Hot‐Spot‐Regionen der Aβ‐IAPP‐Wechselwirkungsdomänen als hochaffine Bindungsstellen bei Kreuz‐ und Selbstassoziation

Andreetto, Erika; Yan, Limei; Tatarek‐Nossol, Marianna; Velkova, Aleksandra; Frank, Ronald; Kapurniotu, Aphrodite

doi:10.1002/ange.200904902

Cited by 24 publications

(52 citation statements)

References 38 publications

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“…Data obtained by using several techniques, including fluorescence, gel filtration chromatography, and crosslinking, suggest that an IAPP dimer is a favorable oligomeric state in solution and on membranes, where it is the dominant oligomer at low protein/lipid ratios. [4,14] Doubling the amount of donor-labeled rIAPP increased the high ET eff population by a factor of two, as expected for a dimer rather than a higher-order oligomer (see Figure S1f in the Supporting Information). The fraction of high ET eff events (ca.…”

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confidence: 60%

A Membrane‐Bound Antiparallel Dimer of Rat Islet Amyloid Polypeptide

2011

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Islet amyloid polypeptide (IAPP, also known as amylin) is a 37-residue peptide hormone co-secreted with insulin by pancreatic b cells. IAPP is natively unstructured, but gains a-helical structure on binding to anionic membranes [1] and forms b-sheet-rich amyloid fibers during the progression of type II diabetes. [2] Membrane disruption by nonfibrillar ahelical oligomers of IAPP has been implicated in b-cell death and dysfunction. [3] Anionic membranes also dramatically accelerate the formation of IAPP fibrils, [4] possibly by favoring an oligomeric nucleating state. Therefore, membrane-bound states of IAPP are of significant interest. [5] Lipid-bound monomeric IAPP has been structurally characterized at high resolution, [6, 7] but oligomers are dynamic, heterogeneous, and transient, thus presenting a challenge for traditional structure determination approaches. Several research groups have studied these oligomeric states, [8,9] but fundamental questions about their topology and stoichiometry remain.We approached this problem by using intermolecular single-pair Fçrster resonance energy transfer (spFRET) measurements to selectively study membrane-bound IAPP oligomers from a predominantly monomeric population. To avoid experimental complications arising from fiber formation, we used the rat isoform of IAPP (rIAPP), which differs from the human isoform (hIAPP) in six residues. Similar to hIAPP, rIAPP can cause membranes to become permeable [10] and causes cell toxicity, [11] but it does not form amyloid. [12] The rIAPP was labeled with either a single donor (Alexa 488) at one of five residues, or an acceptor (Atto 610) at residue 1 ( Figure 1). Measurements were made in a dilute mixture of labeled rIAPP and 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1glycerol)] (DOPG) nanodiscs [13] as the particles diffused through a focused laser beam. The energy-transfer efficiency (ET eff ) was calculated for each transit of a fluorescent particle through the focal volume. Energy transfer only occurs when at least one donor-labeled and one acceptor-labeled rIAPP are bound to the same nanodisc (see Figure S1c in the Supporting Information). Intramolecular spFRET using double-labeled rIAPP served to verify the expected conversion from a compact disordered state in solution to a helical state in the presence of membranes (Figure 1 F).Under our experimental conditions, we expected rIAPP to be largely monomeric (free in solution or membranebound) as reflected by the major peak centered at ET eff = 0 in all histograms (Figure 1 A-E). A minor but significant population of events with ET eff > 0.25 (ca. 0.5 %) results from nanodiscs containing at least one donor-acceptor rIAPP pair. Residue pairs 1-36 and 1-1 displayed the highest peak ET eff , followed by 1-22, 1-30, and 1-17. As an Figure 1. A-E) spFRET histograms collected from a mixture of rIAPP, separately labeled with donor (d) or acceptor (a) at the positions indicated, and nanodiscs. A small fraction of rIAPP forms membranebound dimers, and the minor species ET eff peak reports on...

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confidence: 60%

A Membrane‐Bound Antiparallel Dimer of Rat Islet Amyloid Polypeptide

2011

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“…[3][4][5] In addition, AD and T2D appear to be linked also on the molecular level. [6][7][8][9] The key amyloid forming polypeptide in AD is the 40-42 residue b-amyloid peptide (Ab) while the major component of pancreatic amyloid is the 37 residue islet amyloid polypeptide (IAPP). [1,10] These two conformationally flexible but highly amyloidogenic polypeptides share 25 % sequence similarity and 50 % identity; the highest degrees of identity and similarity are within the b-strand forming regions.…”

Section: Introductionmentioning

confidence: 99%

“…[1,10] These two conformationally flexible but highly amyloidogenic polypeptides share 25 % sequence similarity and 50 % identity; the highest degrees of identity and similarity are within the b-strand forming regions. [6,7,9] We have recently found that [(N-Me)G24, (N-Me)I26]-IAPP (IAPP-GI), which is a conformationally constrained, double Nmethylated IAPP analogue and mimic of a nonamyloidogenic and nontoxic IAPP conformation, is able to bind Ab with nanomolar affinity and to completely block Ab self-assembly into cytotoxic aggregates and fibrils. [7,9,11] Consistent with these findings, nonfibrillar and nontoxic IAPP and Ab species have been also found to bind each other with nanomolar affinity and to form soluble and nontoxic hetero-oligomers.…”

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confidence: 99%

Dissecting the Role of Single Regions of an IAPP Mimic and IAPP in Inhibition of Aβ40 Amyloid Formation and Cytotoxicity

et al. 2011

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Alzheimer's disease (AD) and type 2 diabetes (T2D) are linked to the self-association of β-amyloid peptide (Aβ) and islet amyloid polypeptide (IAPP), respectively. We have shown that IAPP-GI, a soluble IAPP analogue and mimic of nonamyloidogenic and nontoxic IAPP, binds Aβ with high affinity and blocks its cytotoxic self-assembly and fibrillogenesis. We have also shown that IAPP and Aβ interact with each other into nonfibrillar and nontoxic heterocomplexes that suppress cytotoxic self-association by both polypeptides. The Aβ-IAPP interaction might thus be a molecular link between AD and T2D. We studied the role of individual IAPP-GI and IAPP regions in their inhibitory function on Aβ40 self-association and cytotoxicity. We found that the presence of the two hot-spot regions of the Aβ-IAPP interaction interface in IAPP(8-28) is not sufficient for inhibitory function and that, in addition to IAPP(8-28), the presence of the N-terminal region IAPP(1-7) is absolutely required. By contrast, the C-terminal region, IAPP(30-37), is not required although its presence together with IAPP(1-7) in IAPP-GI results in a marked enhancement of the inhibitory effect as compared to IAPP(1-28)-GI. We suggest that the inhibitory effect of IAPP-GI and IAPP on Aβ40 fibrillogenesis and cell toxicity is mediated primarily by interactions involving the hot regions of the Aβ-IAPP interaction interface and the N terminus of IAPP while a concerted and likely structure-stabilizing action of the N- and C-terminal IAPP regions potentiates this effect. These results identify important molecular determinants of the amyloid suppressing function of the Aβ40-IAPP interaction and could contribute to the design of novel inhibitors of Aβ40 aggregation and cell degeneration.

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“…[8] In this context, it has also been shown that the IAPP analogue [(N-Me)G24, (N-Me)I26]-IAPP or IAPP-GI, a mimic of nonamyloidogenic IAPP, forms nonfibrillar and nontoxic heteroassemblies with Ab and thus blocks the cytotoxic oligomer and fibril formation by Ab. [8,[12][13][14] As Ab and IAPP are present in blood and cerebrospinal fluid at similar concentrations, an in vivo interaction might be possible, which could be a molecular link between AD and T2DM. [9][10][11] Several studies have shown that lipid-peptide interactions can play a crucial role in amyloid formation of both IAPP and Ab, [1,3,[15][16][17][18][19][20][21][22][23][24][25][26][27][28] and the enhancement of fibrillation in the presence of membranes is believed to be causatively linked to the cellular damage caused by Ab or IAPP assemblies.…”

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confidence: 98%

Cross‐Amyloid Interaction of Aβ and IAPP at Lipid Membranes

Seeliger¹,

Evers²,

Jeworrek³

et al. 2011

Angew Chem Int Ed

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Several proteins and peptides are known to form cytotoxic oligomers and amyloid fibrils-mainly consisting of intermolecular cross-b-sheets-upon misfolding and self-association.[1] As these amyloid aggregates deposit in tissues, they are associated with cell degenerative diseases, such as type-2 diabetes mellitus (T2DM) or Alzheimer's disease (AD).[1]The present study is focused on the membrane-mediated aggregation of heteroassemblies of the islet amyloid polypeptide (IAPP) and the b-amyloid (Ab) peptide. The extracellular deposits in the pancreas of patients with T2DM are mainly composed of the 37-residue IAPP, which is produced, stored, and secreted together with insulin by bcells in the pancreatic islets of Langerhans. [2,3] The major component of the extracellular plaques in AD brains is Ab, a 40-or 42-residue fragment of the membrane-associated amyloid precursor protein. [4,5] Recent clinical studies have pointed to a correlation between T2DM and AD, that is, patients with T2DM have a higher risk to suffer from AD and vice versa.[6] Remarkably, the sequences of IAPP and Ab show a 25 % identity and 50 % similarity and it has been shown that fibrillation of IAPP can be cross-seeded by Ab fibrils (Figure 1). [7] Most importantly, recent studies in vitro in the bulk phase have shown that early nonfibrillar and nontoxic Ab and IAPP species bind each other with high affinity forming soluble, nonfibrillar, and nontoxic heterooligomers and that this interaction delays the cytotoxic selfassociation and amyloidogenesis of both Ab and IAPP. [8] In this context, it has also been shown that the IAPP analogue [(N-Me)G24, (N-Me)I26]-IAPP or IAPP-GI, a mimic of nonamyloidogenic IAPP, forms nonfibrillar and nontoxic heteroassemblies with Ab and thus blocks the cytotoxic oligomer and fibril formation by Ab. [8,[12][13][14] As Ab and IAPP are present in blood and cerebrospinal fluid at similar concentrations, an in vivo interaction might be possible, which could be a molecular link between AD and T2DM. [9][10][11] Several studies have shown that lipid-peptide interactions can play a crucial role in amyloid formation of both IAPP and Ab, [1,3,[15][16][17][18][19][20][21][22][23][24][25][26][27][28] and the enhancement of fibrillation in the presence of membranes is believed to be causatively linked to the cellular damage caused by Ab or IAPP assemblies. [25,26,28] Here, the interaction of IAPP and Ab with a complex heterogeneous (raft-like) model biomembrane system comprising 15 % DOPC, 10 % DOPG, 40 % DPPC, 10 % DPPG, and 25 % cholesterol has been studied. This lipid system allows for addressing effects of lateral heterogeneity (i.e., coexisting liquid-disordered and liquid-ordered domains) as well as charge effects upon peptide-membrane interactions. Both effects have been shown to be important for the membrane interaction of these peptides. [16,18,20,27,28] Furthermore, the cross-interaction of IAPP and Ab in the presence of this membrane system was analyzed.To gain a detailed picture of the membrane-mediated aggregation proc...

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Hot‐Spot‐Regionen der Aβ‐IAPP‐Wechselwirkungsdomänen als hochaffine Bindungsstellen bei Kreuz‐ und Selbstassoziation

Cited by 24 publications

References 38 publications

A Membrane‐Bound Antiparallel Dimer of Rat Islet Amyloid Polypeptide

A Membrane‐Bound Antiparallel Dimer of Rat Islet Amyloid Polypeptide

Dissecting the Role of Single Regions of an IAPP Mimic and IAPP in Inhibition of Aβ40 Amyloid Formation and Cytotoxicity

Cross‐Amyloid Interaction of Aβ and IAPP at Lipid Membranes

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