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Down-regulation of class II phosphoinositide 3-kinase alpha expression below a critical threshold induces apoptotic cell death.

Elis, Winfried and Triantafellow, Ellen and Wolters, Natalie M and Sian, Katie R and Caponigro, Giordano and Borawski, Jason and Gaither, Larry and Murphy, Leo and Finan, Peter and Mackeigan, Jeff (2008) Down-regulation of class II phosphoinositide 3-kinase alpha expression below a critical threshold induces apoptotic cell death. Molecular Cancer Research : MCR, 6 (4). pp. 614-623. ISSN 1541-7786


Members of the phosphoinositide 3-kinase (PI3K) family collectively control multiple cellular responses, including proliferation, growth, chemotaxis, and survival. These diverse effects can partly be attributed to the broad range of downstream effectors being regulated by the products of these lipid kinases, the 3'-phosphoinositides. However, an additional layer of complexity is introduced by the existence of multiple PI3K enzyme isoforms. Much has been learned over the last years on the roles of the classes I and III PI3K members in cellular signaling, but little is known about the isoform-specific tasks done by the class II PI3Ks (C2alpha, beta, and gamma). In this study, we used quantitative reverse transcription-PCR and RNA interference in mammalian cells to gain further insight into the function of these lesser studied PI3K enzymes. We find that PI3K-C2alpha, but not PI3K-C2beta, has an important role in controlling cell survival and by using a panel of RNA interference reagents, we were able to determine a critical threshold of PI3K-C2alpha mRNA levels, below which the apoptotic program is switched on, via the intrinsic cell death pathway. In addition, knockdown of PI3K-C2alpha to levels that by themselves do not induce apoptosis sensitize cells to the anticancer agent Taxol (paclitaxel). Lastly, we report that lowering the levels of PI3K-C2alpha in a number of cancer cell lines reduces their proliferation and cell viability, arguing that PI3K inhibitors targeting not only the class Ialpha isoform but also class IIalpha may contribute to an effective anticancer strategy.

Item Type: Article
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Additional Information: author can archive post-print (ie final draft post-refereeing); Authors final version may be deposited on institutional website/ repository if required by institution
Keywords: PIK3C2A; phosphoinositide 3-kinase; RNAi; apoptosis
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Date Deposited: 14 Dec 2009 13:52
Last Modified: 31 Jan 2013 01:05


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