RanBP9 at the intersection between cofilin and Aβ pathologies: rescue of neurodegenerative changes by RanBP9 reduction

Molecular pathways underlying the neurotoxicity and production of amyloid β protein (Aβ) represent potentially promising therapeutic targets for Alzheimer's disease (AD). We recently found that overexpression of the scaffolding protein RanBP9 increases Aβ production in cell lines and in transgenic mice while promoting cofilin activation and mitochondrial dysfunction. Translocation of cofilin to mitochondria and induction of cofilin–actin pathology require the activation/dephosphorylation of cofilin by Slingshot homolog 1 (SSH1) and cysteine oxidation of cofilin. In this study, we found that endogenous RanBP9 positively regulates SSH1 levels and mediates Aβ-induced translocation of cofilin to mitochondria and induction of cofilin–actin pathology in cultured cells, primary neurons, and in vivo. Endogenous level of RanBP9 was also required for Aβ-induced collapse of growth cones in immature neurons (days in vitro 9 (DIV9)) and depletion of synaptic proteins in mature neurons (DIV21). In vivo, amyloid precursor protein (APP)/presenilin-1 (PS1) mice exhibited 3.5-fold increased RanBP9 levels, and RanBP9 reduction protected against cofilin–actin pathology, synaptic damage, gliosis, and Aβ accumulation associated with APP/PS1 mice. Brains slices derived from APP/PS1 mice showed significantly impaired long-term potentiation (LTP), and RanBP9 reduction significantly enhanced paired pulse facilitation and LTP, as well as partially rescued contextual memory deficits associated with APP/PS1 mice. Therefore, these results underscore the critical importance of endogenous RanBP9 not only in Aβ accumulation but also in mediating the neurotoxic actions of Aβ at the level of synaptic plasticity, mitochondria, and cofilin–actin pathology via control of the SSH1-cofilin pathway in vivo.

Mitochondrial dysfunction and calcium deregulation by the RanBP9-cofilin pathway

Mitochondrial dysfunction and synaptic damage are important features of Alzheimer's disease (AD) associated with amyloid β (Aβ) and tau. We reported previously that the scaffolding protein RanBP9, which is overall increased in brains of patients with AD and in mutant APP transgenic mice, simultaneously promotes Aβ generation and focal adhesion disruption by accelerating the endocytosis of APP and β1-integrin, respectively. Moreover, RanBP9 induces neurodegeneration in vitro and in vivo and mediates Aβ-induced neurotoxicity. Here we show in primary hippocampal neurons that RanBP9 potentiates Aβ-induced reactive oxygen species (ROS) overproduction, apoptosis, and calcium deregulation. Analyses of calcium-handling measures demonstrate that RanBP9 selectively delays the clearance of cytosolic Ca(2+) mediated by the mitochondrial calcium uniporter through a process involving the translocation of cofilin into mitochondria and oxidative mechanisms. Further, RanBP9 retards the anterograde axonal transport of mitochondria in primary neurons and decreases synaptic mitochondrial activity in brain. These data indicate that RanBP9, cofilin, and Aβ mimic and potentiate each other to produce mitochondrial dysfunction, ROS overproduction, and calcium deregulation, which leads to neurodegenerative changes reminiscent of those seen in AD.

Randomized phase II study of the safety and efficacy of a human anti-αv integrin monoclonal antibody (CNTO 95) alone and in combination with dacarbazine in patients with stage IV metastatic melanoma: 12-month results

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Objectives: Evaluate the safety and efficacy of CNTO 95, a human anti-αv integrin monoclonal antibody, when administered alone or in combination with dacarbazine (DTIC). Methods: Patients with Stage IV metastatic melanoma were randomized 1:1:1:1 to receive 5 or 10mg/kg CNTO 95 alone, or DTIC (1000mg/m2) + either 10mg/kg CNTO 95 or placebo administered intravenously once every 3 weeks for 8 cycles in the absence of disease progression or unacceptable toxicity. DTIC arms were blinded; single-agent arms were open-label. The primary endpoint was progression free survival (PFS); secondary endpoints included partial response (PR), complete response (CR), stable disease (SD) and overall survival (OS). Major safety endpoints included the incidence of adverse events (AEs) and serious AEs (SAEs). Results: Patients were randomized to receive 5mg/kg CNTO 95 (n=32), 10mg/kg CNTO 95 (n=33), CNTO 95+DTIC (n=32), or placebo+DTIC (n=32). Baseline demographics were similar across groups. The median PFS for CNTO 95+DTIC was 75 days, placebo+DTIC was 54 days and both CNTO 95 alone arms were 42 days. Six patients achieved PR (2–10mg/kg CNTO 95, 1-CNTO 95+DTIC, 3-placebo+DTIC); one patient achieved CR (CNTO 95+DTIC). A higher proportion (43.3%) of patients achieved SD ≥ 12 wks in the CNTO 95+DTIC group compared with the other 3 groups (<20.0%). The median survival was 11.0 months for the patients in the CNTO 95+DTIC arm, 9.8 months and 14.9 months for the 5mg/kg and 10mg/kg arms, and 8.0 months for those in the DTIC control arm. The most common AEs were headache, nausea, fatigue, pyrexia, vomiting and transient uveitic reactions. Three patients (1–5mg/kg, 2-CNTO 95+DTIC) discontinued treatment due to AEs. A higher proportion of patients experienced SAEs in the placebo+DTIC group (29.0%) than in the 5mg/kg (12.9%), 10mg/kg (16.2%) or CNTO 95+DTIC (18.8%) groups. Conclusions: CNTO 95 alone or combined with DTIC was generally well tolerated. In patients with Stage IV metastatic melanoma, a trend toward improvement in PFS, OS and disease control was demonstrated with CNTO 95+DTIC.

Centocor, Centocor Research and Development, Inc.

Centocor Research and Development, Inc.

Johnson & Johnson

Centocor Research and Development, Inc.

No significant financial relationships to disclose.