Research Article: Dissecting the Signaling Events That Impact Classical Nuclear Import and Target Nuclear Transport Factors

Date Published: December 24, 2009

Publisher: Public Library of Science

Author(s): Mohamed Kodiha, Dan Tran, Andreea Morogan, Cynthia Qian, Ursula Stochaj, Simon Williams. http://doi.org/10.1371/journal.pone.0008420

Abstract: Signaling through MEK→ERK1/2 and PI3 kinases is implicated in many aspects of cell physiology, including the survival of oxidant exposure. Oxidants play a role in numerous physiological and pathophysiological processes, many of which rely on transport in and out of the nucleus. However, how oxidative stress impacts nuclear trafficking is not well defined.

Partial Text: Elevated levels of reactive oxygen species play a major role in human disease by contributing to type 2 diabetes, ischemia/reperfusion damage, cardiovascular diseases, stroke, Alzheimer’s disease as well as numerous neurodegenerative disorders and syndromes [1]–[7]. In response to oxidative stress, cells activate multiple signaling cascades, including the PI3 kinase→Akt/PKB and MEK→ERK1/2 pathways. Moreover, crosstalk between PI3 kinase and MEK→ERK1/2 signaling cascades has been described in different model systems [8]–[11]. Activation of PI3 kinase and MEK induces a large number of downstream events that occur both in the nuclear and cytoplasmic compartment [12]; however, the impact of signaling on nuclear transport is only beginning to emerge.

For the studies described here we have exposed HeLa cells to mild stress in order to limit the irreversible damage of cellular functions. We have previously shown that under these conditions nuclear envelopes remain intact; moreover, most of the cells remain viable and will recover from this treatment [21]. Our research further suggested that oxidative stress targets several factors that are crucial for nuclear protein transport. To date, only a limited number of quantitative studies have been undertaken to define the impact of stress and signaling events on nuclear import. Such quantitative analyses, however, will provide a better understanding of how changes in cell physiology regulate intracellular trafficking. In addition, quantitative studies are necessary to reliably identify small but significant changes that can not easily be substantiated with qualitative approaches. Towards this aim, we have now performed a systematic investigation under normal and stress conditions of classical nuclear import and key factors that are essential for nuclear trafficking. Our research reveals how oxidant exposure and signaling events control classical nuclear import and target multiple components of the nuclear transport apparatus.

With the present study we examined in a quantitative fashion the link between oxidative stress, intracellular signaling and the nuclear transport apparatus. Our results show that the activation of MEK and PI3 kinase cascades provides a novel mechanism to govern the distribution of multiple nuclear transport factors. Moreover, we demonstrate that oxidant treatment not only relocated importin-α, CAS, Nup153 and Nup88, it also altered their post-translational modification.

Source:

http://doi.org/10.1371/journal.pone.0008420

 

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