Alzheimer's β‐amyloid peptide specifically interacts with and is degraded by insulin degrading enzyme

Abstract

Cerebral deposition of B-amyloid peptide @A) is a hallmark of Alzheimer's disease. Concentration of /IA could play a critical role in the rate of amyloid deposition. It is therefore of considerable importance to identify proteases involved in processing ofpA. '251-labeled synthetic /IA specifically cross-linked to a single protein with M, = 110,000 in cytosol fractions from rat brain and liver. This protein was identified as insulin degrading enzyme (IDE) since the labeling of the 110 kDa protein was completely blocked by an excess of insulin, and anti-IDE monoclonal antibodies precipitated the labeled protein. Purified rat IDE effectively degraded /IA.Key wor& Alzheirner's disease; p-Amyloid;Insulin degrading enzyme; Oxidative modification; Protein degradation; Brain; Rat IntrodwtionAlzheimer's disease amyloid is composed of a 39-43 residue /I-amyloid protein (BA) [l-3] that is derived from a set of larger transmembrane precursor proteins @4PPs) [4,5]. G rowing evidence is accumulating that processing of jL4PP may occur intracellularly [6-81 and that /IA is a normal product of cell metabolism [9-l 11. A recent finding that cultured human neurons generate /IA intracellularly before it is released into the medium [12] suggests the possibility that PA accumulation in Alzheimer's brain could result from defects in intracellular proteolytic machinery responsible for its breakdown. Thus, protease involved in processing ofBA is a potential target for pharmacological treatment of the disease.We considered that among intracellular proteases which could participate in degradation of PA, the insulin degrading enzyme (IDE; EC 3.4.22.11) is a very likely candidate. IDE is a highly selective protease involved in the breakdown of certain peptide hormones [ 13-151. IDE does not have a strict specificity for any amino acid residue [16]. It has been suggested, however, that its specificity is based on recognition of specific secondary structures rather than specific peptide bonds [16]. It is interesting to note that although the IDE substrates, insulin, atria1 natriuretic peptide and glucagon, are greatly different in primary structure, they probably share a common structural motif allowing them to form amyloid fibrils under certain conditions in vitro [ 171 and in vivo [18,19]. In amyloid fibrils, different proteins have been shown to be organized in a cross-j? conformation [ 171. Therefore, IDE specificity could be based on recognition of/3-structures either present on the surface of the substrate molecules or adopted upon binding to the protease. This possibility suggests that IDE might also degrade PA.Here we show that PA is a substrate for rat liver IDE. Furthermore, we demonstrate that IDE is the only protein that can be specifically cross-linked to PA in crude extracts of rat brain and liver, suggesting for a role for IDE in the cellular processing of /3A. Materials and methods MaterialsThe following materials were obtained: ['2SI]insulin (1.2 kCiimmo1) from Dainabott (Tokyo, Japan), /JA,,, and PAi, from Bachem ...

Metal ions affect insulin-degrading enzyme activity

“…It is also interesting to outline that if we compare these parameters with those obtained for the amyloid peptides Aβ [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and Aβ [16][17][18][19][20][21][22][23][24][25][26][27][28] several similarities and some differences emerge [54]. In particular, the overall proteolytic activity toward the main cleavage sites (i.e., Phe 24 [16][17][18][19][20][21][22][23][24][25][26][27][28] ) is somewhat higher in the case of the B20-30 peptide due to a slightly more efficient cleavage rate-limiting step (see Table 2), whereas the substrate affinity of B20-30 appears intermediate between that of Aβ [1][2][3]…”

“…Since the discovery of insulin and Aβ cleavage by IDE [11], much effort has been put in trying to understand some key questions regarding cleavage sites [12,13], kinetics of substrate interaction [14,15] and the mechanism of IDE modulation [16,17].…”

Rosiglitazone Rescues Memory Impairment in Alzheimer's Transgenic Mice: Mechanisms Involving a Reduced Amyloid and Tau Pathology

“…The brain possesses robust intrinsic Ab clearance mechanisms (Tanzi et al, 2004). Ab peptides are proteolytically degraded within the brain mainly by neprilysin (NEP) (Iwata et al, 2000) and insulin-degrading enzyme (IDE) (Kurochkin and Goto, 1994). It has been recently reported that ApoE facilitates the proteolytic clearance of soluble Ab from the brain both within microglia by NEP and extracellularly by IDE, in a process dependent on ApoE isoform and its lipidation level, where the cholesterol transporter ABCA1 and the nuclear liver X receptors (LXR) have a major role .…”

Degradation of the Alzheimer's Amyloid β Peptide by Endothelin-converting Enzyme

“…Recent reports suggest a role for both insulin-degrading enzyme and neprilysin (NEP) in the degradation of extracellular A␤ (3)(4)(5)(6)(7)(8)(9)(10). Matrix metalloproteinase-9, EC 3.4.24.15, and ␣ 2 -macroglobulin complexes have also been reported to play a role in A␤ degradation (11)(12)(13).…”