Essential Role of Class II Phosphatidylinositol-3-kinase-C2α in Sphingosine 1-Phosphate Receptor-1-mediated Signaling and Migration in Endothelial Cells |
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| Authors: | Kuntal Biswas Kazuaki Yoshioka Ken Asanuma Yasuo Okamoto Noriko Takuwa Takehiko Sasaki Yoh Takuwa |
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| Institution: | From the ‡Department of Physiology, Kanazawa University School of Medicine, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan.;the §Department of Medical Biology, Graduate School of Medicine and Research Center for Biosignal, Akita University, Akita 010-8543, Japan, and ;the ¶Department of Health and Medical Sciences, Ishikawa Prefectural Nursing University, Kahoku, Ishikawa 929-1210, Japan |
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| Abstract: | The phosphatidylinositol (PtdIns) 3-kinase (PI3K) family regulates diverse cellular processes, including cell proliferation, migration, and vesicular trafficking, through catalyzing 3′-phosphorylation of phosphoinositides. In contrast to class I PI3Ks, including p110α and p110β, functional roles of class II PI3Ks, comprising PI3K-C2α, PI3K-C2β, and PI3K-C2γ, are little understood. The lysophospholipid mediator sphingosine 1-phosphate (S1P) plays the important roles in regulating vascular functions, including vascular formation and barrier integrity, via the G-protein-coupled receptors S1P1–3. We studied the roles of PI3K-C2α in S1P-induced endothelial cell (EC) migration and tube formation. S1P stimulated cell migration and activation of Akt, ERK, and Rac1, the latter of which acts as a signaling molecule essential for cell migration and tube formation, via S1P1 in ECs. Knockdown of either PI3K-C2α or class I p110β markedly inhibited S1P-induced migration, lamellipodium formation, and tube formation, whereas that of p110α or Vps34 did not. Only p110β was necessary for S1P-iduced Akt activation, but both PI3K-C2α and p110β were required for Rac1 activation. FRET imaging showed that S1P induced Rac1 activation in both the plasma membrane and PtdIns 3-phosphate (PtdIns(3)P)-enriched endosomes. Knockdown of PI3K-C2α but not p110β markedly reduced PtdIns(3)P-enriched endosomes and suppressed endosomal Rac1 activation. Also, knockdown of PI3K-C2α but not p110β suppressed S1P-induced S1P1 internalization into PtdIns(3)P-enriched endosomes. Finally, pharmacological inhibition of endocytosis suppressed S1P-induced S1P1 internalization, Rac1 activation, migration, and tube formation. These observations indicate that PI3K-C2α plays the crucial role in S1P1 internalization into the intracellular vesicular compartment, Rac1 activation on endosomes, and thereby migration through regulating vesicular trafficking in ECs. |
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| Keywords: | Cell Migration Endosomes Phosphatidylinositol 3-Kinase Rac Sphingosine 1-Phosphate S1P1 Receptor |
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