Rapid inactivation and phosphorylation of pyroglutamyl peptidase II in Y-79 human retinoblastoma cells after exposure to phorbol ester.

Abstract

Pyroglutamyl peptidase II (EC 3.4.19.-), a membrane-bound metalloproteinase, is a highly specific TRH-degrading enzyme. Exposure of Y-79 human retinoblastoma cells to 12-0-tetradecanoyl phorbol 13-acetate (TPA) decreased the activity of this enzyme in a time- and concentration-dependent manner (IC50 5 x 10(-9) M). After 15 min of TPA treatment, only 10% of pyroglutamyl peptidase II activity remained. TPA treatment did not affect the activity of the cytosolic enzyme pyroglutamyl peptidase I (EC 3.4.19.3) or the membrane-bound enzyme dipeptidyl peptidase IV (EC 3.4.19.3). Pretreatment of the cells with the protein kinase C inhibitors H-7 or sphingosine prevented the inactivation of pyroglutamyl peptidase II by TPA. The time course of the TPA-mediated effect paralleled the time course of translocation and activation of protein kinase C in this cell line. Immunoblot analysis demonstrated that inactivation of pyroglutamyl peptidase II was not due to dissociation or internalization of this enzyme molecule. Incubation of TPA-activated Y-79 cell membranes with gamma-[32P]-ATP followed by immunoprecipitation revealed a time-dependent phosphorylation of a 48 kilodalton subunit of pyroglutamyl peptidase II. These studies indicate that the phorbol ester effect is mediated by protein kinase C, and reveal a mechanism of potentiation of the action of TRH at its target sites.

• Authors: C S Suen, S Wilk
• Journal: Endocrinology (Endocrinology) Vol. 127 Issue 6 Pg. 3038-46 (Dec 1990) ISSN: 0013-7227 [Print] United States
• PMID: 1979029 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Immune Sera
• Isoquinolines
• Piperazines
• Phorbol 12,13-Dibutyrate
• 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
• Protein Kinase C
• Pyroglutamyl-Peptidase I
• Sphingosine
• Tetradecanoylphorbol Acetate
• Epinephrine

Topics

• 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine
• Cell Line
• Epinephrine (pharmacology)
• Eye Neoplasms
• Humans
• Immune Sera
• Immunoblotting
• Isoquinolines (pharmacology)
• Kinetics
• Molecular Weight
• Phorbol 12,13-Dibutyrate (pharmacology)
• Phosphorylation
• Piperazines (pharmacology)
• Protein Kinase C (metabolism)
• Pyroglutamyl-Peptidase I (antagonists & inhibitors, isolation & purification, metabolism)
• Retinoblastoma
• Sphingosine (pharmacology)
• Tetradecanoylphorbol Acetate (pharmacology)