μ-Amyloid Peptide-induced Apoptosis Regulated by a Novel Protein Containing a G Protein Activation Module

Abstract

Degeneration of neurons in Alzheimer's disease is mediated by ␤-amyloid peptide by diverse mechanisms, which include a putative apoptotic component stimulated by unidentified signaling events. This report describes a novel ␤-amyloid peptide-binding protein (denoted BBP) containing a G protein-coupling module. BBP is one member of a family of three proteins containing this conserved structure. The BBP subtype bound human ␤-amyloid peptide in vitro with high affinity and specificity. Expression of BBP in cell culture induced caspase-dependent vulnerability to ␤-amyloid peptide toxicity. Expression of a signaling-deficient dominant negative BBP mutant suppressed sensitivity of human Ntera-2 neurons to ␤-amyloid peptide mediated toxicity. These findings suggest that BBP is a target of neurotoxic ␤-amyloid peptide and provide new insight into the molecular pathophysiology of Alzheimer's disease.Genetic and biochemical data have coalesced to establish that ␤-amyloid peptide (A␤) 1 is a causative factor in neuron death and the consequent dimunition of cognitive abilities observed in Alzheimer's disease (1, 2). Plasma lipoproteins and their cell surface receptors influence sequestration and clearance of soluble A␤, contributing to the etiology of the disease (3-6). Inflammatory responses and oxidative damage also appear to contribute to the loss of neurons in Alzheimer's disease (7-10). Although the earliest cellular perturbations remain unclear, recent findings indicate that A␤ may act as an initiating factor in the death of neurons by inducing signaling pathways leading to apoptosis (11-17). However, the specific molecular target(s) transducing these A␤ effects has not been identified. The intracellular protein ERAB can bind A␤ in vitro, and neuroblastoma cells expressing recombinant ERAB undergo apoptosis when treated with exogenously added A␤ (18), but the mechanism by which ERAB may affect apoptotic signaling remains obscure. We identified a novel human ␤-amyloid peptide binding protein (BBP) utilizing yeast 2-hybrid technology. Analysis of the BBP amino acid sequence revealed the presence of a structural module related to that of the 7 transmembrane domain G protein-coupled receptor superfamily and known to be important in heterotrimeric G protein activation. Data suggest that BBP mediates cellular vulnerability to A␤ toxicity through a G protein-regulated program of cell death. Two related proteins (BLP1, BLP2; BBP-like proteins) were identified by sequence and structural similarities to BBP, but only the BBP subtype regulates a response to A␤. EXPERIMENTAL PROCEDURESYeast Two-hybrid Systems-Yeast 2-hybrid (Y2H) expression plasmids were constructed in the vectors pAS2 and pACT2 (19). Strain CY770 (20) served as host for Y2H assays. Sequences encoding A␤ 42 were amplified by PCR using primers incorporating restriction sites for subsequent ligation into pAS2, using a human APP (amyloid precursor protein) cDNA clone as template. A Y2H plasmid library consisting of cDNA fragments isolated from human fetal brain clone...

Amyloid-β neurotoxicity is mediated by FISH adapter protein and ADAM12 metalloprotease activity

“…Several reports have suggested that activation of tyrosine kinases may play a role in A␤-induced neuronal death (12,13) or may have a neuroprotective function, as was shown for nicotinic receptor-dependent Jak2 kinase activation, which is induced by nicotine, but not A␤, binding to the receptor (14). Some other putative A␤ receptors are thought to signal through G proteins (5,15), which might implicate tyrosine kinase activity in downstream signaling (reviewed in ref. 16), although the kinase substrates functionally involved in A␤ toxicity are not known.…”

“…It has been shown that A␤ induces neuronal death in vitro (2), and several proteins have been proposed for the role of the specific A␤ receptor (3)(4)(5)(6), although little information is available about early steps of the signaling pathway that mediates A␤ neurotoxicity (7). c-Jun N-terminal kinase as well as the p38 kinase cascades have been implicated as downstream effectors mediating the A␤-induced neuronal death (8)(9)(10)(11).…”

Molecular characterization of neurohybrid cell death induced by Alzheimer's amyloid‐β peptides via p75NTR/PLAIDD

“…Multiple proteins have been so far claimed to be candidates for the Ab receptor. They include the receptors for the endoplasmic reticulum Ab-binding dehydrogenase (ERAB; Yan et al 1997a), the advanced glycation end products (Yan et al 1997b), the a7 nicotinic acetylcholine receptor , the formyl peptide receptor like-1 (Le et al 2001), the b-amyloid binding protein-1 (BBP-1; Kajkowski et al 2001) and APP (Lorenzo et al 2000). Among them, ERAB, BBP-1 and APP are able to cause neuronal cell death when ectopically overexpressed (Kawasumi et al 2002 for review).…”

Translocation t(1;16)(p31;q24) rearranging CBFA2T3 is specific for acute erythroid leukemia

“…The G-banding analysis of short-term cultured bone marrow cells revealed an abnormal karyotype interpreted as 46,XY,-der(1)t(1;1)(p31;q21),t(1;16)(p31;q24) [11]/46,XY [9]. Fluorescence in situ hybridization, using the CBFB Dual Color Break Apart Rearrangement probe, indicated no rearrangement of CBFB; hence, the found translocation could not be a variant of the known AML-associated inv(16) or t(16;16).…”

“…10 The TM2D1 gene encodes a b-amyloid peptide-binding protein. 11 It contains a structural module related to that of the seven transmembrane domain G protein-coupled receptor superfamily known to be important in heterotrimeric G protein activation (UCSC Genome Browser at http://genome. ucsc.edu/cgi-bin/).…”