Dynamic mislocalizations of nuclear pore complex proteins after focal cerebral ischemia in rat

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The nuclear pore complex (NPC) is large protein complex embedded in the nuclear envelope (NE) that consists of about 30 different nucleoporins including Ran GTPase‐activating protein 1 (RanGap1) and nucleoporin 50 (Nup50) for protein import, glycoprotein‐210 (Gp210) and nucleoporin 205 (Nup205) as nuclear membrane and pore, and nucleoporin 107 (Nup107) for RNA export (Alber et al., 2007; Freibaum et al., 2015). Cytoplasmic RanGap1 provides the driving force of protein import into the nucleus for nucleocytoplasmic transport (NCT) (Wente and Rout, 2010; Kodiha and Stochaj, 2012). Gp210 anchors the NE and distinguishes the distinct domains of nucleoplasm from cytoplasm (Wozniak and Blobel, 1992). Nup205 exists in the nuclear pore and functions as a structural scaffold (Toyama et al., 2013). Nup107 is symmetrically located in both sides of the NPC, which is involved in RNA export (Freibaum et al., 2015). Intranuclear Nup50 involves protein import through the NPC (Ben‐Efraim and Gerace, 2001).
It has been demonstrated that nucleoporins such as RanGap1 and Nup205 showed intense nuclear localization and aberrant nuclear aggregates, and they were colocalized in C9orf72ALS cases; the disrupted NCT at the NPC may lead to the dysfunction of cells and is a fundamental mechanism for neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) (Zhang et al., 2015).
Subcellular localization of such proteins may change in response to various sources of stress (Suntharalingam and Wente, 2003; Chu et al., 2007). The dysfunctional NCT system has been demonstrated to be involved in the pathogenesis of neurodegenerative diseases such as ALS, FTD, and Alzheimer disease (AD) (Sheffield et al., 2006; Kinoshita et al., 2009; Zhang et al., 2015), which has also been reported to be associated with heart disease (Zhang et al., 2008; Cortes et al., 2010; Tarazón et al., 2012), neoplasms, and many other disorders (Cronshaw and Matunis, 2004). However, there has been no investigations on the changes of NPC proteins in cerebral ischemia. Furthermore, emerging evidence has demonstrated that oxidative stress could significantly damage NCT and affect nucleocytoplasmic trafficking (Kodiha et al., 2008; Crampton et al., 2009; Kotwaliwale and Dernburg, 2009). Oxidative stress is also known to participate in the pathophysiology of cerebral ischemia (Hayashi et al., 1999). The NPCs play an important role in coordinating the critical steps of the selective bidirectional transport across the nuclear pore (Suntharalingam and Wente, 2003; Chu et al., 2007); therefore, in the present study, we investigated the temporal alterations of nucleoporins and their interactions in ischemic rat brains.
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