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KMID : 0380220070400010130
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Journal of Biochemistry and Molecular Biology
2007 Volume.40 No. 1 p.130 ~ p.134
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Protein Kinase C-delta Stimulates Haptoglobin Secretion
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Oh Mi-Kyung
Park Seon-Joo
Kim Nam-Hoon
Kim In-Sook
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Abstract
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Haptoglobin (Hp) is a glycoprotein that is produced by hepatic cells and secreted into the circulation. While studying the physiologic functions of Hp, we found that Hp synthesized in THP-1 monocytic cells was largely retained within cells, although Hp is considered a secretory protein. To investigate the molecular mechanism on Hp secretion in THP-1 cells, in the present study, we examined the effect of protein kinase C (PKC) on Hp secretion. When several inhibitors of PKC isoforms were tested, only Rottlerin, a specific inhibitor of PKC-δ, completely blocked Hp secretion from cells to culture medium. To confirm the role of PKC-δ in Hp secretion, Hp-overexpressing COS7 cells were transiently transfected with a wild-type or a dominantnegative mutant of the PKC-δ gene. Mutant PKC-δ significantly inhibited Hp secretion, whereas the wild-type gene slightly increased Hp secretion. These results demonstrate that the PKC-δ signal is involved in Hp secretion.
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KEYWORD
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Haptoglobin, Protein kinase C-δ, Secretion, Rottlerin, THP-1 cells
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