Epidermal growth factor stimulates translocation of the class II phosphoinositide 3-kinase PI3K-C2β to the nucleus

Hrvoje Banfic , Dora Visnjic , Nikica Mise , Sanjeevi Balakrishnan , Simona Deplano , Yuri E. Korchev , Jan Domin (1)

1 Renal Section

Although the class II phosphoinositide 3-kinase enzymes PI3K-C2α and PI3K-C2β act acutely downstream of cell surface receptors they have also been localized to nuclei in mammalian cells. As with the class I PI3K enzymes, the relationship between the pool of enzyme present in cytoplasm and nuclei remains poorly understood. In this study we test the hypothesis that PI3K-C2β translocates to nuclei in response to growth factor stimulation. Fractionating homogenates of quiescent cells revealed that less than 5% of total PI3K-C2β resides in nuclei. Stimulation with epidermal growth factor sequentially increased levels of this enzyme in the cytosol and then in nuclei. Using detergent treated nuclei, PI3K-C2β co-localized with lamin A/C in the nuclear matrix. This was confirmed biochemically and phosphoinositide kinase assay showed a statistically significant increase in nuclear PI3K-C2β levels and lipid kinase activity following epidermal growth factor stimulation. C-terminal deletion and point mutation of PI3K-C2β demonstrated that epidermal growth factor driven translocation to the nucleus is dependent on a sequence of basic amino acid residues (KxKxK) that form a nuclear localization motif within the C-terminal C2 domain. Furthermore, when this sequence was expressed as an EGFP fusion protein, it translocated fluorescence into nuclei with an efficiency dependent upon copy number. These data demonstrate that epidermal growth factor stimulates the appearance of PI3K-C2β in nuclei. Further, this effect is dependent on a nuclear localization signal present within the C-terminal C2 domain indicating its bimodal function regulating phospholipid binding and shuttling PI3K-C2β into the nucleus.

Mots clés: Life Sciences

Hrvoje Banfic, Dora Visnjic, Nikica Mise, Sanjeevi Balakrishnan, Simona Deplano, et al.. Epidermal growth factor stimulates translocation of the class II phosphoinositide 3-kinase PI3K-C2β to the nucleus. Biochemical Journal, 2009, 422 (1), pp.53-60. ⟨10.1042/BJ20090654⟩. ⟨hal-00479189⟩