The Journal of Physiological Sciences

, Volume 69, Issue 2, pp 263–280 | Cite as

The class II phosphoinositide 3-kinases PI3K-C2α and PI3K-C2β differentially regulate clathrin-dependent pinocytosis in human vascular endothelial cells

  • Khin Thuzar Aung
  • Kazuaki Yoshioka
  • Sho Aki
  • Kazuhiro Ishimaru
  • Noriko Takuwa
  • Yoh TakuwaEmail author
Original Paper


Pinocytosis is an important fundamental cellular process that is used by the cell to transport fluid and solutes. Phosphoinositide 3-kinases (PI3Ks) regulate a diverse array of dynamic membrane events. However, it is not well-understood which PI3K isoforms are involved in specific mechanisms of pinocytosis. We performed knockdown studies of endogenous PI3K isoforms and clathrin heavy chain (CHC) mediated by small interfering RNA (siRNA). The results demonstrated that the class II PI3K PI3K-C2α and PI3K-C2β, but not the class I or III PI3K, were required for pinocytosis, based on an evaluation of fluorescein-5-isothiocyanate (FITC)–dextran uptake in endothelial cells. Pinocytosis was partially dependent on both clathrin and dynamin, and both PI3K-C2α and PI3K-C2β were required for clathrin-mediated—but not clathrin-non-mediated—FITC-dextran uptake at the step leading up to its delivery to early endosomes. Both PI3K-C2α and PI3K-C2β were co-localized with clathrin-coated pits and vesicles. However, PI3K-C2β, but not PI3K-C2α, was highly co-localized with actin filament-associated clathrin-coated structures and required for actin filament formation at the clathrin-coated structures. These results indicate that PI3K-C2α and PI3K-C2β play differential, indispensable roles in clathrin-mediated pinocytosis.


Class II PI3K PI3K-C2α PI3K-C2β Pinocytosis Clathrin Endothelial cell 



We thank Ms. Chiemi Hirose for secretarial assistance, and also thank the members of Department of Physiology for their support and assistance.

Author contributions

KTA, KY, SA, and YT designed the study. KTA, KY, and SA performed experiments. KI and NT helped experiments. KTA, KY, SA, and YT analyzed the data. KTA, KY, and YT wrote the manuscript. NT helped to draft the manuscript. All authors approved the final version of the manuscript.


This study was supported by grants from the Japan International Cooperation Agency (JICA, J-14-10306 to KTA), the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (25116711 to Y.T.), and the Japan Society for the Promotion of Science (17K08532 to K.Y., 16K18988 to S.A., 16K15409 to K.I., 17K08542 to N.T., 15H04673 to Y.T.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Supplementary material

12576_2018_644_MOESM1_ESM.mp4 (2.4 mb)
Supplementary material 1 (MP4 2460 kb)
12576_2018_644_MOESM2_ESM.mp4 (2.1 mb)
Supplementary material 2 (MP4 2119 kb)
12576_2018_644_MOESM3_ESM.docx (20 kb)
Supplementary material 3 (DOCX 20 kb)


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Copyright information

© The Physiological Society of Japan and Springer Japan KK, part of Springer Nature 2018

Authors and Affiliations

  • Khin Thuzar Aung
    • 1
  • Kazuaki Yoshioka
    • 1
  • Sho Aki
    • 1
  • Kazuhiro Ishimaru
    • 1
  • Noriko Takuwa
    • 1
    • 2
  • Yoh Takuwa
    • 1
    Email author
  1. 1.Department of PhysiologyKanazawa University School of MedicineKanazawaJapan
  2. 2.Department of Health ScienceIshikawa Prefectural UniversityKahokuJapan

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