Protein kinase C-delta stimulates haptoglobin secretion.
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-delta, completely blocked Hp secretion from cells to culture medium. To confirm the role of PKC-delta in Hp secretion, Hp-overexpressing COS7 cells were transiently transfected with a wild-type or a dominantnegative mutant of the PKC-delta gene. Mutant PKC-delta significantly inhibited Hp secretion, whereas the wild-type gene slightly increased Hp secretion. These results demonstrate that the PKC-delta signal is involved in Hp secretion.
Oh
Mi-Kyung
MK
Department of Natural Sciences, Chemistry Section, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
Park
Seon-Joo
SJ
Kim
Nam-Hoon
NH
Kim
In-Sook
IS
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006242:Haptoglobins / Q000378:metabolism*; D006801:Humans; D051745:Protein Kinase C-delta / Q000378:metabolism / Q000502:physiology*; D021381:Protein Transport / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
C485359:HP protein, human; D006242:Haptoglobins; D051745:Protein Kinase C-delta; D013755:Tetradecanoylphorbol Acetate