ErbB4 cleavage by gonadotropin-releasing hormone receptor stimulation in cultured gonadotroph cells.
The receptor for gonadotropin-releasing hormone (GnRH) belongs to the G-protein-coupled receptors, and its stimulation activates extracellular signal-regulated protein kinase (ERK). In the present study, we first examined the actions of GnRH on the ErbB family using two types of cultured gonadotroph cells. As reported previously, AG1478, an inhibitor of the ErbB family tyrosine kinase, inhibited GnRH-induced ERK activation in undifferentiated gonadotroph αT3-1 cells. However, AG1478 did not inhibit ERK activation in differentiated gonadotroph LβT2 cells, suggesting that transactivation of the ErbB family was not necessary for ERK activation in LβT2 cells. We found that ErbB4 was expressed in αT3-1 cells but not in LβT2 cells. GnRH induced the cleavage of ErbB4 and accumulation of an 80-kDa fragment in αT3-1 cells. Pharmacological experiments suggested that Gq/11and tumor necrosis factor-α-converting enzyme (TACE) were essential for GnRH-induced ErbB4 cleavage. GnRH increased the phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS), indicating that GnRH activated protein kinase C (PKC). Down-regulation of PKC and bisindolylmaleimide I, a PKC inhibitor, strongly inhibited the GnRH-induced cleavage of ErbB4. It was surprising that GnRH treatment of LβT2 cells after overexpression of ErbB4 induced ErbB4 cleavage in a TACE-dependent manner. ErbB4 cleavage was induced also by treatment of αT3-1 cells, ErbB4-overexpressing LβT2 cells, and immortalized GnRH neurons (GT1-7 cells) with leuprorelin acetate. These results may suggest that the pharmacological effects of leuprorelin acetate are conducted through TACE-mediated proteolysis of membrane proteins, including ErbB4, in gonadotroph cells and GnRH neurons.
Department of Biochemistry, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan.
Yujiro
Y
Omoto
Department of Biochemistry, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan.
Sayomi
S
Higa-Nakamine
Department of Biochemistry, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan.
Airi
A
Higa
Department of Biochemistry, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan. Electronic address: hideyuki@med.u-ryukyu.ac.jp.
Hideyuki
H
Yamamoto
D000072198:ADAM17 Protein / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D052681:Gonadotrophs / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D016729:Leuprolide / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D066247:Receptor, ErbB-4 / Q000378:metabolism*; D011966:Receptors, LHRH / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology
D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; C016658:phorbolol myristate acetate; D066247:Receptor, ErbB-4; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D000072198:ADAM17 Protein; D019204:GTP-Binding Proteins; D016729:Leuprolide; D013755:Tetradecanoylphorbol Acetate
ERK; ErbB4; GnRH; Gonadotrophs; Leuprorelin; TACE