neprilysin activity and expression are also lowered by gamma-secretase inhibitors and by PS1/PS2 deficiency in mouse brain. Neprilysin activity is restored by transient expression of PS1 or PS2 and by expression of the amyloid intracellular domain (AICD), which is cogenerated with Abeta, during gamma-secretase cleavage of betaAPP. Neprilysin gene promoters are transactivated by AICDs from APP-like proteins (APP, APLP1, and APLP2), but not by Abeta or by the gamma-secretase cleavage products of Notch, N- or E- cadherins. The presenilin-dependent regulation of neprilysin, mediated by AICDs, provides a physiological means to modulate Abeta levels with varying levels of gamma-secretase activity.

Aged↗

PubMed2004

Amyloid-beta protein precursor (AbetaPP) intracellular domain-associated protein-1 proteins bind to AbetaPP and modulate its processing in an isoform-specific manner.

The amyloid-beta protein precursor (AbetaPP) is a type I transmembrane molecule that undergoes several finely regulated cleavage events. The physiopathological relevance of AbetaPP derives from the fact that its aberrant processing strongly correlates with the onset of Alzheimer's disease (AD). AD is a neurodegenerative disorder characterized by neuronal cell death, loss of synapses, and deposition of misfolded protein plaques in the brain; the main constituent of these plaques is the amyloid-beta peptide, a 40-42 amino-acid-long protein fragment derived by AbetaPP upon two sequential processing events. Mutations in the genes encoding for AbetaPP and some of the enzymes responsible for its processing are strongly associated with familial forms of early onset AD. Therefore, the elucidation of the mechanisms underlying AbetaPP metabolism appears crucial to understanding the basis for the onset of AD. Apart from Abeta, upon processing of AbetaPP other fragments are generated. The long extracellular domain is released in the extracellular space, whereas the short cytoplasmic tail, named AbetaPP intracellular domain (AID) is released intracellularly. AID appears be involved in several cellular processes, apoptosis, calcium homeostasis, and transcriptional regulation. We have recently reported the cloning and characterization of different isoforms of AID associated protein-1 (AIDA-1), a novel AID-binding protein. Here we further analyzed the interaction between several AIDA-1 isoforms and the cytoplasmic tail of AbetaPP. Our data demonstrated that the interaction between the two molecules is regulated by alternative splicing of the AIDA-1 proteins. Furthermore, we provide data supporting a possible function for AIDA-1a as a modulator of AbetaPP processing.

Amino Acid Motifs↗

PubMed2004

Growth factor receptor-bound protein 2 interaction with the tyrosine-phosphorylated tail of amyloid beta precursor protein is mediated by its Src homology 2 domain.

The sequential processing of the familial disease gene product amyloid beta precursor protein (AbetaPP) by beta- and gamma-secretases generates amyloid beta, which is considered to be the pathogenic factor of Alzheimer's disease, and the AID peptide (AbetaPP intracellular domain). The AID peptide acts as a positive regulator of apoptosis and modulates transcription and calcium release. To gain clues about the molecular mechanisms regulating the function of AbetaPP and AID, proteins interacting with the AID region of AbetaPP have been isolated using the yeast two-hybrid system. Recent evidence indicates that AbetaPP undergoes post-translational modification events in the AID region and that phosphorylation might regulate its affinity for interacting proteins. To test this possibility and to uncover AbetaPP-binding partners whose interaction depends on AbetaPP phosphorylation, we used a proteomic approach. Here we describe a protein, growth factor receptor-bound protein 2 (Grb2), that specifically binds AbetaPP, phosphorylated in Tyr(682). Furthermore, we show that this interaction is direct and that Grb2 binds to phospho-AbetaPP via its Src homology 2 region. Together with the evidence that Grb2 is in complex with AbetaPP in human brains and that these complexes are augmented in brains from Alzheimer's cases, our data indicate that Grb2 may mediate some biological and possibly pathological AbetaPP-AID function.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Gadd45 beta mediates the NF-kappa B suppression of JNK signalling by targeting MKK7/JNKK2.

NF-kappa B/Rel transcription factors control apoptosis, also known as programmed cell death. This control is crucial for oncogenesis, cancer chemo-resistance and for antagonizing tumour necrosis factor alpha (TNFalpha)-induced killing. With regard to TNFalpha, the anti-apoptotic activity of NF-kappa B involves suppression of the c-Jun N-terminal kinase (JNK) cascade. Using an unbiased screen, we have previously identified Gadd45 beta/Myd118, a member of the Gadd45 family of inducible factors, as a pivotal mediator of this suppressive activity of NF-kappa B. However, the mechanisms by which Gadd45 beta inhibits JNK signalling are not understood. Here, we identify MKK7/JNKK2--a specific and essential activator of JNK--as a target of Gadd45 beta, and in fact, of NF-kappa B itself. Gadd45 beta binds to MKK7 directly and blocks its catalytic activity, thereby providing a molecular link between the NF-kappa B and JNK pathways. Importantly, Gadd45 beta is required to antagonize TNFalpha-induced cytotoxicity, and peptides disrupting the Gadd45 beta/MKK7 interaction hinder the ability of Gadd45 beta, as well as of NF-kappa B, to suppress this cytotoxicity. These findings establish a basis for the NF-kappa B control of JNK activation and identify MKK7 as a potential target for anti-inflammatory and anti-cancer therapy.

Amino Acid Sequence↗

PubMed2004

The intracellular localization of amyloid beta protein precursor (AbetaPP) intracellular domain associated protein-1 (AIDA-1) is regulated by AbetaPP and alternative splicing.

The Amyloid-beta Protein Precursor (AbetaPP) is a widely expressed transmembrane protein that is extensively processed in intracellular vesicular compartments and on the cell membrane. As a result of two sequential proteolytic cleavages, AbetaPP releases the Amyloid-beta (Abeta) peptide, which accumulates in insoluble plaques in the brain of patients affected by Alzheimer's Disease (AD). Another peptide, a C-terminal fragment named AbetaPP Intracellular Domain (AID), is generated by AbetaPP processing and is released intracellularly. Several functions for AID have been proposed: pro-apoptotic peptide, regulator of calcium homeostasis, molecule involved in transcriptional regulation. Many intracellular proteins, such as Fe65, Jip-1, Shc, Numb and X11alpha, interact with AID and modulate its function by different mechanisms. Here we report the cloning and initial characterization of two isoforms of a novel protein that we named AID Associated protein-1a (AIDA-1a), AIDA-1b and AIDA-1bDeltaAnk. We show that AbetaPP and the AIDA-1 proteins interact in vitro, in living cells and, endogenously, in leukemia cell lines. Transfected AIDA-1a, AIDA-1b and AIDA-1bDeltaAnk localize in different compartments and the intracellular distribution of AIDA-1a can be modified by over-expression of AbetaPP. AIDA-1 proteins are expressed at high levels in the brain; thus, studying their involvement in AbetaPP processing and AID function might give new insights regarding a possible role for these molecules in normal brain development and in the pathogenesis of AD.

Alternative Splicing↗

PubMed2003

Amyloid beta protein precursor is phosphorylated by JNK-1 independent of, yet facilitated by, JNK-interacting protein (JIP)-1.

Alzheimer's disease (AD) is genetically linked to the processing of amyloid beta protein precursor (AbetaPP). Aside from being the precursor of the amyloid beta (Abeta) found in plaques in the brains of patients with AD, little is known regarding the functional role of AbetaPP. We have recently reported biochemical evidence linking AbetaPP to the JNK signaling cascade by finding that JNK-interacting protein-1 (JIP-1) binds AbetaPP. In order to study the functional implications of this interaction we assayed the carboxyl-terminal of AbetaPP for phosphorylation. We found that the threonine 668 within the AbetaPP intracellular domain (AID or elsewhere AICD) is indeed phosphorylated by JNK1. We surprisingly found that although JIP-1 can facilitate this phosphorylation, it is not required for this process. We also found that JIP-1 only facilitated phosphorylation of AbetaPP but not of the two other family members APLP1 (amyloid precursor-like protein 1) and APLP2. Understanding the connection between AbetaPP phosphorylation and the JNK signaling pathway, which mediates cell response to stress may have important implications in understanding the pathogenesis of Alzheimer's disease.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Amyloid beta protein precursor (AbetaPP), but not AbetaPP-like protein 2, is bridged to the kinesin light chain by the scaffold protein JNK-interacting protein 1.

Proteolytic processing of amyloid beta protein precursor (AbetaPP) generates peptides that regulate normal cell signaling and are implicated in Alzheimer's disease pathogenesis. AbetaPP processing also occurs in nerve processes where AbetaPP is transported from the cell body by kinesin-I, a microtubule motor composed of two kinesin heavy chain and two kinesin light chain (Klc) subunits. AbetaPP transport is supposedly mediated by the direct AbetaPP-Klc1 interaction. Here we demonstrate that the AbetaPP-Klc1 interaction is not direct but is mediated by JNK-interacting protein 1 (JIP1). The phosphotyrosine binding domain of JIP1 binds the cytoplasmic tail of AbetaPP, whereas the JIP1 C-terminal region interacts with the tetratrico-peptide repeats of Klc1. We also show that JIP1 does not bridge the AbetaPP gene family member AbetaPP-like protein 2, APLP2, to Klc1. These results support a model where JIP1 mediates the interaction of AbetaPP to the motor protein kinesin-I and that this JIP1 function is unique for AbetaPP relative to its family member APLP2. Our data suggest that kinesin-I-dependent neuronal AbetaPP transport, which controls AbetaPP processing, may be regulated by JIP1.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Autosomal recessive hypercholesterolemia protein interacts with and regulates the cell surface level of Alzheimer's amyloid beta precursor protein.

The familial Alzheimer's disease gene product amyloid beta protein precursor (A beta PP) is sequentially processed by beta- and gamma-secretases to generate the A beta peptide. Although much is known about the biochemical pathway leading to A beta formation, because extracellular aggregates of A beta peptides are considered the cause of Alzheimer's disease, the biological role of A beta PP processing is only recently being investigated. Cleavage of A beta PP by gamma-secretase releases, together with A beta, a COOH-terminal A beta PP intracellular domain, termed AID. Hoping to gain clues about proteins that regulates A beta PP processing and function, we used the yeast two-hybrid system to identify proteins that interact with the AID region of A beta PP. One of the interactors isolated is the autosomal recessive hypercholesterolemia (ARH) adapter protein. This molecular interaction is confirmed in vitro and in vivo by fluorescence resonance energy transfer and in cell lysates. Moreover, we show that reduction of ARH expression by RNA interference results in increased levels of cell membrane A beta PP. These data assert a physiological role for ARH in A beta PP internalization, transport, and/or processing.

Amino Acid Sequence↗

PubMed2003

JNK-interacting protein-1 promotes transcription of A beta protein precursor but not A beta precursor-like proteins, mechanistically different than Fe65.

Processing of the amyloid beta protein precursor (A beta PP) by the beta and gamma secretases leads to the production of two small peptides, amyloid beta and the A beta PP intracellular domain (AID, or called elsewhere AICD). Whereas the role of amyloid beta in the pathogenesis of Alzheimer's disease has been studied extensively, only recently has information begun to accumulate as to the role of AID. Functions identified for AID include its ability to trigger apoptosis and a role in regulating gene transcription, particularly in combination with the A beta PP binding protein Fe65. Here, we report that AID in combination with Janus kinase interacting protein-1 (JIP-1) can activate gene expression. We demonstrate that the mechanism is different from activation in combination with Fe65 by first showing that although Fe65 enters the nucleus in the absence of full-length A beta PP, JIP-1 does not. Additionally, JIP-1-induced activation is Tip60 independent, whereas a complex with AID, Fe65, and Tip60 is formed for Fe65-induced activation. Finally, and probably most interestingly, we show that although the A beta PP family members APLP1 and APLP2 (for amyloid beta precursor-like protein) can cause activation in combination with Fe65, APLP1 and APLP2 show little or no activation in combination with JIP-1. This activity for the AID fragment may help explain the unique functions of A beta PP relative to its other family members, and changes in gene expression found in Alzheimer's disease.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Processing of beta-amyloid precursor-like protein-1 and -2 by gamma-secretase regulates transcription.

The familial Alzheimer's disease gene product beta-amyloid (Abeta) precursor protein (APP) is processed by the beta- and gamma-secretases to produce Abeta as well as AID (APP Intracellular Domain) which is derived from the extreme carboxyl terminus of APP. AID was originally shown to lower the cellular threshold to apoptosis and more recently has been shown to modulate gene expression such that it represses Notch-dependent gene expression while in combination with Fe65 it enhances gene activation. Here we report that the two other members of the APP family, beta-amyloid precursor-like protein-1 and -2 (APLP1 and APLP2), are also processed by the gamma-secretase in a Presenilin 1-dependent manner. Furthermore, the extreme carboxyl-terminal fragments produced by this processing (here termed APP-like Intracellular Domain or ALID1 and ALID2) are able to enhance Fe65-dependent gene activation, similar to what has been reported for AID. Considering that only APP and not the APLPs have been linked to familial Alzheimer's disease (AD), this data should help in understanding the physiologic roles of the APP family members and in differentiating these functions from the pathologic role of APP in Alzheimer's disease.

Alzheimer Disease↗

PubMed2002

Evidence for a role of the nerve growth factor receptor TrkA in tyrosine phosphorylation and processing of beta-APP.

The cytoplasmic tail of the beta-amyloid precursor protein (APP) contains a Y(682)ENPTY(687) sequence through which APP associates with phosphotyrosine binding (PTB) domain containing proteins in a tyrosine phosphorylation-independent manner. We have recently found that tyrosine phosphorylation of APP-Y(682) promotes docking of Shc proteins that modulate growth factor signaling to the ERK and PI3K/Akt pathways. We have also shown that APP is phosphorylated on Y(682) in cells that overexpress a constitutively active form of the tyrosine kinase abl. Here we present evidence that the nerve growth factor receptor TrkA may also promote phosphorylation of APP. Overexpression of TrkA, but not of mutated, kinase inactive TrkA resulted in tyrosine phosphorylation of APP. Site-directed mutagenesis studies showed that TrkA overexpression was associated with phosphorylation of APP-Y(682). Moreover, overexpression of TrkA also affected APP processing reducing the generation of the APP intracellular domain (AID). Thus, tyrosine phosphorylation of APP may functionally link APP processing and neurotrophic signaling to intracellular pathways associated with cellular differentiation and survival.

Amyloid beta-Protein Precursor↗

PubMed2002

The gamma-secretase-generated intracellular domain of beta-amyloid precursor protein binds Numb and inhibits Notch signaling.

The beta-amyloid precursor protein (APP) and the Notch receptor undergo intramembranous proteolysis by the Presenilin-dependent gamma-secretase. The cleavage of APP by gamma-secretase releases amyloid-beta peptides, which have been implicated in the pathogenesis of Alzheimer's disease, and the APP intracellular domain (AID), for which the function is not yet well understood. A similar gamma-secretase-mediated cleavage of the Notch receptor liberates the Notch intracellular domain (NICD). NICD translocates to the nucleus and activates the transcription of genes that regulate the generation, differentiation, and survival of neuronal cells. Hence, some of the effects of APP signaling and Alzheimer's disease pathology may be mediated by the interaction of APP and Notch. Here, we show that membrane-tethered APP binds to the cytosolic Notch inhibitors Numb and Numb-like in mouse brain lysates. AID also binds Numb and Numb-like, and represses Notch activity when released by APP. Thus, gamma-secretase may have opposing effects on Notch signaling; positive by cleaving Notch and generating NICD, and negative by processing APP and generating AID, which inhibits the function of NICD.

Amyloid Precursor Protein Secretases↗

PubMed2002

Tyrosine phosphorylation of the beta-amyloid precursor protein cytoplasmic tail promotes interaction with Shc.

beta-Amyloid precursor protein (APP) is a widely expressed transmembrane protein of unknown function that is involved in the pathogenesis of Alzheimer's disease. The cytoplasmic tail of APP interacts with phosphotyrosine binding (PTB) domain containing proteins (Fe65, X11, mDab-1, and JIP-1) and may modulate gene expression and apoptosis. We now identify Shc A and Shc C, PTB-containing adapter proteins that signal to cellular differentiation and survival pathways, as novel APP-interacting proteins. The APP cytoplasmic tail contains a PTB-binding motif (Y(682)ENPTY(687)) that, when phosphorylated on Tyr(682), precipitated the PTB domain of Shc A and Shc C, as well as endogenous full-length Shc A. APP and Shc C were physically associated in adult mouse brain homogenates. Increase in phosphorylation of APP by overexpression of the nerve growth factor receptor Trk A in 293T cells promoted the interaction of transfected APP and endogenous Shc A. Pervanadate treatment of N2a neuroblastoma cells resulted in tyrosine phosphorylation and association of endogenous APP and Shc A. Thus, APP and Shc proteins interact in vitro, in cells, and in the mouse brain. Tyrosine phosphorylation of APP may promote the interaction with Shc proteins.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Apoptosis-linked gene 2-deficient mice exhibit normal T-cell development and function.

The apoptosis-linked gene product, ALG-2, is a member of the family of intracellular Ca(2+)-binding proteins and a part of the apoptotic machinery controlled by T-cell receptor (TCR), Fas, and glucocorticoid signals. To explore the physiologic function of ALG-2 in T-cell development and function, we generated mice harboring a null mutation in the alg-2 gene. The alg-2 null mutant mice were viable and fertile and showed neither gross developmental abnormality nor immune dysfunction. Analyses of apoptotic responses of ALG-2-deficient T cells demonstrated that ALG-2 deficiency failed to block apoptosis induced by TCR, Fas, or dexamethasone signals. These findings indicate that ALG-2 is physiologically dispensable for apoptotic responses induced by the above signaling pathways and suggest that other functionally redundant proteins might exist in mammalian cells.

Animals↗