β-Sheet breaker peptides inhibit fibrogenesis in a myocyte model of Aβ production: implication for Alzheimer's disease therapy

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Amyloid βprotein (Aβ), the major component of Alzheimer's senile plaques, is neurotoxic when aggregated into fibrils. Varying in length from 39 to 43 amino acids, Aβ, particularly the longer Aβ42, is thought to play a significant role in Alzheimer's disease (AD) pathogenesis. Recently, short synthetic peptides (LPFFD) homologous to the central region of Aβ17-21 (LVFFA) as β-sheet breaker peptide (iAβ35) have been shown in vitro to bind to Aβ with high affinity, partially inhibit Aβ fibrillogenesis, and redissolve preformed fibrils. We developed cultured myocyte systems under chloroquine (CQN) as an experimental model to study APP processing for Aβ production. Human rhabdomyosarcoma (CCL-136) was transfected with iAβ5 cDNA (BRS73). To understand the role iAβ5 plays in the sequestration mechanism of Aβ, we have investigated interactions of iAβ5, with Aβ1-40 and Aβ1-42 molecules by immunological methods in this model.1. Microvacuoles were recognizable in perinuclear region of the cultured … More CCL-136 and BRS73 after 12 h CQN treatment. After 24 h, the vacuoles increased in number and large together with thick rim.2. Perinuclear and heterogeneous materials surrounding vacuoles containing stained granular bodies of CCL136 cells reacted with BC42 and BC40 (C-terminal end-specific polyclonal antibodies of Aβ that react with Aβ42 and Aβ40). Double immunostaining with BC42 and anti-iAβ5 antibodies demonstrated that Aβ42 and iAβ5 were co-localized in microvacuoles of BRS73 in the presence of CQN.3. 4 Kda band was detectable by Western blot analysis using BC42 and BC40 in mitochondrial fraction of CQN-treated CCL-136 and BRS73. 15 kDa protein bands were labeled with all antibodies in mitochondorial fraction of CQN-treated BRS73.4. When Aβ1-42 was incubated with iAβ5, 4〜15 kDa smear bands were observed with BC42 and anti-iAβ5 in in vitro binding assay. This finding showed that iAp5 bound Aβ1-42 preferentially.β-sheet breaker peptide amyloid formation by binding to Aβ42, thereby blocked the formation of β-sheet conformation, β-sheet breaker peptide may prove to be an effective inhibitor of amyloidogenesis in vitro and, hence, would provide an important therapy for AD. Less