Ayumi Uesugi and Ayako Kataoka contributed equally to this work.
Involvement of protein kinase D in uridine diphosphate-induced microglial macropinocytosis and phagocytosis
Article first published online: 4 APR 2012
Copyright © 2012 Wiley Periodicals, Inc.
Volume 60, Issue 7, pages 1094–1105, July 2012
How to Cite
Uesugi, A., Kataoka, A., Tozaki-Saitoh, H., Koga, Y., Tsuda, M., Robaye, B., Boeynaems, J.-M. and Inoue, K. (2012), Involvement of protein kinase D in uridine diphosphate-induced microglial macropinocytosis and phagocytosis. Glia, 60: 1094–1105. doi: 10.1002/glia.22337
- Issue published online: 8 MAY 2012
- Article first published online: 4 APR 2012
- Manuscript Accepted: 13 MAR 2012
- Manuscript Received: 1 MAY 2011
- Ministry of Education, Culture, Sports, Science and Technology of Japan
- P2Y6 receptor
The clearance of tissue debris by microglia is a crucial component of maintaining brain homeostasis. Microglia continuously survey the brain parenchyma and utilize extracellular nucleotides to trigger the initiation of their dynamic responses. Extracellular uridine diphosphate (UDP), which leaks or is released from damaged neurons, has been reported to stimulate the phagocytotic activity of microglia through P2Y6 receptor activation. However, the intracellular mechanisms underlying microglial P2Y6 receptor signals have not been identified. In this study, we demonstrated that UDP stimulation induced immediate and long-lasting dynamic movements in the cell membrane. After 60 min of UDP stimulation, there was an upregulation in the number of large vacuoles formed in the cell that incorporate extracellular fluorescent-labeled dextran, which indicates microglial macropinocytosis. In addition, UDP-induced vacuole formation and continuous membrane motility were suppressed by the protein kinase D (PKD) inhibitors, Gö6976 and CID755673, unlike Gö6983, which is far less sensitive to PKD. The inhibition of PKD also reduced UDP-induced incorporation of fluorescent-labeled dextran and soluble β-amyloid and phagocytosis of microspheres. UDP induced rapid phosphorylation and membrane translocation of PKD, which was abrogated by the inhibition of protein kinase C (PKC) with Gö6983. However, Gö6983 failed to suppress UDP-induced incorporation of microspheres. Finally, we found that inhibition of PKD by CID755673 significantly suppressed UDP-induced engulfment of IgG-opsonized microspheres. These data suggest that a PKC-independent function of PKD regulates UDP-induced membrane movement and contributes to the increased uptake of extracellular fluid and microspheres in microglia. © 2012 Wiley Periodicals, Inc.