Phosphoinositide 3-Kinase Beta Protects Nuclear Envelope Integrity by Controlling RCC1 Localization and Ran Activity

Abstract

The nuclear envelope (NE) forms a barrier between the nucleus and the cytosol that preserves genomic integrity. The nuclear lamina and nuclear pore complexes (NPCs) are NE components that regulate nuclear events through interaction with other proteins and DNA. Defects in the nuclear lamina are associated with the development of laminopathies. As cells depleted of phosphoinositide 3-kinase beta (PI3Kβ) showed an aberrant nuclear morphology, we studied the contribution of PI3Kβ to maintenance of NE integrity. pik3cb depletion reduced the nuclear membrane tension, triggered formation of areas of lipid bilayer/lamina discontinuity, and impaired NPC assembly. We show that one mechanism for PI3Kβ regulation of NE/NPC integrity is its association with RCC1 (regulator of chromosome condensation 1), the activator of nuclear Ran GTPase. PI3Kβ controls RCC1 binding to chromatin and, in turn, Ran activation. These findings suggest that PI3Kβ regulates the nuclear envelope through upstream regulation of RCC1 and Ran.

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01184-14.

ACKNOWLEDGMENTS

We thank B. Vanhaesebroeck for the p110β plasmid, R. A. Cerione for pET28-His6-Impβ, A. Nieto for the pPA-GFP-C1 plasmid, L. Zhao for VP19C-YFP cDNA, T. M. Roberts and J. Zhao for p110β-deficient MEFs, S. Gutiérrez-Erlandsson for help with confocal microscopy, and C. Mark for editorial assistance

J.R.-M. held a Juan de la Cierva postdoctoral fellowship from the Spanish Ministry of Science and Innovation (MICINN). We thank the Network of Cooperative Research in Cancer, the Spanish Ministry of Science and Innovation, and the Madrid regional government for financial support.

J.R.-M. performed the experiments and wrote the manuscript, V.P.-G. helped with IF and immunoprecipitation experiments, M.J.R. and J.M.V. performed and interpreted the results of the EM experiments, and A.C.C. designed the research, interpreted the results, and wrote the manuscript.

We declare no financial conflict of interest.