Abstract
We studied the effect of thrombopoietin (TPO) on interleukin-3 (IL-3)-dependent bone marrow cell colony formation of mice to clarify the role of protein kinase C (PKC) in the signal transduction of TPO for the proliferation of primitive hematopoietic progenitors. TPO alone hardly yielded colonies. However, TPO in combination with IL-3 increased colony numbers synergistically from 2- to 4-fold, compared with those supported by IL-3 alone. Serial observation of colony development showed that TPO may hasten the appearance of colonies by shortening the dormant period (G0) of primitive progenitors. Immunocytochemical studies on PKC isoforms in progenitor cells stimulated with TPO have revealed that the expression pattern of PKC-ε is changed, but not that of PKC-α, -β, -γ, -δ, or -ζ. Selective PKC inhibitors, such as calphostin C and GF 109203X, and PKC-ε-specific translocation inhibitor peptide abrogated the enhancing effect of TPO on IL-3-dependent colony formation and the changes in the intracellular expression pattern of PKC-ε. These data taken together suggest that TPO has a direct effect on primitive progenitors and enhances IL-3-dependent colony formation, at least partly through the activation of PKC-ε.
Footnotes
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Send reprint requests to: Dr. Manabu Musashi, Health Administration Center, Hokkaido University, Kita-8, Nishi-5, Kita-ku, Sapporo 060-0808, Japan. E-mail: musashim{at}med.hokudai.ac.jp
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This work was supported in part by a grant-in-aid from the Ministry of Education, Science, and Culture of Japan (No. 04671504), by a special grant-in-aid for the Promotion of Education and Science at Hokkaido University from the same source, and by the Suhara Foundation.
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Dr. Tamotsu Miyazaki is Professor Emeritus, Hokkaido University, Sapporo, Japan.
- Abbreviations:
- TPO
- thrombopoietin
- IL-3
- interleukin-3
- EPO
- erythropoietin
- GEMM
- granulocyte/erythrocyte/macrophage/megakaryocyte
- GM
- granulocyte/macrophage
- PLC
- phospholipase C
- PKC
- protein kinase C
- JAK
- Janus kinase
- STAT
- signal transducer and activator of transcription
- MAPK
- mitogen-activated protein kinase
- FU
- fluorouracil
- Day-2 post 5-FU marrow cells
- bone marrow cells obtained from mice that had received 5-FU 2 days before
- Lin−
- lineage-negative
- Lin+
- lineage-positive
- Sca-1+
- stem cell antigen-positive
- KL
- kit ligand
- BSA
- bovine serum albumin
- TPA
- 12-O-tetradecanoyl phorbol-13-acetate
- Received August 16, 2000.
- Accepted January 15, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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Involvement of Protein Kinase C-ε in Signal Transduction of Thrombopoietin in Enhancement of Interleukin-3-Dependent Proliferation of Primitive Hematopoietic Progenitors
