Bath application of DAPT or Compound E over the whole recording period of field excitatory postsynaptic potential (fEPSP) caused a reduction of synaptic potentiation within 1 h after 3 x 1 s100 Hz/10 min stimulation (HFS) of Schaffer-collateral CA1 synapses. Notably, DAPT and Compound E inhibited effectively long-term potentiation (LTP) of fEPSPs when it was applied after HFS, but not if applied only during the tetanization paradigm. Compounds did
not affect basal synaptic transmission, paired-pulse facilitation and NMDA mediated fEPSPs. Our data thus imply that gamma-secretase plays a role in LTP and most notably for the persistence of activity dependent synaptic plasticity, presumably through the reduction of endogenous amyloid beta and/or Notch receptor activation. Targeting of gamma-secretase to prevent the onset of AD might by VE-821 nmr itself alter memory formation. (C) 2013 Elsevier Ireland Ltd. All rights reserved.”
“Identification of ambiguous encoding in protein secondary structure is paramount to develop an understanding of key protein segments underlying amyloid diseases. We investigate two types of structurally ambivalent peptides, which were hypothesized in the literature as indicators
of amyloidogenic proteins: discordant alpha-helices and chameleon sequences. Chameleon sequences are peptides discovered experimentally in different Selleckchem Momelotinib secondary-structure types. Discordant alpha-helices are alpha-helical stretches learn more with strong beta-strand propensity or prediction. To assess the distribution of these features in known protein structures, and their potential role in amyloidogenesis, we analyzed the occurrence of
discordant alpha-helices and chameleon sequences in nonredundant sets of protein domains (n = 4263) and amyloidogenic proteins extracted from the literature (n = 77). Discordant alpha-helices were identified if discordance was observed between known secondary structures and secondary-structure predictions from the GOR-IV and PSIPRED algorithms. Chameleon sequences were extracted by searching for identical sequence words in alpha-helices and beta-strands. We defined frustrated chameleons and very frustrated chameleons based on varying degrees of total beta propensity >=alpha propensity. To our knowledge, this is the first study to discern statistical relationships between discordance, chameleons, and amyloidogenicity. We observed varying enrichment levels for some categories of discordant and chameleon sequences in amyloidogenic sequences. Chameleon sequences are also significantly enriched in proteins that have discordant helices, indicating a clear link between both phenomena. We identified the first set of discordant-chameleonic protein segments we predict may be involved in amyloidosis.